ROLL
Internet Engineering Task Force (IETF) P. Thubert, Ed.
Internet-Draft
Request for Comments: 9914
Updates: 6550, 6553, 8138 (if approved) R.A. Jadhav
Intended status:
Category: Standards Track AccuKnox
Expires: 11 September 2025
ISSN: 2070-1721 M. Richardson
Sandelman
10 March 2025
Root-initiated
February 2026
Root-Initiated Routing State in RPL
draft-ietf-roll-dao-projection-40 the Routing Protocol for Low-Power and
Lossy Networks (RPL)
Abstract
The Routing Protocol for Low-Power and Lossy Networks (RPL, RFC (RPL) (RFC
6550) enables data packet routing along a Destination-Oriented
Directed Acyclic Graph . (DODAG). However, the default route
establishment mechanism relies on hop-by-hop forwarding along the
DODAG, which may not always provide optimal routing efficiency. This
document introduces the concept of DAO Destination Advertisement Object
(DAO) Projection, a mechanism that allows a RPL root or an external
controller to install optimized routes within the RPL domain. DAO
Projections enable the creation of optimized unicast or multicast
routes that do not strictly follow the DODAG structure, thereby
improving routing efficiency, reliability, availability, and resource
utilization in the RPL domain. The This document specifies two types of projected routes—storing mode
Projected Routes (P-Routes) -- Storing Mode and Non-Storing Mode --
and non-storing mode
projections—and outlines the signaling procedures necessary to establish,
maintain, and remove these routes. This document extends
RFC updates RFCs 6550, RFC
6553, and RFC 8138.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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(IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of six months RFC 7841.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 11 September 2025.
https://www.rfc-editor.org/info/rfc9914.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
2.2. References . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. Domain Terms . . . . . . . . . . . . . . . . . . . . . . 7
2.4.1. Projected Route . . . . . . . . . . . . . . . . . . . 7
2.4.2. Projected DAO . . . . . . . . . . . . . . . . . . . . 7
2.4.3. Path . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4.4. Routing Stretch . . . . . . . . . . . . . . . . . . . 8
2.4.5. Track . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Context and Goal . . . . . . . . . . . . . . . . . . . . . . 11
3.1. RPL Applicability . . . . . . . . . . . . . . . . . . . . 12
3.2. Multi-Topology Routing and Loop Avoidance . . . . . . . . 13
3.3. Requirements . . . . . . . . . . . . . . . . . . . . . . 15
3.3.1. Loose Source Routing . . . . . . . . . . . . . . . . 15
3.3.2. forward Forward Routes . . . . . . . . . . . . . . . . . . . 17
3.4. On Tracks . . . . . . . . . . . . . . . . . . . . . . . . 18
3.4.1. Building Tracks with RPL . . . . . . . . . . . . . . 18
3.4.2. Tracks and RPL Instances . . . . . . . . . . . . . . 19
3.5. path Path Signaling . . . . . . . . . . . . . . . . . . . . . 20
3.5.1. Using Storing Mode Segments . . . . . . . . . . . . . 22
3.5.2. Using Non-Storing Mode joining Joining Tracks . . . . . . . . 29
3.6. Complex Tracks . . . . . . . . . . . . . . . . . . . . . 36
3.7. Scope and Expectations . . . . . . . . . . . . . . . . . 38
3.7.1. External Dependencies . . . . . . . . . . . . . . . . 38
3.7.2. Positioning vs. Versus Related IETF Standards . . . . . . . 38
4. Extending existing Existing RFCs . . . . . . . . . . . . . . . . . . . 40
4.1. Extending RPL RFC 6550 . . . . . . . . . . . . . . . . . 41
4.1.1. Projected DAO . . . . . . . . . . . . . . . . . . . . 41
4.1.2. Projected DAO-ACK . . . . . . . . . . . . . . . . . . 43
4.1.3. Via Information Option . . . . . . . . . . . . . . . 44
4.1.4. Sibling Information Option . . . . . . . . . . . . . 44
4.1.5. P-DAO Request . . . . . . . . . . . . . . . . . . . . 45
4.1.6. Amending the RPI . . . . . . . . . . . . . . . . . . 45
4.1.7. Additional Flag in the RPL DODAG Configuration Option . . . . . . . . . . . . . . . . . . . . . . . 46
4.2. Extending RPL RFC 6553 . . . . . . . . . . . . . . . . . 47
4.3. Extending RPL RFC 8138 . . . . . . . . . . . . . . . . . 48
5. New RPL Control Messages and Options . . . . . . . . . . . . 49
5.1. New P-DAO Request Control Message . . . . . . . . . . . . 49
5.2. New PDR-ACK Control Message . . . . . . . . . . . . . . . 50
5.3. Via Information Options . . . . . . . . . . . . . . . . . 52
5.4. Sibling Information Option . . . . . . . . . . . . . . . 55
6. Root Initiated Root-Initiated Routing State . . . . . . . . . . . . . . . . 57
6.1. RPL Network Setup . . . . . . . . . . . . . . . . . . . . 57
6.2. Requesting a Track . . . . . . . . . . . . . . . . . . . 58
6.3. Identifying a Track . . . . . . . . . . . . . . . . . . . 59
6.4. Installing a Track . . . . . . . . . . . . . . . . . . . 60
6.4.1. Signaling a Projected Route . . . . . . . . . . . . . 61
6.4.2. Installing a Track Segment with a Storing Mode P-Route . . . . . . . . . . . . . . . . . . . . . . . 62
6.4.3. Installing a protection path Protection Path with a Non-Storing Mode
P-Route . . . . . . . . . . . . . . . . . . . . . . . 64
6.5. Tearing Down a P-Route . . . . . . . . . . . . . . . . . 66
6.6. Maintaining a Track . . . . . . . . . . . . . . . . . . . 66
6.6.1. Maintaining a Track Segment . . . . . . . . . . . . . 67
6.6.2. Maintaining a protection path . . . . . . . . . . . . 67 Protection Path
6.7. Encapsulating and Forwarding Along a Track . . . . . . . 68
6.8. Compression of the RPL Artifacts . . . . . . . . . . . . 71
7. Less-Constrained Variations . . . . . . . . . . . . . . . . . 73
7.1. Storing Mode main Main DODAG . . . . . . . . . . . . . . . . . 73
7.2. A Track as a Full DODAG . . . . . . . . . . . . . . . . . 75
8. Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . 76
9. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 78
10. Security Considerations . . . . . . . . . . . . . . . . . . . 78
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 79
11.1. RPL DODAG Configuration Option Flag . . . . . . . . . . 79
11.2. Elective 6LoWPAN Routing Header Type . . . . . . . . . . 80
11.3. Critical 6LoWPAN Routing Header Type . . . . . . . . . . 80
11.4. Registry For The for RPL Option Flags . . . . . . . . . . . 80
11.5. RPL Control Codes . . . . . . . . . . . . . . . . . . . 81
11.6. RPL Control Message Options . . . . . . . . . . . . . . 81
11.7. SubRegistry Registry for the Projected DAO Request Flags . . . . 82
11.8. SubRegistry Registry for the PDR-ACK Flags . . . . . . . . . . . 82
11.9. Registry for the PDR-ACK Acceptance Status Values . . . 83
11.10. Registry for the PDR-ACK Rejection Status Values . . . . 83
11.11. SubRegistry Registry for the Via Information Options Flags . . . 84
11.12. SubRegistry Registry for the Sibling Information Option Flags . . 84
11.13. Destination Advertisement Object Flag . . . . . . . . . 85
11.14. Destination Advertisement Object Acknowledgment Flag . . 85
11.15. New ICMPv6 Error Code . . . . . . . . . . . . . . . . . 86
11.16. RPL Rejection Status values . . . . . . . . . . . . . . 86 Values
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 86
13. References
12.1. Normative References . . . . . . . . . . . . . . . . . . . . 87
14.
12.2. Informative References . . . . . . . . . . . . . . . . . . . 88
Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 91
1. Introduction
RPL, the "Routing
The Routing Protocol for Low Power Low-Power and Lossy Networks" [RPL]
(LLNs), Networks (RPL) [RPL], is
a Distance Vector protocol, which protocol that is well-suited for application in a
variety of low energy low-energy Internet of Things (IoT) networks where
constrained nodes cannot maintain the full view of the
topology, topology and
stretched P2P paths are acceptable vs. (versus the signaling and state
overhead involved in maintaining the shortest paths across. across).
Additionally, RPL is anisotropic, meaning that its operation depends
on the orientation of the links, down from or up towards the Root,
with the default route advertised down and more specific more-specific paths
advertised up along a limited set of links.
RPL forms Destination Oriented Destination-Oriented Directed Acyclic Graphs (DODAGs) in
which the Root often acts as the Border border router to connect the RPL
domain to the IP backbone. Routers inside the DODAG route along that the
graph up towards the Root for the default route and down towards
destinations in the RPL domain for more specific more-specific routes. This As a
prerequisite, this specification expects as a pre-requisite a pre-existing RPL Instance
with an associated DODAG and RPL Root, which are referred to as the
main Instance, main DODAG DODAG, and main Root Root, respectively. The main
Instance is operated in RPL Non-Storing Mode of Operation (MOP).
With this specification, an abstract routing function called a Path
Computation Element (PCE) (e.g., located in a central controller or
collocated with the main Root) interacts with the main Root to
compute additional paths between nodes in the main Instance. In Non-
Storing Mode, the base topological information to be passed to the
PCE, that is i.e., the knowledge of the main DODAG, is already available at
the Root. This specification introduces protocol extensions that
enrich the topological information available to the Root with sibling
relationships that are usable but not leveraged to form the main
DODAG.
Based on usage, path length, and knowledge of available resources
such as battery levels and reservable buffers in the nodes, the PCE
with PCE,
which has a global visibility of the system system, can optimize the
computed routes for the application needs, including the capability to
provide path redundancy. This specification also introduces protocol
extensions that enable the Root to project (i.e., advertise from a
remote location) the computed paths in the RPL domain as Projected
Routes (a.k.a. P-Routes) on behalf of the PCE.
A P-Route may be installed in either Storing or Non-Storing Mode,
potentially resulting in hybrid situations where the Mode in which
the P-Route operates is different from that of the RPL main Instance.
P-Routes can be used as stand-alone segments meant to reduce the size
of the source routing headers, Source Routing Headers (SRHs), leveraging loose source routing
operations down the main RPL DODAG. A P-Route can also be used as a
protection path, and it can be combined and interleaved with other
P-Routes to form a Recovery Graph recovery graph called a Track. A Track is
signaled as a separate RPL Instance that is associated with a main
RPL Instance, Instance such that the RPL routers that form the Track are also
members of the main DODAG. The Track provides underlay shortcuts
using its own RIB, that which is separate from the RIB of the main
Instance and has a higher precedence.
2. Terminology
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119][RFC8174] [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
In addition, the terms "Extends" and "Amends" are used as per
[I-D.kuehlewind-update-tag] section
[NEW-TAGS], Section 3.
2.2. References
In this document, readers will encounter terms and concepts that are
discussed in the "Routing "RPL: IPv6 Routing Protocol for Low Power Low-Power and Lossy
Networks"
[RPL], the "6TiSCH Architecture" [RFC9030], [RPL]; "An Architecture for IPv6 over the Time-Slotted
Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)" [RFC9030];
"Deterministic Networking Architecture" [RFC8655], the [RFC8655]; "Using RPI Option
Type, Routing Header for Source Routes, and IP-in-IP IPv6-in-IPv6
Encapsulation in the RPL Data Plane" [RFC9008], the [RFC9008]; "Reliable and
Available Wireless (RAW) Architecture" [RAW-ARCHI], [RAW-ARCH]; and "Terminology "Terms Used in Low power And
Routing for Low-Power and Lossy Networks" [RFC7102]. The 6TiSCH 6TiSCH,
Deterministic Networking (DetNet), and DetNet/RAW RAW architectures utilize the
terms "Track" and "Recovery Graph" "recovery graph" to represent the same concept even
though they are in different environments. This document uses
"Track" to represent that concept, concept and only builds Tracks that are
DODAGs, meaning that all links are oriented from Ingress to Egress.
This specification also utilizes the terms segment "segment" and protection path
that "protection
path", which are also defined in the RAW Architecture. architecture.
As opposed to routing trees, RPL DODAGs are typically constructed to
provide redundancy and dynamically adapt the forwarding operation to
the state of the LLN Low-Power and Lossy Network (LLN) links. Note that
the plain forwarding operation over DODAGs does not provide
redundancy for all nodes, since at least the node nearest to the Root
does not have an alternate feasible successor.
RAW solves that problem by defining Protection Paths protection paths that can be
interleaved to form new paths that can be activated dynamically upon
failures. This requires additional control to take the routing
decision early enough along the Track to route around the failure.
RAW only uses single-ended DODAGs, meaning that they can be reversed
in another DODAG by reversing all the links. The Ingress of the
Track is the Root of the DODAG, whereas the Egress is the Root of the
reversed DODAG. From the RAW perspective, single-ended DODAGs are
special Tracks that only have forward links, and that can be
leveraged to provide Protection protection services by defining destination-
oriented Protection Paths protection paths within the DODAG.
2.3. Glossary
This document often uses the following abbreviations:
6LR: 6LoWPAN Router , e.g., (e.g., a RPL router in an LLN LLN)
6LoRH: 6LoWPAN Routing Header
ARQ: Automatic Repeat Request, in Request (in other words retries words, retries)
FEC: Forward Error Correction
HARQ: Hybrid Automatic Repeat Request, combining Request (combines FEC and ARQ ARQ)
CMO: Control Message Option
DAO: Destination Advertisement Object
DAG: Directed Acyclic Graph
DODAG: Destination-Oriented Directed Acyclic Graph; Graph. A DAG with
only one vertex (i.e., node) that has no outgoing edge
(i.e., link) link).
GUA: IPv6 Global Unicast Address
LLN: Low-Power and Lossy Network
MOP: RPL Mode of Operation
P-DAO: Projected DAO
P-Route: Projected Route
PDR: P-DAO Request
PCE: Path Computation Element
PLR: Point of Local Repair
RAN: RPL-Aware Node (either a RPL router or a RPL-Aware Leaf)
RAL: RPL-Aware Leaf
RH: Routing Header
RIB: Routing Information Base, i.e., Base (i.e., the routing table. table)
RPI: RPL Packet Information
RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks
RTO: RPL Target Option
RUL: RPL-Unaware Leaf
SIO: RPL Sibling Information Option
ULA: IPv6 Unique Local Address
NSM-VIO: A Source-Routed Non-Storing Mode Via Information Option, Option. Source-routed
VIO used in Non-Storing Mode P-DAO messages messages.
SLO: Service Level Objective
SRH: Source Routing Header, i.e., the Header (i.e., IPv6 RH type 3, 3); see
Section 2.4.5.7.2
SRH-6loRH: 2.4.5.7.2.
SRH-6LoRH: Source Routing Header 6LoRH, a 6LoRH. A compressed form of SRH
defined in " IPv6 "IPv6 over Low-Power Wireless Personal Area
Network (6LoWPAN) Routing Header" [RFC8138] [RFC8138].
TIO: RPL Transit Information Option
SM-VIO: A strict Storing Mode Via Information Option, Option. Strict VIO used in
Storing Mode P-DAO
messages messages.
VIO: A Via Information Option; it Option. It can be an SM-VIO or a NSM-VIO NSM-VIO.
2.4. Domain Terms
This specification uses the following terminology: terminology defined in the sections that
follow.
2.4.1. Projected Route
A RPL P-Route is a RPL route that is computed remotely by a PCE, PCE and
installed and maintained by a RPL Root on behalf of the PCE. It is
installed as a state that signals that destinations (i.e., Targets)
are reachable via or along a sequence of nodes.
2.4.2. Projected DAO
A Projected DAO (P-DAO) is a DAO message that is used to install a
P-Route.
2.4.3. Path
Quoting (non-normatively) section 1.1.3 the definition of path in Section 1.3.3 of [INT-ARCHI]:
[INT-ARCH]:
| At a given moment, all the IP datagrams from a particular source
| host to a particular destination host will typically traverse the
| same sequence of gateways. We use the term "path" for this
| sequence. Note that a path is uni-directional; it is not unusual
| to have different paths in the two directions between a given host
| pair.
Section 2 of [I-D.irtf-panrg-path-properties] [RFC9473] points to a longer, more modern definition of path, which begins as follows:
path:
| A sequence of adjacent path elements over which a packet can be
| transmitted, starting and ending with a node. A path is
| unidirectional. Paths are time-dependent, i.e., the sequence of
| path elements over which packets are sent from one node to another
| may change. A path is defined between two nodes.
It follows that the general acceptance of a path is a linear sequence
of nodes, as opposed to a multi-dimensional graph. In the context of
this document, a path is observed by following one copy of a packet
that is injected in a Track and possibly replicated within.
2.4.4. Routing Stretch
RPL is anisotropic, meaning that it is directional, or directional or, more exactly
precisely, polar. RPL does not behave the same way "downwards" (root
towards leaves) with _multicast_ DIO DODAG Information Object (DIO)
messages that form the DODAG and "upwards" (leaves towards root) with
_unicast_ DAO messages that follow the DODAG. This is in contrast
with traditional IGPs that operate the same way in all directions and
are thus called isotropic.
The term Routing Stretch "routing stretch" denotes the length of a path, in
comparison to the length of the shortest path, which can be an
abstract concept in RPL when the metrics are statistical and dynamic,
and the concept of distance varies with the Objective Function.
The RPL DODAG optimizes the P2MP (Point-to-Multipoint) Point-to-Multipoint (P2MP) paths (from the
Root) and MP2P (Multipoint-to-Point) Multipoint-to-Point (MP2P) paths (towards the Root) paths, Root), but
the P2P (Point-to-Point) Point-to-Point (P2P) traffic has to follow the same DODAG.
Following the DODAG, the RPL datapath passes via a common parent in
Storing Mode and via the Root in Non-Storing Mode. This typically
involves more hops and more latency than the minimum possible for a
directional (i.e., forward) P2P path that an isotropic protocol would
compute. We refer to this elongated path as stretched.
2.4.5. Track
The concept of Track is inherited from the "6TiSCH Architecture" 6TiSCH architecture
[RFC9030] and matches that of a Protection Path protection path in the RAW
Architecture" [RAW-ARCHI].
architecture [RAW-ARCH]. A Track is a networking graph that can be
followed to transport packets with equivalent treatment; as opposed
to the definition of a path above, a Track is not necessarily linear.
It may contain multiple paths that may fork and rejoin, rejoin and that may
enable the RAW Packet ARQ, Replication, Elimination, and Overhearing
(PAREO) operations.
Figure 1 illustrates the mapping of the DODAG with the generic
concept of a Track, with the DODAG Root acting as the Ingress for the
Track, and the mapping of protection paths and segments, and i.e., only
forward segments, meaning that they are directional and progressing
towards the destination. Note that East is represented on the left
since the packets are forwarded East-West.
North East North West
A ==> B ==> C -=- F ==> G ==> H T1 I: Ingress
/ \ / \ / E: Egress
I O E -=- T2 T1, T2, T3:
\ / \ / \ External
P ==> Q ==> R -=- T ==> U ==> V T3 Targets
South East South West
I: Ingress
E: Egress
T1, T2, T3: external targets
Figure 1: A Track and Its Components
Of note:
I ==> A ==> B ==> C : a Segment C: A segment to targets F and O
I --> F --> E : a E: A protection path to targets T1, T2, T3
I, A, B, C, F, G, H, E : a E: A path to T1, T2, T3
Figure 1: A Track and its Components
This specification builds Tracks that are DODAGs oriented towards a
Track Ingress, and the forward direction for packets is from the
Track Ingress to one of the possibly possible multiple Track Egress Nodes,
which is also down the DODAG.
The Track may be strictly connected, meaning that the vertices are
adjacent, or loosely connected, meaning that the vertices are
connected using segments that are associated to the same Track.
2.4.5.1. TrackID
A RPL InstanceID RPLInstanceID (typically of a Local Instance) that identifies a Track
using the namespace owned by the Track Ingress. For Local Instances,
the TrackID is associated with the IPv6 Address address of the Track Ingress
that is used as the DODAGID, and together they form a unique
identification of the Track (see the definition of DODAGID in
section
Section 2 of [RPL]. [RPL]).
2.4.5.2. Namespace
The term namespace "namespace" is used to refer to the scope of the TrackID.
The TrackID is locally significant within its namespace. For Local
Instances, the namespace is identified by the DODAGID for the Track Track,
and the tuple (DODAGID, TrackID) is globally unique. For Global
Instances, the namespace is the whole RPL domain.
2.4.5.3. Complex Track
A complex Track is a Track that can be traversed via more than one
path (e.g., a DODAG).
2.4.5.4. Stand-Alone
Refers Stand Alone
Stand alone refers to a segment or a protection path that is
installed with a single P-DAO that fully defines the path, e.g., a
stand-alone segment is installed with a single Storing Mode Via
Information option (SM-
VIO) Option (SM-VIO) all the way between the Ingress and
Egress.
