rfc9854.original   rfc9854.txt 
ROLL C.E. Perkins Internet Engineering Task Force (IETF) C.E. Perkins
Internet-Draft Blue Meadow Networks Request for Comments: 9854 Blue Meadow Networks
Intended status: Standards Track S.V.R.Anand Category: Standards Track S.V.R. Anand
Expires: 3 September 2025 Indian Institute of Science ISSN: 2070-1721 Indian Institute of Science
S. Anamalamudi S. Anamalamudi
SRM University-AP SRM University-AP
B. Liu B. Liu
Huawei Technologies Huawei Technologies
2 March 2025 August 2025
Supporting Asymmetric Links in Low Power Networks: AODV-RPL Supporting Asymmetric Links in Low-Power Networks: AODV-RPL
draft-ietf-roll-aodv-rpl-20
Abstract Abstract
Route discovery for symmetric and asymmetric Peer-to-Peer (P2P) Route discovery for symmetric and asymmetric Peer-to-Peer (P2P)
traffic flows is a desirable feature in Low power and Lossy Networks traffic flows is a desirable feature in Low-Power and Lossy Networks
(LLNs). For that purpose, this document specifies a reactive P2P (LLNs). For that purpose, this document specifies a reactive P2P
route discovery mechanism for both hop-by-hop routes and source route discovery mechanism for both hop-by-hop routes and source
routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL
protocol (AODV-RPL). Paired Instances are used to construct protocol (AODV-RPL). Paired instances are used to construct
directional paths, for cases where there are asymmetric links between directional paths for cases where there are asymmetric links between
source and target nodes. source and target nodes.
Status of This Memo Status of This Memo
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https://www.rfc-editor.org/info/rfc9854.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology
3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 7 3. Overview of AODV-RPL
4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 9 4. AODV-RPL DIO Options
4.1. AODV-RPL RREQ Option . . . . . . . . . . . . . . . . . . 9 4.1. AODV-RPL RREQ Option
4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 11 4.2. AODV-RPL RREP Option
4.3. AODV-RPL Target Option . . . . . . . . . . . . . . . . . 13 4.3. AODV-RPL Target Option
5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 14 5. Symmetric and Asymmetric Routes
6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 17 6. AODV-RPL Operation
6.1. Route Request Generation . . . . . . . . . . . . . . . . 17 6.1. Route Request Generation
6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 18 6.2. Receiving and Forwarding RREQ Messages
6.2.1. Step 1: RREQ reception and evaluation . . . . . . . . 18 6.2.1. Step 1: RREQ Reception and Evaluation
6.2.2. Step 2: TargNode and Intermediate Router 6.2.2. Step 2: TargNode and Intermediate Router Determination
determination . . . . . . . . . . . . . . . . . . . . 18 6.2.3. Step 3: Intermediate Router RREQ Processing
6.2.3. Step 3: Intermediate Router RREQ processing . . . . . 19
6.2.4. Step 4: Symmetric Route Processing at an Intermediate 6.2.4. Step 4: Symmetric Route Processing at an Intermediate
Router . . . . . . . . . . . . . . . . . . . . . . . 20 Router
6.2.5. Step 5: RREQ propagation at an Intermediate Router . 20 6.2.5. Step 5: RREQ Propagation at an Intermediate Router
6.2.6. Step 6: RREQ reception at TargNode . . . . . . . . . 21 6.2.6. Step 6: RREQ Reception at TargNode
6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 21 6.3. Generating Route Reply (RREP) at TargNode
6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 21 6.3.1. RREP-DIO for Symmetric Route
6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 22 6.3.2. RREP-DIO for Asymmetric Route
6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 22 6.3.3. RPLInstanceID Pairing
6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 23 6.4. Receiving and Forwarding Route Reply
6.4.1. Step 1: Receiving and Evaluation . . . . . . . . . . 23 6.4.1. Step 1: Receiving and Evaluation
6.4.2. Step 2: OrigNode or Intermediate Router . . . . . . . 23 6.4.2. Step 2: OrigNode or Intermediate Router
6.4.3. Step 3: Build Route to TargNode . . . . . . . . . . . 23 6.4.3. Step 3: Build Route to TargNode
6.4.4. Step 4: RREP Propagation . . . . . . . . . . . . . . 24 6.4.4. Step 4: RREP Propagation
7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 24 7. Gratuitous RREP
8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 25 8. Operation of Trickle Timer
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 9. IANA Considerations
10. Security Considerations . . . . . . . . . . . . . . . . . . . 26 10. Security Considerations
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27 11. References
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27 11.1. Normative References
12.1. Normative References . . . . . . . . . . . . . . . . . . 27 11.2. Informative References
12.2. Informative References . . . . . . . . . . . . . . . . . 28 Appendix A. Example: Using ETX/RSSI Values to Determine Value of S
Bit
Appendix A. Example: Using ETX/RSSI Values to determine value of S Appendix B. Some Example AODV-RPL Message Flows
bit . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 B.1. Example Control Message Flows in Symmetric and Asymmetric
Appendix B. Some Example AODV-RPL Message Flows . . . . . . . . 32 Networks
B.1. Example control message flows in symmetric and asymmetric B.2. Example RREP_WAIT Handling
networks . . . . . . . . . . . . . . . . . . . . . . . . 32 B.3. Example G-RREP Handling
B.2. Example RREP_WAIT handling . . . . . . . . . . . . . . . 34 Acknowledgements
