< draft-ietf-roll-dao-projection-03.txt   draft-ietf-roll-dao-projection-04.txt >
ROLL P. Thubert, Ed. ROLL P. Thubert, Ed.
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track R. Jadhav, Ed. Intended status: Standards Track R. Jadhav
Expires: September 20, 2018 Huawei Tech Expires: December 21, 2018 Huawei Tech
J. Pylakutty J. Pylakutty
Cisco Cisco
March 19, 2018 June 19, 2018
Root initiated routing state in RPL Root initiated routing state in RPL
draft-ietf-roll-dao-projection-03 draft-ietf-roll-dao-projection-04
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 September 20, 2018. This Internet-Draft will expire on December 21, 2018.
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.
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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
3. New RPL Control Message Options . . . . . . . . . . . . . . . 3 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Via Information Option . . . . . . . . . . . . . . . . . 4 2.2. References . . . . . . . . . . . . . . . . . . . . . . . 4
4. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Subset of a 6LoWPAN Glossary . . . . . . . . . . . . . . 4
4.1. Non-storing Mode Projected DAO . . . . . . . . . . . . . 6 2.4. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Storing-Mode Projected DAO . . . . . . . . . . . . . . . 8 3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 5
5. Applications . . . . . . . . . . . . . . . . . . . . . . . . 10 4. New RPL Control Message Options . . . . . . . . . . . . . . . 5
5.1. Loose Source Routing in Non-storing Mode . . . . . . . . 10 5. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Transversal Routes in storing and non-storing modes . . . 11 5.1. Non-storing Mode Projected Route . . . . . . . . . . . . 8
6. RPL Instances . . . . . . . . . . . . . . . . . . . . . . . . 13 5.2. Storing-Mode Projected Route . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 6.1. Loose Source Routing in Non-storing Mode . . . . . . . . 11
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 6.2. Transversal Routes in storing and non-storing modes . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 7. RPL Instances . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
A.1. Using storing mode P-DAO in non-storing mode MOP . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
A.2. Projecting a storing-mode transversal route . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 11.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 18
A.1. Using storing mode P-DAO in non-storing mode MOP . . . . 18
A.2. Projecting a storing-mode transversal route . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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) for application in a variety of low energy Internet of Things (IoT)
networks. RPL forms Destination Oriented Directed Acyclic Graphs networks. RPL forms Destination Oriented Directed Acyclic Graphs
(DODAGs) in which the root often acts as the Border Router to connect (DODAGs) in which the root often acts as the Border Router to connect
the RPL domain to the Internet. The root is responsible to select the RPL domain to the Internet. The root is responsible to select
the RPL Instance that is used to forward a packet coming from the the RPL Instance that is used to forward a packet coming from the
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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, with optionally the assistance of a This draft enables a RPL root to install and maintain projected
PCE, to install and maintain additional storing and non-storing mode routes (P-routes) within its DODAG, along a selected set of nodes
routes within the RPL domain, along a selected set of nodes and for a that may or may not include self, for a chosen duration. This
selected duration, thus providing routes more suitable than those potentially enables routes that are more optimized than those
obtained with the distributed operation of RPL. Those routes may be obtained with the distributed operation of RPL, either in terms of
installed in either storing and non-storing modes RPL instances, the size of a source-route header or in terms of path length, which
resulting in potentially hybrid situations where the mode of the impacts both the latency and the packet delivery ratio. P-routes may
projected routes is different from that of the other routes in the be installed in either Storing and Non-Storing Modes Instances of the
instance. classical RPL operation, resulting in potentially hybrid situations
where the mode of some P-routes is different from that of the other
routes in the RPL Instance.
Projected routes must be used with the parsimony to limit the amount
of state that is installed in each device to fit within its
resources, and to limit the amount of rerouted traffic to fit within
the capabilities of the transmission links. The algorithm used to
compute the paths and the protocol used to learn the topology of the
network and the resources that are available in devices and in the
network are out of scope for this document. Possibly with the
assistance of a Path Computation Element ([PCE]) that could have a
better visibility on the larger system, the root computes which
segment could be optimized and uses this draft to install the
corresponding projected routes.
2. Terminology 2. Terminology
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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
The Terminology used in this document is consistent with and 2.2. References
incorporates that described in "Terminology in Low power And Lossy
Networks"[RFC7102] and [RFC6550].