2.4.5.5. Stitching
This specification uses the term stitching "stitching" to indicate that a track Track
is piped to another one, meaning that traffic out of the first track Track
is injected into the other track. Track.
2.4.5.6. Protection Path
The concept of protection path is defined in the RAW Architecture"
[RAW-ARCHI] architecture
[RAW-ARCH] as an end-to-end forward serial path. With this
specification, a protection path is installed by the Root of the main
DODAG using a Non-Storing Mode P-DAO message, e.g., I --> F --> E in
Figure 1.
As the Non-Storing Mode Via Information option Option (NSM-VIO) can only
signal sequences of nodes, it takes one Non-Storing Mode P-DAO
message per protection path to signal the structure of a complex
Track.
Each NSM-VIO for the same TrackID but with a different Segment ID
signals a different protection path that the Track Ingress adds to
the topology.
2.4.5.7. Segment
A segment is a serial path formed by a strict sequence of nodes, nodes along
which a P-Route is installed, e.g., I ==> A ==> B ==> C in Figure 1.
With this specification, a segment is typically installed by the Root
of the main DODAG using Storing Mode P-DAO messages. A segment is
used as the topological edge of a Track joining the loose steps along
the protection paths that form the structure of a complex Track. The
same segment may be leveraged by more than one protection path where
the protection paths overlap.
Since this specification builds only DODAGs, all segments are
oriented from the Ingress (East) to Egress (West), as opposed to the
general Track model in the RAW Architecture [RAW-ARCHI], architecture [RAW-ARCH], which allows
North/South segments that can be bidirectional as well.
2.4.5.7.1. Section of a Segment
A
The section of a segment refers to a continuous subset of a segment
that may be replaced while the segment remains. For instance, in
segment A=>B=>C=>D=>E=>F, say that the link C to D might be
misbehaving. The section B=>C=>D=>E in the segment may be replaced
by B=>C’=>D’=>E B=>C'=>D'=>E to route around the problem. The segment becomes A=>B=>C’=>D’=>E=>F.
A=>B=>C'=>D'=>E=>F.
2.4.5.7.2. Segment Routing and SRH
In a Non-Storing mode Mode RPL domain, the IPv6 RH used for source-routing source routing
is the (RPL) SRH as defined in [RFC6554]. This specification
operates in that context and uses the acronym SRH to mean the IPv6 RH
type 3 3, as opposed to the IPv6 RH type 4 defined in [RFC8754] for the Segment
Routing over IPv6 (SRv6) operation.
If the network is a 6LoWPAN Network, network, the expectation is that the SRH
is compressed and encoded as a 6LoWPAN Routing Header (6LoRH), as
specified in section Section 5 of [RFC8138].
This specification uses the term "Segment Routing" generically, generically to
refer to using source-routing source routing to hop over segments. As such,
forwarding along segments as specified hereafter can be seen as a
form of Segment Routing [RFC8402], but leveraging [RFC8402] that leverages the (RPL) SRH for
its operation.
Outside of LLNs, the RPL Network network may be less constrained and operated
in Storing Mode, as discussed in Section 7.1. In that case, this
specification could be extended to accommodate the SRv6 RH.
3. Context and Goal
3.1. RPL Applicability
RPL is optimized for situations where the power is scarce, the
bandwidth is constrained constrained, and the transmissions are unreliable. This
matches the use case of an IoT LLN where RPL is typically used today,
but today
and also situations of high relative mobility between the nodes in
the network (a.k.a. swarming), e.g., within a variable set of
vehicles with a similar global motion, motion or a platoon of drones. In
contrast, this specification only applies when the platoon has a
relatively stable topology where the segments can be attributed a
reliability and availability for a certain lifetime, lifetime; see [RAW-ARCHI]. [RAW-ARCH].
To reach this goal, RPL is primarily designed to minimize the control
plane activity, that is i.e., the relative amount of routing protocol
exchanges vs. versus data traffic, and the amount of state that is
maintained in each node. RPL does not need to converge, and it
provides connectivity to most nodes most of the time.
RPL may form multiple topologies called instances. Instances can be
created to enforce various optimizations through objective functions, functions
or to reach out through different Root Nodes. The concept of
objective function allows to adapt adapting the activity of the routing
protocol to the use case, e.g., type, speed, and quality of the LLN
links.
RPL instances operate in parallel, unaware of one another. Yet, it
is possible to define a model whereby if a route cannot be found in
the current instance A where a packet is being forwarded, then the
router may lookup look up the routing table (RIB) (i.e., the RIB) in an instance B
and forward along instance B if the route is found there. To avoid
loops, this must happen in such a way that the instances themselves
form a directed acyclic graph Directed Acyclic Graph (DAG) leading to the last resort
instance that
instance, which is the "lowest" instance if instance A is considered
"higher" then instance B. This specification uses underlay Tracks as
"lower" instances, with the main instance being the "highest" of all.
The RPL Root is responsible for selecting the RPL Instance that is
used to forward a packet coming from the Backbone backbone into the RPL domain
and for setting the related RPL information in the packets. Each
Instance creates its own routing table (RIB) (i.e., a RIB) in participating
nodes, and the RIB associated to the instance must be used end to end
in the RPL domain. To that effect, RPL tags the packets with the
Instance ID in a Hop-by-Hop extension Header. header. 6TiSCH leverages RPL
for its distributed routing operations.
To reduce the routing exchanges, RPL leverages an anisotropic
Distance Vector approach, which does not need a global knowledge of the topology,
topology and only optimizes the routes to and from the RPL Root,
allowing P2P paths to be stretched. Although RPL installs its routes
proactively, it only maintains them lazily, in reaction to actual
traffic,
traffic or as a slow background activity.
This is simple and efficient in situations where the traffic is
mostly directed from or to a central node, such as the control
traffic between routers and a controller of a Software Defined Software-Defined
Networking (SDN) infrastructure or an Autonomic Control Plane (ACP).
But stretch in P2P routing is counter-productive to both reliability
and latency as it introduces additional delay and chances of loss.
As a result, [RPL] is not a good fit for the use cases listed in the
RAW use cases document [RFC9450], which demand high availability and
reliability, and
reliability and, as a consequence consequence, require both short and diverse
paths.
3.2. Multi-Topology Routing and Loop Avoidance
RPL first forms a default route in each node towards the Root, and
those routes together coalesce as a Directed Acyclic Graph DAG oriented upwards. RPL then
constructs routes to destinations signaled as Targets in the reverse
direction, down the same DODAG. To do so, a RPL Instance can be
operated either in either RPL Storing Mode or Non-Storing Mode of Operation
(MOP). The default route towards the Root is maintained aggressively
and may change while a packet progresses without causing loops, so
the packet will still reach the Root.
In Non-Storing Mode, each node advertises itself as a Target directly
to the Root, indicating the parents that may be used to reach itself.
Recursively, the Root builds and maintains an image of the whole
DODAG in memory, memory and leverages that abstraction to compute source
route paths for the packets to their destinations down the DODAG.
When a node changes its point(s) of attachment to the DODAG, it takes
a single unicast packet to the Root along the default route to update
it, and the connectivity to the node is restored immediately; this
mode is preferable for use cases where internet connectivity is
dominant,
dominant or when the Root controls the network activity in the nodes,
which is the case of in this specification.
In Storing Mode, the routing information percolates upwards, and each
node maintains the routes to the subDAG of its descendants down the
DODAG. The maintenance is lazy, either reactive upon traffic or as a
slow background process. Packets flow via the common parent and the
routing stretch is reduced reduced, compared to the Non-Storing MOP, for
better P2P connectivity. However, a new route takes a longer time to
propagate to the Root, since it takes time for the Distance-Vector Distance Vector
protocol to operate hop-by-hop, hop by hop, and the connectivity from the
internet
Internet to the node is restored more slowly upon node movement.
Either way, the RPL routes are injected by the Target nodes, nodes in a
distributed fashion. To complement RPL and eliminate routing
stretch, this specification introduces a hybrid mode that combines
Storing and Non-Storing operations to build and project routes onto
the nodes where they should be installed. This specification uses
the term Projected Route (P-Route) "P-Route" to refer to those routes.
In the simplest mode of this specification, Storing-Mode Storing Mode P-Routes can
be deployed to join the dots of a loose source routing header (SRH) SRH in the main DODAG. In
that case, all the routes (source routed and P-Routes) belong to the
Routing Information base Base (RIB) associated with the main Instance. Storing-Mode
Storing Mode P-Routes are referred to as segments in this
specification.
A set of P-Routes can also be projected to form a dotted-line
underlay of the main Instance and provide Traffic Engineered Traffic-Engineered paths
for an application. In that case, the P-Routes are installed in Non-
Storing Mode Mode, and the set of P-Routes is called a Track. A Track is
associated with its own RPL Instance, Instance and, as any RPL Instance, with
its own Routing Information base (RIB). RIB. As a result, each Track defines a routing topology in
the RPL domain. As for the main DODAG, segments associated to the
Track Instance may be deployed to join the dots using Storing-Mode Storing Mode
P-Routes.
Routing in a multi-topology domain may cause loops unless strict
rules are applied. This specification defines two strict orders to
ensure loop avoidance when projected routes P-Routes are used in a RPL domain, domain: one
between forwarding methods and one between RPL Instances, seen as which are
routing topologies.
The first and strict order relates to the forwarding method and the and, more specifically
specifically, the origin of the information used in the next-hop
computation. The possible forwarding methods are: 1) to a direct
next hop, 2) to an indirect neighbor via a common neighbor, 3) along
a segment, and 4) along a nested Track. The methods are strictly
ordered as listed above, above; see more in Section 6.7. A forwarding
method may leverage any of the lower order lower-order ones, but never one with a
higher order; for instance, when forwarding a packet along a segment,
the router may use direct or indirect neighbors but cannot use a
Track. The lower order lower-order methods have a strict precedence, so the
router will always prefer a direct neighbor over an indirect one, one or a
segment within the current RPL Instance vs. over another Track.
The second strict and partial order is between RPL Instances. It
allows the RPL node to detect an error in the state installed by the
PCE, e.g., after a desynchronization. That order must be defined by
the administrator for the RPL domain and defines a DODAG of underlays
with the main Instance as Root. The relation of RPL instances may be
represented as a DODAG of instances where the main instance is the
Root. The rule is that a RPL Instance may leverage another RPL
instance as an underlay if and only if that other Instance is one of
its descendants in the graph. Supporting this method is OPTIONAL for
nested Tracks and REQUIRED between a Track instance and the main
instance. It may be done using network management, management or future
extensions to this specifications. When it is not communicated, then the
RPL nodes consider by default that all Track instances are children
of the main instance, and they do not attempt to validate the order
for nested Tracks, trusting the PCE implicitly. As a result, a
packet that is being forwarded along the main Instance may be
encapsulated in any Track, but a packet that was forwarded along a
Track MUST NOT be forwarded along the default route of the main
Instance.
3.3. Requirements
3.3.1. Loose Source Routing
A RPL implementation operating in a very constrained LLN typically
uses the Non-Storing Mode of Operation as represented in Figure 2.
In that mode, a RPL node indicates a parent-child relationship to the
Root, using a destination Destination Advertisement Object (DAO) that is unicast
from the node directly to the Root, and the Root typically builds a
source routed
source-routed path to a destination down the DODAG by recursively
concatenating this information.
+-----+
| | Border router Router
| | (RPL Root)
+-----+ ^ | |
| | DAO | ACK |
o o o o | | | Strict
o o o o o o o o o | | | Source
o o o o o o o o o o | | | Route
o o o o o o o o o | | |
o o o o o o o o | v v
o o o o
LLN
Figure 2: RPL Non-Storing Mode of operation Operation
Based on the parent-children relationships expressed in the Non-
Storing DAO messages, the Root possesses topological information
about the whole network, though this information is limited to the
structure of the DODAG for which it is the destination. A packet
that is generated within the domain will always reach the Root, which
can then apply a source routing information to reach the destination if
the destination is also in the DODAG. Similarly, a packet coming
from the outside of the domain for a destination that is expected to
be in a RPL domain reaches the Root. This results in the wireless
bandwidth near the Root being the limiting factor for all
transmissions towards or within the domain, and that the Root is a single
point of failure for all connectivity to nodes within its domain.
The RPL Root must add a source routing header to all downward
packets. As a network grows, the size of the source routing header
increases with the depth of the network. In some use cases, a RPL
network forms long lines along physical structures such as like streets
for with
lighting. Limiting the packet size is beneficial to the energy
budget, directly for the current transmission, but transmission and also indirectly
since it reduces the chances of frame loss and energy spent in
retries, e.g., by ARQ over one hop at Layer-2, Layer 2 or end-to-end end to end at upper
layers. Using smaller packets also reduces the chances of packet
fragmentation, which is highly detrimental to the LLN operation, in
particular when fragments are forwarded but not recovered, recovered; see
[RFC8930] vs. compared to [RFC8931] for more. more details.
A limited amount of well-targeted routing state would allow the
source routing operation to be loose as opposed to strict, strict and would
reduce the overhead of routing information in packets. Because the
capability to store routing state in every node is limited, the
decision of which route is installed where can only be optimized with
global knowledge of the system, knowledge that the Root or an
associated PCE may possess by means that are outside the scope of
this specification.
Being on-path on path for all packets in Non-Storing mode, Mode, the Root may
determine the number of P2P packets in its RPL domain per source and
destination, the latency incurred, and the amount of energy and
bandwidth that is consumed to reach itself and then back down,
including possible fragmentation when encapsulating larger packets.
Enabling a shorter path that would not traverse the Root for select
P2P source/destinations sources/destinations may improve the latency, lower the
consumption of constrained resources, free bandwidth at the
bottleneck near the Root, improve the delivery ratio ratio, and reduce the
latency for those P2P flows with flows; this would be a global benefit for all
flows by reducing the load at the Root.
To limit the need for source route headers in deep networks, one
possibility is to store a routing state associated with the main
DODAG in select RPL routers down the path. The Root may elide the
sequence of routers that is installed in the network from its source
route header, which therefore becomes loose, in contrast to being
strict in [RPL].
3.3.2. forward Forward Routes
[RPL] optimizes P2MP routes from the Root, MP2P routes towards the
Root, and as a consequence routes from/to the outside of the RPL domain when the Root
also serves as Border Router. the border router. All routes are installed North-South North-
South (a.k.a. up/down) along the RPL DODAG. Peer to
Peer Peer-to-Peer (P2P)
forward routes in a RPL network will generally experience elongated
(stretched) paths versus rather than direct (optimized) paths, since routing
between two nodes always happens via a common parent, as illustrated
in Figure 3:
------+---------
| Internet
+-----+
| | Border router Router
| | (RPL Root)
+-----+
X
^ v o o
^ o o v o o o o o
^ o o o v o o o o o
^ o o v o o o o o
S o o o D o o o
o o o o
LLN
Figure 3: Routing Stretch between Between S and D via common parent Common Parent X
along
Along North-South Paths
As described in [RFC9008], the amount of stretch depends on the Mode
of Operation: MOP:
* in In Non-Storing Mode, all packets routed within the DODAG flow all
the way up to the Root of the DODAG. If the destination is in the
same DODAG, the Root must encapsulate the packet to place an RH
that has the strict source route information down the DODAG to the
destination. This will be the case even if the destination is
relatively close to the source and the Root is relatively far off.
* In Storing Mode, unless the destination is a child of the source,
the packets will follow the default route up the DODAG as well.
If the destination is in the same DODAG, they will eventually
reach a common parent that has a route to the destination; at
worse,
worst, the common parent may also be the Root. From that common
parent, the packet will follow a path down the DODAG that is
optimized for the Objective Function that was used to build the
DODAG.
It turns out that it is often beneficial to enable direct P2P routes,
either routes
if either the RPL route presents a stretch from the shortest path, path or
if
the new route is engineered with a different objective, and this is
even more critical in Non-Storing Mode than it is in Storing Mode, Mode
because the routing stretch is wider. For that reason, earlier work
at
within the IETF introduced was introduced: the "Reactive Discovery of
Point-to-Point Routes in Low Power Low-Power and Lossy Networks" [RFC6997],
which specifies a distributed method for establishing optimized P2P
routes. This specification proposes an alternative based on
centralized route computation.
+-----+
| | Border router Router
| | (RPL Root)
+-----+
|
o o o o
o o o o o o o o o
o o o o o o o o o o
o o o o o o o o o
S>>A>>>B>>C>>>D o o o
o o o o
LLN
Figure 4: More direct forward Direct Forward Route between Between S and D
The requirement is to install additional routes in the RPL routers,
to reduce the stretch of some P2P routes and maintain the
characteristics within a given SLO, Service Level Objective (SLO), e.g.,
in terms of latency and/or reliability.
3.4. On Tracks
3.4.1. Building Tracks with RPL
The concept of a Track was introduced in the "6TiSCH Architecture"
[RFC9030], 6TiSCH architecture
[RFC9030] as a collection of potential paths that leverage redundant
forwarding solutions along the way. This can be a DODAG or a more
complex structure that is only partially acyclic (e.g., per packet).
With this specification, a Track is shaped as a DODAG, and following
the directed edges leads to a Track Ingress. Storing Mode P-DAO
messages follow the direction of the edges to set up routes for
traffic that flows the other way, towards the Track Egress(es). If
there is a single Track Egress, then the Track is reversible to form so that
another DODAG may be formed by reversing the direction of each edge.
A node at the Ingress of more than one segment in a Track may use one
or more of these segments to forward a packet inside the Track.
A RPL Track is a collection of (one or more) parallel loose source source-
routed sequences of nodes ordered from Ingress to Egress, each
forming a protection path. The nodes in a Track are directly
connected, reachable via existing Tracks as illustrated in
Section 3.5.2.3 or joined with strict segments of other nodes as
shown in Section 3.5.1.3. The protection paths are expressed in RPL
Non-Storing Mode and require an encapsulation to add a Source Route
Header, whereas the segments are expressed in RPL Storing Mode.
A path provides only one path between the Ingress and Egress. It
comprises exactly one protection path. A Stand-Alone stand-alone segment
implicitly defines a path from its Ingress to Egress.
A complex Track forms a graph that provides a collection of potential
paths to provide redundancy for the packets, either as a collection
of protection paths that may be parallel or interleaved at certain
points,
points or as a more generic DODAG.
3.4.2. Tracks and RPL Instances
Section 5.1. 5.1 of [RPL] describes the RPL Instance and its encoding.
There can be up to 128 Global RPL Instances, for which there can be
one or more DODAGs, and there can be 64 local Local RPL Instances, with a
namespace that is indexed by a DODAGID, where the DODAGID is a Unique
Local Address (ULA) or a Global Unicast Address (GUA) of the Root of
the DODAG. Bit 0 (most significant) is set to 1 to signal a Local
RPLInstanceID, as shown in Figure 5. By extension, this
specification expresses the value of the RPLInstanceID as a single
integer between 128 and 191, representing both the Local
RPLInstanceID in 0..63 in the rightmost bits and Bit bit 0 set.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|1|D| ID | Local RPLInstanceID in 0..63
+-+-+-+-+-+-+-+-+
| |
\ \
\ Bit 1 is set to 0 in Track IDs
Bit 0 set to 1 signals a local Local RPLInstanceID
Figure 5: Local RPLInstanceID Encoding
A Track typically forms an underlay to the main Instance, Instance and is
associated with a Local RPL Instance from which the RPLInstanceID is
used as the TrackID. When a packet is placed on a Track, it is IP-
in-IP encapsulated IP-in-IP with a RPL Option containing a RPI which RPL Packet
Information (RPI) that signals the RPLInstanceID. The encapsulating
source IP address and RPI Instance are set to the Track Ingress IP
address and local Local RPLInstanceID, respectively, respectively; see more in
Section 6.3.
A Track typically offers service protection across several protection
paths. As a degraded form of a Track, a path made of a single
protection path (i.e., offering no protection) can be used as an
alternative to a segment for forwarding along a RPL Instance. In
that case, instead of following native routes along the instance, the
packets are encapsulated to signal a more specific more-specific source-routed path
between the loose hops in the encapsulated source routing header.
If the encapsulated packet follows a global instance, then the
protection path may be part of that global instance as well, for
instance e.g.,
the global instance of the main DODAG. This can only be done for
global instances because the Ingress node that encapsulates the
packets over the protection path is not the Root of the instance, so
the source address of the encapsulated packet cannot be used to
determine the Track along the way.
3.5. path Path Signaling
This specification enables setting up a P-Route along either a
protection path or a segment. A P-Route is installed and maintained
by the Root of the main DODAG using an extended RPL DAO message
called a Projected DAO (P-DAO), P-DAO, and a Track is composed of the combination of one or
more P-Routes. In order to clarify the techniques that may be used
to install a P-Route, this section takes uses the simple case of the path
illustrated in Figure 6. So Thus, the goal is to build a path from node
A to E for packets towards E's neighbors F and G along A, B, C, D D,
and E as opposed to via the Root:
/===> F
A ===> B ===> C ===> D===> E <
\===> G
Figure 6: Reference Track
A P-DAO message for a Track signals the TrackID in the RPLInstanceID
field. In the case of a local Local RPL Instance, the address of the Track
Ingress is used as the source to encapsulate packets along the Track.
