< draft-ietf-roll-dao-projection-04.txt   draft-ietf-roll-dao-projection-05.txt >
ROLL P. Thubert, Ed. ROLL P. Thubert, Ed.
Internet-Draft Cisco Internet-Draft Cisco Systems
Intended status: Standards Track R. Jadhav Intended status: Standards Track R. Jadhav
Expires: December 21, 2018 Huawei Tech Expires: June 24, 2019 Huawei Tech
M. Gillmore
Itron
J. Pylakutty J. Pylakutty
Cisco Cisco
June 19, 2018 December 21, 2018
Root initiated routing state in RPL Root initiated routing state in RPL
draft-ietf-roll-dao-projection-04 draft-ietf-roll-dao-projection-05
Abstract Abstract
This document proposes a protocol extension to RPL that enables to This document proposes a protocol extension to RPL that enables to
install a limited amount of centrally-computed routes in a RPL graph, install a limited amount of centrally-computed routes in a RPL graph,
enabling loose source routing down a non-storing mode DODAG, or enabling loose source routing down a non-storing mode DODAG, or
transversal routes inside the DODAG. As opposed to the classical transversal routes inside the DODAG. As opposed to the classical
route injection in RPL that are injected by the end devices, this route injection in RPL that are injected by the end devices, this
draft enables the root of the DODAG to projects the routes that are draft enables the root of the DODAG to projects the routes that are
needed on the nodes where they should be installed. needed on the nodes where they should be installed.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 21, 2018. This Internet-Draft will expire on June 24, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. References . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Subset of a 6LoWPAN Glossary . . . . . . . . . . . . . . 4
2.3. Subset of a 6LoWPAN Glossary . . . . . . . . . . . . . . 4 2.3. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 4
2.4. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5 2.4. References . . . . . . . . . . . . . . . . . . . . . . . 5
3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 5 3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 5
4. New RPL Control Message Options . . . . . . . . . . . . . . . 5 3.1. RPL Instances . . . . . . . . . . . . . . . . . . . . . . 5
5. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. New RPL Control Message Options . . . . . . . . . . . . . 6
5.1. Non-storing Mode Projected Route . . . . . . . . . . . . 8 3.3. Projected DAO . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Storing-Mode Projected Route . . . . . . . . . . . . . . 9 3.3.1. Non-Storing Mode P-Route . . . . . . . . . . . . . . 8
6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11 3.3.2. Storing-Mode P-Route . . . . . . . . . . . . . . . . 10
6.1. Loose Source Routing in Non-storing Mode . . . . . . . . 11 4. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6.2. Transversal Routes in storing and non-storing modes . . . 13 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. RPL Instances . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1. New RPL Control Codes . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 5.2. Error in Projected Route ICMPv6 Code . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Normative References . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 16 7.2. Informative References . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . 17 Appendix A. Applications . . . . . . . . . . . . . . . . . . . . 15
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 18 A.1. Loose Source Routing in Non-storing Mode . . . . . . . . 15
A.1. Using storing mode P-DAO in non-storing mode MOP . . . . 18 A.2. Transversal Routes in storing and non-storing modes . . . 17
A.2. Projecting a storing-mode transversal route . . . . . . . 19 Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 B.1. Using storing mode P-DAO in non-storing mode MOP . . . . 19
B.2. Projecting a storing-mode transversal route . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
The "Routing Protocol for Low Power and Lossy Networks" [RFC6550] The "Routing Protocol for Low Power and Lossy Networks" [RFC6550]
(LLN)(RPL) is a generic Distance Vector protocol that is well suited (LLN)(RPL) is a generic Distance Vector protocol that is well suited
for application in a variety of low energy Internet of Things (IoT) low energy Internet of Things (IoT) networks. RPL forms Destination
networks. RPL forms Destination Oriented Directed Acyclic Graphs Oriented Directed Acyclic Graphs (DODAGs) in which the root often
(DODAGs) in which the root often acts as the Border Router to connect acts as the Border Router to connect the RPL domain to the Internet.
the RPL domain to the Internet. The root is responsible to select The root is responsible to select the RPL Instance that is used to
the RPL Instance that is used to forward a packet coming from the forward a packet coming from the Internet into the RPL domain and set
Internet into the RPL domain and set the related RPL information in the related RPL information in the packets.
the packets.
The 6TiSCH architecture [I-D.ietf-6tisch-architecture] leverages RPL The 6TiSCH architecture [I-D.ietf-6tisch-architecture] leverages RPL
for its routing operation and considers the Deterministic Networking for its routing operation and considers the Deterministic Networking
Architecture [I-D.ietf-detnet-architecture] as one possible model Architecture [I-D.ietf-detnet-architecture] as one possible model
whereby the device resources and capabilities are exposed to an whereby the device resources and capabilities are exposed to an
external controller which installs routing states into the network external controller which installs routing states into the network
based on some objective functions that reside in that external based on some objective functions that reside in that external
entity. entity.
Based on heuristics of usage, path length, and knowledge of device Based on heuristics of usage, path length, and knowledge of device
capacity and available resources such as battery levels and capacity and available resources such as battery levels and
reservable buffers, a Path Computation Element ([PCE]) with a global reservable buffers, a Path Computation Element ([PCE]) with a global
visibility on the system could install additional P2P routes that are visibility on the system could install additional P2P routes that are
more optimized for the current needs as expressed by the objective more optimized for the current needs as expressed by the objective
function. function.