3. New RPL Control Message Options 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:
6BBR: 6LoWPAN Backbone Router
6LBR: 6LoWPAN Border Router
6LN: 6LoWPAN Node
6LR: 6LoWPAN Router
6CIO: Capability Indication Option
EARO: (Extended) Address Registration Option -- (E)ARO
EDAR: (Extended) Duplicate Address Request -- (E)DAR
EDAC: (Extended) Duplicate Address Confirmation -- (E)DAC
DAD: Duplicate Address Detection
DODAG: Destination-Oriented Directed Acyclic Graph
LLN: Low-Power and Lossy Network
NA: Neighbor Advertisement
NCE: Neighbor Cache Entry
ND: Neighbor Discovery
NDP: Neighbor Discovery Protocol
NS: Neighbor Solicitation
RPL: IPv6 Routing Protocol for LLNs (pronounced ripple) [RFC6550]
RA: Router Advertisement
RS: Router Solicitation
2.4. New Terms
Projected Route: A route that is installed remotely by a RPL root.
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; the former indicates a
node to be reached and the latter specifies a parent that can be used node to be reached and the latter specifies a parent that can be used
to reach that node. Options may be factorized; one or more to reach that node. Options may be factorized; one or more
contiguous TIOs apply to the one or more contiguous Target options contiguous TIOs apply to the one or more contiguous Target options
that immediately precede the TIOs in the RPL message. that immediately precede the TIOs in the RPL message.
This specification introduces a new Control Message Option, the Via This specification introduces 2 new Control Message Options referred
Information option (VIO). Like the TIO, the VIO MUST be preceded by to as Route Projection Options (RPO). One RPO is the Information
one or more RPL Target options to which it applies. Unlike the TIO, option (VIO) and the other is the Source-Routed VIO (SRVIO). The VIO
the VIO are not factorized: multiple contiguous Via options indicate installs a route on each hop along a projected route (in a fashion
an ordered sequence of routers to reach the target(s), presented in analogous to RPL Storing Mode) whereas the SRVIO installs a source-
the order of the packet stream, source to destination, and in which a routing state at the ingress node, which uses it to insert a routing
routing state must be installed. header in a fashion similar to Non-Storing Mode.
The Via Information option MUST contain at least one Via Address. 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
contiguous RPOs indicate alternate paths to the target(s).
3.1. Via Information Option 4. New RPL Control Message Options
The Via Information option MAY be present in DAO messages, and its The format of RPOs is as follows:
format 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 = 0x0A | Option Length | Path Sequence | Path Lifetime | | Type | Option Length | Path Sequence | Path Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
. . . .
. Via Address 1 . . Via Address 1 .
. . . .
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
skipping to change at page 4, line 40 skipping to change at page 6, line 33
+ + + +
. . . .
. Via Address n . . Via Address n .
. . . .
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Via Information option format Figure 1: Via Information option format
Option Type: 0x0A (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
skipping to change at page 5, line 17 skipping to change at page 7, line 10
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 all one bits
(0xFF) represents infinity. A value of all zero bits (0x00) (0xFF) represents infinity. A value of all zero bits (0x00)
indicates a loss of reachability. A DAO message that contains indicates a loss of reachability. A DAO message that contains
a Via Information option with a Path Lifetime of 0x00 for a a Via Information option with a Path Lifetime of 0x00 for a
Target is referred as a No-Path (for that Target) in this Target is referred as 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 VIO. TBD: See how the /64 prefix can be elided if precede the RPO. Via Addresses are indicated in the order of
it is the same as that of (all of) the target(s). In that the data path from the ingress to the egress nodes. TBD: See
case, the Next-Hop Address could be expressed as the 8-bytes how the /64 prefix can be elided if it is the same as that of
suffix only, otherwise it is expressed as 16 bytes, at least in (all of) the target(s). In that case, the Next-Hop Address
storing mode. could be expressed as the 8-bytes suffix only.
4. Projected DAO 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.
This draft adds a capability to RPL whereby the root projects a route 5. Projected DAO
through an extended DAO message called a Projected-DAO (P-DAO) to an
arbitrary router down the DODAG, indicating a next hop or a sequence
of routers via which a certain destination indicated in the Target
Information option may be reached.
A P-DAO message MUST contain at least a Target Information option and This draft adds a capability to RPL whereby the root of a DODAG
at least one VIA Information option following it. projects a route by sending an extended DAO message called a
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
target(s) indicated in the Target Information Option(s) (TIO) can be
reached.
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
back to a global address of the root.
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
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 VIO 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 a VIO 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 P-DAO, the storing mode and the non-storing
mode ones.
The non-storing mode P-DAO discussed in section Section 4.1 has a
single VIO with one or more Via Addresses in it, the list of Via
Addresses indicating the source-routed path to the target to be
installed in the router that receives the message, which replies
to the root directly with a DAO-ACK message.