The Track is signaled in the DODAGID field of the Projected DAO P-DAO Base
Object, Object;
see Figure 8.
This specification introduces the Via Information Option (VIO) to
signal a sequence of hops in a protection path or a segment in the
P-DAO messages, either in Storing Mode (SM-VIO) or in Non-Storing
Mode (NSM-VIO). One P-DAO message contains a single VIO, which is
associated to one or more RPL Target Options that signal the
destination IPv6 addresses that can reached along the Track (more (see more
in Section 5.3).
Before diving deeper into Track and segment signaling and operation,
this section provides examples of how route projection works through
variations of a simple example. This simple example illustrates the
case of host routes, though RPL Targets can also be prefixes.
Conventionally
Conventionally, we use ==> to represent a strict hop and --> for a
loose hop. We use "-to-", such as in C==>D==>E-to-F C==>D==>E-to-F, to represent
coma-separated Targets, e.g., F is a Target for segment C==>D==>E.
In this example, the example below, A is the Track Ingress and E is the Track
Egress. C is a stitching point. F and G are "external” "external" Targets for
the Track, Track and become reachable from A via the Track A (Ingress) to E
(Egress and implicit Target in Non-Storing Mode) Mode), leading to F and G
(explicit Targets).
In a general manner manner, the desired outcome is as follows:
* Targets are E, F, and G
* P-DAO 1 signals C==>D==>E
* P-DAO 2 signals A==>B==>C
* P-DAO 3 signals F and G via the A-->E Track
P-DAO 3 may be omitted if P-DAO P-DAOs 1 and 2 signal F and G as Targets.
Loose sequences of hops are expressed in Non-Storing Mode; this is
why P-DAO 3 contains a an NSM-VIO. With this specification:
* the The DODAGID to be used by the Ingress as the source address is
signaled in the DAO base object Base Object (see Figure 8) . 8).
* the The via list in the VIO is encoded as an SRH-6LoRH (see
Figure 16), and it starts with the address of the first hop first-hop node
after the Ingress node in the loose hop sequence.
* the The via list ends with the address of the Egress node.
Note well:
| Note 1: The Egress of a Non-Storing Mode P-Route is implicitly
| a target;
| it is not listed in the RPL Target Options but is
| still accounted for
| as if it was. The only exception is when
| the Egress is the only
| address listed in the VIO, in which case
| it would indicate via
| itself itself, which would be non-sensical.
Also: nonsensical.
| Note 2: By design, the list of nodes in a VIO in Non-Storing
| Mode is
| exactly the list that shows in the encapsulation SRH.
| So in the
| cases detailed below, if the Mode of the P-DAO is Non-Storing,
| Non-Storing, then the VIO row can be read as indicating the SRH
| as well.
3.5.1. Using Storing Mode Segments
A==>B==>C and C==>D==>E are segments of the same Track. Note that
the Storing Mode signaling imposes strict continuity in a segment,
since the P-DAO is passed hop by hop, as a classical DAO is, along
the reverse datapath that it signals. One benefit of strict routing
is that loops are avoided along the Track.
3.5.1.1. Stitched Segments
In this formulation:
* P-DAO 1 signals C==>D==>E-to-F,G
* P-DAO 2 signals A==>B==>C-to-F,G
Storing Mode P-DAO 1 is sent to E E, and when it is successfully
acknowledged, Storing Mode P-DAO 2 is sent to C, C as follows:
+====================+==============+==============+
| Field | P-DAO 1 to E | P-DAO 2 to C |
+====================+==============+==============+
| Mode | Storing | Storing |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| Track Ingress | A | A |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| (DODAGID, TrackID) | (A, 129) | (A, 129) |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| SegmentID | 1 | 2 |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| VIO | C, D, E | A, B, C |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| Targets | F, G | F, G |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
Table 1: P-DAO Messages
As a result result, the RIBs are set as follows:
+======+=============+=========+=============+==========+
| Node | Destination | Origin | Next Hop(s) | TrackID |
+======+=============+=========+=============+==========+
| E | F, G | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| D | E | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | F, G | P-DAO 1 | E | (A, 129) |
+------+-------------+---------+-------------+----------+
| C | D | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | F, G | P-DAO 1 | D | (A, 129) |
+------+-------------+---------+-------------+----------+
| B | C | P-DAO 2 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | F, G | P-DAO 2 | C | (A, 129) |
+------+-------------+---------+-------------+----------+
| A | B | P-DAO 2 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | F, G | P-DAO 2 | B | (A, 129) |
+------+-------------+---------+-------------+----------+
Table 2: RIB setting
Note: Settings
| the Note: The " sign is used throughout those the tables in this document
| to indicate the same
| value as in the row above.
Packets originating at A and going to F or G do not require
encapsulation as the RPI can be placed in the native header chain.
For packets that it routes, A must encapsulate to add the RPI that
signals the TrackID; the outer headers of the packets that are
forwarded along the Track have the following settings:
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. Address | IPv6 Dest. Addr. Destination | TrackID |
| | | Address | in RPI |
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Outer | A | F or G | (A, |
| | | | 129) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Inner | Any but A | F or G | N/A |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
Table 3: Packet Header Settings
As an example, say that A has a packet for F. Using the RIB in
Table 2:
* From P-DAO 2: A forwards to B B, and B forwards to C.
* From P-DAO 1: C forwards to D D, and D forwards to E.
* From Neighbor Cache Entry: E delivers the packet to F.
3.5.1.2. External Routes
In this example, we consider F and G as destinations that are
external to the Track as a DODAG, as discussed in section 4.1.1. Section 4.1.1 of
[RFC9008]. We then apply the directives for encapsulating in that
case (more (see more in Section 6.7).
In this formulation, we set up the protection path explicitly, which
creates less routing state in intermediate hops at the expense of
larger packets to accommodate source routing:
* P-DAO 1 signals C==>D==>E-to-E
* P-DAO 2 signals A==>B==>C-to-E
* P-DAO 3 signals F and G via the A-->E-to-F,G Track
Storing Mode P-DAO P-DAOs 1 and 2, 2 and Non-Storing Mode P-DAO 3, 3 are sent to
E, C C, and A, respectively, as follows:
+====================+==============+==============+==============+
| | P-DAO 1 to E | P-DAO 2 to C | P-DAO 3 to A |
+====================+==============+==============+==============+
| Mode | Storing | Storing | Non-Storing |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Track Ingress | A | A | A |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| (DODAGID, TrackID) | (A, 129) | (A, 129) | (A, 129) |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| SegmentID | 1 | 2 | 3 |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| VIO | C, D, E | A, B, C | E |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Targets | E | E | F, G |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
Table 4: P-DAO Messages
Note in the above that E is not an implicit Target in Storing mode, Mode,
so it must be added in the RTO RPL Target Option (RTO) for P-DAO P-DAOs 1 and
2. E is not an implicit Target for P-DAO 3 either, since E is the
only entry in the VIO.
As a result result, the RIBs are set as follows:
+======+=============+=========+=============+==========+
| Node | Destination | Origin | Next Hop(s) | TrackID |
+======+=============+=========+=============+==========+
| E | F, G | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| D | E | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| C | D | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | E | P-DAO 1 | D | (A, 129) |
+------+-------------+---------+-------------+----------+
| B | C | P-DAO 2 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | E | P-DAO 2 | C | (A, 129) |
+------+-------------+---------+-------------+----------+
| A | B | P-DAO 2 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | E | P-DAO 2 | B | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | F, G | P-DAO 3 | E | (A, 129) |
+------+-------------+---------+-------------+----------+
Table 5: RIB setting Settings
Packets from A to E do not require an encapsulation. This is why in In the tables
below, this is why E may show as an IPv6 Destination Address destination address only if
the IPv6 Source Address source address X is different from A. Conversely, the
encapsulation is always done when the IPv6 Destination Address destination address is F
or G. Other destination addresses do not match this P-Route and are
not subject to encapsulation.
The outer headers of the packets that are forwarded along the Track
have the following settings:
+========+===================+===========================+=========+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. | IPv6 Dest. Addr. Destination Address | TrackID |
| | Address | | in RPI |
+========+===================+===========================+=========+
+========+=====================+==========================+=========+
| Outer | A | E | (A, |
| | | | 129) |
+--------+-------------------+---------------------------+---------+
+--------+---------------------+--------------------------+---------+
| Inner | X | Either F or G. If X!=A, | N/A |
| | | then E is also permitted. | |
+--------+-------------------+---------------------------+---------+
+--------+---------------------+--------------------------+---------+
Table 6: Packet Header Settings
As an example, say that A has a packet for F. Using the RIB in
Table 5:
* From P-DAO 3: A encapsulates the packet and sends it down the
Track signaled by P-DAO 3, with the outer header above. Now the
packet destination is E.
* From P-DAO 2: A forwards to B B, and B forwards to C.
* From P-DAO 1: C forwards to D D, and D forwards to E; E decapsulates
the packet.
* From Neighbor Cache Entry: E delivers packets to F or G.
3.5.1.3. Segment Routing
In this formulation formulation, protection paths are leveraged to combine
segments and form a Graph. graph. The packets are source routed from a
segment to the next to adapt the path:
* P-DAO 1 signals C==>D==>E-to-E
* P-DAO 2 signals A==>B-to-B,C
* P-DAO 3 signals F and G via the A-->C-->E-to-(E),F,G Track
Storing Mode P-DAO P-DAOs 1 and 2, 2 and Non-Storing Mode P-DAO 3, 3 are sent to
E, B B, and A, respectively, as follows:
+====================+==============+==============+==============+
| | P-DAO 1 to E | P-DAO 2 to B | P-DAO 3 to A |
+====================+==============+==============+==============+
| Mode | Storing | Storing | Non-Storing |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Track Ingress | A | A | A |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| (DODAGID, TrackID) | (A, 129) | (A, 129) | (A, 129) |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| SegmentID | 1 | 2 | 3 |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| VIO | C, D, E | A, B | C, E |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Targets | E | B, C | F, G |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
Table 7: P-DAO Messages
Note in the table above that the segment can terminate at the loose
hop as used in the example of P-DAO 1 or at the previous hop as done
with P-DAO 2. Both methods are possible on any segment joined by a
loose protection path. P-DAO 1 generates more signaling since E is
the segment Egress when D could be, but has the a benefit is that it
validates that the connectivity between D and E still exists.
As a result result, the RIBs are set as follows:
+======+=============+=========+=============+==========+
| Node | Destination | Origin | Next Hop(s) | TrackID |
+======+=============+=========+=============+==========+
| E | F, G | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| D | E | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| C | D | P-DAO 1 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | E | P-DAO 1 | D | (A, 129) |
+------+-------------+---------+-------------+----------+
| B | C | P-DAO 2 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| A | B | P-DAO 2 | Neighbor | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | C | P-DAO 2 | B | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | E, F, G | P-DAO 3 | C, E | (A, 129) |
+------+-------------+---------+-------------+----------+
Table 8: RIB setting Settings
Packets originated at A to E do not require an encapsulation, but
they carry a an SRH via C. The outer headers of the packets that are
forwarded along the Track have the following settings:
+========+===================+===========================+=========+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. | IPv6 Dest. Addr. Destination Address | TrackID |
| | Address | | in RPI |
+========+===================+===========================+=========+
+========+=====================+==========================+=========+
| Outer | A | C until C then E | (A, |
| | | | 129) |
+--------+-------------------+---------------------------+---------+
+--------+---------------------+--------------------------+---------+
| Inner | X | Either F or G. If X!=A, | N/A |
| | | then E is also permitted. | |
+--------+-------------------+---------------------------+---------+
+--------+---------------------+--------------------------+---------+
Table 9: Packet Header Settings
As an example, say that A has a packet for F. Using the RIB in
Table 8:
* From P-DAO 3: A encapsulates the packet the Track signaled by
P-DAO 3, with the outer header above. Now the destination in the
IPv6 Header header is C, and a an SRH signals that the final destination is
E.
* From P-DAO 2: A forwards to B B, and B forwards to C.
* From P-DAO 3: C processes the SRH and sets the destination in the
IPv6 Header header to E.
* From P-DAO 1: C forwards to D D, and D forwards to E; E decapsulates
the packet.
* From the Neighbor Cache Entry: E delivers packets to F or G.
3.5.2. Using Non-Storing Mode joining Joining Tracks
In this formulation:
* P-DAO 1 signals C==>D==>E-to-(E),F,G
* P-DAO 2 signals A==>B==>C-to-(C),E,F,G
A==>B==>C and C==>D==>E are Tracks expressed as Non-Storing Mode
P-DAOs.
3.5.2.1. Stitched Tracks
Non-Storing Mode P-DAO 1 and 2 are sent to C and A A, respectively, as
follows:
+====================+==============+==============+
| | P-DAO 1 to C | P-DAO 2 to A |
+====================+==============+==============+
| Mode | Non-Storing | Non-Storing |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| Track Ingress | C | A |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| (DODAGID, TrackID) | (C, 131) | (A, 131) |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| SegmentID | 1 | 1 |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| VIO | D, E | B, C |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
| Targets | F, G | E, F, G |
+--------------------+--------------+--------------+
+====================+--------------+--------------+
Table 10: P-DAO Messages
As a result result, the RIBs are set as follows (using ND "ND" to indicate that
the address is discovered by IPv6 Neighbor Discovery
[RFC4861][RFC8505] [RFC4861]
[RFC8505] or an equivalent method: method):
+======+=============+=========+=============+==========+
| Node | Destination | Origin | Next Hop(s) | TrackID |
+======+=============+=========+=============+==========+
| E | F, G | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| D | E | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| C | D | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| " | E, F, G | P-DAO 1 | D, E | (C, 131) |
+------+-------------+---------+-------------+----------+
| B | C | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| A | B | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| " | C, E, F, G | P-DAO 2 | B, C | (A, 131) |
+------+-------------+---------+-------------+----------+
Table 11: RIB setting Settings
Packets originated at A to E, F F, and G could be generated with the
RPI and the SRH, SRH and no encapsulation. Alternatively, A may generate
a native packet to the target, target and then encapsulate it with an RPI and
an SRH indicating the source-routed path leading to E, as it would
for a packet that it routes coming from another node. This is
effectively the same case as for packets generated by the root in a
RPL network in Non-Storing mode, Mode; see section Section 8.1.3 of [RFC9008]. The
latter is often preferred since it leads to a single code path, and
when the destination when it is F or G, it does not need to understand and
process the RPI or the SRH. Either way, the packets to E, F, or G
carry an SRH via B and C, and when they reach C, C needs to
encapsulate them again to add an SRH via D and E. The encapsulating
headers of packets that are forwarded along the Track between C and E
have the following settings:
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. Address | IPv6 Dest. Addr. Destination | TrackID |
| | | Address | in RPI |
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Outer | C | D until D then E | (C, |
| | | | 131) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Inner | X | E, F, or G | N/A |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
Table 12: Packet Header Settings between Between C and E
As an example, say that A has a packet for F. Using the RIB in
Table 11:
* From P-DAO 2: A encapsulates the packet with a destination of F in
the Track signaled by P-DAO 2. The outer header has source A,
destination B, an SRH that indicates C as the next loose hop, and
a
an RPI indicating a TrackID of 131 from A's namespace, which is
distinct from a TrackID of 131 from C's.
* From the SRH: Packets forwarded by B have source A, destination C,
a consumed SRH, and a an RPI indicating a TrackID of 131 from A's
namespace. C decapsulates.
* From P-DAO 1: C encapsulates the packet with a destination of F in
the Track signaled by P-DAO 1. The outer header has source C,
destination D, an SRH that indicates E as the next loose hop, and
a
an RPI indicating a TrackID of 131 from C's namespace. E
decapsulates.
3.5.2.2. External Routes
In this formulation:
* P-DAO 1 signals C==>D==>E-to-(E)
* P-DAO 2 signals A==>B==>C-to-(C),E
* P-DAO 3 signals F and G via the A-->E-to-F,G Track
Non-Storing Mode P-DAO 1 is sent to C C, and Non-Storing Mode P-DAO P-DAOs 2
and 3 are sent to A, as follows:
+====================+==============+==============+==============+
| | P-DAO 1 to C | P-DAO 2 to A | P-DAO 3 to A |
+====================+==============+==============+==============+
| Mode | Non-Storing | Non-Storing | Non-Storing |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Track Ingress | C | A | A |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| (DODAGID, TrackID) | (C, 131) | (A, 129) | (A, 141) |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| SegmentID | 1 | 1 | 1 |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| VIO | D, E | B, C | E |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Targets | | E | F, G |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
Table 13: P-DAO Messages
Note in the table above that E is an implicit Target in P-DAO 1 and
so is C in P-DAO 2. As Non-Storing Mode Egress nodes node addresses, they
are not listed in the respective RTOs.
As a result result, the RIBs are set as follows:
+======+=============+=========+=============+==========+
| Node | Destination | Origin | Next Hop(s) | TrackID |
+======+=============+=========+=============+==========+
| E | F, G | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| D | E | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| C | D | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| " | E | P-DAO 1 | D, E | (C, 131) |
+------+-------------+---------+-------------+----------+
| B | C | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| A | B | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| " | C, E | P-DAO 2 | B, C | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | F, G | P-DAO 3 | E | (A, 141) |
+------+-------------+---------+-------------+----------+
Table 14: RIB setting Settings
The encapsulating headers of packets that are forwarded along the
Track between C and E have the following settings:
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. Address | IPv6 Dest. Addr. Destination | TrackID |
| | | Address | in RPI |
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Outer | C | D until D then E | (C, |
| | | | 131) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Middle | A | E | (A, |
| | | | 141) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Inner | X | E, F F, or G | N/A |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
Table 15: Packet Header Settings
As an example, say that A has a packet for F. Using the RIB in
Table 14:
* From P-DAO 3: A encapsulates the packet with a destination of F in
the Track signaled by P-DAO 3. The outer header has source A,
destination E, and a an RPI indicating a TrackID of 141 from A's
namespace. This recurses with: with the following.
* From P-DAO 2: A encapsulates the packet with a destination of E in
the Track signaled by P-DAO 2. The outer header has source A,
destination B, an SRH that indicates C as the next loose hop, and
a
an RPI indicating a TrackID of 129 from A's namespace.
* From the SRH: Packets forwarded by B have source A, destination C
, C,
a consumed SRH, and a an RPI indicating a TrackID of 129 from A's
namespace. C decapsulates.
* From P-DAO 1: C encapsulates the packet with a destination of E in
the Track signaled by P-DAO 1. The outer header has source C,
destination D, an SRH that indicates E as the next loose hop, and
a
an RPI indicating a TrackID of 131 from C's namespace. E
decapsulates.
3.5.2.3. Segment Routing
In this formulation:
* P-DAO 1 signals C==>D==>E-to-(E)
* P-DAO 2 signals A==>B-to-C
* P-DAO 3 signals F and G via the A-->C-->E-to-(E),F,G Track
Non-Storing Mode P-DAO 1 is sent to C C, and Non-Storing Mode P-DAO P-DAOs 2
and 3 are sent to A, as follows:
+====================+==============+==============+==============+
| | P-DAO 1 to C | P-DAO 2 to A | P-DAO 3 to A |
+====================+==============+==============+==============+
| Mode | Non-Storing | Non-Storing | Non-Storing |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Track Ingress | C | A | A |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| (DODAGID, TrackID) | (C, 131) | (A, 129) | (A, 141) |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| SegmentID | 1 | 1 | 1 |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| VIO | D, E | B | C, E |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
| Targets | | C | F, G |
+--------------------+--------------+--------------+--------------+
+====================+--------------+--------------+--------------+
Table 16: P-DAO Messages
As a result result, the RIBs are set as follows:
+======+=============+=========+=============+==========+
| Node | Destination | Origin | Next Hop(s) | TrackID |
+======+=============+=========+=============+==========+
| E | F, G | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| D | E | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| C | D | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| " | E | P-DAO 1 | D, E | (C, 131) |
+------+-------------+---------+-------------+----------+
| B | C | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| A | B | ND | Neighbor | Any |
+------+-------------+---------+-------------+----------+
| " | B, C | P-DAO 2 | C | (A, 129) |
+------+-------------+---------+-------------+----------+
| " | E, F, G | P-DAO 3 | C, E | (A, 141) |
+------+-------------+---------+-------------+----------+
Table 17: RIB setting Settings
The encapsulating headers of packets that are forwarded along the
Track between A and B have the following settings:
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. Address | IPv6 Dest. Addr. Destination | TrackID |
| | | Address | in RPI |
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Outer | A | B until D then E | (A, |
| | | | 129) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Middle | A | C | (A, |
| | | | 141) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Inner | X | E, F F, or G | N/A |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
Table 18: Packet Header Settings
The encapsulating headers of packets that are forwarded along the
Track between B and C have the following settings:
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. Address | IPv6 Dest. Addr. Destination | TrackID |
| | | Address | in RPI |
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Outer | A | C | (A, |
| | | | 141) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Inner | X | E, F F, or G | N/A |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
Table 19: Packet Header Settings
The encapsulating headers of packets that are forwarded along the
Track between C and E have the following settings:
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Header | IPv6 Source Addr. Address | IPv6 Dest. Addr. Destination | TrackID |
| | | Address | in RPI |
+========+===================+===================+================+
+========+=====================+==========================+=========+
| Outer | C | D until D then E | (C, |
| | | | 131) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Middle | A | E | (A, |
| | | | 141) |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
| Inner | X | E, F F, or G | N/A |
+--------+-------------------+-------------------+----------------+
+--------+---------------------+--------------------------+---------+
Table 20: Packet Header Settings
As an example, say that A has a packet for F. Using the Table 18:
* From P-DAO 3: A encapsulates the packet with a destination of F in
the Track signaled by P-DAO 3. The outer header has source A,
destination C, an SRH that indicates E as the next loose hop, and
a
an RPI indicating a TrackID of 141 from A's namespace. This
recurses with: with the following.