This draft enables a RPL root to install and maintain projected This draft enables a RPL root to install and maintain projected
routes (P-routes) within its DODAG, along a selected set of nodes routes (P-Routes) within its DODAG, along a selected set of nodes
that may or may not include self, for a chosen duration. This that may or may not include self, for a chosen duration. This
potentially enables routes that are more optimized than those potentially enables routes that are more optimized than those
obtained with the distributed operation of RPL, either in terms of obtained with the distributed operation of RPL, either in terms of
the size of a source-route header or in terms of path length, which the size of a source-route header or in terms of path length, which
impacts both the latency and the packet delivery ratio. P-routes may impacts both the latency and the packet delivery ratio. P-routes may
be installed in either Storing and Non-Storing Modes Instances of the be installed in either Storing and Non-Storing Modes Instances of the
classical RPL operation, resulting in potentially hybrid situations classical RPL operation, resulting in potentially hybrid situations
where the mode of some P-routes is different from that of the other where the mode of some P-routes is different from that of the other
routes in the RPL Instance. routes in the RPL Instance.
Projected routes must be used with the parsimony to limit the amount P-Routes must be used with the parsimony to limit the amount of state
of state that is installed in each device to fit within its that is installed in each device to fit within its resources, and to
resources, and to limit the amount of rerouted traffic to fit within limit the amount of rerouted traffic to fit within the capabilities
the capabilities of the transmission links. The algorithm used to of the transmission links. The algorithm used to compute the paths
compute the paths and the protocol used to learn the topology of the and the protocol used to learn the topology of the network and the
network and the resources that are available in devices and in the resources that are available in devices and in the network are out of
network are out of scope for this document. Possibly with the scope for this document. Possibly with the assistance of a Path
assistance of a Path Computation Element ([PCE]) that could have a Computation Element ([PCE]) that could have a better visibility on
better visibility on the larger system, the root computes which the larger system, the root computes which segment could be optimized
segment could be optimized and uses this draft to install the and uses this draft to install the corresponding P-Routes.
corresponding projected routes.
2. Terminology 2. Terminology
2.1. BCP 14 2.1. BCP 14
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all 14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2.2. References 2.2. Subset of a 6LoWPAN Glossary
In this document, readers will encounter terms and concepts that are
discussed in the following documents:
o "Routing Protocol for Low Power and Lossy Networks" [RFC6550], and
o "Terminology in Low power And Lossy Networks" [RFC7102].
2.3. Subset of a 6LoWPAN Glossary
This document often uses the following acronyms: This document often uses the following acronyms:
6BBR: 6LoWPAN Backbone Router 6BBR: 6LoWPAN Backbone Router
6LBR: 6LoWPAN Border Router 6LBR: 6LoWPAN Border Router
6LN: 6LoWPAN Node 6LN: 6LoWPAN Node
6LR: 6LoWPAN Router 6LR: 6LoWPAN Router
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ND: Neighbor Discovery ND: Neighbor Discovery
NDP: Neighbor Discovery Protocol NDP: Neighbor Discovery Protocol
NS: Neighbor Solicitation NS: Neighbor Solicitation
RPL: IPv6 Routing Protocol for LLNs (pronounced ripple) [RFC6550] RPL: IPv6 Routing Protocol for LLNs (pronounced ripple) [RFC6550]
RA: Router Advertisement RA: Router Advertisement
RS: Router Solicitation RS: Router Solicitation
2.4. New Terms 2.3. New Terms
Projected Route: A route that is installed remotely by a RPL root. P-Route: A route that is installed remotely by a RPL root.
2.4. References
In this document, readers will encounter terms and concepts that are
discussed in the following documents:
o "Routing Protocol for Low Power and Lossy Networks" [RFC6550], and
o "Terminology in Low power And Lossy Networks" [RFC7102].
3. Extending RFC 6550 3. Extending RFC 6550
Section 6.7 of RPL [RFC6550] specifies Control Message Options (CMO) Section 6.7 of RPL [RFC6550] specifies Control Message Options (CMO)
to be placed in RPL messages such as the Destination Advertisement to be placed in RPL messages such as the Destination Advertisement
Object (DAO) message. The RPL Target Option and the Transit Object (DAO) message. The RPL Target Option and the Transit
Information Option (TIO) are such options; the former indicates a Information Option (TIO) are such options. In Non-Storing Mode, the
node to be reached and the latter specifies a parent that can be used TIO option is used in the DAO message to indicate the immediate
to reach that node. Options may be factorized; one or more parent of a given path. The TIO applies to the Target options that
contiguous TIOs apply to the one or more contiguous Target options immedially preceed it. Options may be factorized; multiple TIOs may
that immediately precede the TIOs in the RPL message. be present to indicate multiple routes to the one or more contiguous
addressed indicated in the Target Options that immediately precede
the TIOs in the RPL message.
This specification introduces 2 new Control Message Options referred This specification introduces two new Control Message Options
to as Route Projection Options (RPO). One RPO is the Information referred to as Route Projection Options (RPO). One RPO is the
option (VIO) and the other is the Source-Routed VIO (SRVIO). The VIO Information option (VIO) and the other is the Source-Routed VIO
installs a route on each hop along a projected route (in a fashion (SRVIO). The VIO installs a route on each hop along a P-Route (in a
analogous to RPL Storing Mode) whereas the SRVIO installs a source- fashion analogous to RPL Storing Mode) whereas the SRVIO installs a
routing state at the ingress node, which uses it to insert a routing source-routing state at the ingress node, which uses it to insert a
header in a fashion similar to Non-Storing Mode. routing header in a fashion similar to Non-Storing Mode.