The storing mode P-DAO discussed in section Section 4.2 has at
least two Via Information options with one Via Address each, for
the ingress and the egress of the path, and more if there are
intermediate routers. The Via Addresses indicate the routers in
which the routing state to the target have to be installed via the
next Via Address in the sequence of VIO. In normal operations,
the P-DAO is propagated along the chain of Via Routers from the
egress router of the path till the ingress one, which confirms the
installation to the root with a DAO-ACK message. Note that the
root may be the ingress and it may be the egress of the path, that
it can also be neither but it cannot be both.
The root is expected to use these mechanisms optimally and with There are two kinds of operation for the projected routes, the
required parsimony to limit the state installed in the devices to fit Storing Mode and the Non-Storing Mode.
within their resources, but how the root figures the amount of
resources that is available in each device is out of scope for this
document.
In particular, the draft expects that the root has enough information The Non-Storing Mode is discussed in section Section 5.1. It uses
about the capability for each node to store a number of routes, which an SRVIO that carries a list of Via Addresses to be used as a
can be discovered for instance using a Network Management System source-routed path to the target. The recipient of the P-DAO is
(NMS) and/or the RPL routing extensions specified in "Routing for the ingress router of the source-routed path. Upon a Non-Storing
Path Calculation in LLNs" [RFC6551]. Mode P-DAO, the ingress router installs a source-routed state to
the target and replies to the root directly with a DAO-ACK
message.
A route that is installed by a P-DAO is not necessarily installed The Storing Mode is discussed in section Section 5.2. It uses a
along the DODAG, though how the root and the optional PCE obtain the VIO with one Via Address per consecutive hop, from the ingress to
additional topological information to compute other routes is out of the egress of the path, including the list of all intermediate
scope for this document routers in the data path order. The Via Addresses indicate the
routers in which the routing state to the target have to be
installed via the next Via Address in the VIO. In normal
operations, the P-DAO is propagated along the chain of Via Routers
from the egress router of the path till the ingress one, which
confirms the installation to the root with a DAO-ACK message.
Note that the root may be the ingress and it may be the egress of
the path, that it can also be neither but it cannot be both.
4.1. Non-storing Mode Projected DAO 5.1. Non-storing Mode Projected Route
As illustrated in Figure 2, the non-storing mode P-DAO 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 path to any packet for which the source routed header reflecting the P-route to any packet for which
current destination either is the said target or can be reached via the current destination either is the said target or can be reached
the target, for instance a loose source routed packet for which the via the target.
next loose hop is the target, or a packet for which the router has a
routing state to the final destination via the target.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
| | Border Router | | Border Router
| | (RPL Root) | | (RPL Root)
+-----+ | P ^ | +-----+ | P ^ |
| | DAO | ACK | Loose | | DAO | ACK | Loose
o o o o router V | | Source o o o o router V | | Source
skipping to change at page 7, line 25 skipping to change at page 8, line 46
o o o o o o o o o o | Source . Path o o o o o o o o o o | Source . Path
o o o o o o o o o | Route . From o o o o o o o o o | Route . From
o o o o o o o o | Path . Root o o o o o o o o | Path . Root
o o o o o target V . To o o o o o target V . To
o o o o | Desti- o o o o | Desti-
o o o o | nation o o o o | nation
destination V destination V
LLN LLN
Figure 2: Projecting a Non-Storing route Figure 2: Projecting a Non-Storing Route
A router that receives a non-storing P-DAO installs a source routed A route indicated by an SRVIO may be loose, meaning that the node
path towards each of the consecutive targets via a source route path that owns the next listed Via Address is not necessarily a neighbor.
indicated in the following VIO. Without proper loop avoidance mechanisms, the interaction of loose
source routing and other mechanisms may effectively cause loops. In
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
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
route to the next loose hop under the control of the same route
computation 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. 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
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
hop; in the latter case, another encapsulation takes place and the
process possibly recurses; otherwise the packet is dropped.
In order to do so, the router encapsulates the packet with an IP in In order to add a source-routing header, the router encapsulates the
IP header and a non-storing mode source routing header (SRH) packet with an IP-in-IP header and a non-storing mode source routing
[RFC6554]. header (SRH) [RFC6554].
In the uncompressed form the source of the packet would be self, the In the uncompressed form the source of the packet would be self, the
destination would be the first Via Address in the VIO, and the SRH destination would be the first Via Address in the SRVIO, and the SRH
would contain the list of the remaining Via Addresses and then the would contain the list of the remaining Via Addresses and then the
target. 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.