* From P-DAO 2: A encapsulates the packet with a destination of C in
the Track signaled by P-DAO 2. The outer header has source A,
destination B, and a an RPI indicating a TrackID of 129 from A's
namespace. B decapsulates forwards to C based on a sibling
connected route.
* From the SRH: C consumes the SRH and makes the destination E.
* From P-DAO 1: C encapsulates the packet with a destination of E in
the Track signaled by P-DAO 1. The outer header has source C,
destination D, an SRH that indicates E as the next loose hop, and
a
an RPI indicating a TrackID of 131 from C's namespace. E
decapsulates.
3.6. Complex Tracks
To increase the reliability of the P2P transmission, this
specification enables building a collection of protection paths
between the same Ingress and Egress Nodes and combining them within
the same TrackID, as shown in Figure 7. Protection paths may be
interleaved at the edges of loose hops or remain parallel.
The segments that join the loose hops of a protection path are
installed with the same TrackID as the protection path. But each
individual protection path and segment has its own P-RouteID which that
allows it to be managed separately. Two protection paths of the same
Track may cross at a common node that participates to a segment of
Each
each protection path, path or that may be joined by additional segments.
The final path of a packet may then be the result of interleaving
those two (and possibly more) protection paths. In that case case, the
common node has more than one next hop in its RIB associated to the Track,
Track but no specific signal in the packet to indicate which segment
is being followed. A next hop that can reach the loose hop is
selected.
< Controller Plane Functions >
Southbound API
_-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-
_-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-._-
+----------+
| RPL Root |
+----------+
( main DODAG )
( all around )
<- Protection path 1 via B, E ->
<--- Segment 1 A,B ---> <------- Segment 2 C,D,E ------->
FWD -- Relay -- FWD -- FWD Target 1
/-- Node -- Node -- Node -- Node \ /
--/ (A) (B) \ (C) (D) \ /
Track \ Track
Ingress Segment 5 Egress -- Target
(I) \ -- (E) 2
\ \ / \
\ FWD -- FWD -- Relay -- FWD --/ \
Node -- Node -- Node -- Node Target 3
(F) (G) (H) (J)
<------ Segment 3 F,G,H ------> <---- Segment 4 J,E ---->
<- Protection path 2 via H, E ->
<--- Segment 1 A,B ---> <- S5-> <---- Segment 4 J,E ---->
<- Protection path 3 via B, H, E ->
)
(
( )
Figure 7: Segments and Tracks
Note that while this specification enables building both segments
inside a protection path, for instance segment 2 above which is
within protection path 1, and Inter-protection-path segments (i.e.,
North-South), for instance segment 5 above which joins protection
path 1 and protection path 2, it does not signal to the Ingress which
Inter-protection-path segments are available, so the use of North-
South segments and associated path redundancy functions is currently
limited. The only possibility available at this time is to define
overlapping protection paths as illustrated in Figure 7, with
protection path 3 that is congruent with protection path 1 until node
B and that is congruent with protection path 2 from node H on,
abstracting segment 5 as a forward segment.
3.7. Scope and Expectations
3.7.1. External Dependencies
This specification expects that the main DODAG is operated in RPL
Non-Storing Mode to sustain the exchanges with the Root. Based on
its comprehensive knowledge of the parent-child relationship, the
Root can form an abstracted view of the whole DODAG topology. This
document adds the capability for nodes to advertise additional
sibling information to complement the topological awareness of the
Root to be passed on to the PCE, PCE and enable enables the PCE to build more / more/
better paths that traverse those siblings.
P-Routes require resources such as routing table space in the routers
and bandwidth on the links; the amount of state that is installed in
each node must be computed to fit within the node's memory, and the
amount of rerouted traffic must fit within the capabilities of the
transmission links. The methods used to learn the node capabilities
and the resources that are available in the devices and in the
network are out of scope for this document. The method to capture
and report the LLN link capacity and reliability statistics are also
out of scope. They may be fetched from the nodes through network
management functions or other forms of telemetry such as OAM. Operations,
Administration, and Maintenance (OAM).
3.7.2. Positioning vs. Versus Related IETF Standards
3.7.2.1. Extending 6TiSCH
The "6TiSCH Architecture" 6TiSCH architecture [RFC9030] leverages a centralized model that
is similar to that of "Deterministic Networking Architecture" the DetNet architecture [RFC8655], whereby the
device resources and capabilities are exposed to an external
controller which that installs routing states into the network based on its
own objective functions that reside in that external entity.
3.7.2.2. Mapping to DetNet
DetNet Forwarding Nodes only understand the simple 1-to-1 forwarding
sublayer transport operation along a segment whereas the more
sophisticated Relay nodes can also provide service sublayer functions
such as Replication and Elimination.
One possible mapping between DetNet and this specification is to
signal the Relay Nodes as the hops of a protection path and the
forwarding Nodes nodes as the hops in a segment that join the Relay nodes
as illustrated in Figure 7.
3.7.2.3. Leveraging PCE
With DetNet and 6TiSCH, the component of the controller that is
responsible of for computing routes is a PCE. The PCE computes its
routes based on its own objective functions such functions, as described in
[RFC4655], and typically controls the routes using the PCE
Communication Protocol (PCEP) by [RFC5440]. While this specification
expects a PCE PCE, and while PCEP might effectively be used between the
Root and the PCE, the control protocol between the PCE and the Root
is out of scope.
This specification also expects a single PCE with a full view of the
network. Distributing the PCE function for a large network is out of
scope. This specification uses the RPL Root as a proxy to the PCE.
The PCE may be collocated with the Root, Root or may reside in an external
Controller.
controller. In that case, the protocol between the Root and the PCE
is out of scope and mapped to RPL inside the DODAG; one possibility
is for the Root to transmit to the PCEs the information it received
in RPL DAOs including all the SIOs that detail the parent/child and
sibling information.
The algorithm to compute the paths, the protocol used by the PCE PCE, and
the metrics and link statistics involved in the computation are also
out of scope. The effectiveness of the route computation by the PCE
depends on the quality of the metrics that are reported from the RPL
network. Which metrics are used and how they are reported is are out of
scope, but the expectation is that they are mostly of a long-term,
statistical nature, nature and provide visibility on link throughput,
latency, stability stability, and availability over relatively long periods.
3.7.2.4. Providing for RAW
The RAW Architecture [RAW-ARCHI] architecture [RAW-ARCH] extends the definition of Track, as
being composed of forward directional segments and North-South
bidirectional segments, to enable additional path diversity, using
Packet ARQ, Replication, Elimination, and Overhearing (PAREO)
PAREO functions over the available paths, to provide a dynamic
balance between the reliability and availability requirements of the
flows and the need to conserve energy and spectrum. This
specification prepares for RAW by setting up the Tracks, but it only
forms DODAGs, which are composed of aggregated end-to-end loose source routed
source-routed protection paths, joined by strict routed segments, all
oriented forward.
The RAW Architecture architecture defines a dataplane data plane extension of the PCE called
the Point of Local Repair (PLR), (PLR) that adapts the use of the path
redundancy within a Track to defeat the diverse causes of packet
loss. The PLR controls the forwarding operation of the packets
within a Track. This specification can use but does not impose a PLR
and does not provide the policies that would select which packets are
routed through which path within a Track, in Track (in other words, how the PLR
may use the path redundancy within the Track. Track). By default, the use
of the available redundancy is limited to simple load balancing, and
all the segments are forward unidirectional only.
A Track may be set up to reduce the load around the Root, Root or to enable
urgent traffic to flow more directly. This specification does not
provide the policies that would decide which flows are routed through
which Track. In a Non-Storing Mode RPL Instance, the main DODAG
provides a default route via the Root, and the Tracks provide
more more-
specific routes to the Track Targets.
4. Extending existing Existing RFCs
This section explains which changes are extensions to existing
specifications, and which changes are
amendments to existing specifications. It is expected that
extensions to existing specifications do will not cause existing code on
legacy 6LRs to malfunction, as the extensions will simply be ignored.
New code is required for an extension. Those 6LRs will be unable to
participate in the new mechanisms, but mechanisms and may also cause projected DAOs P-DAOs to be
impossible to install. Amendments to existing specifications are
situations where there are semantic changes required to existing
code, code
and which may require where new unit tests may be required to confirm that legacy
operations will continue unaffected.
4.1. Extending RPL RFC 6550
This specification Extends RPL [RPL] to enable the Root to install
forward routes inside a main DODAG that is operated as Non-Storing
Mode. The Root issues a Projected DAO (P-DAO) P-DAO message (see Section 4.1.1) to the
Track Ingress; the P-DAO message contains a new
Via Information Option (VIO) VIO that installs a
strict or a loose sequence of hops to form a Track segment or a
protection path, respectively.
The P-DAO Request (PDR) is a new message detailed in Section 5.1. As
per [RPL] section 6, Section 6 of [RPL], if a node receives this message and it does
not understand this new Code, code, it then discards the message. When the Root
initiates communication to a node that it has not communicated with
before and which that it has not ascertained to implement this
specification (by means such as capabilities), then the Root SHOULD
request a PDR-ACK.
A P-DAO Request (PDR) PDR message enables a Track Ingress to request the Track from the
Root. The resulting Track is also a DODAG for which the Track
Ingress is the Root, and the owner is the address that serves as the
DODAGID and is authoritative for the associated namespace from which
the TrackID is selected. In the context of this specification, the
installed route appears as a more specific more-specific route to the Track
Targets, and the Track Ingress forwards the packets towards toward the
Targets via the Track using normal longest match IP forwarding.
To ensure that the PDR and P-DAO messages can flow at most times, it
is RECOMMENDED that the nodes involved in a Track maintain multiple
parents in the main DODAG, advertise them all to the Root, and use
them in turn to retry similar packets. It is also RECOMMENDED that
the Root uses diverse source route paths to retry similar messages to
the nodes in the Track.
4.1.1. Projected DAO
Section 6 of [RPL] introduces the RPL Control Message Options (CMO), (CMOs),
including the RPL Target Option (RTO) and Transit Information Option
(TIO), which can be placed in RPL messages such as the destination
Advertisement Object (DAO). DAO. A DAO
message signals routing information to one or more Targets indicated
in RTOs, the RTOs and provides one and only one via-node in the TIO, with
the via-node being the tunnel
end-point endpoint to reach the targets.
This document Amends the specification of the DAO to create the P-DAO
message. This Amended DAO is signaled with a new "Projected DAO" (P)
flag,
flag; see Figure 8.
A Projected DAO (P-DAO) P-DAO is a special DAO message generated by the Root to install a
P-Route formed of multiple hops in its DODAG. This provides a RPL-based RPL-
based method to install the Tracks as expected by the
6TiSCH Architecture [RFC9030] as a collection of multiple P-Routes.
P-Routes as expected by the 6TiSCH architecture [RFC9030].
The Root MUST source the P-DAO message with its address that serves
as the DODAGID for the main DODAG. The receiver MUST NOT accept a
P-DAO message that is not sent by the Root of its DODAG and MUST
ignore such messages silently.
The 'P' flag is encoded in bit position 2 (to be confirmed by IANA) of the Flags field in the
DAO Base Object. The Root MUST set it to 1 in a Projected DAO P-DAO message. Otherwise
Otherwise, it MUST be set to 0. It is set to 0 in Legacy legacy
implementations as specified respectively specified, respectively, in Sections 20.11 and 6.4
of [RPL].
The P-DAO is a part of control plane signaling and should not be
stuck behind high traffic levels. The expectation is that the P-DAO
message is be sent at a high QoS level, above that of data traffic,
typically with the Network Control precedence.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TrackID |K|D|P| Flags | Reserved | DAOSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| DODAGID field is set to the |
+ IPv6 Address address of the Track Ingress +
| used to source encapsulated packets |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 8: Projected DAO Base Object
New fields:
TrackID: The local Local or global Global RPLInstanceID of the DODAG that serves
as the Track (more (see more in Section 6.3).
P: 1-bit flag (position to be confirmed by IANA). flag.
The 'P' flag is set to 1 by the Root to signal a Projected DAO,
and P-DAO; otherwise,
it is set to 0 otherwise. 0.
The D flag is set to one 1 to signal that the DODAGID field is present.
It may be set to zero 0 if and only if the destination address of the
P-DAO-ACK P-
DAO-ACK message is set to the IPv6 address that serves as DODAGID the
DODAGID, and it MUST be set to one otherwise, meaning that the
DODAGID field MUST then be present.
In RPL Non-Storing Mode, the TIO and RTO are combined in a DAO
message to inform the DODAG Root of all the edges in the DODAG, which
are formed by the directed parent-child relationships. The DAO
message signals to the Root that a given parent can be used to reach
a given child. The P-DAO message generalizes the DAO to signal to
the Track Ingress that a Track for which it is the Root can be used
to reach children and siblings of the Track Egress. In both cases,
options may be factorized and multiple RTOs may be present to signal
a collection of children that can be reached through the parent or
the Track, respectively.
4.1.2. Projected DAO-ACK
This document also Amends the DAO-ACK message. The new P flag
signals the projected form.
The format of the P-DAO-ACK message is thus as illustrated in Figure 9:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TrackID |D|P| Reserved | DAOSequence | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| DODAGID field is set to the |
+ IPv6 Address address of the Track Ingress +
| used to source encapsulated packets |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 9: Projected DAO-ACK Base Object
New fields:
TrackID: The local Local or global Global RPLInstanceID of the DODAG that serves
as the Track (more (see more in Section 6.3).
P: 1-bit flag (position to be confirmed by IANA). flag.
The 'P' flag is set to 1 by the Root to signal a Projected DAO,
and P-DAO; otherwise,
it is set to 0 otherwise. 0.
The D flag is set to one 1 to signal that the DODAGID field is present.
It may be set to zero 0 if and only if the source address of the P-DAO-
ACK P-DAO-ACK
message is set to the IPv6 address that serves as DODAGID the DODAGID, and it
MUST be set to one otherwise, meaning that the DODAGID field MUST
then be present.
4.1.3. Via Information Option
This document Extends the CMO to create new objects called the Via
Information Options (VIO). (VIOs). The VIOs are the multihop multi-hop alternative
to the TIO (more TIOs (see more in Section 5.3). One VIO is the stateful
Storing Mode VIO (SM-VIO); an SM-VIO installs a strict hop-by-hop
P-Route called a Track segment. The other is the Non-Storing Mode
VIO (NSM-VIO); the NSM-VIO installs a loose source-routed P-Route
called a protection path at the Track Ingress, which uses that state
to encapsulate a
packet an IP-in-IP packet with a new Routing Header (RH) to
the Track Egress
(more (see more in Section 6.7).
A P-DAO contains one or more RTOs to indicate the Target
(destinations) that can be reached via the P-Route, followed by
exactly one VIO that signals the sequence of nodes to be followed
(more
(see more in Section 6). There are two modes of operation for the
P-Routes, the
P-Routes: Storing Mode and the Non-Storing Mode, see
Section Mode (see more in Sections
6.4.2 and Section 6.4.3 respectively for more. 6.4.3, respectively).
4.1.4. Sibling Information Option
This specification Extends the CMO to create the Sibling Information
Option (SIO). The SIO is used by a RPL Aware RPL-Aware Node (RAN) to advertise
a selection of its candidate neighbors as siblings to the Root (more (see
more in Section 5.4). The SIO is placed in DAO messages that are
sent directly to the main Root, including multicast DAO (see section
Section 9.10 of [RPL]).
This specification AMENDS Amends rules 1 and 2 listed in section Section 9.10 of
[RPL])
[RPL] for the multicast DAO operation as follows:
OLD:
| 1. A node MAY multicast a DAO message to the link-local scope all-
RPL-nodes
| all-RPL-nodes multicast address.
|
| 2. A multicast DAO message MUST be used only to advertise
| information about the node itself, i.e., prefixes directly
| connected to or owned by the node, such as a multicast group
| that the node is subscribed to or a global address owned by
| the node
NEW:
| 1. A multicast DAO message MUST be used only to advertise
| information about the node (using the Target Option), Option) and
| direct Link Neighbors such as learned by Neighbor Discovery
| (using the
Sibling Information Option). SIO).
|
| 2. The multicast DAO may be used to enable direct and indirect
| (via a common neighbor) P2P communication without needing the
| DODAG to relay the packets. The multicast DAO exposes the
| sender's addresses as Targets in RTOs and the sender's
| neighbors addresses as siblings in SIOs; this tells the
| sender's neighbors that the sender is willing to act as a
| relay between those of its neighbors that are too far apart.
4.1.5. P-DAO Request
The set of RPL Control Messages is Extended to include the P-DAO
Request (PDR) PDR and
P-DAO Request Acknowledgement (PDR-ACK). These two new RPL Control
Messages enable an RPL-Aware Node a RAN to request the establishment of a Track between
itself as (as the Track Ingress Node Node) and a Track Egress. The node
makes its request by sending a new P-DAO
Request (PDR) Message PDR message to the Root. The Root
confirms with a new PDR-
ACK PDR-ACK message back to the requester RAN, RAN; see
Section 5.1 for more.
4.1.6. Amending the RPI
Sending a Packet packet within a RPL Local Instance requires the presence of
the abstract RPL Packet Information (RPI) RPI described in section 11.2. Section 11.2 of [RPL] in the outer IPv6 Header
header chain (see [RFC9008]). The RPI carries a local Local RPLInstanceID which,
that, in association with either the source or the destination
address in the IPv6 Header, header, indicates the RPL Instance that the
packet follows.
This specification Amends [RPL] to create a new flag that signals
that
when a packet is forwarded along a P-Route.
Projected-Route 'P': 1-bit flag. It is set to 1 in the RPI that is
added in the encapsulation when a packet is sent over a Track. It
is set to 0 when a packet is forwarded along the main DODAG (as a
Track), including when the packet follows a segment that joins
loose hops of the main DODAG. The flag is not mutable en-route. en route.
The encoding of the 'P' flag in native format is shown in Section 4.2
while the compressed format is indicated in Section 4.3.
4.1.7. Additional Flag in the RPL DODAG Configuration Option
The DODAG Configuration Option option is defined in Section 6.7.6 of [RPL].
Its purpose is extended to distribute configuration information
affecting the construction and maintenance of the DODAG, as well as
operational parameters for RPL on the DODAG, through the DODAG. This
Option
option was originally designed with 4 four bit positions reserved for
future use as Flags.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x04 |Opt Length = 14|D| | | |A| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
|4 bits |
Figure 10: DODAG Configuration Option (Partial View)
This specification Amends the specification [RPL] to define a the new flag "Projected Routes
Support" (D). (D) flag. The 'D' flag is encoded in bit position 0 of the
reserved Flags in the DODAG Configuration Option option (this is the most
significant bit)(to be confirmed by IANA but
there's little choice). bit). It is set to 0 in legacy implementations as
specified respectively in Sections 20.14 and 6.7.6 of [RPL].
The 'D' flag is set to 1 to indicate that this specification is
enabled in the network and that the Root will install the requested
Tracks when feasible upon receiving a PDR message.
Section 4.1.2. 4.1.2 of [RFC9008] Amends [RPL] to indicate that the
definition of the Flags applies to Mode of Operation MOP values from zero (0) to six
(6) only. For a MOP value of 7, the implementation MUST consider
that the Root accepts PDR messages and will install
Projected Routes. P-Routes.
The RPL DODAG Configuration option is typically placed in a DODAG
Information Object (DIO) DIO
message. The DIO message propagates down the DODAG to form and then
maintain its structure. The DODAG Configuration option is copied
unmodified from parents to children.
[RPL] states that:
| Nodes other than the DODAG root MUST NOT modify this information
| when propagating the DODAG Configuration option.
Therefore, a legacy parent propagates the 'D' flag as set by the
root, and when the 'D' flag is set to 1, it is transparently flooded
to all the nodes in the DODAG.