Like the TIO, the RPOs MUST be preceded by one or more RPL Target Like the TIO, the RPOs MUST be preceded by one or more RPL Target
Options to which they apply, and they can be factorized: multiple Options to which they apply, and they can be factorized: multiple
contiguous RPOs indicate alternate paths to the target(s). contiguous RPOs indicate alternate paths to the target(s).
4. New RPL Control Message Options 3.1. RPL Instances
It must be noted that RPL has a concept of instance but does not have
a concept of an administrative distance, which exists in certain
proprietary implementations to sort out conflicts between multiple
sources of routing information. This draft conforms the instance
model as follows:
o If the PCE needs to influence a particular instance to add better
routes in conformance with the routing objectives in that
instance, it may do so. When the PCE modifies an existing
instance then the added routes must not create a loop in that
instance. This is achieved by always preferring a route obtained
from the PCE over a route that is learned via RPL.
o If the PCE installs a more specific (say, Traffic Engineered)
route between a particular pair of nodes then it SHOULD use a
Local Instance from the ingress node of that path. A packet
associated with that instance will be routed along that path and
MUST NOT be placed over a Global Instance again. A packet that is
placed on a Global Instance may be injected in the Local Instance
based on node policy and the Local Instance paramenters.
In all cases, the path is indicated by a new Via Information option,
and the flow is similar to the flow used to obtain loose source
routing.
3.2. New RPL Control Message Options
The format of RPOs is as follows: The format of RPOs is as follows:
0 1 2 3 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 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 | Path Sequence | Path Lifetime | | Type | Option Length | Path Sequence | Path Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
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. . . .
. Via Address n . . Via Address n .
. . . .
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Via Information option format Figure 1: Via Information option format
Option Type: 0x0A for VIO, 0x0B for SRVIO (to be confirmed by IANA) Option Type: 0x0A for VIO, 0x0B for SRVIO (to be confirmed by IANA)
Option Length: In bytes; variable, depending on the number of Via Option Length: In bytes; variable, depending on the number of Via
Addresses. Addresses.
Path Sequence: 8-bit unsigned integer. When a RPL Target option is Path Sequence: 8-bit unsigned integer. When a RPL Target option is
issued by the root of the DODAG (i.e. in a DAO message), that issued by the root of the DODAG (i.e. in a DAO message), that
root sets the Path Sequence and increments the Path Sequence root sets the Path Sequence and increments the Path Sequence
each time it issues a RPL Target option with updated each time it issues a RPL Target option with updated
information. The indicated sequence deprecates any state for a information. The indicated sequence deprecates any state for a
given Target that was learned from a previous sequence and adds given Target that was learned from a previous sequence and adds
to any state that was learned for that sequence. to any state that was learned for that sequence.
Path Lifetime: 8-bit unsigned integer. The length of time in Path Lifetime: 8-bit unsigned integer. The length of time in
Lifetime Units (obtained from the Configuration option) that Lifetime Units (obtained from the Configuration option) that
the prefix is valid for route determination. The period starts the prefix is valid for route determination. The period starts
when a new Path Sequence is seen. A value of all one bits when a new Path Sequence is seen. A value of 255 (0xFF)
(0xFF) represents infinity. A value of all zero bits (0x00) represents infinity. A value of zero (0x00) indicates a loss
indicates a loss of reachability. A DAO message that contains of reachability. A DAO message that contains a Via Information
a Via Information option with a Path Lifetime of 0x00 for a option with a Path Lifetime of zero for a Target is referred as
Target is referred as a No-Path (for that Target) in this a No-Path (for that Target) in this document.
document.
Via Address: 16 bytes. IPv6 Address of the next hop towards the Via Address: 16 bytes. IPv6 Address of the next hop towards the
destination(s) indicated in the target option that immediately destination(s) indicated in the target option that immediately
precede the RPO. Via Addresses are indicated in the order of precede the RPO. Via Addresses are indicated in the order of
the data path from the ingress to the egress nodes. TBD: See the data path from the ingress to the egress nodes.
how the /64 prefix can be elided if it is the same as that of
(all of) the target(s). In that case, the Next-Hop Address
could be expressed as the 8-bytes suffix only.
An RPO MUST contain at least one Via Address, and a Via Address MUST An RPO MUST contain at least one Via Address, and a Via Address MUST
NOT be present more than once, otherwise the RPO MUST be ignored. NOT be present more than once, otherwise the RPO MUST be ignored.
5. Projected DAO 3.3. Projected DAO
This draft adds a capability to RPL whereby the root of a DODAG This draft adds a capability to RPL whereby the root of a DODAG
projects a route by sending an extended DAO message called a projects a route by sending an extended DAO message called a
Projected-DAO (P-DAO) to an arbitrary router in the DODAG, indicating Projected-DAO (P-DAO) to an arbitrary router in the DODAG, indicating
one or more sequence(s) of routers inside the DODAG via which the one or more sequence(s) of routers inside the DODAG via which the
target(s) indicated in the Target Information Option(s) (TIO) can be target(s) indicated in the Target Information Option(s) (TIO) can be
reached. reached.
