< draft-ietf-roll-dao-projection-07.txt   draft-ietf-roll-dao-projection-08.txt >
ROLL P. Thubert, Ed. ROLL P. Thubert, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Updates: 6550 (if approved) R.A. Jadhav Updates: 6550 (if approved) R.A. Jadhav
Intended status: Standards Track Huawei Tech Intended status: Standards Track Huawei Tech
Expires: 6 May 2020 M. Gillmore Expires: 7 May 2020 M. Gillmore
Itron Itron
3 November 2019 4 November 2019
Root initiated routing state in RPL Root initiated routing state in RPL
draft-ietf-roll-dao-projection-07 draft-ietf-roll-dao-projection-08
Abstract Abstract
This document proposes a protocol extension to RPL that enables to This document enables a RPL Root to install and maintain Projected
install a limited amount of centrally-computed routes in a RPL graph, Routes within its DODAG, along a selected set of nodes that may or
enabling loose source routing down a non-storing mode DODAG, or may not include self, for a chosen duration. This potentially
transversal routes inside the DODAG. As opposed to the classical enables routes that are more optimized or resilient than those
route injection in RPL that are injected by the end devices, this obtained with the classical distributed operation of RPL, either in
draft enables the Root of the DODAG to projects the routes that are terms of the size of a source-route header or in terms of path
needed on the nodes where they should be installed. length, which impacts both the latency and the packet delivery ratio.
Projected Routes may be installed in either Storing and Non-Storing
Modes Instances of the classical RPL operation, resulting in
potentially hybrid situations where the mode of some Projected Routes
is different from that of the other routes in the RPL Instance.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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
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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 6 May 2020. This Internet-Draft will expire on 7 May 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Subset of a 6LoWPAN Glossary . . . . . . . . . . . . . . 4 2.2. Subset of a 6LoWPAN Glossary . . . . . . . . . . . . . . 4
2.3. Other Terms . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Other Terms . . . . . . . . . . . . . . . . . . . . . . . 5
2.4. References . . . . . . . . . . . . . . . . . . . . . . . 5 2.4. References . . . . . . . . . . . . . . . . . . . . . . . 5
3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 5 3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 6
4. Identifying a Path . . . . . . . . . . . . . . . . . . . . . 6 4. Identifying a Path . . . . . . . . . . . . . . . . . . . . . 7
5. New RPL Control Messages and Options . . . . . . . . . . . . 7 5. New RPL Control Messages and Options . . . . . . . . . . . . 7
5.1. New P-DAO Request Control Message . . . . . . . . . . . . 7 5.1. New P-DAO Request Control Message . . . . . . . . . . . . 7
5.2. New PDR-ACK Control Message . . . . . . . . . . . . . . . 8 5.2. New PDR-ACK Control Message . . . . . . . . . . . . . . . 8
5.3. Route Projection Options . . . . . . . . . . . . . . . . 8 5.3. Route Projection Options . . . . . . . . . . . . . . . . 10
5.4. Sibling Information Option . . . . . . . . . . . . . . . 10 5.4. Sibling Information Option . . . . . . . . . . . . . . . 11
6. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 12 6. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1. Non-Storing Mode Projected Route . . . . . . . . . . . . 13 6.1. Non-Storing Mode Projected Route . . . . . . . . . . . . 14
6.2. Storing-Mode Projected Route . . . . . . . . . . . . . . 15 6.2. Storing-Mode Projected Route . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17 7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8.1. New RPL Control Codes . . . . . . . . . . . . . . . . . . 17 8.1. New RPL Control Codes . . . . . . . . . . . . . . . . . . 18
8.2. Error in Projected Route ICMPv6 Code . . . . . . . . . . 18 8.2. New RPL Control Message Options . . . . . . . . . . . . . 18
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 8.3. New SubRegistry for the Projected DAO Request (PDR)
10. Normative References . . . . . . . . . . . . . . . . . . . . 18 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 19
11. Informative References . . . . . . . . . . . . . . . . . . . 19 8.4. New SubRegistry for the PDR-ACK Flags . . . . . . . . . . 19
Appendix A. Applications . . . . . . . . . . . . . . . . . . . . 20 8.5. New Subregistry for the PDR-ACK Acceptance Status
A.1. Loose Source Routing in Non-storing Mode . . . . . . . . 20 values . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.6. New Subregistry for the PDR-ACK Rejection Status
values . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.7. New SubRegistry for the Route Projection Options (RPO)
Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.8. New SubRegistry for the Sibling Information Option
(SIO) Flags . . . . . . . . . . . . . . . . . . . . . . . 21
8.9. Error in Projected Route ICMPv6 Code . . . . . . . . . . 21
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
10. Normative References . . . . . . . . . . . . . . . . . . . . 22
11. Informative References . . . . . . . . . . . . . . . . . . . 22
Appendix A. Applications . . . . . . . . . . . . . . . . . . . . 23
A.1. Loose Source Routing in Non-storing Mode . . . . . . . . 23
A.2. Transversal Routes in storing and non-storing A.2. Transversal Routes in storing and non-storing
modes . . . . . . . . . . . . . . . . . . . . . . . . . . 22 modes . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 23 Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 27
B.1. Using storing mode P-DAO in non-storing mode MOP . . . . 23 B.1. Using storing mode P-DAO in non-storing mode MOP . . . . 27
B.2. Projecting a storing-mode transversal route . . . . . . . 24 B.2. Projecting a storing-mode transversal route . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
The "Routing Protocol for Low Power and Lossy Networks" [RFC6550] RPL, the "Routing Protocol for Low Power and Lossy Networks"
(LLN)(RPL) is a generic Distance Vector protocol that is well suited [RFC6550] (LLNs), is a generic Distance Vector protocol that is well
for application in a variety of low energy Internet of Things (IoT) suited for application in a variety of low energy Internet of Things
networks. RPL forms Destination Oriented Directed Acyclic Graphs (IoT) networks. RPL forms Destination Oriented Directed Acyclic
(DODAGs) in which the Root often acts as the Border Router to connect Graphs (DODAGs) in which the Root often acts as the Border Router to
the RPL domain to the Internet. The Root is responsible to select connect the RPL domain to the Internet. The Root is responsible to
the RPL Instance that is used to forward a packet coming from the select the RPL Instance that is used to forward a packet coming from
Internet into the RPL domain and set the related RPL information in the Internet into the RPL domain and set the related RPL information
the packets. in the packets.