4.2. Extending RPL RFC 6553
"The RPL Routing Protocol for Low-Power and Lossy Networks (RPL) Option
for Carrying RPL Information in Data-Plane Datagrams" [RFC6553]
describes the RPL Option for use among RPL routers to include the
abstract RPL Packet Information (RPI) RPI described in
section 11.2. Section 11.2 of [RPL] in data packets.
The RPL Option is commonly referred to as the RPI even though the RPI
is really the abstract information that is transported in the RPL
Option. [RFC9008] updated the Option Type from 0x63 to 0x23.
This specification Extends the RPL Option to encode the 'P' flag as
follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|O|R|F|P|0|0|0|0| RPLInstanceID | SenderRank |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| (sub-TLVs) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Amended RPL Option Format
Option Type: 0x23 or 0x63, 0x63; see [RFC9008] [RFC9008].
Opt Data Len: See [RFC6553] [RFC6553].
'O', 'R' 'R', and 'F' flags: See [RFC6553]. Those These flags MUST be set to
0 by the sender and ignored by the receiver if the 'P' flag is
set.
Projected-Route 'P': 1-bit flag as defined in Section 4.1.6.
RPLInstanceID: See [RFC6553]. Indicates the TrackID if the 'P' flag
is set, as discussed in Section 4.1.1.
SenderRank: See [RFC6553]. This field MUST be set to 0 by the
sender and ignored by the receiver if the 'P' flag is set.
4.3. Extending RPL RFC 8138
The 6LoWPAN Routing Header [RFC8138] specification [RFC8138] introduces a new
IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN)
6LoWPAN [RFC6282] dispatch type for use in 6LoWPAN route-over
topologies, which initially covers the needs of RPL data packet
compression.
Section 4 of [RFC8138] presents the generic formats of the 6LoWPAN
Routing Header (6LoRH) with 6LoRH in
two forms, one Elective that forms: Elective, which can be ignored and skipped when the router
does not understand it, and one
Critical Critical, which causes the packet to be
dropped when the router cannot process it. The 'E' Flag flag in the 6LoRH
indicates its form. In order to skip the Elective 6LoRHs, their
format imposes a fixed expression of the size, whereas the size of a
Critical 6LoRH may be signaled in variable forms to enable additional
optimizations.
When the [RFC8138] compression as described in [RFC8138] is used, the Root of the
main DODAG that sets up the Track also constructs the compressed
routing header (SRH-6LoRH) on behalf of the Track Ingress, which saves
avoids the complexities of optimizing the SRH-6LoRH encoding in
constrained code. The SRH-6LoRH is signaled in the NSM-VIO, in a
fashion that it is ready to be placed as is in the packet
encapsulation by the Track Ingress.
Section 6.3 of [RFC8138] presents the formats of the 6LoWPAN Routing
Header RH of
type 5 (RPI-6LoRH) that compresses the RPI for normal RPL operation.
The format of the RPI-6LoRH is not suited for P-Routes since the O,R,F O,
R, and F flags are not used and the Rank is unknown and ignored.
This specification extends Extends [RFC8138] to introduce a new 6LoRH, the P-
RPI-6LoRH
RPI-6LoRH, that can be used in either Elective or Critical 6LoRH form,
form; see Table Tables 22 and Table 23 23, respectively. The new 6LoRH MUST be used
as a Critical 6LoRH, unless an SRH-6LoRH is present and controls the
routing decision, in which case it MAY be used in Elective form.
The P-RPI-6LoRH is designed to compress the RPI along RPL P-Routes.
Its format is as follows:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|E| Length | 6LoRH Type | RPLInstanceID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: P-RPI-6LoRH Format
6LoRH Type: IANA is requested to define has defined the same value of the type 8 for both the Elective and
Critical forms. A type of 8 is suggested.
Elective 'E': See [RFC8138]. The 'E' flag is set to 1 to indicate
an Elective 6LoRH, meaning that it can be ignored when forwarding.
RPLInstanceID : In the context of this specification, the
RPLInstanceID field signals the TrackID, TrackID; see Section Sections 3.4 and
Section 6.3 . 6.3.
Section 6.8 details how a Track Ingress leverages the P-RPI-6LoRH
Header as part of the encapsulation of a packet to place it into a
Track.
5. New RPL Control Messages and Options
5.1. New P-DAO Request Control Message
The P-DAO Request (PDR) PDR message is sent by a Node node in the main DODAG to the Root. It
is a request to establish or refresh a Track where the node sending
the PDR is the Track Ingress, and it signals whether or not an
acknowledgment called PDR-ACK is requested or not. requested. A positive PDR-
ACK PDR-ACK
indicates that the Track was built and that the Root commits to
maintaining the Track for the negotiated lifetime.
The main Root MAY indicate to the Track Ingress that the Track was
terminated before its time and time; to do so, it MUST use an asynchronous
PDR-ACK with a negative status. A status of "Transient Failure" (see
Section 11.10) is an indication that the PDR may be retried after a
reasonable time that depends on the deployment. Other negative
status values indicate a permanent error; the attempt must be
abandoned until a corrective action is taken at the application layer
or through network management.
The Track Ingress to-be to be of the requested Track is indicated in the
source IPv6 address of the PDR, and the TrackID is indicated in the
message itself. At least one RPL Target Option MUST be present in
the message. If more than one RPL Target Option is present, the Root
will provide a Track that reaches the first listed Target and a
subset of the other Targets; the details of the subset selection are
out of scope. The RTO signals the Track Egress (more (see more in
Section 6.2).
The RPL Control Code for the PDR is 0x09, to be confirmed by IANA. 0x09. The format of the PDR Base
Object is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TrackID |K|R| Flags | ReqLifetime | PDRSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+-+
Figure 13: New P-DAO Request Format
TrackID: 8-bit field. In the context of this specification, the
TrackID field signals the RPLInstanceID of the DODAG formed by the
Track,
Track; see Section Sections 3.4 and Section 6.3. To allocate a new Track, the
Ingress Node must provide a value that is not in use at this time.
K: The 'K' flag is set to indicate that the recipient is expected to
send a PDR-ACK back.
R: The 'R' flag is set to request a Complex Track for redundancy.
Flags: Reserved. The Flags field MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
ReqLifetime: 8-bit unsigned integer. The requested lifetime for the
Track expressed in Lifetime Units (obtained from the DODAG
Configuration option). The value of 255 (0xFF) represents
infinity (never time out).
A PDR with a fresher PDRSequence refreshes the lifetime, and a
PDRLifetime of 0 indicates that the Track MUST be destroyed, e.g.,
when the application that requested the Track terminates.
PDRSequence: 8-bit wrapping sequence number, obeying the operation
in section Section 7.2 of [RPL]. The PDRSequence is used to correlate a
PDR-ACK message with the PDR message that triggered it. It is
incremented at each PDR message and echoed in the PDR-ACK by the
Root.
5.2. New PDR-ACK Control Message
The new PDR-ACK is sent as a response to a PDR message with the 'K'
flag set. The RPL Control Code for the PDR-ACK is 0x0A, to be
confirmed by IANA. 0x0A. Its format
is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TrackID | Flags | Track Lifetime| PDRSequence |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PDR-ACK Status| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)...
+-+-+-+-+-+-+-+
Figure 14: New PDR-ACK Control Message Format
TrackID: Set to the TrackID indicated in the TrackID field of the
PDR messages that this replies to.
Flags: Reserved. The Flags field MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
Track Lifetime: Indicates the remaining Lifetime lifetime for the Track,
expressed in Lifetime Units; Units. The value of 255 (0xFF) represents
infinity. The value of zero (0x00) indicates that the Track was
destroyed or not created.
PDRSequence: 8-bit wrapping sequence number. It is incremented at
each PDR message and echoed in the PDR-ACK.
PDR-ACK Status: 8-bit field indicating the completion. The PDR-ACK
Status is substructured as indicated in Figure 15:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|E|R| Value |
+-+-+-+-+-+-+-+-+
Figure 15: PDR-ACK status Status Format
E: 1-bit flag. Set to indicate a rejection. When not set, a
Value field that is set to 0 indicates Success/Unqualified
Acceptance
Acceptance, and other values indicate "not an outright
rejection".
R: 1-bit flag. Reserved, Reserved; MUST be set to 0 by the sender and
ignored by the receiver.
Status Value: 6-bit unsigned integer. Values depending depend on the
setting of the 'E' flag, flag; see Table Tables 28 and Table 29.
Reserved: The Reserved field MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
5.3. Via Information Options
A VIO signals the ordered list of IPv6 Via Addresses that constitutes
the hops of either a protection path (using Non-Storing Mode) or a
segment (using Storing mode) Mode) of a Track. A Storing Mode P-DAO
contains one Storing Mode VIO (SM-VIO) SM-VIO whereas a Non-Storing Mode P-DAO contains one Non-Storing Mode VIO (NSM-VIO).
NSM-VIO.
The duration of the validity of a VIO is indicated in a segment Segment
Lifetime field. A P-DAO message that contains a VIO with a segment Segment
Lifetime of zero 0 is referred as a No-Path P-DAO.
The VIO contains one or more SRH-6LoRH header(s), headers, each formed of a an
SRH-6LoRH head and a collection of compressed Via Addresses, except
in the case of a Non-Storing Mode No-Path P-DAO where the SRH-6LoRH
header is not present.
In the case of a an SM-VIO, or if [RFC8138] is not used in the data
packets, then the Root MUST use only one SRH-6LoRH per Via
Information Option, and the compression is the same for all the
addresses, as shown in Figure 16, for simplicity.
In case of an NSM-VIO NSM-VIO, and if [RFC8138] is in use in the main DODAG,
the Root SHOULD optimize the size of the NSM-VIO if using different
SRH-6LoRH Types would make the VIO globally shorter; this means that
more than one SRH-6LoRH may be present.
The format of the Via Information Option VIO is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Flags | P-RouteID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Segm.
| Seg. Sequence | Seg. Lifetime | SRH-6LoRH head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Via Address 1 (compressed by RFC 8138) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .... .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Via Address n (compressed by RFC 8138) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. Additional SRH-6LoRH Header(s) header(s) .
| |
. .... .
Figure 16: VIO format Format
Option Type: 0x0E for SM-VIO, 0x0F for SM-VIO and 0x10 for NSM-VIO (to be confirmed by
IANA) (see Table 26).
Option Length: 8-bit unsigned integer, representing the length in
octets of the option, not including the Option Type and Length
fields (see section 6.7.1. Section 6.7.1 of [RPL]); the Option Length is
variable, depending on the number of Via Addresses and the
compression applied.
Flags: 8-bit field. No flag is defined in this specification. The
field MUST be set to 0 by the sender and ignored by the receiver.
P-RouteID: 8-bit field that identifies a component of a Track or the
main DODAG as indicated by the TrackID field. The value of 0 is
used to signal a path, i.e., made of a single segment/protection
path. In an SM-VIO, the P-RouteID indicates a Segment ID. In an
NSM-VIO, it indicates the ID of a protection path that is added
(or updated) to the overall topology of the Track.
Segment Sequence: 8-bit unsigned integer. The Segment Sequence
obeys the operation in section Section 7.2 of [RPL] [RPL], and the initial value
is 255.
When the Root of the DODAG needs to refresh or update a segment in
a Track, it increments the Segment Sequence individually for that
segment.
The segment information indicated in the VIO deprecates any state
for the segment indicated by the P-RouteID within the indicated
Track and sets up the new information.
A VIO with a Segment Sequence that is not as fresh as the current
one is ignored.
A VIO for a given DODAGID with the same (TrackID, P-RouteID,
Segment Sequence) indicates a retry; it MUST NOT change the
segment and MUST be propagated or answered as the first copy.
Segment Lifetime: 8-bit unsigned integer. The length of time in
Lifetime Units (obtained from the Configuration option) that the
segment is usable.
The period starts when a new Segment Sequence is seen. The value
of 255 (0xFF) represents infinity. The value of zero (0x00)
indicates a loss of reachability.
SRH-6LoRH head: The first 2 bytes of the (first) SRH-6LoRH as shown
in Figure 6 of [RFC8138]. As an example, a 6LoRH Type of 4 means
that the VIA Via Addresses are provided in full with no compression.
Via Address: An IPv6 ULA or GUA of a node along the segment. The
VIO contains one or more IPv6 Via Addresses listed in the datapath
order from Ingress to Egress. The list is expressed in a
compressed form as signaled by the preceding SRH-6LoRH header.
In a Storing Mode P-DAO that updates or removes a section of an
already existing segment, the list in the SM-VIO may represent
only the section of the segment that is being updated; at the
extreme, the SM-VIO updates only one node, in which case it
contains only one IPv6 address. In all other cases, the list in
the VIO MUST be complete.
In the case of an SM-VIO, the list indicates a sequential (strict)
path through direct neighbors, neighbors; the complete list starts at the
Ingress and ends at the Egress, and the nodes listed in the VIO,
including the Egress, MAY be considered as implicit Targets.
In the case of an NSM-VIO, the complete list can be loose and
excludes the Ingress node, starting at the first loose hop and
ending at a Track Egress; the Track Egress MUST be considered as
an implicit Target, so it MUST NOT be signaled in a RPL Target
Option.
5.4. Sibling Information Option
The Sibling Information Option (SIO) provides information about
siblings that could be used by the Root to form P-Routes. One or
more SIO(s) SIOs may be placed in the DAO messages that are sent to the Root
in Non-Storing Mode.
To advertise a neighbor node, the router MUST have an active Address
Registration from that sibling using [RFC8505], per [RFC8505] for an address (ULA or
GUA) that serves as an identifier for the node. If this router also
registers an address to that sibling, and the link has similar
properties in both directions, only the router with the lowest
Interface ID in its registered address needs to report the SIO, with
the B flag set, and the Root will assume symmetry.
The SIO carries a flag (B) that is set when similar performance can
be expected in both directions, so the routing can consider that the
information provided for one direction is valid for both. If the SIO
is effectively received from both sides sides, then the B flag MUST be
ignored. The policy that describes the performance criteria, criteria and how
they are asserted is out of scope. In the absence of an external
protocol to assert the link quality, the flag SHOULD NOT be set.
The format of the SIO is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Option Length |S|B|Flags|Comp.| Opaque |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Step in Rank | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
. .
. Sibling DODAGID (if the D flag is not set) .
. .
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
. .
. Sibling Address .
. .
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: Sibling Information Option Format
Option Type: 0x10 0x11 for SIO (to be confirmed by IANA) (see Table 26).
Option Length: 8-bit unsigned integer, representing the length in
octets of the option, not including the Option Type and Length
fields (see section 6.7.1. Section 6.7.1 of [RPL]).
Reserved for Flags: MUST be set to zero 0 by the sender and MUST be
ignored by the receiver.
B: 1-bit flag that is set to indicate that the connectivity to the
sibling is bidirectional and roughly symmetrical. In that case,
only one of the siblings needs to report the SIO for the hop. If
'B' is not set set, then the SIO only indicates connectivity from the
sibling to this node, and it does not provide information on the
hop from this node to the sibling.
S: 1-bit flag that is set to indicate that the sibling belongs to
the same DODAG. When not set, the Sibling DODAGID is indicated.
Flags: Reserved. The Flags field MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
Comp.: Compression Type, Type; a 3-bit unsigned integer. This is the SRH-
6LoRH Type as defined in figure Figure 7 in section Section 5.1 of [RFC8138] that
corresponds to the compression used for the Sibling Address and
its DODAGID if present. The Compression reference is the Root of
the main DODAG.
Opaque: MAY be used to carry information that the node and the Root
understand, e.g., a particular representation of the Link link
properties such as a proprietary Link Quality Information for
packets received from the sibling. In some scenarios such as the
case of an
Industrial Alliances that uses use RPL for a particular use
/ use/
environment, this field MAY be redefined to fit the needs of
that the
case.
Step in Rank: 16-bit unsigned integer. This is the Step in Rank
[RPL] as computed by the Objective Function between this node and
the sibling, that which reflects the abstract Rank increment that would
be computed by the OF Objective Function if the sibling was the
preferred parent.
Reserved: The Reserved field MUST be initialized to zero by the
sender and MUST be ignored by the receiver
Sibling DODAGID: 2 to 16 bytes, the bytes. The DODAGID of the sibling in a
[RFC8138]
compressed form [RFC8138] as indicated by the Compression Type
field. This field is present if and only if the D flag is not
set.
Sibling Address: 2 to 16 bytes, an bytes. An IPv6 Address address of the sibling, sibling with
a scope that MUST make it reachable from the Root, e.g., it cannot
be a Link Local Address. The IPv6 address is encoded in the
[RFC8138]
compressed form [RFC8138] indicated by the Compression Type field.
An SIO MAY be immediately followed by a DAG Metric Container. In
that case case, the DAG Metric Container provides additional metrics for
the hop from the Sibling to this node.
6. Root Initiated Root-Initiated Routing State
6.1. RPL Network Setup
To avoid the need of Path MTU Discovery by 6LoWPAN end-points, endpoints, 6LoWPAN
links are normally defined with a an MTU of 1280 (see section Section 4 of
[6LoWPAN]). Injecting packets in a Track typically involves an
IP-in-IP IP-
in-IP encapsulation and additional IPv6 Extension Headers. extension headers. This may
cause fragmentation if the resulting packets exceed the MTU that is
defined for the RPL domain.
Though fragmentation is possible in a 6LoWPAN LLN, e.g., using
[6LoWPAN], [RFC8930], and/or [RFC8931], it is RECOMMENDED to define
an MTU that is larger than 1280 between the RPL routers that form the
main DODAG to allow for the necessary header additions, while still
exposing 1280 to the 6LoWPAN end-point endpoint stacks.
6.2. Requesting a Track
This specification introduces the PDR message, which is used by an
LLN node to request the formation of a new Track for which this the LLN
node is the Ingress. Note that the namespace for the TrackID is
owned by the Ingress node, and in the absence of a PDR, there must be
some procedure for the Root to assign TrackIDs in that namespace
while avoiding collisions (more (see more in Section 6.3).
The PDR signals the desired TrackID and the duration for which the
Track should be established. Upon a PDR, the Root MAY install the
Track as requested, in which case it answers with a PDR-ACK
indicating the granted Track Lifetime. All the segments MUST be of a
the same mode, either Storing or Non-Storing. All the segments MUST
be created with the same TrackID and the same DODAGID signaled in the
P-DAO.
The Root designs the Track as it sees best, fit and updates / changes updates/changes the
segments over time to serve the Track as needed. Note that there is
no protocol element to notify to the requesting Track Ingress when
changes happen deeper down the Track, so they are transparent to the
Track Ingress. If the main Root cannot maintain an expected service
level, then it needs to tear down the Track completely. The Segment
Lifetime in the P-DAO messages does not need to be aligned to the
Requested Lifetime in the PDR, PDR or between P-DAO messages for different
segments. E.g., The For example, the Root may use shorter lifetimes for the
segments and renew them or change them during the lifetime of the
Track. All the components (protection paths and segments) of a Track
MUST be destroyed (or have their lifetime elapsed) before the TrackID
can be reused.
When the Track Lifetime is relatively close to elapse - -- meaning in
the order of the trip time from the node to the Root - -- the
requesting node SHOULD resend a PDR using the TrackID in the PDR-ACK
to extend the lifetime of the Track, else Track; otherwise, the Track will time out
out, and the Root will tear down the whole structure.
If the Track fails and cannot be restored, the Root notifies the
requesting node asynchronously with a PDR-ACK with a Track Lifetime
of 0, indicating that the Track has failed, and a PDR-ACK Status Status,
indicating the reason of the fault.
6.3. Identifying a Track
RPL defines the concept of an Instance to signal an individual
routing topology, and multiple topologies can coexist in the same
network. The RPLInstanceID is tagged in the RPI of every packet to
signal which topology the packet actually follows.
This specification leverages the RPL Instance model as follows:
* The main Root MAY use P-DAO messages to add better routes in the
main Instance in conformance with the routing objectives in that
Instance.
To achieve this, the main Root MAY install a segment along a path
down the main DODAG, which is operated in Non-Storing Mode. This
enables a loose source routing and reduces the size of the Routing
Header,
Header; see Section 3.3.1. The main Root MAY also install a
protection path across the main DODAG to complement the routing
topology.
When adding a P-Route to the RPL main DODAG, the main Root MUST
set the RPLInstanceID field of the P-DAO Base Object (see section
6.4.1.
Section 6.4.1 of [RPL]) to the RPLInstanceID of the main DODAG,
and it MUST NOT use the DODAGID field. A P-Route provides a
longer match to the Target Address than the default route via the
main Root, so it is preferred.
* The main Root MAY also use P-DAO messages to install a Track as an
independent routing topology (say, Traffic Engineered) to achieve
particular routing characteristics from an Ingress to Egress
Endpoints.
endpoints. To achieve this, the main Root MUST set up a Local RPL
Instance (see section Section 5 of [RPL]), and the Local RPLInstanceID
serves as the TrackID. The TrackID MUST be unique for the IPv6
ULA or GUA of the Track Ingress that serves as the DODAGID for the
Track.