A P-DAO is sent from a global address of the root to a global address A P-DAO is sent from a global address of the root to a global address
of the recipient, and MUST be confirmed by a DAO-ACK, which is sent of the recipient, and MUST be confirmed by a DAO-ACK, which is sent
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A P-DAO message MUST contain at least one TIO and at least one RPO A P-DAO message MUST contain at least one TIO and at least one RPO
following it. There can be at most one such sequence of TIOs and following it. There can be at most one such sequence of TIOs and
then RPOs. then RPOs.
Like a classical DAO message, a P-DAO is processed only if it is Like a classical DAO message, a P-DAO is processed only if it is
"new" per section 9.2.2. "Generation of DAO Messages" of the RPL "new" per section 9.2.2. "Generation of DAO Messages" of the RPL
specification [RFC6550]; this is determined using the Path Sequence specification [RFC6550]; this is determined using the Path Sequence
information from the RPO as opposed to a TIO. Also, a Path Lifetime information from the RPO as opposed to a TIO. Also, a Path Lifetime
of 0 in an RPO indicates that a route is to be removed. of 0 in an RPO indicates that a route is to be removed.
There are two kinds of operation for the projected routes, the There are two kinds of operation for the P-Routes, the Storing Mode
Storing Mode and the Non-Storing Mode. and the Non-Storing Mode.
The Non-Storing Mode is discussed in section Section 5.1. It uses o The Non-Storing Mode is discussed in Section 3.3.1. It uses an
an SRVIO that carries a list of Via Addresses to be used as a SRVIO that carries a list of Via Addresses to be used as a source-
source-routed path to the target. The recipient of the P-DAO is routed path to the target. The recipient of the P-DAO is the
the ingress router of the source-routed path. Upon a Non-Storing ingress router of the source-routed path. Upon a Non-Storing Mode
Mode P-DAO, the ingress router installs a source-routed state to P-DAO, the ingress router installs a source-routed state to the
the target and replies to the root directly with a DAO-ACK target and replies to the root directly with a DAO-ACK message.
message.
The Storing Mode is discussed in section Section 5.2. It uses a o The Storing Mode is discussed in Section 3.3.2. It uses a VIO
VIO with one Via Address per consecutive hop, from the ingress to with one Via Address per consecutive hop, from the ingress to the
the egress of the path, including the list of all intermediate egress of the path, including the list of all intermediate routers
routers in the data path order. The Via Addresses indicate the in the data path order. The Via Addresses indicate the routers in
routers in which the routing state to the target have to be which the routing state to the target have to be installed via the
installed via the next Via Address in the VIO. In normal next Via Address in the VIO. In normal operations, the P-DAO is
operations, the P-DAO is propagated along the chain of Via Routers propagated along the chain of Via Routers from the egress router
from the egress router of the path till the ingress one, which of the path till the ingress one, which confirms the installation
confirms the installation to the root with a DAO-ACK message. to the root with a DAO-ACK message. Note that the root may be the
Note that the root may be the ingress and it may be the egress of ingress and it may be the egress of the path, that it can also be
the path, that it can also be neither but it cannot be both. neither but it cannot be both.
5.1. Non-storing Mode Projected Route In case of a forwarding error along a P-Route, an ICMP error is sent
to the root with a new Code "Error in Projected Route" (See
Section 5.2). The root can then modify or remove the P-Route. The
"Error in Projected Route" message has the same format as the
"Destination Unreachable Message", as specified in RFC 4443
[RFC4443]. The portion of the invoking packet that is sent back in
the ICMP message SHOULD record at least up to the routing header if
one is present, and the routing header 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)
[RFC8138] is used to carry the IPv6 routing information in the outter
header then that whole 6LoRH information SHOULD be present in the
ICMP message. The sender and exact operation depend on the Mode and
is described in Section 3.3.1 and Section 3.3.2 respectively.
3.3.1. Non-Storing Mode P-Route
As illustrated in Figure 2, a P-DAO that carries an SRVIO enables the As illustrated in Figure 2, a P-DAO that carries an SRVIO enables the
root to install a source-routed path towards a target in any root to install a source-routed path towards a target in any
particular router; with this path information the router can add a particular router; with this path information the router can add a
source routed header reflecting the P-route to any packet for which source routed header reflecting the P-route to any packet for which
the current destination either is the said target or can be reached the current destination either is the said target or can be reached
via the target. via the target.
------+--------- ------+---------
| Internet | Internet
skipping to change at page 9, line 6 skipping to change at page 9, line 34
Figure 2: Projecting a Non-Storing Route Figure 2: Projecting a Non-Storing Route
A route indicated by an SRVIO may be loose, meaning that the node A route indicated by an SRVIO may be loose, meaning that the node
that owns the next listed Via Address is not necessarily a neighbor. that owns the next listed Via Address is not necessarily a neighbor.
Without proper loop avoidance mechanisms, the interaction of loose Without proper loop avoidance mechanisms, the interaction of loose
source routing and other mechanisms may effectively cause loops. In source routing and other mechanisms may effectively cause loops. In
order to avoid those loops, if the router that installs a P-route order to avoid those loops, if the router that installs a P-route
does not have a connected route (a direct adjacency) to the next does not have a connected route (a direct adjacency) to the next
soure routed hop and fails to locate it as a neighbor or a neighbor soure routed hop and fails to locate it as a neighbor or a neighbor
of a neighbor, then it MUST ensure that it has another projected of a neighbor, then it MUST ensure that it has another P-Route to the
route to the next loose hop under the control of the same route next loose hop under the control of the same route computation
computation system, otherwise the P-DAO is rejected. system, otherwise the P-DAO is rejected.