B.3. Example G-RREP handling . . . . . . . . . . . . . . . . . 35 Contributors
Appendix C. Changelog . . . . . . . . . . . . . . . . . . . . . 36 Authors' Addresses
C.1. Changes from version 19 to version 20 . . . . . . . . . . 36
C.2. Changes from version 18 to version 19 . . . . . . . . . . 37
C.3. Changes from version 17 to version 18 . . . . . . . . . . 37
C.4. Changes from version 16 to version 17 . . . . . . . . . . 37
C.5. Changes from version 15 to version 16 . . . . . . . . . . 38
C.6. Changes from version 14 to version 15 . . . . . . . . . . 38
C.7. Changes from version 13 to version 14 . . . . . . . . . . 39
C.8. Changes from version 12 to version 13 . . . . . . . . . . 40
C.9. Changes from version 11 to version 12 . . . . . . . . . . 40
C.10. Changes from version 10 to version 11 . . . . . . . . . . 41
C.11. Changes from version 09 to version 10 . . . . . . . . . . 42
C.12. Changes from version 08 to version 09 . . . . . . . . . . 42
C.13. Changes from version 07 to version 08 . . . . . . . . . . 43
C.14. Changes from version 06 to version 07 . . . . . . . . . . 44
C.15. Changes from version 05 to version 06 . . . . . . . . . . 44
C.16. Changes from version 04 to version 05 . . . . . . . . . . 44
C.17. Changes from version 03 to version 04 . . . . . . . . . . 44
C.18. Changes from version 02 to version 03 . . . . . . . . . . 44
Appendix D. Contributors . . . . . . . . . . . . . . . . . . . . 45
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46
1. Introduction 1. Introduction
Routing Protocol for Low-Power and Lossy Networks (RPL) [RFC6550] is The Routing Protocol for Low-Power and Lossy Networks (RPL) [RFC6550]
an IPv6 distance vector routing protocol designed to support multiple is an IPv6 distance vector routing protocol designed to support
traffic flows through a root-based Destination-Oriented Directed multiple traffic flows through a root-based Destination-Oriented
Acyclic Graph (DODAG). Typically, a router does not have routing Directed Acyclic Graph (DODAG). Typically, a router does not have
information for destinations attached to most other routers. routing information for destinations attached to most other routers.
Consequently, for traffic between routers within the DODAG (i.e., Consequently, for traffic between routers within the DODAG (i.e., P2P
Peer-to-Peer (P2P) traffic) data packets either have to traverse the traffic), data packets either have to traverse the root in non-
root in non-storing mode, or traverse a common ancestor in storing storing mode or traverse a common ancestor in storing mode. Such P2P
mode. Such P2P traffic is thereby likely to traverse longer routes traffic is thereby likely to traverse longer routes and may suffer
and may suffer severe congestion near the root (for more information severe congestion near the root (for more information, see [RFC6687],
see [RFC6687], [RFC6997], [RFC6998], [RFC9010]). The network [RFC6997], [RFC6998], and [RFC9010]). The network environment that
environment that is considered in this document is assumed to be the is considered in this document is assumed to be the same as that
same as described in Section 1 of [RFC6550]. Each radio interface/ described in Section 1 of [RFC6550]. Each radio interface/link and
link and the associated address should be treated as an independent the associated address should be treated as an independent
intermediate router. Such routers have different links and the rules intermediate router. Such routers have different links, and the
for the link symmetry apply independently for each of these. rules for link symmetry apply independently for each of these.
The route discovery process in AODV-RPL is modeled on the analogous The route discovery process in AODV-RPL is modeled on the analogous
peer-to-peer procedure specified in AODV [RFC3561]. The on-demand P2P procedure specified in AODV [RFC3561]. The on-demand property of
property of AODV route discovery is useful for the needs of routing AODV route discovery is useful for the needs of routing in RPL-based
in RPL-based LLNs when routes are needed but aren't yet established. LLNs when routes are needed but aren't yet established. P2P routing
Peer-to-peer routing is desirable to discover shorter routes, and is desirable to discover shorter routes, especially when it is
especially when it is desired to avoid directing additional traffic desired to avoid directing additional traffic through a root or
through a root or gateway node of the network. It may happen that gateway node of the network. It may happen that some routes need to
some routes need to be established proactively when known beforehand be established proactively when known beforehand and when AODV-RPL's
and when AODV-RPL's route discovery process introduces unwanted delay route discovery process introduces unwanted delay when the
at the time when the application is launched. application is launched.
AODV terminology has been adapted for use with AODV-RPL messages, AODV terminology has been adapted for use with AODV-RPL messages,
namely RREQ for Route Request, and RREP for Route Reply. AODV-RPL namely "RREQ" for "Route Request", and "RREP" for "Route Reply".
currently omits some features compared to AODV -- in particular, AODV-RPL currently omits some features compared to AODV -- in
flagging Route Errors, "blacklisting" unidirectional links particular, flagging route errors, "blacklisting" unidirectional
([RFC3561]), multihoming, and handling unnumbered interfaces. links [RFC3561], multihoming, and handling unnumbered interfaces.