This way, a Track is uniquely identified by the tuple (DODAGID,
TrackID) where the TrackID is always represented with the D flag
set to 0 (see also section 5.1. Section 5.1 of [RPL]), indicating that when
used in an RPI that RPI, the source address of the IPv6 packet signals the
DODAGID.
The P-DAO Base Object MUST indicate the tuple (DODAGID, TrackID)
that identifies the Track as shown in Figure 8, and the P-RouteID
that identifies the P-Route MUST be signaled in the VIO as shown
in Figure 16.
The Track Ingress is the Root of the DODAG ID DODAGID formed by the local Local
RPL Instance. It owns the namespace of its TrackIDs, so it can
pick any unused value to request a new Track with a PDR. In a
particular deployment where PDRs are not used, a portion of the
namespace can be administratively delegated to the main Root,
meaning that the main Root is authoritative for assigning the
TrackIDs for the Tracks it creates.
With this specification, the main Root is aware of all the active
Tracks, so it can also pick any unused value to form Tracks
without a PDR. To avoid a collision of the main Root and the
Track Ingress picking the same value at the same time, it is
RECOMMENDED that the Track Ingress starts allocating the ID value
of the Local RPLInstanceID (see section 5.1. Section 5.1 of [RPL]) used as
TrackIDs with the value 0 incrementing, while the Root starts with
63 decrementing.
6.4. Installing a Track
A path can be installed by a single P-Route that signals the sequence
of consecutive nodes, nodes either in Storing Mode as a single-segment
Track, Track
or in Non-Storing Mode as a single-protection-path Track. A
single-protection-path single-
protection-path Track can be installed as a loose Non-Storing Mode
P-Route, in which case the next loose entry must recursively be
reached over a path.
A Complex Track can be installed as a collection of P-Routes with the
same DODAGID and Track ID. The Ingress of a Non-Storing Mode P-Route
is the owner and Root of the DODAGID. The Ingress of a Storing Mode
P-Route must be either the owner of the DODAGID, DODAGID or a hop of a
protection path of the same Track. In the latter case, the Targets
of the P-Route must include the next hop of the protection path if
there is one, one to ensure forwarding continuity. In the case of a
Complex Track, each segment is maintained independently and
asynchronously by the Root, with its own lifetime that may be
shorter, the same, or longer than that of the Track.
A route along a Track for which the TrackID is not the RPLInstanceID
of the main DODAG MUST be installed with a higher precedence than the
routes along the main DODAG, meaning that:
* Longest The longest match MUST be the prime comparison for routing.
* In case of equal length For an equal-length match, the route along the Track MUST be
preferred vs. over the one along the main DODAG.
* There SHOULD NOT be 2 two different Tracks leading to the same
Target from same Ingress node, unless there's a policy for
selecting which packets use which Track; such a policy is out of
scope.
* A packet that was routed along a Track MUST NOT be routed along
the main DODAG again; if the destination is not reachable as a
neighbor by the node where the packet exits the Track Track, then the
packet MUST be dropped.
6.4.1. Signaling a Projected Route
This specification adds a capability whereby the Root of a main DODAG
installs a Track as a collection of P-Routes, using a Projected-DAO
(P-DAO) P-DAO message
for each individual protection path or segment. The P-DAO signals a
collection of Targets in the RPL Target Option(s)
(RTO). one or more RTOs. Those Targets can be
reached via a sequence of routers indicated in a VIO.
Like a classical DAO message, a P-DAO causes a change of state only
if it is "new" per section 9.2.2. "Generation Section 9.2.2 ("Generation of DAO Messages" Messages") of
the RPL specification [RPL]; this is determined using the Segment
Sequence information from the VIO as opposed to the Path Sequence
from a TIO. Also, a Segment Lifetime of 0 in a VIO indicates that
the P-Route associated to the segment is to be removed. There are
two Modes of operation for the P-Routes, the P-Routes: Storing and the Non-
Storing Modes. Non-Storing.
A P-DAO message MUST be sent from the address of the Root that serves
as the DODAGID for the main DODAG. It MUST contain either exactly
one sequence of one or more RTOs followed by one VIO, VIO or any number of
sequences of one or more RTOs followed by one or more TIOs. The
former is the normal expression for this specification, whereas the
latter corresponds to the variation for less-constrained environments
described in Section 7.2.
A P-DAO that creates or updates a protection path MUST be sent to a
GUA or a ULA of the Ingress of the protection path; it MUST contain
the full list of hops in the protection path unless the protection
path is being removed. A P-DAO that creates a new Track segment MUST
be sent to a GUA or a ULA of the segment Egress and MUST signal the
full list of hops in a segment; a P-DAO that updates (including
deletes) a section of a segment MUST be sent to the first node after
the modified segment and signal the full list of hops in the section
starting at the node that immediately precedes the modified section.
In Non-Storing Mode, as discussed in Section 6.4.3, the Root sends
the P-DAO to the Track Ingress where the source-routing source routing state is
applied, whereas in Storing Mode, the P-DAO is sent to the last node
on the installed path and forwarded in the reverse direction,
installing a Storing Mode state at each hop, as discussed in
Section 6.4.2. In both cases cases, the Track Ingress is the owner of the
Track, and it generates the P-DAO-ACK when the installation is
successful.
If the 'K' Flag flag is present in the P-DAO, the P-DAO MUST be
acknowledged using a DAO-ACK that is sent back to the address of the
Root from which the P-DAO was received. In most cases, the first
node of the protection path, segment, or updated section of the
segment is the node that sends the acknowledgment. The exception to
the rule is when an intermediate node in a segment fails to forward a
Storing Mode P-DAO to the previous node in the SM-VIO.
In a No-Path Non-Storing Mode P-DAO, the SRH-6LoRH MUST NOT be
present in the NSM-VIO; the state in the Ingress is erased
regardless. In all other cases, a VIO MUST contain at least one Via
Address, and a Via Address MUST NOT be present more than once, which
would create a loop.
A node that processes a VIO MAY verify whether any of these
conditions happen, and when one does, it MUST ignore the P-DAO and
reject it with a RPL Rejection Status of "Error in VIO" in the DAO-
ACK,
ACK; see Section 11.16.
Other errors
Errors, other than those discussed explicitly explicitly, that prevent the
installation of the route are acknowledged with a RPL Rejection
Status of "Unqualified Rejection" in the DAO-ACK.
6.4.2. Installing a Track Segment with a Storing Mode P-Route
As illustrated in Figure 18, a Storing Mode P-DAO installs a route
along the segment signaled by the SM-VIO towards the Targets
indicated in the Target Options. The segment is to be included in a
DODAG indicated by the P-DAO Base Object, that which may be the one formed
by the main DODAG, or a Track associated with a local Local RPL Instance.
------+---------
| Internet
|
+-----+
| | Border router Router
| | (RPL Root)
+-----+ | ^ |
| | DAO | ACK |
o o o o | | |
o o o o Ingress o o o | ^ | Projected .
o o o o o \\ o o o | | DAO | Route .
o o o o \\ o o o o | ^ | .
o o o o o Egress o o v | DAO v .
o o LLN o o o |
o o o o o Loose Source Route Path |
o o o o v
Figure 18: Projecting a route Route
In order to install the relevant routing state along the segment , segment, the
Root sends a unicast P-DAO message to the Track Egress router of the
routing segment that is being installed. The P-DAO message contains a
an SM-VIO with the a strict sequence of Via Addresses. The SM-
VIO SM-VIO
follows one or more RTOs indicating the Targets to which the Track
leads. The SM-VIO contains a Segment Lifetime for which the state is
to be maintained.
The Root sends the P-DAO directly to the Egress node of the segment.
In that P-DAO, the destination IP address matches the last Via
Address in the SM-VIO. This is how the Egress recognizes its role.
In a similar fashion, the segment Ingress node recognizes its role
because it matches the first Via Address in the SM-VIO.
The Egress node of the segment is the only node in the path that does
not install a route in response to the P-DAO; it is expected to be
already able to route to the Target(s) based on its existing tables.
If one of the Targets is not known, the node MUST answer to the Root
with a DAO-ACK listing the unreachable Target(s) in an RTO and a
rejection status of "Unreachable Target".
If the Egress node can reach all the Targets, then it forwards the P-DAO
with unchanged content to its predecessor in the segment as indicated
in the list of Via Information options, VIOs, and recursively the message is recursively propagated
unchanged along the sequence of routers indicated in the P-DAO, but
in the reverse order, from Egress to Ingress.
The address of the predecessor to be used as the destination of the
propagated DAO message is found in the Via Address list, list at the
position preceding the one that contains the address of the
propagating node, which is used as the source of the message.
Upon receiving a propagated DAO, all except the Egress router MUST
install a route towards the DAO Target(s) via their successor in the
SM-VIO. A router that cannot store the routes to all the Targets in
a P-DAO MUST reject the P-DAO by sending a DAO-ACK to the Root with a
Rejection Status of "Out of Resources" as opposed to forwarding the
DAO to its predecessor in the list. The router MAY install
additional routes towards the Via Addresses that appear in the SM-VIO
after its own address, if any, but in case of a conflict or a lack of
resource, the route(s) to the Target(s) are the ones that MUST be installed in
priority.
If a router cannot reach its predecessor in the SM-VIO, the router
MUST send the DAO-ACK to the Root with a Rejection Status of
"Predecessor Unreachable".
The process continues until the P-DAO is propagated to the Ingress
router of the segment, which answers with a DAO-ACK to the Root. The
Root always expects a DAO-ACK, either from the Track Ingress with a
positive status or from any node along the segment with a negative
status. If the DAO-ACK is not received, the Root may retry the DAO
with the same TID, TID or tear down the route.
6.4.3. Installing a protection path Protection Path with a Non-Storing Mode P-Route
As illustrated in Figure 19, a Non-Storing Mode P-DAO installs a
source-routed path within the Track indicated by the P-DAO Base
Object,
Object towards the Targets indicated in the Target Options. The
source-routed path requires a Source-Routing header Source Routing Header, which implies an
IP-in-IP encapsulation is needed to add the SRH to an existing
packet. It is sent to the Track Ingress Ingress, which creates a tunnel
associated with the
Track, Track and connected routes over the tunnel to the
Targets in the RTO. The tunnel encapsulation MUST incorporate a
routing header via the list addresses listed in the VIO in the same
order. The content of the NSM-VIO starting at the first SRH-6LoRH
header MUST be used verbatim by the Track Ingress when it
encapsulates a packet to forward it over the Track.
------+---------
| Internet
|
+-----+
| | Border router Router
| | (RPL Root)
+-----+ | P ^ ACK
| Track | DAO |
o o o o Ingress X V | X
o o o o o o o X o X Source Source-
o o o o o o o o X o o X Routed
o o ° o o o o X o X Segment
o o o o o o o o X Egress X
o o o o o |
Target
o o LLN o o
o o o o
Figure 19: Projecting a Non-Storing Route
The next entry in the source-routed path must be either a neighbor of
the previous entry, entry or reachable as a Target via another P-Route,
either Storing or Non-Storing, which implies that the nested P-Route
has to be installed before the loose sequence is, is and that P-Routes
must be installed from the last to the first along the datapath. For
instance, a segment of a Track must be installed before the
protection path(s) of the same Track that use uses it, and stitched
segments must be installed in order from the last that reaches to the
Targets first to
reach the first. Targets.
If the next entry in the loose sequence is reachable over a Storing
Mode P-Route, it MUST be the Target of a segment and the Ingress of a
next segment, which are both already setup; set up; the segments are
associated with the same Track, which avoids the need of needing an additional
encapsulation. For instance, in Section 3.5.1.3, segments A==>B-to-C
and C==>D==>E-to-F must be installed with Storing Mode P-DAO messages
1 and 2 before the Track A-->C-->E-to-F that joins them can be
installed with Non-Storing Mode P-DAO 3.
Conversely, if it is reachable over a Non-Storing Mode P-Route, the
next loose source-routed hop of the inner Track is a Target of a
previously installed Track and the Ingress of a next Track, which
requires a de- and a re-encapsulation when switching the outer Tracks
that join the loose hops. This is examplified exemplified in Section 3.5.2.3
where Non-Storing Mode P-DAO P-DAOs 1 and 2 install strict Tracks that Non-
Storing Mode P-DAO 3 joins as a super Track. In such a case, packets
are subject to double IP-in-IP encapsulation.
6.5. Tearing Down a P-Route
A P-DAO with a lifetime of 0 is interpreted as a No-Path DAO and
results in cleaning up existing state as opposed to refreshing an
existing one or installing a new one. To tear down a Track, the Root
must tear down all the Track segments and protection paths that
compose it one by one.
Since the state about a protection path state of a Track is located only on the
Ingress Node, the Root cleans up the protection path by sending an
NSM-VIO to the Ingress indicating to indicate the TrackID and the P-RouteID of
the protection path being removed, a Segment Lifetime of 0 0, and a
newer Segment Sequence. The SRH-6LoRH with the Via Addresses in the
NSM-VIO are NSM-
VIO is not needed; it SHOULD NOT be placed in the message and MUST be
ignored by the receiver. Upon that NSM-VIO, the Ingress node removes
all state for that Track Track, if any, and replies positively anyway.
The Root cleans up a section of a segment by sending an SM-VIO to the
last node of the segment, segment with the an updated TrackID and the P-RouteID of the
segment being updated, P-RouteID, a
Segment Lifetime of zero (0) 0, and a newer Segment Sequence. The Via
Addresses in the SM-VIO indicates indicate the section of the segment being
modified, from the first to the last node that is impacted. This can
be the whole segment if it is totally removed, removed or a sequence of one or
more nodes that have been bypassed by a segment update.
The No-Path P-DAO is forwarded normally along the reverse list, even
if the intermediate node does not find a segment state to clean up.
This results in cleaning up the existing segment state state, if any, as
opposed to refreshing an existing one or installing a new one.
6.6. Maintaining a Track
Repathing a Track segment or protection path may cause jitter and
packet misordering. For critical flows that require timely and/or
in-order delivery, it might be necessary to deploy the PAREO
functions [RAW-ARCHI] [RAW-ARCH] over a highly redundant Track. This
specification allows to the use of more than one protection path for a
Track,
Track and 1+N packet redundancy.
This section provides the steps to ensure that no packet is lost due
to the operation itself. This is ensured by installing the new
section from its last node to the first, so when an intermediate node
installs a route along the new section, all the downstream nodes in
the section have already installed their own. The disabled section
is removed as well when the packets in-flight packets are forwarded along the
new
section as well. section.
6.6.1. Maintaining a Track Segment
To modify a section of a segment between a the first node and a second, second
downstream node (which can be the Ingress and Egress, respectively), respectively)
while retaining those nodes in the segment, the Root sends an SM-VIO
to the second node indicating the sequence of nodes in the new
section of the segment. The SM-VIO indicates the TrackID and the
P-RouteID of the segment being updated, updated and a newer Segment Sequence.
The P-DAO is propagated from the second to the first node node, and on the
way, it updates the state on the nodes that are common to the old and
the
new section of the segment and creates a state in the new nodes.
When the state is updated in an intermediate node, that node might
still receive packets that were in flight from the Ingress to self
over the old section of the segment. Since the remainder of the
segment is already updated, the packets are forwarded along the new
version of the segment from that node on.
After a reasonable time to enable the deprecated sections to drain
their traffic, amount of time, the Root tears down the remaining
section(s) of the old segments as described in Section 6.5. 6.5 to enable
the deprecated sections to drain their traffic.
6.6.2. Maintaining a protection path Protection Path
This specification allows the Root to add protection paths to a Track
by sending a Non-Storing Mode P-DAO to the Ingress associated to the
same TrackID, TrackID and a new Segment ID. If the protection path is loose,
then the segments that join the hops must be created first. It makes
sense to add a new protection path before removing one that is
becoming excessively lossy, lossy and switch to the new protection path
before removing the old. Dropping a Track before the new one is
installed would reroute the traffic via the root; this may increase
the latency beyond acceptable thresholds, thresholds and overload the network
near the root. This may also cause loops in the case of stitched
Tracks: the The packets that cannot be injected in the second Track might
be routed back and reinjected at the Ingress of the first. first Track.
It is also possible to update a protection path by sending a Non-
Storing Mode P-DAO to the Ingress with the same Segment ID, an
incremented Segment Sequence, and the new complete list of hops in
the NSM-VIO. Updating a live protection path means changing one or
more of the intermediate loose hops, and it involves laying out new
segments from and to the new loose hops before the NSM-VIO is issued
for the new protection path is issued. path.
Packets that are in flight over the old version of the protection
path still follow the old source route path over the old segments.
After a reasonable time to enable the deprecated segments to drain
their traffic, time, the Root tears down those segments as
described in Section 6.5. 6.5 to enable the deprecated segments to drain
their traffic.
6.7. Encapsulating and Forwarding Along a Track
When injecting a packet in a Track, the Ingress router must
encapsulate the packet using IP-in-IP to add the Source Routing
Header with the final destination set to the Track Egress.
All properties of a Track's operations are inherited form from the main
Instance that is used to install the Track. For instance, the use of
compression per [RFC8138] is determined by whether it is used in the
RPL main DODAG, e.g., by setting the "T" 'T' flag [RFC9035] in the RPL
configuration option.
The
When the Track Ingress that places a packet in a Track Track, it encapsulates it
with an additional IPv6 header, a Routing Header, and an IPv6 Hop-by-
Hop Option Header that contains the RPL Packet Information (RPI) RPI as follows:
* In the uncompressed form, the source of the packet is the address
that this router uses as the DODAGID for the Track, the
destination is the first Via Address in the NSM-VIO, and the RH is a Source
Routing Header (SRH)
an SRH [RFC6554] that contains the list of the remaining Via
Addresses, ending with the Track Egress.
* The To compress RPL artifacts in data packets as indicated in
[RFC8138], the preferred alternative in a network where 6LoWPAN Header
Compression
header compression [RFC6282] is used is to leverage implement "IPv6 over
Low-Power Wireless Personal Area Network (6LoWPAN) Paging
Dispatch"
[RFC8025] to compress the RPL artifacts as indicated in [RFC8138]. [RFC8025].
In that case, the source routed source-routed header is the exact copy of the
(chain of) SRH-6LoRH found in the NSM-VIO, also ending with the
Track Egress. The RPI-6LoRH is appended next, followed by an IP-
in-IP 6LoRH Header that indicates the Ingress router in the
Encapsulator Address field, field; see as a similar case in Figure 20 of
[RFC8138].
To signal the Track in the packet, this specification leverages the
RPL Forwarding model as follows:
* In the data packets, the Track DODAGID and the TrackID MUST be
respectively signaled as the IPv6 Source Address source address, and the
RPLInstanceID field of the RPI that MUST be placed in the outer chain
of IPv6 Headers. headers.
The RPI carries a local Local RPLInstanceID called the TrackID, which,
in association with the DODAGID, indicates the Track along which
the packet is forwarded.
The D flag in the RPLInstanceID MUST be set to 0 to indicate that
the source address in the IPv6 header is set to the DODAGID (more (see
more in Section 6.3).
* This specification conforms to the principles of [RFC9008] with
regards
regard to packet forwarding and encapsulation along a Track, Track as
follows:
- With this specification, the Track is a RPL DODAG. From the
perspective of that DODAG, the Track Ingress is the Root, the
Track Egress is a RPL-Aware 6LR, and neighbors of the Track
Egress that can be reached via the Track, but are external to
it, are external destinations and treated as RPL-Unaware Leaves
(RULs). The encapsulation rules in [RFC9008] apply.
- If the Track Ingress is the originator of the packet and the
Track Egress is the destination of the packet, there is no need
for an encapsulation.
- So Thus, the Track Ingress must encapsulate the traffic that it
did not originate, and it must include an RPI in the
encapsulation to signal the TrackID.
A packet that is being routed over the RPL Instance associated to
a first Non-Storing Mode Track MAY be placed recursively in a
second Track to cover one loose hop of the first Track Track, as
discussed in more detail in Section 3.5.2.3. On the other hand, a
Storing Mode segment must be strict strict, and a packet that it placed
in a Storing Mode segment MUST follow that segment till the
segment Egress.
It is known that a packet is forwarded along a Track by the source
address and the RPI in the encapsulation. The Track ID is used to
identify the RIB entries associated to that Track, which, in
intermediate nodes, correspond to the P-routes P-Routes for the segments of
the Track that the forwarding router is aware of. The packet
processing uses a precedence that favors self delivery self-delivery or routing
header handling when one is present, then delivery to direct
neighbors, then to indirect neighbors, then routing along a segment
along the Track, and finally as a last resort injecting the packet in
another Track.
To achieve this, the packet handling logic MUST happen in the
following order:
* If the destination of the packet is self:
1. if If the header chain contains a RPL Source Route Header that is
not fully consumed, then the packet is forwarded along the
Track as prescribed by [RFC6554], meaning that the next entry
in the routing header becomes the destination; destination.