When forwarding a packet to a destination for which the router When forwarding a packet to a destination for which the router
determines that routing happens via the target, the router inserts determines that routing happens via the target, the router inserts
the source routing header in the packet to reach the target. In the the source routing header in the packet to reach the target. In the
case of a loose source-routed path, there MUST be either a neighbor case of a loose source-routed path, there MUST be either a neighbor
that is adjacent to the loose next hop, on which case the packet s that is adjacent to the loose next hop, on which case the packet s
forwarded to that neighbor, or a source-routed path to the loose next forwarded to that neighbor, or a source-routed path to the loose next
hop; in the latter case, another encapsulation takes place and the hop; in the latter case, another encapsulation takes place and the
process possibly recurses; otherwise the packet is dropped. process possibly recurses; otherwise the packet is dropped.
In order to add a source-routing header, the router encapsulates the In order to add a source-routing header, the router encapsulates the
packet with an IP-in-IP header and a non-storing mode source routing packet with an IP-in-IP header and a non-storing mode source routing
header (SRH) [RFC6554]. header (SRH) [RFC6554]. In the uncompressed form the source of the
packet would be self, the destination would be the first Via Address
In the uncompressed form the source of the packet would be self, the in the SRVIO, and the SRH would contain the list of the remaining Via
destination would be the first Via Address in the SRVIO, and the SRH Addresses and then the target.
would contain the list of the remaining Via Addresses and then the
target.
In practice, the router will normally use the "IPv6 over Low-Power In practice, the router will normally use the "IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Paging Dispatch" [RFC8025] Wireless Personal Area Network (6LoWPAN) Paging Dispatch" [RFC8025]
to compress the RPL artifacts as indicated in the "6LoWPAN Routing to compress the RPL artifacts as indicated in the "6LoWPAN Routing
Header" [RFC8138] specification. In that case, the router indicates Header" [RFC8138] specification. In that case, the router indicates
self as encapsulator in an IP-in-IP 6LoRH Header, and places the list self as encapsulator in an IP-in-IP 6LoRH Header, and places the list
of Via Addresses in the order of the VIO and then the target in the of Via Addresses in the order of the VIO and then the target in the
SRH 6LoRH Header. SRH 6LoRH Header.
5.2. Storing-Mode Projected Route In case of a forwarding error along a Source Route path, the node
that fails to forward SHOULD send an ICMP error with a code "Error in
Source Routing Header" back to the source of the packet, as described
in section 11.2.2.3. of [RFC6550]. Upon this message, the
encapsulating node SHOULD stop using the source route path for a
period of time and it SHOULD send an ICMP message with a Code "Error
in Projected 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.
3.3.2. Storing-Mode P-Route
As illustrated in Figure 3, the Storing Mode projected iq used by the As illustrated in Figure 3, the Storing Mode projected iq used by the
root to install a routing state towards a target in the routers along root to install a routing state towards a target in the routers along
a segment between an ingress and an egress router; this enables the a segment between an ingress and an egress router; this enables the
routers to forward along that segment any packet for which the next routers to forward along that segment any packet for which the next
loose hop is the said target, for instance a loose source routed loose hop is the said target, for instance a loose source routed
packet for which the next loose hop is the target, or a packet for packet for which the next loose hop is the target, or a packet for
which the router has a routing state to the final destination via the which the router has a routing state to the final destination via the
target. target.
skipping to change at page 10, line 43 skipping to change at page 11, line 24
The root sends the P-DAO directly to the egress node of the segment. The root sends the P-DAO directly to the egress node of the segment.
In that P-DAO, the destination IP address matches the Via Address in In that P-DAO, the destination IP address matches the Via Address in
the last VIO. This is how the egress recognizes its role. In a the last VIO. This is how the egress recognizes its role. In a
similar fashion, the ingress node recognizes its role as it matches similar fashion, the ingress node recognizes its role as it matches
Via Address in the first VIO. Via Address in the first VIO.
The egress node of the segment is the only node in the path that does 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 not install a route in response to the P-DAO; it is expected to be
already able to route to the target(s) on its own. It may either be already able to route to the target(s) on its own. It may either be
the target, or may have some existing information to reach the the target, or may have some existing information to reach the
target(s), such as a connected route or an already installed target(s), such as a connected route or an already installed P-Route.
projected route. If one of the targets cannot be located, the node If one of the targets cannot be located, the node MUST answer to the
MUST answer to the root with a negative DAO-ACK listing the target(s) root with a negative DAO-ACK listing the target(s) that could not be
that could not be located (suggested status 10 to be confirmed by located (suggested status 10 to be confirmed by IANA).
IANA).
If the egress node can reach all the targets, then it forwards the If the egress node can reach all the targets, then it forwards the
P-DAO with unchanged content to its loose predecessor in the segment P-DAO with unchanged content to its loose predecessor in the segment
as indicated in the list of Via Information options, and recursively as indicated in the list of Via Information options, and recursively
the message is propagated unchanged along the sequence of routers the message is propagated unchanged along the sequence of routers
indicated in the P-DAO, but in the reverse order, from egress to indicated in the P-DAO, but in the reverse order, from egress to
ingress. ingress.