AODV-RPL reuses and extends the core RPL functionality to support AODV-RPL reuses and extends the core RPL functionality to support
routes with bidirectional asymmetric links. It retains RPL's DODAG routes with bidirectional asymmetric links. It retains RPL's DODAG
formation, RPL Instance and the associated Objective Function formation, RPL Instance and the associated Objective Function
(defined in [RFC6551]), trickle timers, and support for storing and (defined in [RFC6551]), Trickle timers, and support for storing and
non-storing modes. AODV-RPL adds basic messages RREQ and RREP as non-storing modes. AODV-RPL adds the basic messages RREQ and RREP as
part of RPL DODAG Information Object (DIO) control message, which go part of the RPL DODAG Information Object (DIO) control message, which
in separate (paired) RPL instances. AODV-RPL does not utilize the go in separate (paired) RPL instances. AODV-RPL does not utilize the
Destination Advertisement Object (DAO) control message of RPL. AODV- Destination Advertisement Object (DAO) control message of RPL. AODV-
RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) with RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) with
three new Options for the DIO message, dedicated to discover P2P three new options for the DIO message, dedicated to discovering P2P
routes. These P2P routes may differ from routes discoverable by routes. These P2P routes may differ from routes discoverable by
native RPL. Since AODV-RPL uses newly defined Options and a newly native RPL. Since AODV-RPL uses newly defined options and a newly
allocated multicast group (see Section 9), there is no conflict with allocated multicast group (see Section 9), there is no conflict with
P2P-RPL [RFC6997], a previous document using the same MOP. AODV-RPL P2P-RPL [RFC6997], a previous document using the same MOP. AODV-RPL
can be operated whether or not P2P-RPL or native RPL is running can be operated whether or not P2P-RPL or native RPL is running
otherwise. AODV-RPL could be used for networks in which routes are otherwise. AODV-RPL could be used for networks in which routes are
needed with Objective Functions that cannot be satisfied by routes needed with Objective Functions that cannot be satisfied by routes
that are constrained to traverse the root of the network or other that are constrained to traverse the root of the network or other
common ancestors. P2P routes often require fewer hops and therefore common ancestors. P2P routes often require fewer hops and therefore
consume less resources than routes that traverse the root or other consume less resources than routes that traverse the root or other
common ancestors. Similar in cost to base RPL [RFC6550], the cost common ancestors. Similar in cost to base RPL [RFC6550], the cost
will depend on many factors such as the proximity of the OrigNode and will depend on many factors such as the proximity of the OrigNode and
TargNodes and distribution of symmetric/asymmetric P2P links. TargNodes and distribution of symmetric/asymmetric P2P links.
Experience with AODV [aodv-tot] suggests that AODV-RPL will often Experience with AODV [aodv-tot] suggests that AODV-RPL will often
find routes with improved rank compared to routes constrained to find routes with improved rank compared to routes constrained to
traverse a common ancestor of the source and destination nodes. traverse a common ancestor of the source and destination nodes.
2. Terminology 2. Terminology
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
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
AODV-RPL reuses names for messages and data structures, including AODV-RPL reuses names for messages and data structures, including
Rank, DODAG and DODAGID, as defined in RPL [RFC6550]. Rank, DODAG, and DODAGID, as defined in RPL [RFC6550].
This document also uses the following terms:
AODV AODV
Ad Hoc On-demand Distance Vector Routing [RFC3561]. Ad hoc On-Demand Distance Vector [RFC3561].
ART option ART option
AODV-RPL Target option: a target option defined in this document. The AODV-RPL Target option defined in this document.
Asymmetric Route Asymmetric Route
The route from the OrigNode to the TargNode can traverse different The route from the OrigNode to the TargNode can traverse different
nodes than the route from the TargNode to the OrigNode. An nodes than the route from the TargNode to the OrigNode. An
asymmetric route may result from the asymmetry of links, such that asymmetric route may result from the asymmetry of links, such that
only one direction of the series of links satisfies the Objective only one direction of the series of links satisfies the Objective
Function during route discovery. Function during route discovery.
Bi-directional Asymmetric Link Bidirectional Asymmetric Link
A link that can be used in both directions but with different link A link that can be used in both directions but with different link
characteristics. characteristics.
DIO DIO
DODAG Information Object (as defined in [RFC6550]) DODAG Information Object (as defined in [RFC6550]).
DODAG RREQ-Instance (or simply RREQ-Instance) DODAG RREQ-Instance (or simply RREQ-Instance)
RPL Instance built using the DIO with RREQ option; used for An RPL Instance built using the DIO with RREQ option; used for
transmission of control messages from OrigNode to TargNode, thus transmission of control messages from OrigNode to TargNode, thus
enabling data transmission from TargNode to OrigNode. enabling data transmission from TargNode to OrigNode.
DODAG RREP-Instance (or simply RREP-Instance) DODAG RREP-Instance (or simply RREP-Instance)
RPL Instance built using the DIO with RREP option; used for An RPL Instance built using the DIO with RREP option; used for
transmission of control messages from TargNode to OrigNode thus transmission of control messages from TargNode to OrigNode, thus
enabling data transmission from OrigNode to TargNode. enabling data transmission from OrigNode to TargNode.
Downward Direction Downward Direction
The direction from the OrigNode to the TargNode. The direction from the OrigNode to the TargNode.
Downward Route Downward Route
A route in the downward direction. A route in the downward direction.
hop-by-hop route Hop-by-hop route
A route for which each router along the routing path stores A route for which each router along the routing path stores
routing information about the next hop. A hop-by-hop route is routing information about the next hop. A hop-by-hop route is
created using RPL's "storing mode". created using RPL's "storing mode".
OF OF
An Objective Function as defined in [RFC6550]. Objective Function (as defined in [RFC6550]).
OrigNode OrigNode
The IPv6 router (Originating Node) initiating the AODV-RPL route The IPv6 router (originating node) initiating the AODV-RPL route
discovery to obtain a route to TargNode. discovery to obtain a route to TargNode.
Paired DODAGs Paired DODAGs
Two DODAGs for a single route discovery process between OrigNode Two DODAGs for a single route discovery process between OrigNode
and TargNode. and TargNode.
P2P P2P
Peer-to-Peer -- in other words, not constrained a priori to Peer-to-Peer (in other words, not constrained a priori to traverse
traverse a common ancestor. a common ancestor).