The 6TiSCH architecture [6TiSCH-ARCHI] leverages RPL for its routing The 6TiSCH architecture [6TiSCH-ARCHI] leverages RPL for its routing
operation and considers the Deterministic Networking Architecture operations and considers the Deterministic Networking Architecture
[RFC8655] as one possible model whereby the device resources and [RFC8655] as one possible model whereby the device resources and
capabilities are exposed to an external controller which installs capabilities are exposed to an external controller which installs
routing states into the network based on some objective functions routing states into the network based on some objective functions
that reside in that external entity. that reside in that external entity. With DetNet and 6TiSCH, the
component of the controller that is responsible of computing routes
is called a Path Computation Element ([PCE]).
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 PCE with a global visibility on the system can
visibility on the system could install additional P2P routes that are compute P2P routes that are more optimized for the current needs as
more optimized for the current needs as expressed by the objective expressed by the objective function.
function.
This draft enables a RPL Root to install and maintain Projected This draft proposes a protocol extension to RPL that enables the Root
Routes within its DODAG, along a selected set of nodes that may or to install a limited amount of centrally-computed routes in a RPL
may not include self, for a chosen duration. This potentially graph, on behalf of a PCE that may be collocated or separated from
enables routes that are more optimized than those obtained with the the Root. Those extensions enable loose source routing down in RPL
distributed operation of RPL, either in terms of the size of a Non-Storing Mode and transversal routes inside the DODAG regardless
source-route header or in terms of path length, which impacts both of the RPL Mode of Operation (MOP).
the latency and the packet delivery ratio. Projected Routes may be
installed in either Storing and Non-Storing Modes Instances of the As opposed to the classical RPL operations where routes are injected
classical RPL operation, resulting in potentially hybrid situations by the Target nodes, the protocol extension enables the Root of a
where the mode of some Projected Routes is different from that of the DODAG to project the routes that are needed onto the nodes where they
other routes in the RPL Instance. should be installed. This specification uses the term Projected
Route to refer to those routes. A Projected Route may be a stand-
alone path to a Target or a segment in a complex Track [6TiSCH-ARCHI]
that provides redundant forwarding solutions to a destination to
improve reliability and availability of the wireless transmissions
[RAW-PS].
Projected Routes must be used with the parsimony to limit the amount Projected Routes must be used with the parsimony to limit the amount
of state that is installed in each device to fit within its of state that is installed in each device to fit within its
resources, and to limit the amount of rerouted traffic to fit within resources, and to limit the amount of rerouted traffic to fit within
the capabilities of the transmission links. The algorithm used to the capabilities of the transmission links. The method to learn the
compute the paths and the protocol used to learn the topology of the node capabilities and the resources that are available in the devices
network and the resources that are available in devices and in the and in the network are out of scope for this document.
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.
A Projected Route may be a stand-alone path to a Target or a segment In RPL Non-Storing Mode, the Root has enough information to build a
in a complex Track [6TiSCH-ARCHI] that provides redundant forwarding basic DODAG topology. This document adds the capability for nodes to
solutions to a destination to improve reliability and availability of advertise sibling information in order to improve the topological
the wireless transmissions [RAW-PS]. awareness of the Root. This specification uses the RPL Root as a
proxy to the PCE. The algorithm to compute the paths and the
protocol used by an external PCE to obtain the topology of the
network from the Root are out of scope for this document.