The address of the predecessor to be used as destination of the The address of the predecessor to be used as destination of the
propagated DAO message is found in the Via Information option the propagated DAO message is found in the Via Information option the
skipping to change at page 11, line 43 skipping to change at page 12, line 23
router in the P-DAO, the router MUST answer to the root with a router in the P-DAO, the router MUST answer to the root with a
negative DAO-ACK indicating the successor that is unreachable negative DAO-ACK indicating the successor that is unreachable
(suggested status 11 to be confirmed by IANA). (suggested status 11 to be confirmed by IANA).
A Path Lifetime of 0 in a Via Information option is used to clean up A Path Lifetime of 0 in a Via Information option is used to clean up
the state. The P-DAO is forwarded as described above, but the DAO is the state. The P-DAO is forwarded as described above, but the DAO is
interpreted as a No-Path DAO and results in cleaning up existing interpreted as a No-Path DAO and results in cleaning up existing
state as opposed to refreshing an existing one or installing a new state as opposed to refreshing an existing one or installing a new
one. one.
6. Applications In case of a forwarding error along a Storing Mode P-Route, the node
that fails to forward SHOULD send an ICMP error with a code "Error in
Projected Route" to the root. Failure to do so may result in packet
loss and wasted resources along the P-Route that is broken.
6.1. Loose Source Routing in Non-storing Mode 4. Security Considerations
This draft uses messages that are already present in RPL [RFC6550]
with optional secured versions. The same secured versions may be
used with this draft, and whatever security is deployed for a given
network also applies to the flows in this draft.
TODO: should probably consider how P-DAO messages could be abused by
a) rogue nodes b) via replay of messages c) if use of P-DAO messages
could in fact deal with any threats?
5. IANA Considerations
5.1. New RPL Control Codes
This document extends the IANA registry created by RFC 6550 for RPL
Control Codes as follows:
+------+-------------------+---------------+
| Code | Description | Reference |
+------+-------------------+---------------+
| 0x0A | Via | This document |
| | | |
| 0x0B | Source-Routed Via | This document |
+------+-------------------+---------------+
RPL Control Codes
This document is updating the registry created by RFC 6550 for the
RPL 3-bit Mode of Operation (MOP) as follows:
+-----------+----------------------------------------+--------------+
| MOP value | Description | Reference |
+-----------+----------------------------------------+--------------+
| 5 | Non-Storing mode of operation with | This |
| | P-Routes | document |
| | | |
| 6 | Storing mode of operation with | This |
| | P-Routes | document |
+-----------+----------------------------------------+--------------+
DIO Mode of operation
5.2. Error in Projected Route ICMPv6 Code
In some cases RPL will return an ICMPv6 error message when a message
cannot be forwarded along a P-Route. This ICMPv6 error message is
"Error in Projected Route".
IANA has defined an ICMPv6 "Code" Fields Registry for ICMPv6 Message
Types. ICMPv6 Message Type 1 describes "Destination Unreachable"
codes. This specification requires that a new code is allocated from
the ICMPv6 Code Fields Registry for ICMPv6 Message Type 1, for "Error
in Projected Route", with a suggested code value of 8, to be
confirmed by IANA.
6. Acknowledgments
The authors wish to acknowledge JP Vasseur and Patrick Wetterwald for
their contributions to the ideas developed here.
7. References
7.1. 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>.
[RFC6550] 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>.
[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>.
[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>.
7.2. Informative References
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-19 (work
in progress), December 2018.
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-10 (work in progress), December 2018.
[PCE] IETF, "Path Computation Element",
<https://datatracker.ietf.org/doc/charter-ietf-pce/>.
[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>.
Appendix A. Applications
A.1. Loose Source Routing in Non-storing Mode
A RPL implementation operating in a very constrained LLN typically A RPL implementation operating in a very constrained LLN typically
uses the Non-Storing Mode of Operation as represented in Figure 4. uses the Non-Storing Mode of Operation as represented in Figure 4.
In that mode, a RPL node indicates a parent-child relationship to the In that mode, a RPL node indicates a parent-child relationship to the
root, using a Destination Advertisement Object (DAO) that is unicast root, using a Destination Advertisement Object (DAO) that is unicast
from the node directly to the root, and the root typically builds a from the node directly to the root, and the root typically builds a
source routed path to a destination down the DODAG by recursively source routed path to a destination down the DODAG by recursively
concatenating this information. concatenating this information.
------+--------- ------+---------
skipping to change at page 13, line 18 skipping to change at page 17, line 16
This specification enables to store source-routed or storing mode This specification enables to store source-routed or storing mode
state in intermediate routers, which enables to limit the excursion state in intermediate routers, which enables to limit the excursion
of the source route headers in deep networks. Once a P-DAO exchange of the source route headers in deep networks. Once a P-DAO exchange
has taken place for a given target, if the root operates in non has taken place for a given target, if the root operates in non
storing mode, then it may elide the sequence of routers that is storing mode, then it may elide the sequence of routers that is
installed in the network from its source route headers to destination installed in the network from its source route headers to destination
that are reachable via that target, and the source route headers that are reachable via that target, and the source route headers
effectively become loose. effectively become loose.