REJOIN_REENABLE REJOIN_REENABLE
The duration during which a node is prohibited from joining a The duration during which a node is prohibited from joining a
DODAG with a particular RREQ-InstanceID, after it has left a DODAG DODAG with a particular RREQ-InstanceID, after it has left a DODAG
with the same RREQ-InstanceID. The default value of with the same RREQ-InstanceID. The default value of
REJOIN_REENABLE is 15 minutes. REJOIN_REENABLE is 15 minutes.
RREQ RREQ
A RREQ-DIO message. A RREQ-DIO message.
RREQ-DIO message RREQ-DIO message
A DIO message containing the RREQ option. The RPLInstanceID in A DIO message containing the RREQ option. The RPLInstanceID in
RREQ-DIO is assigned locally by the OrigNode. The RREQ-DIO RREQ-DIO is assigned locally by the OrigNode. The RREQ-DIO
message has a secure variant as noted in [RFC6550]. message has a secure variant as noted in [RFC6550].
RREQ-InstanceID RREQ-InstanceID
The RPLInstanceID for the RREQ-Instance. The RREQ-InstanceID is The RPLInstanceID for the RREQ-Instance. The RREQ-InstanceID is
formed as the ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr), formed as the ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr),
where Orig_RPLInstanceID is the local RPLInstanceID allocated by where Orig_RPLInstanceID is the local RPLInstanceID allocated by
OrigNode, and OrigNode-IPaddr is an IP address of OrigNode. The OrigNode and OrigNode-IPaddr is an IP address of OrigNode. The
RREQ-InstanceID uniquely identifies the RREQ-Instance. RREQ-InstanceID uniquely identifies the RREQ-Instance.
RREP RREP
A RREP-DIO message. A RREP-DIO message.
RREP-DIO message RREP-DIO message
A DIO message containing the RREP option. OrigNode pairs the A DIO message containing the RREP option. OrigNode pairs the
RPLInstanceID in RREP-DIO to the one in the associated RREQ-DIO RPLInstanceID in RREP-DIO to the one in the associated RREQ-DIO
message (i.e., the RREQ-InstanceID) as described in Section 6.3.2. message (i.e., the RREQ-InstanceID) as described in Section 6.3.2.
The RREP-DIO message has a secure variant as noted in [RFC6550]. The RREP-DIO message has a secure variant as noted in [RFC6550].
RREP-InstanceID RREP-InstanceID
The RPLInstanceID for the RREP-Instance. The RREP-InstanceID is The RPLInstanceID for the RREP-Instance. The RREP-InstanceID is
formed as the ordered pair (Targ_RPLInstanceID, TargNode-IPaddr), formed as the ordered pair (Targ_RPLInstanceID, TargNode-IPaddr),
where Targ_RPLInstanceID is the local RPLInstanceID allocated by where Targ_RPLInstanceID is the local RPLInstanceID allocated by
TargNode, and TargNode-IPaddr is an IP address of TargNode. The TargNode and TargNode-IPaddr is an IP address of TargNode. The
RREP-InstanceID uniquely identifies the RREP-Instance. The RREP-InstanceID uniquely identifies the RREP-Instance. The
RPLInstanceID in the RREP message along with the Delta value RPLInstanceID in the RREP message along with the Delta value
indicates the associated RREQ-InstanceID. The InstanceIDs are indicates the associated RREQ-InstanceID. The InstanceIDs are
matched by mechanism explained in Section 6.3.3 matched by the mechanism explained in Section 6.3.3.
Source routing Source routing
A mechanism by which the source supplies a vector of addresses A mechanism by which the source supplies a vector of addresses
towards the destination node along with each data packet towards the destination node along with each data packet
[RFC6550]. [RFC6550].
Symmetric route Symmetric route
The upstream and downstream routes traverse the same routers and The upstream and downstream routes traverse the same routers and
over the same links. over the same links.
TargNode TargNode
The IPv6 router (Target Node) for which OrigNode requires a route The IPv6 router (target node) for which OrigNode requires a route
and initiates Route Discovery within the LLN. and initiates route discovery within the LLN.
Upward Direction Upward Direction
The direction from the TargNode to the OrigNode. The direction from the TargNode to the OrigNode.
Upward Route Upward Route
A route in the upward direction. A route in the upward direction.
3. Overview of AODV-RPL 3. Overview of AODV-RPL
With AODV-RPL, routes from OrigNode to TargNode within the LLN do not With AODV-RPL, routes from OrigNode to TargNode within the LLN do not
become established until they are needed. The route discovery become established until they are needed. The route discovery
mechanism in AODV-RPL is invoked when OrigNode has data for delivery mechanism in AODV-RPL is invoked when OrigNode has data for delivery
to a TargNode, but existing routes do not satisfy the application's to a TargNode, but existing routes do not satisfy the application's
requirements. For this reason AODV-RPL is considered to be an requirements. For this reason, AODV-RPL is considered to be an
example of "on-demand" routing protocols. Such protocols are also example of an "on-demand" routing protocol. Such protocols are also
known as "reactive" routing protocols since their operations are known as "reactive" routing protocols since their operations are
triggered in reaction to a determination that a new route is needed. triggered in reaction to a determination that a new route is needed.
AODV-RPL works without requiring the use of RPL or any other routing AODV-RPL works without requiring the use of RPL or any other routing
protocol. protocol.