4.2. Storing-Mode Projected DAO 5.2. Storing-Mode Projected Route
As illustrated in Figure 3, the storing mode P-DAO enables the root As illustrated in Figure 3, the Storing Mode projected iq used by the
to install a routing state towards a target in the routers along a root to install a routing state towards a target in the routers along
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.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
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o o o o o o o o o | ^ | Projected . o o o o o o o o o | ^ | Projected .
o o o o o o o o o o | | DAO | Route . o o o o o o o o o o | | DAO | Route .
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 | DAO v . o o o o o o o o v | DAO v .
o o LLN o o o | o o LLN o o o |
o o o o o Loose Source Route Path | o o o o o Loose Source Route Path |
o o o o From Root To Destination v o o o o From Root To Destination v
Figure 3: Projecting a route Figure 3: Projecting a route
Based on available topological, usage and capabilities node
information, the root or an associated PCE computes which segment
should be optimized and which relevant state should be installed in
which nodes. The algorithm is out of scope but it is envisaged that
the root could compute the ratio between the optimal path (existing
path not traversing the root, and the current path), the application
service level agreement (SLA) for specific flows that could benefit
from shorter paths, the energy wasted in the network, local
congestion on various links that would benefit from having flows
routed along alternate paths.
In order to install the relevant routing state along the segment In order to install the relevant routing state along the segment
between an ingress and an egress routers, the root sends a unicast between an ingress and an egress routers, the root sends a unicast
P-DAO message to the egress router of the routing segment that must P-DAO message to the egress router of the routing segment that must
be installed. The P-DAO message contains the ordered list of hops be installed. The P-DAO message contains the ordered list of hops
along the segment as a direct sequence of Via Information options along the segment as a direct sequence of Via Information options
that are preceded by one or more RPL Target options to which they that are preceded by one or more RPL Target options to which they
relate. Each Via Information option contains a Path Lifetime for relate. Each Via Information option contains a Path Lifetime for
which the state is to be maintained. which the state is to be maintained.
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.
which In that P-DAO, the destination IP address matches the Via In that P-DAO, the destination IP address matches the Via Address in
Address in the last VIO. This is how the egress recognizes its role. the last VIO. This is how the egress recognizes its role. In a
In a similar fashion, the ingress node recognizes its role as it similar fashion, the ingress node recognizes its role as it matches
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
projected route. If one of the targets cannot be located, the node projected route. If one of the targets cannot be located, the node
MUST answer to the root with a negative DAO-ACK listing the target(s) MUST answer to the root with a negative DAO-ACK listing the target(s)
that could not be located (suggested status 10 to be confirmed by that could not be located (suggested status 10 to be confirmed by
IANA). IANA).
skipping to change at page 10, line 17 skipping to change at page 11, line 43
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.
5. Applications 6. Applications
5.1. Loose Source Routing in Non-storing Mode 6.1. 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 11, line 40 skipping to change at page 13, line 18
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.
5.2. Transversal Routes in storing and non-storing modes 6.2. 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), root to leaves and
Multipoint-to-Point (MP2P) leaves to root operations, whereby routes Multipoint-to-Point (MP2P) leaves to root operations, whereby routes
are always installed along the RPL DODAG. Transversal Peer to Peer are always installed along the RPL DODAG. Transversal Peer to Peer
(P2P) routes in a RPL network will generally suffer from some stretch (P2P) routes in a RPL network will generally suffer from some stretch
since routing between 2 peers always happens via a common parent, as since routing between 2 peers 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
skipping to change at page 13, line 32 skipping to change at page 15, 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.
6. RPL Instances 7. RPL Instances
It must be noted that RPL has a concept of instance but does not have 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 a concept of an administrative distance, which exists in certain
proprietary implementations to sort out conflicts between multiple proprietary implementations to sort out conflicts between multiple
sources of routing information. This draft conforms the instance sources of routing information. This draft conforms the instance
model as follows: model as follows:
o If the PCE needs to influence a particular instance to add better o If the PCE needs to influence a particular instance to add better
routes in conformance with the routing objectives in that routes in conformance with the routing objectives in that
instance, it may do so. When the PCE modifies an existing instance, it may do so. When the PCE modifies an existing
skipping to change at page 14, line 11 skipping to change at page 15, line 37
Local Instance from the ingress node of that path. A packet Local Instance from the ingress node of that path. A packet
associated with that instance will be routed along that path and associated with that instance will be routed along that path and
MUST NOT be placed over a Global Instance again. A packet that is 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 placed on a Global Instance may be injected in the Local Instance
based on node policy and the Local Instance paramenters. based on node policy and the Local Instance paramenters.