2. otherwise: Otherwise, if the packet was encapsulated, then the packet is
decapsulated and the forwarding process recurses; else else, the
packet is delivered to the stack.
* Otherwise, the packet is forwarded as follows:
1. If the destination of the packet is a direct neighbor, e.g.,
installed by IPv6 Neighbor Discovery, then the packet MUST be
forwarded to that neighbor; neighbor.
2. Else If Else, if the destination of the packet is an indirect
neighbor, e.g., installed by a multicast DAO message from a
common
neighbor, see neighbor (see Section 4.1.4, 4.1.4), then the packet MUST be
forwarded to the common neighbor; neighbor.
3. Else, if there is a RIB entry for the same Track (e.g.,
installed by an SM-VIO in a DAO message with the destination
as target), the target) and the next hop in the RIB entry is a direct
neighbor, then the packet is passed to that neighbor; neighbor.
4. Else, if there is a RIB entry for the different Track (e.g.,
installed by an NSM-VIO in a DAO message with the destination
as the target), then the packet is encapsulated to be
forwarded along that Track and the forwarding process
recurses;
otherwise otherwise, the packet is dropped.
5. To avoid loops, and as opposed to packets that were not
encapsulated, a packet that was decapsulated from a Track MUST
NOT be routed along the default route of the main DODAG; this
would mean that the end-to-end path is uncontrolled. The node
that discovers the fault MUST discard the packet.
The node that drops a packet for either of the reasons above MUST
send an ICMPv6 Error error message [RFC4443] to the Root, with a the new Code code
"Error in P-Route" (See (see Section 11.15). The Root can then repair by
updating the broken segment and/or Tracks, and in the case of a
broken segment, remove the leftover sections of the segment using SM-
VIOs with a lifetime of 0 indicating the section to one or more nodes
being removed (See (see Section 6.6).
In case of a permanent forwarding error along a Source Route source route path,
the node that fails to forward SHOULD send an ICMP error with a the
code "Error in Source Routing Header" back to the source of the
packet, as described in section 11.2.2.3. Section 11.2.2.3 of [RPL]. Upon receiving
this message, the encapsulating node SHOULD stop using the source
route path for a reasonable period of time time, which depends on the
deployment, and it SHOULD send an ICMP message with a Code the code "Error
in P-Route" to the Root. Failure to follow these steps may result in
packet loss and wasted resources along the source route path that is
broken.
Either way, the ICMP message MUST be throttled in case of consecutive
occurrences. It MUST be sourced at the ULA or a GUA that is used in
this Track for the source node, so the Root can establish where the
error happened.
The portion of the invoking packet that is sent back in the ICMP
message SHOULD record at least up to the RH if one is present, and
this
the hop of the RH SHOULD be consumed by this node so that the
destination in the IPv6 header is the next hop that this node could
not reach. If a 6LoWPAN Routing Header (6LoRH) 6LoRH [RFC8138] is used to carry the IPv6 routing
information in the outer header header, then that the whole 6LoRH information
SHOULD be present in the ICMP message.
6.8. Compression of the RPL Artifacts
When using [RFC8138] in the main DODAG operated in Non-Storing Mode
in a 6LoWPAN LLN, a typical packet that circulates in the main DODAG
is formatted as shown in Figure 20, representing the case where an
IP-in-IP encapsulation is needed (see Table 19 of [RFC9008]):
+-+ ... -+- ... -+- ... -+-+- ... +-+-+-+ ... +-+-+ ... -+ ... +-...
|11110001| SRH- | RPI- | IP-in-IP | NH=1 |11110CPP| UDP | UDP
| Page 1 | 6LoRH | 6LoRH | 6LoRH |LOWPAN_IPHC| UDP | hdr |Payld
+-+ ... -+- ... -+- ... -+-+- ... +-+-+-+ ... +-+-+ ... -+ ... +-...
<= RFC 6282 =>
<================ Inner packet ==================== = =
Figure 20: A Packet as Forwarded along Along the main Main DODAG
Since there is no page switch between the encapsulated packet and the
encapsulation, the first octet of the compressed packet that acts as
the page selector is actually removed at encapsulation, so encapsulation; therefore,
the inner packet used in the descriptions below starts with the SRH-6LoRH, SRH-
6LoRH and is exactly the packet represented in Figure 20, from the
second octet onward.
When encapsulating that the inner packet to place it in the Track, the first
header that the Ingress appends at the head of the inner packet is an
IP-in-IP 6LoRH Header; in that header, the encapsulator address,
which maps to the IPv6 source address in the uncompressed form,
contains a GUA or ULA IPv6 address of the Ingress node that serves as DODAG ID
the DODAGID for the Track, expressed in the a compressed form
and using the
DODAGID of the main DODAG as compression reference. a reference for the compression. If the
address is compressed to 2 bytes, the resulting value for the Length
field shown (shown in Figure 21 21) is 3, meaning that the SRH-6LoRH as a
whole is 5-octets 5 octets long.
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
|1|0|1| Length | 6LoRH Type 6 | Hop Limit | Track DODAGID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- ... -+
Figure 21: The IP-in-IP 6LoRH Header
At the head of the resulting sequence of bytes, the track Track Ingress
then adds the RPI that carries the TrackID as RPLinstanceID RPLInstanceID as a P-
RPI-6LoRH Header, as illustrated in Figure 12, using the TrackID as
RPLInstanceID. Combined with the IP-in-IP 6LoRH Header, this allows
to identify
identifying the Track without ambiguity.
The SRH-6LoRH is then added at the head of the resulting sequence of
bytes as a verbatim copy of the content of the SR-VIO SM-VIO that signaled
the selected protection path.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 .. .. ..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
|1|0|0| Size |6LoRH Type 0..4| Hop1 | Hop2 | | HopN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- -+- -+ ... +- -+
Where N = Size + 1
Figure 22: The SRH 6LoRH SRH-6LoRH Header
The format of the resulting encapsulated packet packet, which is in [RFC8138]
compressed form per [RFC8138], is illustrated in Figure 23:
+-+ ... -+-+-+- ... -+-+-+- ... -+-+-+-+-+- ... +-+-+-+-+-+-+- ...
| Page 1 | SRH-6LoRH | P-RPI-6LoRH | IP-in-IP 6LoRH | Inner Packet
+-+ ... -+-+-+- ... -+-+-+- ... -+-+-+-+-+- ... +-+-+-+-+-+-+- ...
Signals : Loose Hops : TrackID : Track DODAGID :
Figure 23: A Packet as Forwarded along Along a Track
7. Less-Constrained Variations
7.1. Storing Mode main Main DODAG
This specification expects that the main DODAG is operated in Non-
Storing Mode. The reasons for that limitation are mostly related to
LLN operations, power power, and spectrum conservation:
* In Non-Storing Mode, the Root already knowns knows the DODAG topology, so
the additional topological information is reduced to the siblings.
* The downward routes are updated with unicast messages to the Root,
which ensures that the Root can reach back to the LLN nodes after
a repair faster than in the case of Storing Mode. Also Also, the Root
can control the use of the path diversity in the DODAG to reach the
LLN nodes. For both reasons, Non-Storing Mode provides better
capabilities for the Root to maintain the P-Routes.
* When the main DODAG is operated in Non-Storing Mode, P-Routes
enable loose Source Routing, source routing, which is only an advantage in that
mode. Storing Mode does not use Source Routing Headers, Headers and does
not derive the same benefits from this capability.
On the other hand, since RPL is a Layer-3 Layer 3 routing protocol, its
applicability extends beyond LLNs to a generic IP network. RPL
requires less fewer resources than alternative IGPs like such as OSPF, ISIS, EIGRP,
BABEL IS-IS,
the Enhanced Interior Gateway Routing Protocol (EIGRP), BABEL, or RIP
at the expense of a route stretch vs. versus the shortest path routes to
a destination that those protocols compute. P-Routes add the
capability to install the shortest and/or constrained routes to
special destinations such as discussed in section A.9.4. Appendix A.9.4 of the ANIMA ACP
[RFC8994].
In a powered and wired network, when enough memory to store the
needed routes is available, the RPL Storing Mode proposes a better
trade-off than the Non-Storing, Non-Storing Mode, as it reduces the route stretch
and lowers the load on the Root. In that case, the control path
between the Root and the RPL nodes can be maintained more
aggressively and with more redundancy than in LLNs, and the nodes can
be reached to maintain the P-Routes at most times for a finer and
more reactive control.
This section specifies the additions that are needed to support
Projected Routes
P-Routes when the main DODAG is operated in Storing Mode. As long as
the RPI can be processed adequately by the dataplane, data plane, the changes to in
this specification are limited to the DAO message. The Track
structure, routes routes, and forwarding operations remain the same. Since
there is no capability negotiation, the expectation is that all the
nodes in the network support this specification in the same
fashion, fashion
or are configured the same way through management.
In Storing Mode, the Root misses the Child to Parent Child-to-Parent relationship
that forms the main DODAG, DODAG as well as the sibling information. To
provide that knowledge knowledge, the nodes in the network MUST send additional
DAO messages that are unicast to the Root just like Non-Storing DAO
messages are.
In the DAO message, the originating router advertises a set of
neighbor nodes using Sibling Information Options (SIO)s, SIOs, regardless of the relative position in the
DODAG of the advertised node vs. versus this router.
The DAO message MUST be formed as follows:
* The originating router is identified by the source address of the
DAO. That address MUST be the one that this router registers to
the neighbor routers so the Root can correlate the DAOs from those
routers when they advertise this router as their neighbor. The
DAO contains one or more sequences of one Transit Information
Option TIO and one or more Sibling Information Options.
SIOs. There is no RPL Target Option so that the Root is not
confused into adding a Storing Mode route to the Target.
* The TIO is formed as in Storing Mode, and the Parent Address is
not present. The Path Sequence and Path Lifetime fields are
aligned with the values used in the Address Registration of the
node(s) advertised in the SIO, as explained in Section 9.1. 9.1 of
[RFC9010]. Having similar values in all nodes allows factorising factorizing
the TIO for multiple SIOs as done with in [RPL].
* The TIO is followed by one or more SIOs that provide an address
(ULA or GUA) of the advertised neighbor node.
But
However, the RPL routing information headers may not be supported on
all
type types of routed network infrastructures, especially not in high-speed high-
speed routers. When the RPI is not supported in the dataplane, data plane,
there cannot be local Local RPL Instances and RPL can only operate as a
single topology (the main DODAG). The RPL Instance is that of the
main
DODAG DODAG, and the Ingress node that encapsulates is not the Root.
The routes along the Tracks are alternate routes to those available
along the main DODAG. They MAY conflict with routes to children and
MUST take precedence in the routing table. The Targets MUST be
adjacent to the Track Egress to avoid loops that may form if the
packet is reinjected in the main DODAG.
7.2. A Track as a Full DODAG
This specification builds Tracks with parallel or interleaved
protection paths as opposed to a more complex DODAG with
interconnections at any place desirable. The reason for that
limitation is related to constrained node operations, operations and the
capability to store a large amount of topological information and
compute complex paths:
* With this specification, the node in the LLN has no topological
awareness,
awareness and does not need to maintain dynamic information about
the link quality and availability.
* The Root has a complete topological information and statistical
metrics that allow it it, or its PCE PCE, to perform a global
optimization of all Tracks in its DODAG. Based on that
information, the Root computes the protection path and produces
the source route paths.
* The node merely selects one of the proposed paths and applies the
associated pre-computed routing header in the encapsulation. This
alleviates both the complexity of computing a path and the
compressed form of the routing header.
The RAW Architecture [RAW-ARCHI] architecture [RAW-ARCH] actually expects the PLR at the Track
Ingress to react to changes in the forwarding conditions along the Track,
Track and reroute packets to maintain the required degree of
reliability. To achieve this, the PLR needs the full richness of a
DODAG to form any path that could meet the Service Level Objective
(SLO). SLO.
This section specifies the additions that are needed to turn the
Track into a full DODAG and enable the main Root to provide the
necessary topological information to the Track Ingress. The
expectation is that the metrics that the PLR uses are of an order
other than that of the PCE, because of the difference of time scale timescale
between routing and forwarding, forwarding; see more in [RAW-ARCHI]. [RAW-ARCH]. It follows
that the PLR will learn the metrics it needs from an alternate
source, e.g., OAM frames.
To pass the topological information to the Ingress, the Root uses a
P-DAO messages message that contains sequences of Target Targets and Transit
Information options TIOs that
collectively represent the Track, expressed in the same fashion as in
classical Non-Storing Mode. The difference is that the Root is the
source as opposed to the destination, and the Root can report
information on many Targets, possibly the full Track, with one P-DAO.
Note that the Path Sequence and Lifetime in the TIO are selected by
the Root, Root and that the Target/Transit information tuples in the P-DAO
are not those received by the Root in the DAO messages about the said
Targets. The Track may follow sibling routes and does not need to be
congruent with the main DODAG.
8. Profiles
This document provides a set of tools that may or may not be needed
by an implementation depending on the type of application it serves.
This section describes profiles that can be implemented separately
and can be used to discriminate what an implementation can and cannot
do. This section describes profiles that enable implementing only a
portion of this specification to meet a particular use case.
Profiles 0 to 2 operate in the main Instance and do not require the
support of local Local RPL Instances or the indication of the RPL Instance
in the data plane. Profile 3 and above leverage Local RPL Instances
to build arbitrary Tracks Rooted rooted at the Track Ingress and using its
namespace for the TrackID.
Profiles 0 and 1 are REQUIRED by all implementations that may be used
in LLNs; Profile 1 leverages Storing Mode to reduce the size of the
Source Route Header in the most common LLN deployments. Profile 2 is
RECOMMENDED in high speed / a high-speed or wired environment to enable traffic Traffic
Engineering and network automation. All the other profile / profile/
environment combinations are OPTIONAL.
Profile 0 0:
Profile 0 is the Legacy legacy support of [RPL] Non-Storing Mode, with
default routing Northwards (up) and strict source routing
Southwards (down the main DODAG). It provides the minimal common
functionality that must be implemented as a prerequisite to all
the Track-supporting profiles. The other Profiles profiles extend Profile
0 with selected capabilities that this specification introduces on
top.
Profile 1 (Storing Mode P-Route segments along the main DODAG) DODAG):
Profile 1 does not create new paths; compared to Profile 0, it
combines Storing and Non-Storing Modes to balance the size of the
Routing Header in the packet and the amount of state in the
intermediate routers in a Non-Storing Mode RPL DODAG.
Profile 2 (Non-Storing Mode P-Route segments along the main DODAG)
DODAG):
Profile 2 extends Profile 0 with Strict Source-Routing strict source routing Non-Storing
Mode P-Routes along the main DODAG, which is the same as Profile 1
but using NSM VIOs NSM-VIOs as opposed to SM VIOs. SM-VIOs. Profile 2 provides the
same capability to compress the SRH in packets down the main DODAG
as Profile 1, but it requires an encapsulation, encapsulation in order to insert
an additional SRH between the loose source routing hops. In that
case, With
Profile 2, the Tracks MUST be installed as subTracks of the main
DODAG, and the main Instance MUST be used as the TrackID. Note
that the Ingress node encapsulates but is not the Root, as it does
not own the DODAGID.
Profile 3 3:
In order to form the best path possible, this Profile profile requires the
support of Sibling Information Option an SIO to inform the Root of additional possible hops.
Profile 3 extends Profile 1 with additional Storing Mode P-Routes
that install segments that do not follow the main DODAG. If the
segment Ingress (in the SM-
VIO) SM-VIO) is the same as the IPv6 Address address of
the Track Ingress (in the
projected Projected DAO base Base Object), the P-DAO
creates an implicit Track between the segment Ingress and the
segment Egress.
Profile 4 4:
Profile 4 extends Profile 2 with Strict Source-Routing strict source routing Non-Storing
Mode P-Routes to form forward Tracks that are inside the main
DODAG but do not necessarily follow it. A Track is formed as one
or more strict source routed source-routed paths between the Root that is the
Track Ingress, Ingress and the Track Egress that is the last node.
Profile 5 5:
Profile 5 Combines combines Profile 4 with Profile 1 and enables loose
source routing between the Ingress and the Egress of the Track.
As in Profile 1, Storing Mode P-Routes form the connections in the
loose source route.
Profile 6 6:
Profile 6 Combines combines Profile 4 with Profile 2 and also enables loose
source routing between the Ingress and the Egress of the Track.
Profile 7 7:
Profile 7 implements Profile 5 in a main DODAG that is operated in
Storing Mode as presented in Section 7.1. As in
Profile Profiles 1 and 2,
the TrackID is the RPLInstanceID of the main DODAG. Longest match
rules decide whether a packet is sent along the main DODAG or
rerouted in a track. Track.
Profile 8 8:
Profile 8 is offered in preparation of the RAW work, work and for use
cases where an arbitrary node in the network can afford the same
code complexity as the RPL Root in a traditional deployment. It
offers a full DODAG visibility to the Track
Ingress Ingress, as specified
in Section 7.2 7.2, in a Non-Storing Mode main DODAG.
Profile 9 9:
Profile 9 combines profiles Profiles 7 and 8, operating the Track as a full
DODAG within a Storing Mode main DODAG, using only the main DODAG
RPLInstanceID as the TrackID.
9. Backwards Compatibility
This specification can operate in a mixed network where some nodes
support it and some do not. There are restrictions, though. All
nodes that need to process a P-DAO MUST support this specification.
As discussed in Section 3.7.1, how the root knows the node
capabilities and whether they support this specification is are out of
scope.
This specification defines the 'D' flag in the RPL DODAG
Configuration Option option (see Section 4.1.7) to signal that the RPL nodes
can request the creation of Tracks. The requester may not know
whether the Track can effectively be constructed, and constructed or whether enough
nodes along the preferred paths support this specification.
Therefore, it makes sense to only set the 'D' flags in the DIO when
the conditions of for success are in place, in particular when all the
nodes that could be on the path of tracks the Tracks are upgraded.
10. Security Considerations
It is worth noting that with per [RPL], every node in the LLN is RPL-
aware RPL-aware
and can inject any RPL-based attack in the network. This
specification uses messages that are already present in RPL [RPL]
with optional secured versions. The same secured versions may be
used with this specification, and whatever security is deployed for a
given network also applies to the flows in this specification.
The LLN nodes depend on the RPL Root and the RANs for their operation. A
trust model is necessary to ensure that the right devices are acting
in these roles, avoiding sinkhole attacks (as is done in [RFC7416] section 7). Section 7 of
[RFC7416]). This trust model could be be, at a minimum minimum, based on a Layer-2 Secure
Layer 2 secure joining and the Link-Layer link-layer security. This is a generic
6LoWPAN requirement, requirement; see Req5.1 Req-5.1 in Appendix B.5 of [RFC8505].
In a general manner, the Security Considerations in [RPL], [RPL] and
[RFC7416] apply to this specification as well. The Link-Layer In particular, link-
layer security is needed in particular to prevent Denial-Of-Service attacks denial-of-service attacks,
whereby a rogue router creates a high churn in the RPL network by
constantly injecting forged P-DAO messages and using up all the
available storage in the attacked routers.
When applied to radio LLNs such as IEEE std Std 802.15.4, the lower-layer
frame protection can be leveraged with an appropriate join protocol.
6TiSCH defined [RFC9031] with the RPL Root acting as 6LBR. The join
protocol could be extended to provide additional key material for
pledge
pledges to 6LBR communication when additional end-to-end security is
desired beyond the hop-by-hop security from the lower layer.
With this specification, the Root MAY generate P-DAO messages but
other nodes MUST NOT do so. PDR messages MUST be sent to the Root.
This specification expects that the communication with the Root is
authenticated but does not enforce which method is used.
Additionally, the trust model could include a role validation (e.g.,
using a role-based authorization) to ensure that the node that claims
to be a RPL Root is entitled to do so. That trust should propagate
from Egress to Ingress in the case of a Storing Mode P-DAO.
This specification suggests some validation of the VIO to prevent
basic loops by avoiding that a node appears twice. But that is only
a minimal protection. Arguably, an attacker that can inject P-DAOs
can reroute any traffic and rapidly deplete critical resources such
as the spectrum and battery in the LLN rapidly. LLN.
11. IANA Considerations
11.1. RPL DODAG Configuration Option Flag
IANA is requested to assign has assigned a flag from in the "DODAG Configuration Option Flags for
MOP 0..6" [RFC9010] registry [RFC9008] under the heading "Routing Protocol for Low
Power and Lossy Networks (RPL)" registry group [IANA-RPL] as follows:
+---------------+------------------------------+-----------+
+============+==============================+===========+
| Bit Number | Capability Description | Reference |
+---------------+------------------------------+-----------+
+============+==============================+===========+
| 0 (suggested) | Projected Routes Support (D) | THIS RFC 9914 |
+---------------+------------------------------+-----------+
+------------+------------------------------+-----------+
Table 21: New DODAG Configuration Option Flag
IANA is requested to add [THIS RFC] has added this RFC as a an additional reference for MOP 7 in the
Mode
"Mode of Operation Operation" registry that is part of under the Routing "Routing Protocol for Low
Power and Lossy Networks (RPL) (RPL)" registry group [IANA-RPL].