The routes discovered by AODV-RPL are not constrained to traverse a The routes discovered by AODV-RPL are not constrained to traverse a
common ancestor. AODV-RPL can enable asymmetric communication paths common ancestor. AODV-RPL can enable asymmetric communication paths
in networks with bidirectional asymmetric links. For this purpose, in networks with bidirectional asymmetric links. For this purpose,
AODV-RPL enables discovery of two routes: namely, one from OrigNode AODV-RPL enables discovery of two routes: namely, one from OrigNode
to TargNode, and another from TargNode to OrigNode. AODV-RPL also to TargNode and another from TargNode to OrigNode. AODV-RPL also
enables discovery of symmetric routes along Paired DODAGs, when enables discovery of symmetric routes along paired DODAGs, when
symmetric routes are possible (see Section 5). symmetric routes are possible (see Section 5).
In AODV-RPL, routes are discovered by first forming a temporary DAG In AODV-RPL, routes are discovered by first forming a temporary
rooted at the OrigNode. Paired DODAGs (Instances) are constructed Directed Acyclic Graph (DAG) rooted at the OrigNode. Paired DODAGs
during route formation between the OrigNode and TargNode. The RREQ- (Instances) are constructed during route formation between the
Instance is formed by route control messages from OrigNode to OrigNode and TargNode. The RREQ-Instance is formed by route control
TargNode whereas the RREP-Instance is formed by route control messages from OrigNode to TargNode, whereas the RREP-Instance is
messages from TargNode to OrigNode. The route discovered in the formed by route control messages from TargNode to OrigNode. The
RREQ-Instance is used for transmitting data from TargNode to route discovered in the RREQ-Instance is used for transmitting data
OrigNode, and the route discovered in RREP-Instance is used for from TargNode to OrigNode, and the route discovered in RREP-Instance
transmitting data from OrigNode to TargNode. is used for transmitting data from OrigNode to TargNode.
Intermediate routers join the DODAGs based on the Rank [RFC6550] as Intermediate routers join the DODAGs based on the Rank [RFC6550] as
calculated from the DIO messages. AODV-RPL uses the same notion of calculated from the DIO messages. AODV-RPL uses the same notion of
rank as defined in RFC6550: "The Rank is the expression of a relative rank as defined in [RFC6550]:
position within a DODAG Version with regard to neighbors, and it is
not necessarily a good indication or a proper expression of a | The Rank is the expression of a relative position within a DODAG
distance or a path cost to the root." The Rank measurements provided | Version with regard to neighbors, and it is not necessarily a good
in AODV messages do not indicate a distance or a path cost to the | indication or a proper expression of a distance or a path cost to
root. | the root.
The Rank measurements provided in AODV messages do not indicate a
distance or a path cost to the root.
Henceforth in this document, "RREQ-DIO message" means the DIO message Henceforth in this document, "RREQ-DIO message" means the DIO message
from OrigNode toward TargNode, containing the RREQ option as from OrigNode toward TargNode, containing the RREQ option as
specified in Section 4.1. The RREQ-InstanceID is formed as the specified in Section 4.1. The RREQ-InstanceID is formed as the
ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr), where ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr), where
Orig_RPLInstanceID is the local RPLInstanceID allocated by OrigNode, Orig_RPLInstanceID is the local RPLInstanceID allocated by OrigNode
and OrigNode-IPaddr is the IP address of OrigNode. A node receiving and OrigNode-IPaddr is the IP address of OrigNode. A node receiving
the RREQ-DIO can use the RREQ-InstanceID to identify the proper OF the RREQ-DIO can use the RREQ-InstanceID to identify the proper OF
whenever that node receives a data packet with Source Address == whenever that node receives a data packet with Source Address ==
OrigNode-IPaddr and IPv6 RPL Option having the RPLInstanceID == OrigNode-IPaddr and IPv6 RPL Option having the RPLInstanceID ==
Orig_RPLInstanceID. The 'D' bit of the RPLInstanceID field is set to Orig_RPLInstanceID. The D bit of the RPLInstanceID field is set to 0
0 to indicate that the source address of the IPv6 packet is the to indicate that the source address of the IPv6 packet is the
DODAGID. DODAGID.
Similarly, "RREP-DIO message" means the DIO message from TargNode Similarly, "RREP-DIO message" means the DIO message from TargNode
toward OrigNode, containing the RREP option as specified in toward OrigNode, containing the RREP option as specified in
Section 4.2. The RREP-InstanceID is formed as the ordered pair Section 4.2. The RREP-InstanceID is formed as the ordered pair
(Targ_RPLInstanceID, TargNode-IPaddr), where Targ_RPLInstanceID is (Targ_RPLInstanceID, TargNode-IPaddr), where Targ_RPLInstanceID is
the local RPLInstanceID allocated by TargNode, and TargNode-IPaddr is the local RPLInstanceID allocated by TargNode and TargNode-IPaddr is
the IP address of TargNode. A node receiving the RREP-DIO can use the IP address of TargNode. A node receiving the RREP-DIO can use
the RREP-InstanceID to identify the proper OF whenever that node the RREP-InstanceID to identify the proper OF whenever that node
receives a data packet with Source Address == TargNode-IPaddr and receives a data packet with Source Address == TargNode-IPaddr and
IPv6 RPL Option having the RPLInstanceID == Targ_RPLInstanceID along IPv6 RPL Option having the RPLInstanceID == Targ_RPLInstanceID along
with 'D' == 0 as above. with D == 0 as above.