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. Subset of a 6LoWPAN Glossary 2.2. Subset of a 6LoWPAN Glossary
skipping to change at page 5, line 45 skipping to change at page 6, line 19
3. Extending RFC 6550 3. Extending RFC 6550
This specification introduces two new RPL Control Messages to enable This specification introduces two new RPL Control Messages to enable
a RPL Aware Node (RAN) to request the establisment of a path from a RPL Aware Node (RAN) to request the establisment of a path from
self to a Target. A RAN may request the installation of a path by self to a Target. A RAN may request the installation of a path by
sending a new P-DAO Request PDR) Message to the Root. The Root sending a new P-DAO Request PDR) Message to the Root. The Root
confirms with a new PDR-ACK message back to the requester RAN with a confirms with a new PDR-ACK message back to the requester RAN with a
completion status once it is done installing the path. See completion status once it is done installing the path. See
Section 5.1 for more. Section 5.1 for more.
Section 6.7 of [RFC6550] specifies Control Message Options (CMO) to Section 6.7 of [RFC6550] specifies RPL Control Message Options (CMO)
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 (RTO) and the Transit Object (DAO) message. The RPL Target Option (RTO) and the Transit
Information Option (TIO) are such options. In Non-Storing Mode, the Information Option (TIO) are such options. In Non-Storing Mode, the
TIO option is used in the DAO message to indicate a parent within a TIO option is used in the DAO message to indicate a parent within a
DODAG. The TIO applies to the RTOs that immedially preceed it in the DODAG. The TIO applies to the RTOs that immedially preceed it in the
message. Options may be factorized; multiple TIOs may be present to message. Options may be factorized; multiple TIOs may be present to
indicate multiple routes to the one or more contiguous addresses indicate multiple routes to the one or more contiguous addresses
indicated in the RTOs that immediately precede the TIOs in the RPL indicated in the RTOs that immediately precede the TIOs in the RPL
message. message.
This specification introduces two new CMOs referred to as Route This specification introduces two new CMOs referred to as Route
Projection Options (RPO) to install Projected Routes. One RPO is the Projection Options (RPO) to install Projected Routes. One RPO is the
Via Information Option (VIO) and the other is the Source-Routed VIO Via Information Option (VIO) and the other is the Source-Routed VIO
(SRVIO). The VIO installs a route on each hop along a Projected (SRVIO). The VIO installs a route on each hop along a Projected
Route (in a fashion analogous to RPL Storing Mode) whereas the SRVIO Route (in a fashion analogous to RPL Storing Mode) whereas the SRVIO
installs a source-routing state at the ingress node, which uses that installs a source-routing state at the ingress node, which uses that
state to insert a routing header in a fashion similar to Non-Storing state to encapsulate a packet with an IPv6 Routing Header in a
Mode. Like the TIO, the RPOs MUST be preceded by one or more RTOs to fashion similar to RPL Non-Storing Mode. Like the TIO, the RPOs MUST
which they apply, and they can be factorized: multiple contiguous be preceded by exactly one RTO to which they apply, and they can be
RPOs indicate alternate paths to the Target(s), more in Section 5.3. factorized: multiple contiguous RPOs indicate alternate paths to the
Target, more in Section 5.3.
This specification also introduces a new CMO to enable a RPL Router This specification also introduces a new CMO to enable a RAN to
to indicate its siblings to the Root, more in Figure 4. advertise (some of) its siblings to the Root, using a new Sibling
Information Option (SIO) as specified in Section 5.4.
4. Identifying a Path 4. Identifying a Path
It must be noted that RPL has a concept of Instance to represent It must be noted that RPL has a concept of Instance to represent
different routing topologies but does not have a concept of an different routing topologies but does not have a concept of an
administrative distance, which exists in certain proprietary administrative distance, which exists in certain proprietary
implementations to sort out conflicts between multiple sources of implementations to sort out conflicts between multiple sources of
routing information within one routing topology. This draft conforms routing information within one routing topology. This draft conforms
the Instance model as follows: the Instance model as follows:
* If the PCE needs to influence a particular Instance to add better * 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 as long as it does not create a loop. A Instance, it may do so as long as it does not create a loop. A
Projected Route is always preferred over a route that is learned Projected Route is always preferred over a route that is learned
via RPL. This specification uses the RPL Root as a proxy to the via RPL.
PCE. If the actual PCE is a separate entity, then a protocol that
is out of scope for this specification is needed to relay the
control elements between the RPL Root and the PCE.
* A PCE that installs a more specific (say, Traffic Engineered) and * A PCE that installs a more specific (say, Traffic Engineered) and
possibly complex path (aka a Track) towards a particular Target possibly complex path (aka a Track) towards a particular Target
MUST use a Local RPL Instance (see section 5 of [RFC6550]) MUST use a Local RPL Instance (see section 5 of [RFC6550])
associated to that Target to identify the path. We refer to that associated to that Target to identify the path. We refer to that
Local RPLInstanceID as TrackID. A projected path is uniquely Local RPLInstanceID as TrackID. A projected path is uniquely
identified within the RPL domain by the tuple (Target address, identified within the RPL domain by the tuple (Target address,
TrackID). When packet is placed on a Track, a RPL Packet TrackID). When packet is placed on a Track, a RPL Packet
Information (RPI) is added with the TrackID as RPLInstanceID. The Information (RPI) is added with the TrackID as RPLInstanceID. The
RPLInstanceID has the 'D' flag set, indicating that the RPLInstanceID has the 'D' flag set, indicating that the
skipping to change at page 8, line 37 skipping to change at page 9, line 20
| PDRSequence | Reserved | | PDRSequence | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option(s)... | Option(s)...