In all cases, the path is indicated by a new Via Information option, 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 and the flow is similar to the flow used to obtain loose source
routing. routing.
7. Security Considerations 8. Security Considerations
This draft uses messages that are already present in RPL [RFC6550] This draft uses messages that are already present in RPL [RFC6550]
with optional secured versions. The same secured versions may be with optional secured versions. The same secured versions may be
used with this draft, and whatever security is deployed for a given used with this draft, and whatever security is deployed for a given
network also applies to the flows in this draft. network also applies to the flows in this draft.
8. IANA Considerations 9. IANA Considerations
This document extends the IANA registry created by RFC 6550 for RPL This document extends the IANA registry created by RFC 6550 for RPL
Control Codes as follows: Control Codes as follows:
+------+-------------+---------------+ +------+-------------------+---------------+
| Code | Description | Reference | | Code | Description | Reference |
+------+-------------+---------------+ +------+-------------------+---------------+
| 0x0A | Via | This document | | 0x0A | Via | This document |
+------+-------------+---------------+ | | | |
| 0x0B | Source-Routed Via | This document |
+------+-------------------+---------------+
RPL Control Codes RPL Control Codes
This document is updating the registry created by RFC 6550 for the This document is updating the registry created by RFC 6550 for the
RPL 3-bit Mode of Operation (MOP) as follows: RPL 3-bit Mode of Operation (MOP) as follows:
+----------+------------------------------------------+-------------+ +----------+------------------------------------------+-------------+
| MOP | Description | Reference | | MOP | Description | Reference |
| value | | | | value | | |
+----------+------------------------------------------+-------------+ +----------+------------------------------------------+-------------+
| 5 | Non-Storing mode of operation with | This | | 5 | Non-Storing mode of operation with | This |
| | Projected routes | document | | | Projected routes | document |
| | | | | | | |
| 6 | Storing mode of operation with Projected | This | | 6 | Storing mode of operation with Projected | This |
| | routes | document | | | routes | document |
+----------+------------------------------------------+-------------+ +----------+------------------------------------------+-------------+
DIO Mode of operation DIO Mode of operation
9. Acknowledgments 10. Acknowledgments
The authors wish to acknowledge JP Vasseur and Patrick Wetterwald for The authors wish to acknowledge JP Vasseur and Patrick Wetterwald for
their contributions to the ideas developed here. their contributions to the ideas developed here.
10. References 11. References
10.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550, Low-Power and Lossy Networks", RFC 6550,
skipping to change at page 15, line 43 skipping to change at page 17, line 27
[RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power [RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Paging Dispatch", Wireless Personal Area Network (6LoWPAN) Paging Dispatch",
RFC 8025, DOI 10.17487/RFC8025, November 2016, RFC 8025, DOI 10.17487/RFC8025, November 2016,
<https://www.rfc-editor.org/info/rfc8025>. <https://www.rfc-editor.org/info/rfc8025>.
[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie, [RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
"IPv6 over Low-Power Wireless Personal Area Network "IPv6 over Low-Power Wireless Personal Area Network
(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138, (6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
April 2017, <https://www.rfc-editor.org/info/rfc8138>. April 2017, <https://www.rfc-editor.org/info/rfc8138>.
10.2. Informative References [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] [I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-13 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-14 (work
in progress), November 2017. in progress), April 2018.
[I-D.ietf-detnet-architecture] [I-D.ietf-detnet-architecture]
Finn, N., Thubert, P., Varga, B., and J. Farkas, Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", draft-ietf- "Deterministic Networking Architecture", draft-ietf-
detnet-architecture-04 (work in progress), October 2017. detnet-architecture-05 (work in progress), May 2018.
[PCE] IETF, "Path Computation Element", [PCE] IETF, "Path Computation Element",
<https://datatracker.ietf.org/doc/charter-ietf-pce/>. <https://datatracker.ietf.org/doc/charter-ietf-pce/>.
[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and
J. Martocci, "Reactive Discovery of Point-to-Point Routes J. Martocci, "Reactive Discovery of Point-to-Point Routes
in Low-Power and Lossy Networks", RFC 6997, in Low-Power and Lossy Networks", RFC 6997,
DOI 10.17487/RFC6997, August 2013, DOI 10.17487/RFC6997, August 2013,
<https://www.rfc-editor.org/info/rfc6997>. <https://www.rfc-editor.org/info/rfc6997>.
skipping to change at page 20, line 15 skipping to change at page 21, line 15
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 (editor) 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
James Pylakutty James Pylakutty
Cisco Systems Cisco Systems
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