4. AODV-RPL DIO Options 4. AODV-RPL DIO Options
4.1. AODV-RPL RREQ Option 4.1. AODV-RPL RREQ Option
OrigNode selects one of its IPv6 addresses and sets it in the DODAGID OrigNode selects one of its IPv6 addresses and sets it in the DODAGID
field of the RREQ-DIO message. The address scope of the selected field of the RREQ-DIO message. The address scope of the selected
address MUST encompass the domain where the route is built (e.g, not address MUST encompass the domain where the route is built (e.g, not
link-local); otherwise the route discovery will fail. Exactly one link-local); otherwise, the route discovery will fail. Exactly one
RREQ option MUST be present in a RREQ-DIO message, otherwise the RREQ option MUST be present in a RREQ-DIO message; otherwise, the
message MUST be dropped. message MUST be dropped.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |S|H|X| Compr | L | RankLimit | | Option Type | Option Length |S|H|X| Compr | L | RankLimit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Orig SeqNo | | | Orig SeqNo | |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
| Address Vector (Optional, Variable Length) | | Address Vector (Optional, Variable Length) |
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .
Figure 1: Format for AODV-RPL RREQ Option Figure 1: Format for AODV-RPL RREQ Option
OrigNode supplies the following information in the RREQ option: OrigNode supplies the following information in the RREQ option:
Option Type Option Type
8-bit unsigned integer specifying the type of the option (TBD2) 8-bit unsigned integer specifying the type of the option (0x0B).
Option Length Option Length
8-bit unsigned integer specifying the length of the option in 8-bit unsigned integer specifying the length of the option in
octets, excluding the Type and Length fields. Variable due to the octets, excluding the Type and Length fields. It is variable due
presence of the address vector and the number of octets elided to the presence of the address vector and the number of octets
according to the Compr value. elided according to the Compr value.
S S
Symmetric bit indicating a symmetric route from the OrigNode to Symmetric bit indicating a symmetric route from the OrigNode to
the router transmitting this RREQ-DIO. See Section 5. the router transmitting this RREQ-DIO. See Section 5.
H H
Set to one for a hop-by-hop route. Set to zero for a source Set to one for a hop-by-hop route. Set to zero for a source
route. This flag controls both the downstream route and upstream route. This flag controls both the downstream route and upstream
route. route.
X X
Reserved; MUST be initialized to zero and ignored upon reception. Reserved. This field MUST be initialized to zero and ignored upon
reception.
Compr Compr
4-bit unsigned integer. When Compr is nonzero, exactly that 4-bit unsigned integer. When Compr is nonzero, exactly that
number of prefix octets MUST be elided from each address before number of prefix octets MUST be elided from each address before
storing it in the Address Vector. The octets elided are shared storing it in the Address Vector. The octets elided are shared
with the IPv6 address in the DODAGID. This field is only used in with the IPv6 address in the DODAGID. This field is only used in
source routing mode (H=0). In hop-by-hop mode (H=1), this field source routing mode (H=0). In hop-by-hop mode (H=1), this field
MUST be set to zero and ignored upon reception. MUST be set to zero and ignored upon reception.
L L
2-bit unsigned integer determining the time duration that a node 2-bit unsigned integer determining the time duration that a node
is able to belong to the RREQ-Instance (a temporary DAG including is able to belong to the RREQ-Instance (a temporary DAG including
the OrigNode and the TargNode). Once the time is reached, a node the OrigNode and the TargNode). Once the time is reached, a node
SHOULD leave the RREQ-Instance and stop sending or receiving any SHOULD leave the RREQ-Instance and stop sending or receiving any
more DIOs for the RREQ-Instance; otherwise memory and network more DIOs for the RREQ-Instance; otherwise, memory and network
resources are likely to be consumed unnecessarily. This naturally resources are likely to be consumed unnecessarily. This naturally
depends on the node's ability to keep track of time. Once a node depends on the node's ability to keep track of time. Once a node
leaves an RREQ-Instance, it MUST NOT rejoin the same RREQ-Instance leaves an RREQ-Instance, it MUST NOT rejoin the same RREQ-Instance
for at least the time interval specified by the configuration for at least the time interval specified by the configuration
variable REJOIN_REENABLE. L is independent from the route variable REJOIN_REENABLE. L is independent from the route
lifetime, which is defined in the DODAG configuration option. lifetime, which is defined in the DODAG configuration option.
* 0x00: No time limit imposed. * 0x00: No time limit imposed
* 0x01: 16 seconds * 0x01: 16 seconds
* 0x02: 64 seconds * 0x02: 64 seconds
* 0x03: 256 seconds * 0x03: 256 seconds
RankLimit RankLimit
8-bit unsigned integer specifying the upper limit on the integer 8-bit unsigned integer specifying the upper limit on the integer
portion of the Rank (calculated using the DAGRank() macro defined portion of the Rank (calculated using the DAGRank() macro defined
in [RFC6550]). A value of 0 in this field indicates the limit is in [RFC6550]). A value of 0 in this field indicates the limit is
infinity. infinity.
Orig SeqNo Orig SeqNo
8-bit unsigned integer specifying the sequence Number of OrigNode. 8-bit unsigned integer specifying the sequence Number of OrigNode.
See Section 6.1. See Section 6.1.
Address Vector Address Vector
A vector of IPv6 addresses representing the route that the RREQ- A vector of IPv6 addresses representing the route that the RREQ-
DIO has passed. It is only present when the H bit is set to 0. DIO has passed. It is only present when the H bit is set to 0.
The prefix of each address is elided according to the Compr field. The prefix of each address is elided according to the Compr field.
TargNode can join the RREQ instance at a Rank whose integer portion TargNode can join the RREQ-Instance at a Rank whose integer portion
is less than or equal to the RankLimit. Any other node MUST NOT join is less than or equal to the RankLimit. Any other node MUST NOT join
a RREQ instance if its own Rank would be equal to or higher than a RREQ-Instance if its own Rank would be equal to or higher than the
RankLimit. A router MUST discard a received RREQ if the integer part RankLimit. A router MUST discard a received RREQ if the integer part
of the advertised Rank equals or exceeds the RankLimit. of the advertised Rank equals or exceeds the RankLimit.