+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+
Figure 2: New PDR-ACK Control Message Format Figure 2: New PDR-ACK Control Message Format
TrackID: The RPLInstanceID of the Track that was created. Set to 0 TrackID: The RPLInstanceID of the Track that was created. Set to 0
when no Track is created. when no Track is created.
PDR-ACK Status: Indicates the completion. A value up to 127 means PDR-ACK Status: Indicates the completion. Substructured as
acceptance Values of 128 and above are used for rejection codes; indicated in Figure 3.
Track Lifetime: Indicates that remaining Lifetime for the Track, 0 Track Lifetime: Indicates that remaining Lifetime for the Track, 0
if the Track was destroyed or not created. if the Track was destroyed or not created.
PDRSequence: 8-bit wrapping sequence number. It is incremented at PDRSequence: 8-bit wrapping sequence number. It is incremented at
each PDR message and echoed in the PDR-ACK. each PDR message and echoed in the PDR-ACK.
The PDR-ACK Status is further substructured as follows:
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|E|R| Value |
+-+-+-+-+-+-+-+-+
Figure 3: PDR-ACK status Format
The PDR-ACK Status subfields are:
E: 1-bit flag. Set to indicate a rejection. When not set, a value
of 0 indicates Success/Unqualified acceptance and other values
indicate "not an outright rejection".
R: 1-bit flag. Reserved, MUST be set to 0 by the sender and ignored
by the receiver.
Status Value: 6-bit unsigned integer. Values depedning on the
setting of the 'E' flag as indicated respectively in Table 4 and
Table 5.
5.3. Route Projection Options 5.3. Route Projection Options
The RPOs indicate a series of IPv6 addresses that can be compressed The RPOs indicate a series of IPv6 addresses that can be compressed
using the method defined in the "6LoWPAN Routing Header" [RFC8138] using the method defined in the "6LoWPAN Routing Header" [RFC8138]
specification using the address of the Root found in the DODAGID specification using the address of the Root found in the DODAGID
field of DIO messages as Compression Reference. field of DIO messages as Compression Reference.
An RPO indicates a Projected Route that can be a serial Track in full An RPO indicates a Projected Route that can be a serial Track in full
or a segment of a more complex Track. The Track is identified by a or a segment of a more complex Track. The Track is identified by a
RPLInstanceID that is either Global or local to the Target of the RPLInstanceID that is either Global or local to the Target of the
skipping to change at page 9, line 40 skipping to change at page 10, line 47
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
. . . .
. Via Address n . . Via Address n .
. . . .
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Via Information option format Figure 4: 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.
Compression Type: 16-bit unsigned integer. This is the SRH-6LoRH Compression Type: 3-bit unsigned integer. This is the SRH-6LoRH
Type as defined in figure 7 in section 5.1 of [RFC8138] that Type as defined in figure 7 in section 5.1 of [RFC8138] that
corresponds to the compression used for all the Via Addresses. corresponds to the compression used for all the Via Addresses.
TrackID: 8-bit field indicating the topology Instance associated TrackID: 8-bit field indicating the topology Instance associated
with the Track. with the Track.
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 the Lifetime Units (obtained from the Configuration option) that the
prefix is valid for route determination. The period starts when a prefix is valid for route determination. The period starts when a
new Path Sequence is seen. A value of 255 (0xFF) represents new Path Sequence is seen. A value of 255 (0xFF) represents
skipping to change at page 11, line 21 skipping to change at page 12, line 21
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
. . . .
. Sibling Address . . Sibling Address .
. . . .
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Sibling Information Option Format Figure 5: Sibling Information Option Format
Option Type: 0x0C (to be confirmed by IANA) Option Type: 0x0C (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.
Compression Type: 16-bit unsigned integer. This is the SRH-6LoRH Compression Type: 3-bit unsigned integer. This is the SRH-6LoRH
Type as defined in figure 7 in section 5.1 of [RFC8138] that Type as defined in figure 7 in section 5.1 of [RFC8138] that
corresponds to the compression used for the Sibling Address. corresponds to the compression used for the Sibling Address.
B: 1-bit flag that is set to indicate that the connectivity to the B: 1-bit flag that is set to indicate that the connectivity to the
sibling is bidirectional and roughly symmetrical. In that case, sibling is bidirectional and roughly symmetrical. In that case,
only one of the siblings may report the SIO for the hop. If 'B' only one of the siblings may report the SIO for the hop. If 'B'
is not set then the SIO only indicates connectivity from the is not set then the SIO only indicates connectivity from the
sibling to this node, and does not provide information on the hop sibling to this node, and does not provide information on the hop
from this node to the sibling. from this node to the sibling.
skipping to change at page 12, line 5 skipping to change at page 13, line 5
uses RPL for a particular use / environment MAY redefine the use uses RPL for a particular use / environment MAY redefine the use
of this field to fit its needs. of this field to fit its needs.