6.2. Transversal Routes in storing and non-storing modes A.2. Transversal Routes in storing and non-storing modes
RPL is optimized for Point-to-Multipoint (P2MP), root to leaves and RPL is optimized for Point-to-Multipoint (P2MP) and Multipoint-to-
Multipoint-to-Point (MP2P) leaves to root operations, whereby routes Point (MP2P), whereby routes are always installed along the RPL DODAG
are always installed along the RPL DODAG. Transversal Peer to Peer respectively from and towards the DODAG Root. Transversal Peer to
(P2P) routes in a RPL network will generally suffer from some stretch Peer (P2P) routes in a RPL network will generally suffer from some
since routing between 2 peers always happens via a common parent, as elongated (stretched) path versus the best possible path, since
routing between 2 nodes always happens via a common parent, as
illustrated in Figure 5: illustrated in Figure 5:
o in non-storing mode, all packets routed within the DODAG flow all o 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 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 a same DODAG, the root must encapsulate the packet to place a
Routing Header that has the strict source route information down Routing Header that has the strict source route information down
the DODAG to the destination. This will be the case even if the the DODAG to the destination. This will be the case even if the
destination is relatively close to the source and the root is destination is relatively close to the source and the root is
relatively far off. relatively far off.
skipping to change at page 15, line 10 skipping to change at page 19, line 10
This specification enables to store source-routed or storing mode This specification enables to store source-routed or storing mode
state in intermediate routers, which enables to limit the stretch of state in intermediate routers, which enables to limit the stretch of
a P2P route and maintain the characteristics within a given SLA. An a P2P route and maintain the characteristics within a given SLA. An
example of service using this mechanism oculd be a control loop that example of service using this mechanism oculd be a control loop that
would be installed in a network that uses classical RPL for would be installed in a network that uses classical RPL for
asynchronous data collection. In that case, the P2P path may be asynchronous data collection. In that case, the P2P path may be
installed in a different RPL Instance, with a different objective installed in a different RPL Instance, with a different objective
function. function.
7. RPL Instances Appendix B. Examples
It must be noted that RPL has a concept of instance but does not have
a concept of an administrative distance, which exists in certain
proprietary implementations to sort out conflicts between multiple
sources of routing information. This draft conforms the instance
model as follows:
o If the PCE needs to influence a particular instance to add better
routes in conformance with the routing objectives in that
instance, it may do so. When the PCE modifies an existing
instance then the added routes must not create a loop in that
instance. This is achieved by always preferring a route obtained
from the PCE over a route that is learned via RPL.
o If the PCE installs a more specific (say, Traffic Engineered)
route between a particular pair of nodes then it SHOULD use a
Local Instance from the ingress node of that path. A packet
associated with that instance will be routed along that path and
MUST NOT be placed over a Global Instance again. A packet that is
placed on a Global Instance may be injected in the Local Instance
based on node policy and the Local Instance paramenters.
In all cases, the path is indicated by a new Via Information option,
and the flow is similar to the flow used to obtain loose source
routing.
8. Security Considerations
This draft uses messages that are already present in RPL [RFC6550]
with optional secured versions. The same secured versions may be
used with this draft, and whatever security is deployed for a given
network also applies to the flows in this draft.
9. IANA Considerations
This document extends the IANA registry created by RFC 6550 for RPL
Control Codes as follows:
+------+-------------------+---------------+
| Code | Description | Reference |
+------+-------------------+---------------+
| 0x0A | Via | This document |
| | | |
| 0x0B | Source-Routed Via | This document |
+------+-------------------+---------------+
RPL Control Codes
This document is updating the registry created by RFC 6550 for the
RPL 3-bit Mode of Operation (MOP) as follows:
+----------+------------------------------------------+-------------+
| MOP | Description | Reference |
| value | | |
+----------+------------------------------------------+-------------+
| 5 | Non-Storing mode of operation with | This |
| | Projected routes | document |
| | | |
| 6 | Storing mode of operation with Projected | This |
| | routes | document |
+----------+------------------------------------------+-------------+
DIO Mode of operation
10. Acknowledgments
The authors wish to acknowledge JP Vasseur and Patrick Wetterwald for
their contributions to the ideas developed here.
11. References
11.1. 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>.
[RFC6550] 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>.
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551,
DOI 10.17487/RFC6551, March 2012,
<https://www.rfc-editor.org/info/rfc6551>.
[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>.
[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>.
[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>.
11.2. Informative References
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-14 (work
in progress), April 2018.
[I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf-
detnet-architecture-05 (work in progress), May 2018.
[PCE] IETF, "Path Computation Element",
<https://datatracker.ietf.org/doc/charter-ietf-pce/>.
[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>.
Appendix A. Examples
A.1. Using storing mode P-DAO in non-storing mode MOP B.1. Using storing mode P-DAO in non-storing mode MOP
In non-storing mode, the DAG root maintains the knowledge of the In non-storing mode, the DAG root maintains the knowledge of the
whole DODAG topology, so when both the source and the destination of whole DODAG topology, so when both the source and the destination of
a packet are in the DODAG, the root can determine the common parent a packet are in the DODAG, the root can determine the common parent
that would have been used in storing mode, and thus the list of nodes that would have been used in storing mode, and thus the list of nodes
in the path between the common parent and the destination. For in the path between the common parent and the destination. For
instance in the diagram shown in Figure 7, if the source is node 41 instance in the diagram shown in Figure 7, if the source is node 41
and the destination is node 52, then the common parent is node 22. and the destination is node 52, then the common parent is node 22.