4.2. AODV-RPL RREP Option 4.2. AODV-RPL RREP Option
TargNode sets one of its IPv6 addresses in the DODAGID field of the TargNode sets one of its IPv6 addresses in the DODAGID field of the
RREP-DIO message. The address scope of the selected address must RREP-DIO message. The address scope of the selected address must
encompass the domain where the route is built (e.g, not link-local). encompass the domain where the route is built (e.g, not link-local).
Exactly one RREP option MUST be present in a RREP-DIO message, Exactly one RREP option MUST be present in a RREP-DIO message,
otherwise the message MUST be dropped. TargNode supplies the otherwise, the message MUST be dropped. TargNode supplies the
following information in the RREP option: following information in the RREP option:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |G|H|X| Compr | L | RankLimit | | Option Type | Option Length |G|H|X| Compr | L | RankLimit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Delta |X X| | | Delta |X X| |
+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+ |
| | | |
| | | |
| Address Vector (Optional, Variable Length) | | Address Vector (Optional, Variable Length) |
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .
Figure 2: Format for AODV-RPL RREP option Figure 2: Format for AODV-RPL RREP Option
Option Type Option Type
8-bit unsigned integer specifying the type of the option (TBD3) 8-bit unsigned integer specifying the type of the option (0x0C).
Option Length Option Length
8-bit unsigned integer specifying the length of the option in 8-bit unsigned integer specifying the length of the option in
octets, excluding the Type and Length fields. Variable due to the octets, excluding the Type and Length fields. It is variable due
presence of the address vector and the number of octets elided to the presence of the address vector and the number of octets
according to the Compr value. elided according to the Compr value.
G G
Gratuitous RREP (see Section 7). Gratuitous RREP (see Section 7).
H H
The H bit in the RREP option MUST be set to be the same as the H The H bit in the RREP option MUST be set to be the same as the H
bit in RREQ option. It requests either source routing (H=0) or bit in the RREQ option. It requests either source routing (H=0)
hop-by-hop (H=1) for the downstream route. or hop-by-hop (H=1) for the downstream route.
X X
1-bit Reserved field; MUST be initialized to zero and ignored upon 1-bit Reserved field. This field MUST be initialized to zero and
reception. ignored upon reception.
Compr Compr
4-bit unsigned integer. Same definition as in RREQ option. 4-bit unsigned integer. This field has the same definition as in
the RREQ option.
L L
2-bit unsigned integer defined as in RREQ option. The lifetime of 2-bit unsigned integer defined as in the RREQ option. The
the RREP-Instance SHOULD be no greater than the lifetime of the lifetime of the RREP-Instance SHOULD be no greater than the
RREQ-Instance to which it is paired, so that the memory required lifetime of the RREQ-Instance to which it is paired, so that the
to store the RREP-Instance can be reclaimed when no longer needed. memory required to store the RREP-Instance can be reclaimed when
no longer needed.
RankLimit RankLimit
8-bit unsigned integer specifying the upper limit on the integer 8-bit unsigned integer specifying the upper limit on the integer
portion of the Rank, similarly to RankLimit in the RREQ message. portion of the Rank, similarly to RankLimit in the RREQ message.
A value of 0 in this field indicates the limit is infinity. A value of 0 in this field indicates the limit is infinity.
Delta Delta
6-bit unsigned integer. TargNode uses the Delta field so that 6-bit unsigned integer. TargNode uses the Delta field so that
nodes receiving its RREP message can identify the RREQ-InstanceID nodes receiving its RREP message can identify the RREQ-InstanceID
of the RREQ message that triggered the transmission of the RREP of the RREQ message that triggered the transmission of the RREP
(see Section 6.3.3). (see Section 6.3.3).
X X X X
2-bit Reserved field; MUST be initialized to zero and ignored upon 2-bit Reserved field. This field MUST be initialized to zero and
reception. ignored upon reception.
Address Vector Address Vector
Only present when the H bit is set to 0. The prefix of each Only present when the H bit is set to 0. The prefix of each
address is elided according to the Compr field. For an asymmetric address is elided according to the Compr field. For an asymmetric
route, the Address Vector represents the IPv6 addresses of the route, the Address Vector represents the IPv6 addresses of the
path through the network the RREP-DIO has passed. In contrast, path through the network the RREP-DIO has passed. In contrast,
for a symmetric route, it is the Address Vector when the RREQ-DIO for a symmetric route, it is the Address Vector when the RREQ-DIO
arrives at the TargNode, unchanged during the transmission to the arrives at the TargNode, unchanged during the transmission to the
OrigNode. OrigNode.
4.3. AODV-RPL Target Option 4.3. AODV-RPL Target Option
The AODV-RPL Target (ART) Option is based on the Target Option in The AODV-RPL Target (ART) option is based on the Target option in the
core RPL [RFC6550]. The Flags field is replaced by the Destination core RPL specification [RFC6550]. The Flags field is replaced by the
Sequence Number of the TargNode and the Prefix Length field is Destination Sequence Number of the TargNode, and the Prefix Length
reduced to 7 bits so that the value is limited to be no greater than field is reduced to 7 bits so that the value is limited to be no
127. greater than 127.
A RREQ-DIO message MUST carry at least one ART Option. A RREP-DIO A RREQ-DIO message MUST carry at least one ART option. A RREP-DIO
message MUST carry exactly one ART Option. Otherwise, the message message MUST carry exactly one ART option. Otherwise, the message
MUST be dropped. MUST be dropped.