11.2. Elective 6LoWPAN Routing Header Type
IANA is requested to update has updated the "Elective 6LoWPAN Routing Header Type" registry that was created for
[RFC8138] under the heading
"Elective 6LoWPAN Routing Header Type" in the "IPv6 Low Power Personal Area Network Parameters"
registry group [IANA-6LO] and
assign the following value:
+===============+=============+===========+ as follows:
+=======+=============+===========+
| Value | Description | Reference |
+===============+=============+===========+
+=======+=============+===========+
| 8 (Suggested) | P-RPI-6LoRH | THIS RFC 9914 |
+---------------+-------------+-----------+
+-------+-------------+-----------+
Table 22: New Elective 6LoWPAN
Routing Header Type
11.3. Critical 6LoWPAN Routing Header Type
IANA is requested to update has updated the "Critical 6LoWPAN Routing Header Type" registry that was created for
[RFC8138] under the heading
"Critical 6LoWPAN Routing Header Type" in the "IPv6 Low Power Personal Area Network Parameters"
registry group [IANA-6LO] and
assign the following value:
+===============+=============+===========+ as follows:
+=======+=============+===========+
| Value | Description | Reference |
+===============+=============+===========+
+=======+=============+===========+
| 8 (Suggested) | P-RPI-6LoRH | THIS RFC 9914 |
+---------------+-------------+-----------+
+-------+-------------+-----------+
Table 23: New Critical 6LoWPAN
Routing Header Type
11.4. Registry For The for RPL Option Flags
IANA is requested to create a registry for has created the 8-bit "RPL Option Flags" field, registry, for the 8-bit RPL
Option flags field as detailed in Figure 11, under the heading "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group
[IANA-RPL]. The bits are indexed from 0 (leftmost) to 7. Each bit
is tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Indication When Set when set
* Reference
Registration
The registration procedure is "Standards Action" Standards Action [RFC8126]. The
initial allocation is as indicated in Table 24:
+===============+======================+===========+
+============+======================+===========+
| Bit number Number | Indication When Set | Reference |
+===============+======================+===========+
+============+======================+===========+
| 0 | Down 'O' (O) | [RFC6553] |
+---------------+----------------------+-----------+
+------------+----------------------+-----------+
| 1 | Rank-Error (R) | [RFC6553] |
+---------------+----------------------+-----------+
+------------+----------------------+-----------+
| 2 | Forwarding-Error (F) | [RFC6553] |
+---------------+----------------------+-----------+
+------------+----------------------+-----------+
| 3 (Suggested) | Projected-Route (P) | THIS RFC 9914 |
+---------------+----------------------+-----------+
+------------+----------------------+-----------+
| 4..255 | Unassigned | |
+---------------+----------------------+-----------+
+------------+----------------------+-----------+
Table 24: Initial PDR Flags
11.5. RPL Control Codes
IANA is requested to update has updated the "RPL Control Codes" registry under the heading "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group
[IANA-RPL] as indicated in Table 25:
+==================+=============================+===========+
+======+=============================+===========+
| Code | Description | Reference |
+==================+=============================+===========+
+======+=============================+===========+
| 0x09 (Suggested) | Projected DAO Request (PDR) | THIS RFC 9914 |
+------------------+-----------------------------+-----------+
+------+-----------------------------+-----------+
| 0x0A (Suggested) | PDR-ACK | THIS RFC 9914 |
+------------------+-----------------------------+-----------+
+------+-----------------------------+-----------+
Table 25: New RPL Control Codes
11.6. RPL Control Message Options
IANA is requested to update has updated the "RPL Control Message Options" registry under the heading
"Routing Protocol for Low Power and Lossy Networks (RPL)" registry
group [IANA-RPL] as indicated in Table 26:
+==================+=============================+===========+
+=======+==================================+===========+
| Value | Meaning | Reference |
+==================+=============================+===========+
+=======+==================================+===========+
| 0x0E (Suggested) 0x0F | Stateful VIO (SM-VIO) | THIS RFC 9914 |
+------------------+-----------------------------+-----------+
+-------+----------------------------------+-----------+
| 0x0F (Suggested) 0x10 | Source-Routed VIO (NSM-VIO) | THIS RFC 9914 |
+------------------+-----------------------------+-----------+
+-------+----------------------------------+-----------+
| 0x10 (Suggested) 0x11 | Sibling Information option Option (SIO) | THIS RFC 9914 |
+------------------+-----------------------------+-----------+
+-------+----------------------------------+-----------+
Table 26: RPL Control Message Options
11.7. SubRegistry Registry for the Projected DAO Request Flags
IANA is requested to create a registry for has created the 8-bit "Projected DAO Request (PDR)" field (PDR) Flags" registry
under the heading "Routing Protocol for Low Power and Lossy Networks (RPL)"
registry group [IANA-RPL]. The bits are indexed from 0 (leftmost) to
7. Each bit is tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration
The registration procedure is "Standards Action" Standards Action [RFC8126]. The
initial allocation is as indicated in Table 27:
+============+========================================+===========+
| Bit number Number | Capability description Description | Reference |
+============+========================================+===========+
| 0 | PDR-ACK request (K) | THIS RFC 9914 |
+------------+----------------------------------------+-----------+
| 1 | Requested path should be redundant (R) | THIS RFC 9914 |
+------------+----------------------------------------+-----------+
| 2..255 | Unassigned | |
+------------+----------------------------------------+-----------+
Table 27: Initial PDR Flags
11.8. SubRegistry Registry for the PDR-ACK Flags
IANA is requested to create a registry for has created the 8-bit "PDR-ACK Flags"
field registry under the heading "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group
[IANA-RPL]. The bits are indexed from 0 (leftmost) to 7. Each bit
is tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration
The registration procedure is "Standards Action" Standards Action [RFC8126]. No At the
time of publication of this document, no bit is
currently has been assigned for the PDR-ACK Flags. in
this registry.
11.9. Registry for the PDR-ACK Acceptance Status Values
IANA is requested to create a registry for has created the 8-bit "PDR-ACK Acceptance Status Values" registry
under the heading "Routing Protocol for Low Power and Lossy Networks (RPL)"
registry group [IANA-RPL]. Each value is tracked with the following
qualities:
* Value
* Meaning
* Reference
the
The possible values are expressed as a 6-bit unsigned integer
(0..63). the The registration procedure is "Standards Action" Standards Action [RFC8126].
The (suggested) initial allocation is as indicated in Table 28:
+-------+------------------------+-----------+
+=======+========================+===========+
| Value | Meaning | Reference |
+-------+------------------------+-----------+
+=======+========================+===========+
| 0 | Unqualified Acceptance | THIS RFC 9914 |
+-------+------------------------+-----------+
| 1..63 | Unassigned | |
+-------+------------------------+-----------+
Table 28: Acceptance values Values of the PDR-ACK
Status
11.10. Registry for the PDR-ACK Rejection Status Values
IANA is requested to create a registry for has created the 6-bit "PDR-ACK Rejection Status Values" registry under
the heading "Routing Protocol for Low Power and Lossy Networks (RPL)"
registry group [IANA-RPL]. Each value is tracked with the following
qualities:
* Value
* Meaning
* Reference
the
The possible values are expressed as a 6-bit unsigned integer
(0..63). the The registration procedure is "Standards Action" Standards Action [RFC8126].
The (suggected) initial allocation is as indicated in Table 29:
+-------+-----------------------+-----------+
+=======+=======================+===========+
| Value | Meaning | Reference |
+-------+-----------------------+-----------+
+=======+=======================+===========+
| 0 | Unqualified Rejection | THIS RFC 9914 |
+-------+-----------------------+-----------+
| 1 | Transient Failure | THIS RFC 9914 |
+-------+-----------------------+-----------+
| 2..63 | Unassigned | |
+-------+-----------------------+-----------+
Table 29: Rejection values of the PDR-ACK Rejection Status Values
11.11. SubRegistry Registry for the Via Information Options Flags
IANA is requested to create a registry for has created the 8-bit "Via Information Options (VIO) Flags" field registry
under the heading "Routing Protocol for Low Power and Lossy Networks (RPL)"
registry group [IANA-RPL]. The bits are indexed from 0 (leftmost) to
7. Each bit is tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration
The registration procedure is "Standards Action" Standards Action [RFC8126]. No At the
time of publication of this document, no bit is
currently has been assigned for the VIO Flags, in
this registry (see more in Section 5.3. 5.3).
11.12. SubRegistry Registry for the Sibling Information Option Flags
IANA is requested to create a registry for has created the 5-bit "Sibling Information Option (SIO) Flags" field
registry under the heading "Routing Protocol for Low Power and Lossy Networks
(RPL)" registry group [IANA-RPL]. The bits are indexed from 0
(leftmost) to 4. Each bit is tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration
The registration procedure is "Standards Action" Standards Action [RFC8126]. The
initial allocation is as indicated in Table 30, 30 (see more in
Figure 17:
+===============+========================+===========+ 17):
+============+=========================================+===========+
| Bit number Number | Capability description Description | Reference |
+===============+========================+===========+
+============+=========================================+===========+
| 0 (Suggested) | "S" 'S' flag: Sibling in | THIS RFC |
| | same DODAG as Self self | RFC 9914 |
+---------------+------------------------+-----------+
+------------+-----------------------------------------+-----------+
| 1..4 | Unassigned | |
+---------------+------------------------+-----------+
+------------+-----------------------------------------+-----------+
Table 30: Initial SIO Flags
11.13. Destination Advertisement Object Flag
IANA is requested to update has updated the "Destination Advertisement Object (DAO) Flags" registry
registry, created in Section 20.11 of [RPL] [RPL], under the
heading "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group
[IANA-RPL] as indicated in Table 31, 31 (see more in Section 4.1.1:
+---------------+------------------------+-----------+ 4.1.1):
+============+========================+===========+
| Bit Number | Capability Description | Reference |
+---------------+------------------------+-----------+
+============+========================+===========+
| 2 (Suggested) | Projected DAO (P) | THIS RFC 9914 |
+---------------+------------------------+-----------+
+------------+------------------------+-----------+
Table 31: New Destination Advertisement Object
(DAO) Flag
11.14. Destination Advertisement Object Acknowledgment Flag
IANA is requested to update has updated the "Destination Advertisement Object (DAO)
Acknowledgment Flags" registry registry, created in Section 20.12 of
[RPL] [RPL],
under the heading "Routing Protocol for Low Power and Lossy Networks (RPL)"
registry group [IANA-RPL] as indicated in Table 32, 32 (see more in
Section 4.1.2:
+---------------+------------------------+-----------+ 4.1.2):
+============+========================+===========+
| Bit Number | Capability Description | Reference |
+---------------+------------------------+-----------+
+============+========================+===========+
| 1 (Suggested) | Projected DAO-ACK (P) | THIS RFC 9914 |
+---------------+------------------------+-----------+
+------------+------------------------+-----------+
Table 32: New Destination Advertisement Object
Acknowledgment Flag
11.15. New ICMPv6 Error Code
In some cases cases, RPL will return an ICMPv6 error message when a message
cannot be forwarded along a P-Route.
This specification requires that a new code is allocated from
Per this specification, IANA has updated the
'ICMPv6 "Code" Fields' heading of "Type 1 - Destination
Unreachable" registry, in the "ICMPv6 'Code' Fields" registry, under
the "Internet Control Message Protocol version 6 (ICMPv6) Parameters"
registry group [IANA-ICMP] Registry for
"Type 1 - Destination Unreachable", with a suggested code value of 9,
to be confirmed by IANA to indicate an "Error as indicated in Table 33.
+======+==================+===========+
| Code | Name | Reference |
+======+==================+===========+
| 9 | Error in P-Route". P-Route | RFC 9914 |
+------+------------------+-----------+
Table 33: New ICMPv6 Error Code
11.16. RPL Rejection Status values Values
IANA is requested to update has updated the "RPL Rejection Status" registry under the heading
"Routing Protocol for Low Power and Lossy Networks (RPL)" registry
group [IANA-RPL] as indicated in Table 33:
+---------------+-------------------------+-----------+ 34:
+=======+=========================+===========+
| Value | Meaning | Reference |
+---------------+-------------------------+-----------+
+=======+=========================+===========+
| 2 (Suggested) | Out of Resources | THIS RFC 9914 |
+---------------+-------------------------+-----------+
+-------+-------------------------+-----------+
| 3 (Suggested) | Error in VIO | THIS RFC 9914 |
+---------------+-------------------------+-----------+
+-------+-------------------------+-----------+
| 4 (Suggested) | Predecessor Unreachable | THIS RFC 9914 |
+---------------+-------------------------+-----------+
+-------+-------------------------+-----------+
| 5 (Suggested) | Unreachable Target | THIS RFC 9914 |
+---------------+-------------------------+-----------+
+-------+-------------------------+-----------+
| 6..63 | Unassigned | |
+---------------+-------------------------+-----------+
+-------+-------------------------+-----------+
Table 33: Rejection values of the 34: RPL Rejection Status Values
12. Acknowledgments
The authors wish to acknowledge JP Vasseur, Remy Liubing, James
Pylakutty, and Patrick Wetterwald for their contributions to the
ideas developed here. Many thanks to Dominique Barthel and SVR Anand
for their global contribution to 6TiSCH, RAW and this RFC, as well as
text suggestions that were incorporated. Also special thanks to
Remous-Aris Koutsiamanis, Li Zhao, Dominique Barthel, and Toerless
Eckert for their in-depth reviews, with many excellent suggestions
that improved the readability and well as the content of the
specification. Many thanks to Remous-Aris Koutsiamanis for his
review during WGLC and to Ines Robles for her shepherding and
thorough review. Many thanks to Warren Kumari, Ran Chen, Murray
Kucherawy, Roman Danyliw, Klaas Wierenga, Deb Cooley, Eric Vyncke,
Gunter Van de Velde, Sue Hares and John Scudder for their comments
and suggestions during the IETF last call and IESG review cycle.
13. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<https://www.rfc-editor.org/info/rfc6282>.
[RPL] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<https://www.rfc-editor.org/info/rfc6553>.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554,
DOI 10.17487/RFC6554, March 2012,
<https://www.rfc-editor.org/info/rfc6554>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
"IPv6 over Low-Power Wireless Personal Area Network
(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
April 2017, <https://www.rfc-editor.org/info/rfc8138>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9008] Robles, M.I., Richardson, M., and P. Thubert, "Using RPI
Option Type, Routing Header for Source Routes, and IPv6-
in-IPv6 Encapsulation in the RPL Data Plane", RFC 9008,
DOI 10.17487/RFC9008, April 2021,
<https://www.rfc-editor.org/info/rfc9008>.
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>.
[RAW-ARCHI]
[RAW-ARCH] Thubert, P., Ed., "Reliable and Available Wireless (RAW)
Architecture", Work in Progress, Internet-Draft, draft-
ietf-raw-architecture-24, 25 RFC 9912, DOI 10.17487/RFC9912, February 2025,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-raw-architecture/>.
14.
2026, <https://www.rfc-editor.org/info/rfc9912>.
12.2. Informative References
[INT-ARCHI]
[INT-ARCH] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[6LoWPAN] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<https://www.rfc-editor.org/info/rfc4944>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and
J. Martocci, "Reactive Discovery of Point-to-Point Routes
in Low-Power and Lossy Networks", RFC 6997,
DOI 10.17487/RFC6997, August 2013,
<https://www.rfc-editor.org/info/rfc6997>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/info/rfc7102>.
[RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A.,
and M. Richardson, Ed., "A Security Threat Analysis for
the Routing Protocol for Low-Power and Lossy Networks
(RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
<https://www.rfc-editor.org/info/rfc7416>.
[RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Paging Dispatch",
RFC 8025, DOI 10.17487/RFC8025, November 2016,
<https://www.rfc-editor.org/info/rfc8025>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8930] Watteyne, T., Ed., Thubert, P., Ed., and C. Bormann, "On
Forwarding 6LoWPAN Fragments over a Multi-Hop IPv6
Network", RFC 8930, DOI 10.17487/RFC8930, November 2020,
<https://www.rfc-editor.org/info/rfc8930>.
[RFC8931] Thubert, P., Ed., "IPv6 over Low-Power Wireless Personal
Area Network (6LoWPAN) Selective Fragment Recovery",
RFC 8931, DOI 10.17487/RFC8931, November 2020,
<https://www.rfc-editor.org/info/rfc8931>.
[RFC8994] Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
Autonomic Control Plane (ACP)", RFC 8994,
DOI 10.17487/RFC8994, May 2021,
<https://www.rfc-editor.org/info/rfc8994>.
[RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL
(Routing Protocol for Low-Power and Lossy Networks)
Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021,
<https://www.rfc-editor.org/info/rfc9010>.
[RFC9031] Vučinić, M., Ed., Simon, J., Pister, K., and M.
Richardson, "Constrained Join Protocol (CoJP) for 6TiSCH",
RFC 9031, DOI 10.17487/RFC9031, May 2021,
<https://www.rfc-editor.org/info/rfc9031>.
[RFC9035] Thubert, P., Ed. and L. Zhao, "A Routing Protocol for Low-
Power and Lossy Networks (RPL) Destination-Oriented
Directed Acyclic Graph (DODAG) Configuration Option for
the 6LoWPAN Routing Header", RFC 9035,
DOI 10.17487/RFC9035, April 2021,
<https://www.rfc-editor.org/info/rfc9035>.
[RFC9450] Bernardos, CJ., Ed., Papadopoulos, G., Thubert, P., and F.
Theoleyre, "Reliable and Available Wireless (RAW) Use
Cases", RFC 9450, DOI 10.17487/RFC9450, August 2023,
<https://www.rfc-editor.org/info/rfc9450>.
[I-D.kuehlewind-update-tag]
[RFC9473] Enghardt, R. and C. Krähenbühl, "A Vocabulary of Path
Properties", RFC 9473, DOI 10.17487/RFC9473, September
2023, <https://www.rfc-editor.org/info/rfc9473>.
[NEW-TAGS] Kühlewind, M. and S. Krishnan, "Definition of new tags for
relations between RFCs", Work in Progress, Internet-Draft,
draft-kuehlewind-update-tag-04, 12
draft-kuehlewind-rswg-updates-tag-02, 8 July 2021, 2024,
<https://datatracker.ietf.org/doc/html/draft-kuehlewind-
update-tag-04>.
[I-D.irtf-panrg-path-properties]
Enghardt, R. and C. Krähenbühl, "A Vocabulary of Path
Properties", Work in Progress, Internet-Draft, draft-irtf-
panrg-path-properties-08, 6 March 2023,
<https://datatracker.ietf.org/doc/html/draft-irtf-panrg-
path-properties-08>.
rswg-updates-tag-02>.
[IANA-6LO] IETF, IANA, "IPv6 Low Power Personal Area Network Parameters
registry",
<https://www.iana.org/assignments/icmpv6-parameters/>. Parameters",
<https://www.iana.org/assignments/_6lowpan-parameters>.
[IANA-RPL] IETF, IANA, "Routing Protocol for Low Power and Lossy Networks
(RPL) registry group",
(RPL)", <https://www.iana.org/assignments/rpl/>.
[IANA-ICMP]
IETF,
IANA, "Internet Control Message Protocol version 6
(ICMPv6) Parameters registry group", Parameters",
<https://www.iana.org/assignments/icmpv6-parameters/>.
Acknowledgments
The authors wish to acknowledge JP. Vasseur, Remy Liubing, James
Pylakutty, and Patrick Wetterwald for their contributions to the
ideas developed here. Many thanks to Dominique Barthel and
S.V.R. Anand for their global contribution to 6TiSCH, RAW, and this
RFC, as well as text suggestions that were incorporated. Also,
special thanks to Remous-Aris Koutsiamanis, Li Zhao, Dominique
Barthel, and Toerless Eckert for their in-depth reviews, with many
excellent suggestions that improved the readability and the content
of the specification. Many thanks to Remous-Aris Koutsiamanis for
his review during WG Last Call and to Maria Ines Robles for her
thorough shepherd review. Many thanks to Warren Kumari, Ran Chen,
Murray Kucherawy, Roman Danyliw, Klaas Wierenga, Deb Cooley, Éric
Vyncke, Gunter Van de Velde, Sue Hares, and John Scudder for their
comments and suggestions during the IETF Last Call and IESG review
cycle.
Authors' Addresses
Pascal Thubert (editor)
06330 Roquefort-les-Pins
France
Email: pascal.thubert@gmail.com
Rahul Arvind Jadhav
AccuKnox
Kundalahalli Village, Whitefield, Whitefield
Bangalore 560037
Karnataka
India
Phone: +91-080-49160700
Email: rahul.ietf@gmail.com
Michael C. Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
URI: http://www.sandelman.ca/