Step of Rank: 16-bit unsigned integer. This is the Step of Rank Step of Rank: 16-bit unsigned integer. This is the Step of Rank
[RFC6550] as computed by the Objective Function between this node [RFC6550] as computed by the Objective Function between this node
and the sibling. and the sibling.
Reserved: MUST be set to zero by the sender and MUST be ignored by Reserved: MUST be set to zero by the sender and MUST be ignored by
the receiver. the receiver.
Sibling Address: 2 to 16 bytes, a compressed IPv6 Address. a Via Sibling Address: 2 to 16 bytes, the IPv6 Address of the sibling in a
Address indicates the next hop towards the destination(s) that is [RFC8138] compressed form as indicated by the Compression Type
indicated in the Target option that immediately precede the RPO in field.
the DAO message. Via Addresses are indicated in the order of the
data path from the ingress to the egress nodes. All Via addresses
are expressed in the same size as indicated by the Compression
Type
An SIO MAY be immediately followed by a DAG Metric Container. In An SIO MAY be immediately followed by a DAG Metric Container. In
that case the DAG Metric Container provides additional metrics for that case the DAG Metric Container provides additional metrics for
the hop from the Sibling to this node. the hop from the Sibling to this node.
6. Projected DAO 6. 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
skipping to change at page 13, line 14 skipping to change at page 14, line 10
which the routing state to the Target have to be installed via the 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 next Via Address in the VIO. In normal operations, the P-DAO is
propagated along the chain of Via Routers from the egress router propagated along the chain of Via Routers from the egress router
of the path till the ingress one, which confirms the installation 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 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 ingress and it may be the egress of the path, that it can also be
neither but it cannot be both. neither but it cannot be both.
In case of a forwarding error along a Projected Route, an ICMP error In case of a forwarding error along a Projected Route, an ICMP error
is sent to the Root with a new Code "Error in Projected Route" (See is sent to the Root with a new Code "Error in Projected Route" (See
Section 8.2). The Root can then modify or remove the Projected Section 8.9). The Root can then modify or remove the Projected
Route. The "Error in Projected Route" message has the same format as Route. The "Error in Projected Route" message has the same format as
the "Destination Unreachable Message", as specified in RFC 4443 the "Destination Unreachable Message", as specified in RFC 4443
[RFC4443]. The portion of the invoking packet that is sent back in [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 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 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 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) this node could not reach. if a 6LoWPAN Routing Header (6LoRH)
[RFC8138] is used to carry the IPv6 routing information in the outter [RFC8138] is used to carry the IPv6 routing information in the outter
header then that whole 6LoRH information SHOULD be present in the header then that whole 6LoRH information SHOULD be present in the
ICMP message. The sender and exact operation depend on the Mode and ICMP message. The sender and exact operation depend on the Mode and
is described in Section 6.1 and Section 6.2 respectively. is described in Section 6.1 and Section 6.2 respectively.
6.1. Non-Storing Mode Projected Route 6.1. Non-Storing Mode Projected Route
As illustrated in Figure 5, a P-DAO that carries an SRVIO enables the As illustrated in Figure 6, 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 Projected Route to any packet for source routed header reflecting the Projected Route to any packet for
which the current destination either is the said Target or can be which the current destination either is the said Target or can be
reached via the Target. reached via the Target.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
skipping to change at page 14, line 25 skipping to change at page 15, line 5
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 5: Projecting a Non-Storing Route Figure 6: 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 Projected order to avoid those loops, if the router that installs a Projected
Route does not have a connected route (a direct adjacency) to the 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 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 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 Projected Route to the next loose hop under the control of the same
skipping to change at page 15, line 24 skipping to change at page 16, line 7
Source Routing Header" back to the source of the packet, as described Source Routing Header" back to the source of the packet, as described
in section 11.2.2.3. of [RFC6550]. Upon this message, the in section 11.2.2.3. of [RFC6550]. Upon this message, the
encapsulating node SHOULD stop using the source route path for a 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 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 in Projected Route" to the Root. Failure to follow these steps may
result in packet loss and wasted resources along the source route result in packet loss and wasted resources along the source route
path that is broken. path that is broken.
6.2. Storing-Mode Projected Route 6.2. Storing-Mode Projected Route
As illustrated in Figure 6, the Storing Mode route projection is used As illustrated in Figure 7, the Storing Mode route projection is used
by the Root to install a routing state towards a Target in the by the Root to install a routing state towards a Target in the
routers along a segment between an ingress and an egress router; this routers along a segment between an ingress and an egress router; this
enables the routers to forward along that segment any packet for enables the routers to forward along that segment any packet for
which the next loose hop is the said Target, for Instance a loose which the next loose hop is the said Target, for Instance a loose
source routed packet for which the next loose hop is the Target, or a source routed packet for which the next loose hop is the Target, or a
packet for which the router has a routing state to the final packet for which the router has a routing state to the final
destination via the Target. destination via the Target.