------+--------- ------+---------
skipping to change at page 19, line 15 skipping to change at page 20, line 19
DAO to node 46 indicating target 56 and a Via segment (35, 46). This DAO to node 46 indicating target 56 and a Via segment (35, 46). This
will save one entry in the routing header on both sides. The root will save one entry in the routing header on both sides. The root
may then send a DAO to node 35 indicating targets 55 and 56 a Via may then send a DAO to node 35 indicating targets 55 and 56 a Via
segment (13, 24, 35) to fully optimize that path. segment (13, 24, 35) to fully optimize that path.
Alternatively, the root may send a DAO to node 45 indicating target Alternatively, the root may send a DAO to node 45 indicating target
55 and a Via segment (13, 24, 35, 45) and then a DAO to node 46 55 and a Via segment (13, 24, 35, 45) and then a DAO to node 46
indicating target 56 and a Via segment (13, 24, 35, 46), indicating indicating target 56 and a Via segment (13, 24, 35, 46), indicating
the same DAO Sequence. the same DAO Sequence.
A.2. Projecting a storing-mode transversal route B.2. Projecting a storing-mode transversal route
In this example, say that a PCE determines that a path must be In this example, say that a PCE determines that a path must be
installed between node S and node D via routers A, B and C, in order installed between node S and node D via routers A, B and C, in order
to serve the needs of a particular application. to serve the needs of a particular application.
The root sends a P-DAO with a target option indicating the The root sends a P-DAO with a target option indicating the
destination D and a sequence Via Information option, one for S, which destination D and a sequence Via Information option, one for S, which
is the ingress router of the segment, one for A and then for B, which is the ingress router of the segment, one for A and then for B, which
are an intermediate routers, and one for C, which is the egress are an intermediate routers, and one for C, which is the egress
router. router.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
| | Border Router | | Border Router
| | (RPL Root) | | (RPL Root)
+-----+ +-----+
| Projected DAO message to C | P-DAO message to C
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 o o | o o o o o o
o o V o o o o o o o o V o o o o o o
S A B C D o o o S A B C D o o o
o o o o o o o o
LLN LLN
Figure 8: Projected DAO from root Figure 8: P-DAO from root
Upon reception of the P-DAO, C validates that it can reach D, e.g. Upon reception of the P-DAO, C validates that it can reach D, e.g.
using IPv6 Neighbor Discovery, and if so, propagates the P-DAO using IPv6 Neighbor Discovery, and if so, propagates the P-DAO
unchanged to B. unchanged to B.
B checks that it can reach C and of so, installs a route towards D B checks that it can reach C and of so, installs a route towards D
via C. Then it propagates the P-DAO to A. via C. Then it propagates the P-DAO to A.
The process recurses till the P-DAO reaches S, the ingress of the The process recurses till the P-DAO reaches S, the ingress of the
segment, which installs a route to D via A and sends a DAO-ACK to the segment, which installs a route to D via A and sends a DAO-ACK to the
root. root.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
| | Border Router | | Border Router
| | (RPL Root) | | (RPL Root)
+-----+ +-----+
^ Projected DAO-ACK from S ^ P-DAO-ACK from S
/ 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 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 S A B C D o o o
o o o o o o o o
LLN LLN
Figure 9: Projected DAO-ACK to root Figure 9: P-DAO-ACK to root
As a result, a transversal route is installed that does not need to As a result, a transversal route is installed that does not need to
follow the DODAG structure. follow the DODAG structure.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
| | Border Router | | Border Router
| | (RPL Root) | | (RPL Root)
skipping to change at page 21, line 4 skipping to change at page 22, line 6
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 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 S>>A>>>B>>C>>>D o o o
o o o o o o o o
LLN LLN
Figure 10: Projected Transversal Route Figure 10: Projected Transversal Route
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems Cisco Systems
Village d'Entreprises Green Side Village d'Entreprises Green Side
400, Avenue de Roumanille 400, Avenue de Roumanille
Batiment T3 Batiment T3
Biot - Sophia Antipolis 06410 Biot - Sophia Antipolis 06410
FRANCE FRANCE
Phone: +33 4 97 23 26 34 Phone: +33 4 97 23 26 34
Email: pthubert@cisco.com Email: pthubert@cisco.com
Rahul Arvind Jadhav Rahul Arvind Jadhav
Huawei Tech Huawei Tech
Kundalahalli Village, Whitefield, Kundalahalli Village, Whitefield,
Bangalore, Karnataka 560037 Bangalore, Karnataka 560037
India India
Phone: +91-080-49160700 Phone: +91-080-49160700
Email: rahul.ietf@gmail.com Email: rahul.ietf@gmail.com
Matthew Gillmore
Itron, Inc
Building D
2111 N Molter Road
Liberty Lake 99019
United States
Phone: +1.800.635.5461
Email: matthew.gillmore@itron.com
James Pylakutty James Pylakutty
Cisco Systems Cisco Systems
Cessna Business Park Cessna Business Park
Kadubeesanahalli Kadubeesanahalli
Marathalli ORR Marathalli ORR
Bangalore, Karnataka 560087 Bangalore, Karnataka 560087
INDIA INDIA
Phone: +91 80 4426 4140 Phone: +91 80 4426 4140
Email: mundenma@cisco.com Email: mundenma@cisco.com
 End of changes. 42 change blocks. 
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