------+--------- ------+---------
| Internet | Internet
skipping to change at page 15, line 50 skipping to change at page 16, line 33
| | DAO | ACK | | | DAO | ACK |
o o o o | | | o o o o | | |
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 6: Projecting a route Figure 7: Projecting a route
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.
skipping to change at page 17, line 44 skipping to change at page 18, line 28
network also applies to the flows in this draft. network also applies to the flows in this draft.
TODO: should probably consider how P-DAO messages could be abused by 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 a) rogue nodes b) via replay of messages c) if use of P-DAO messages
could in fact deal with any threats? could in fact deal with any threats?
8. IANA Considerations 8. IANA Considerations
8.1. New RPL Control Codes 8.1. New RPL Control Codes
This document extends the IANA registry created by RFC 6550 for RPL This document extends the IANA Subregistry created by RFC 6550 for
Control Codes as follows: RPL Control Codes as indicated in Table 1:
+------+--------------------------------------+---------------+ +------+-----------------------------+---------------+
| Code | Description | Reference | | Code | Description | Reference |
+======+======================================+===============+ +======+=============================+===============+
| 0x0A | Via Information option | This document | | 0x09 | Projected DAO Request (PDR) | This document |
+------+--------------------------------------+---------------+ +------+-----------------------------+---------------+
| 0x0B | Source-Routed Via Information option | This document | | 0x0A | PDR-ACK | This document |
+------+--------------------------------------+---------------+ +------+-----------------------------+---------------+
Table 1: RPL Control Codes Table 1: New RPL Control Codes
This document is updating the registry created by RFC 6550 for the 8.2. New RPL Control Message Options
RPL 3-bit Mode of Operation (MOP) as follows:
+-----------+-------------------------------+-----------+ This document extends the IANA Subregistry created by RFC 6550 for
| MOP value | Description | Reference | RPL Control Message Options as indicated in Table 2:
+===========+===============================+===========+
| 5 | Non-Storing mode of operation | This |
| | with Projected Routes | document |
+-----------+-------------------------------+-----------+
| 6 | Storing mode of operation | This |
| | with Projected Routes | document |
+-----------+-------------------------------+-----------+
Table 2: DIO Mode of operation +-------+--------------------------------------+---------------+
| Value | Meaning | Reference |
+=======+======================================+===============+
| 0x0B | Via Information option | This document |
+-------+--------------------------------------+---------------+
| 0x0C | Source-Routed Via Information option | This document |
+-------+--------------------------------------+---------------+
| 0x0D | Sibling Information option | This document |
+-------+--------------------------------------+---------------+
8.2. Error in Projected Route ICMPv6 Code Table 2: RPL Control Message Options
8.3. New SubRegistry for the Projected DAO Request (PDR) Flags
IANA is required to create a registry for the 8-bit Projected DAO
Request (PDR) Flags field. Each bit is tracked with the following
qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration procedure is "Standards Action" [RFC8126]. The initial
allocation is as indicated in Table 3:
+------------+------------------------+---------------+
| Bit number | Capability description | Reference |
+============+========================+===============+
| 0 | PDR-ACK request (K) | This document |
+------------+------------------------+---------------+
| 1 | Requested path should | This document |
| | be redundant (R) | |
+------------+------------------------+---------------+
Table 3: Initial PDR Flags
8.4. New SubRegistry for the PDR-ACK Flags
IANA is required to create an subregistry for the 8-bit PDR-ACK Flags
field. Each bit is tracked with the following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration procedure is "Standards Action" [RFC8126]. No bit is
currently defined for the PDR-ACK Flags.
8.5. New Subregistry for the PDR-ACK Acceptance Status values
IANA is requested to create a new subregistry for the PDR-ACK
Acceptance Status values.
* Possible values are 6-bit unsigned integers (0..63).
* Registration procedure is "Standards Action" [RFC8126].
* Initial allocation is as indicated in Table 4:
+-------+------------------------+---------------+
| Value | Meaning | Reference |
+=======+========================+===============+
| 0 | Unqualified acceptance | This document |
+-------+------------------------+---------------+
Table 4: Acceptance values of the PDR-ACK Status
8.6. New Subregistry for the PDR-ACK Rejection Status values
IANA is requested to create a new subregistry for the PDR-ACK
Rejection Status values.
* Possible values are 6-bit unsigned integers (0..63).
* Registration procedure is "Standards Action" [RFC8126].
* Initial allocation is as indicated in Table 5:
+-------+-----------------------+---------------+
| Value | Meaning | Reference |
+=======+=======================+===============+
| 0 | Unqualified rejection | This document |
+-------+-----------------------+---------------+
Table 5: Rejection values of the PDR-ACK Status
8.7. New SubRegistry for the Route Projection Options (RPO) Flags
IANA is requested to create a new subregistry for the 5-bit Route
Projection Options (RPO) Flags field. Each bit is tracked with the
following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration procedure is "Standards Action" [RFC8126]. No bit is
currently defined for the Route Projection Options (RPO) Flags.
8.8. New SubRegistry for the Sibling Information Option (SIO) Flags
IANA is required to create a registry for the 5-bit Sibling
Information Option (SIO) Flags field. Each bit is tracked with the
following qualities:
* Bit number (counting from bit 0 as the most significant bit)
* Capability description
* Reference
Registration procedure is "Standards Action" [RFC8126]. The initial
allocation is as indicated in Table 6:
+------------+-----------------------------------+---------------+
| Bit number | Capability description | Reference |
+============+===================================+===============+
| 0 | Connectivity is bidirectional (B) | This document |
+------------+-----------------------------------+---------------+
Table 6: Initial SIO Flags
8.9. Error in Projected Route ICMPv6 Code
In some cases RPL will return an ICMPv6 error message when a message In some cases RPL will return an ICMPv6 error message when a message
cannot be forwarded along a Projected Route. This ICMPv6 error cannot be forwarded along a Projected Route. This ICMPv6 error
message is "Error in Projected Route". message is "Error in Projected Route".
IANA has defined an ICMPv6 "Code" Fields Registry for ICMPv6 Message IANA has defined an ICMPv6 "Code" Fields Registry for ICMPv6 Message
Types. ICMPv6 Message Type 1 describes "Destination Unreachable" Types. ICMPv6 Message Type 1 describes "Destination Unreachable"
codes. This specification requires that a new code is allocated from codes. This specification requires that a new code is allocated from
the ICMPv6 Code Fields Registry for ICMPv6 Message Type 1, for "Error the ICMPv6 Code Fields Registry for ICMPv6 Message Type 1, for "Error
in Projected Route", with a suggested code value of 8, to be in Projected Route", with a suggested code value of 8, to be
skipping to change at page 19, line 40 skipping to change at page 22, line 45
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
11. Informative References 11. Informative References
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and [RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/info/rfc7102>. 2014, <https://www.rfc-editor.org/info/rfc7102>.
[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>.
[6TiSCH-ARCHI] [6TiSCH-ARCHI]
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", Work in Progress, Internet-Draft, of IEEE 802.15.4", Work in Progress, Internet-Draft,
draft-ietf-6tisch-architecture-27, 18 October 2019, draft-ietf-6tisch-architecture-28, 29 October 2019,
<https://tools.ietf.org/html/draft-ietf-6tisch- <https://tools.ietf.org/html/draft-ietf-6tisch-
architecture-27>. architecture-28>.
[RAW-PS] Thubert, P. and G. Papadopoulos, "Reliable and Available [RAW-PS] Thubert, P. and G. Papadopoulos, "Reliable and Available
Wireless Problem Statement", Work in Progress, Internet- Wireless Problem Statement", Work in Progress, Internet-
Draft, draft-pthubert-raw-problem-statement-04, 23 October Draft, draft-pthubert-raw-problem-statement-04, 23 October
2019, <https://tools.ietf.org/html/draft-pthubert-raw- 2019, <https://tools.ietf.org/html/draft-pthubert-raw-
problem-statement-04>. problem-statement-04>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655, "Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019, DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>. <https://www.rfc-editor.org/info/rfc8655>.
[PCE] IETF, "Path Computation Element", November 2019, [PCE] IETF, "Path Computation Element", November 2019,
<https://datatracker.ietf.org/doc/charter-ietf-pce/>. <https://datatracker.ietf.org/doc/charter-ietf-pce/>.
Appendix A. Applications Appendix A. Applications
A.1. Loose Source Routing in Non-storing Mode 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 7. uses the Non-Storing Mode of Operation as represented in Figure 8.
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.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
skipping to change at page 21, line 5 skipping to change at page 24, line 21
+-----+ ^ | | +-----+ ^ | |
| | DAO | ACK | | | DAO | ACK |
o o o o | | | Strict o o o o | | | Strict
o o o o o o o o o | | | Source o o o o o o o o o | | | Source
o o o o o o o o o o | | | Route o o o o o o o o o o | | | 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 v o o o o o o o o | v v
o o o o o o o o
LLN LLN
Figure 7: RPL non-storing mode of operation Figure 8: RPL non-storing mode of operation
Based on the parent-children relationships expressed in the non- Based on the parent-children relationships expressed in the non-
storing DAO messages,the Root possesses topological information about storing DAO messages,the Root possesses topological information about
the whole network, though this information is limited to the the whole network, though this information is limited to the
structure of the DODAG for which it is the destination. A packet structure of the DODAG for which it is the destination. A packet
that is generated within the domain will always reach the Root, which that is generated within the domain will always reach the Root, which
can then apply a source routing information to reach the destination can then apply a source routing information to reach the destination
if the destination is also in the DODAG. Similarly, a packet coming if the destination is also in the DODAG. Similarly, a packet coming
from the outside of the domain for a destination that is expected to from the outside of the domain for a destination that is expected to
be in a RPL domain reaches the Root. be in a RPL domain reaches the Root.
skipping to change at page 22, line 13 skipping to change at page 25, line 24
effectively become loose. effectively become loose.
A.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) and Multipoint-to- RPL is optimized for Point-to-Multipoint (P2MP) and Multipoint-to-
Point (MP2P), whereby routes are always installed along the RPL DODAG Point (MP2P), whereby routes are always installed along the RPL DODAG
respectively from and towards the DODAG Root. Transversal Peer to respectively from and towards the DODAG Root. Transversal Peer to
Peer (P2P) routes in a RPL network will generally suffer from some Peer (P2P) routes in a RPL network will generally suffer from some
elongated (stretched) path versus the best possible path, since elongated (stretched) path versus the best possible path, since
routing between 2 nodes always happens via a common parent, as routing between 2 nodes always happens via a common parent, as
illustrated in Figure 8: illustrated in Figure 9:
* in non-storing mode, all packets routed within the DODAG flow all * 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.
* In storing mode, unless the destination is a child of the source, * In storing mode, unless the destination is a child of the source,
skipping to change at page 22, line 48 skipping to change at page 26, line 21
+-----+ +-----+
X X
^ v o o ^ v o o
^ o o v o o o o o ^ o o v o o o o o
^ o o o v o o o o o ^ o o o v o o o o o
^ o o v o o o o o ^ o o v o o o o o
S o o o D o o o S o o o D o o o
o o o o o o o o
LLN LLN
Figure 8: Routing Stretch between S and D via common parent X Figure 9: Routing Stretch between S and D via common parent X
It results that it is often beneficial to enable transversal P2P It results that it is often beneficial to enable transversal P2P
routes, either if the RPL route presents a stretch from shortest routes, either if the RPL route presents a stretch from shortest
path, or if the new route is engineered with a different objective. path, or if the new route is engineered with a different objective.
For that reason, earlier work at the IETF introduced the "Reactive For that reason, earlier work at the IETF introduced the "Reactive
Discovery of Point-to-Point Routes in Low Power and Lossy Networks" Discovery of Point-to-Point Routes in Low Power and Lossy Networks"
[RFC6997], which specifies a distributed method for establishing [RFC6997], which specifies a distributed method for establishing
optimized P2P routes. This draft proposes an alternate based on a optimized P2P routes. This draft proposes an alternate based on a
centralized route computation. centralized route computation.
skipping to change at page 23, line 27 skipping to change at page 26, line 48
+-----+ +-----+
| |
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 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 Transversal Route Figure 10: Projected Transversal Route
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.
Appendix B. Examples Appendix B. Examples
B.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 10, if the source is node 41 Instance in the diagram shown in Figure 11, 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.
------+--------- ------+---------
| Internet | Internet
| |
+-----+ +-----+
| | Border Router | | Border Router
| | (RPL Root) | | (RPL Root)
+-----+ +-----+
| \ \____ | \ \____
skipping to change at page 24, line 26 skipping to change at page 27, line 43
o 22 o 23 o 24 o 25 o 22 o 23 o 24 o 25
/ \ | \ \ / \ | \ \
o 31 o 32 o o o 35 o 31 o 32 o o o 35
/ / | \ | \ / / | \ | \
o 41 o 42 o o o 45 o 46 o 41 o 42 o o o 45 o 46
| | | | \ | | | | | \ |
o 51 o 52 o 53 o o 55 o 56 o 51 o 52 o 53 o o 55 o 56
LLN LLN
Figure 10: Example DODAG forming a logical tree topology Figure 11: Example DODAG forming a logical tree topology
With this draft, the Root can install a storing mode routing states With this draft, the Root can install a storing mode routing states
along a segment that is either from itself to the destination, or along a segment that is either from itself to the destination, or
from one or more common parents for a particular source/destination from one or more common parents for a particular source/destination
pair towards that destination (in this particular example, this would pair towards that destination (in this particular example, this would
be the segment made of nodes 22, 32, 42). be the segment made of nodes 22, 32, 42).
In the example below, say that there is a lot of traffic to nodes 55 In the example below, say that there is a lot of traffic to nodes 55
and 56 and the Root decides to reduce the size of routing headers to and 56 and the Root decides to reduce the size of routing headers to
those destinations. The Root can first send a DAO to node 45 those destinations. The Root can first send a DAO to node 45
skipping to change at page 25, line 27 skipping to change at page 28, line 47
+-----+ +-----+
| P-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 11: P-DAO from Root Figure 12: 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
skipping to change at page 26, line 21 skipping to change at page 29, line 28
+-----+ +-----+
^ P-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 12: P-DAO-ACK to Root Figure 13: 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)
+-----+ +-----+
| |
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 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 13: Projected Transversal Route Figure 14: Projected Transversal Route
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
Building D, 45 Allee des Ormes - BP1200 Building D, 45 Allee des Ormes - BP1200
06254 Mougins - Sophia Antipolis 06254 Mougins - Sophia Antipolis
France France
Phone: +33 497 23 26 34 Phone: +33 497 23 26 34
Email: pthubert@cisco.com Email: pthubert@cisco.com
Rahul Arvind Jadhav Rahul Arvind Jadhav
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