OrigNode can include multiple TargNode addresses via multiple AODV- OrigNode can include multiple TargNode addresses via multiple ART
RPL Target Options in the RREQ-DIO, for routes that share the same options in the RREQ-DIO, for routes that share the same requirement
requirement on metrics. This reduces the cost to building only one on metrics. This reduces the cost to building only one DODAG for
DODAG for multiple targets. multiple targets.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Dest SeqNo |X|Prefix Length| | Option Type | Option Length | Dest SeqNo |X|Prefix Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ | + |
| Target Prefix / Address (Variable Length) | | Target Prefix / Address (Variable Length) |
. . . .
. . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . .
Figure 3: ART Option format for AODV-RPL Figure 3: ART Option Format for AODV-RPL
Option Type Option Type
8-bit unsigned integer specifying the type of the option (TBD4) 8-bit unsigned integer specifying the type of the option (0x0D).
Option Length Option Length
8-bit unsigned integer specifying the length of the option in 8-bit unsigned integer specifying the length of the option in
octets excluding the Type and Length fields. octets, excluding the Type and Length fields.
Dest SeqNo Dest SeqNo
8-bit unsigned integer. In RREQ-DIO, if nonzero, it is the 8-bit unsigned integer. In RREQ-DIO, if nonzero, it is the
Sequence Number for the last route that OrigNode stored to the Sequence Number for the last route that OrigNode stored to the
TargNode for which a route is desired. In RREP-DIO, it is the TargNode for which a route is desired. In RREP-DIO, it is the
destination sequence number associated to the route. Zero is used destination sequence number associated to the route. Zero is used
if there is no known information about the sequence number of if there is no known information about the sequence number of
TargNode, and not used otherwise. TargNode and not used otherwise.
X X
A one-bit reserved field. This field MUST be initialized to zero 1-bit Reserved field. This field MUST be initialized to zero by
by the sender and MUST be ignored by the receiver. the sender and MUST be ignored by the receiver.
Prefix Length Prefix Length
7-bit unsigned integer. The Prefix Length field contains the 7-bit unsigned integer. The Prefix Length field contains the
number of valid leading bits in the prefix. If Prefix Length is number of valid leading bits in the prefix. If Prefix Length is
0, then the value in the Target Prefix / Address field represents 0, then the value in the Target Prefix / Address field represents
an IPv6 address, not a prefix. an IPv6 address, not a prefix.
Target Prefix / Address Target Prefix / Address
(variable-length field) An IPv6 destination address or prefix. A variable-length field with an IPv6 destination address or
The length of the Target Prefix / Address field is the least prefix. The length of the Target Prefix / Address field is the
number of octets that can represent all of the bits of the Prefix, least number of octets that can represent all of the bits of the
in other words Ceil(Prefix Length/8) octets. When Prefix Length Prefix, in other words, Ceil(Prefix Length/8) octets. When Prefix
is not equal to 8*Ceil(Prefix Length/8) and nonzero, the Target Length is not equal to 8*Ceil(Prefix Length/8) and nonzero, the
Prefix / Address field will contain some initial bits that are not Target Prefix / Address field will contain some initial bits that
part of the Target Prefix. Those initial bits (if any) MUST be are not part of the Target Prefix. Those initial bits (if any)
set to zero on transmission and MUST be ignored on receipt. If MUST be set to zero on transmission and MUST be ignored on
Prefix Length is zero, the Address field is 128 bits. receipt. If Prefix Length is zero, the Address field is 128 bits.
5. Symmetric and Asymmetric Routes 5. Symmetric and Asymmetric Routes
Links are considered symmetric until indication to the contrary is Links are considered symmetric until indication to the contrary is
received. In Figure 4 and Figure 5, BR is the Border Router, O is received. In Figures 4 and 5, BR is the Border Router, O is the
the OrigNode, each R is an intermediate router, and T is the OrigNode, each R is an intermediate router, and T is the TargNode.
TargNode. In this example, the use of BR is only for illustrative In these examples, the use of BR is only for illustrative purposes;
purposes; AODV does not depend on the use of border routers for its AODV does not depend on the use of border routers for its operation.
operation. If the RREQ-DIO arrives over an interface that is known If the RREQ-DIO arrives over an interface that is known to be
to be symmetric, and the S bit is set to 1, then it remains as 1, as symmetric and the S bit is set to 1, then it remains as 1, as
illustrated in Figure 4. If an intermediate router sends out RREQ- illustrated in Figure 4. If an intermediate router sends out RREQ-
DIO with the S bit set to 1, then each link en route from the DIO with the S bit set to 1, then each link en route from the
OrigNode O to this router has met the requirements of route OrigNode O to this router has met the requirements of route
discovery, and the route can be used symmetrically. discovery, and the route can be used symmetrically.
BR BR
/----+----\ /----+----\
/ | \ / | \
/ | \ / | \
R R R R R R
skipping to change at page 15, line 32 skipping to change at line 645
>---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> >---- RREQ-Instance (Control: O-->T; Data: T-->O) ------->
<---- RREP-Instance (Control: T-->O; Data: O-->T) -------< <---- RREP-Instance (Control: T-->O; Data: O-->T) -------<
Figure 4: AODV-RPL with Symmetric Instances Figure 4: AODV-RPL with Symmetric Instances
Upon receiving a RREQ-DIO with the S bit set to 1, a node determines Upon receiving a RREQ-DIO with the S bit set to 1, a node determines
whether the link over which it was received can be used whether the link over which it was received can be used
symmetrically, i.e., both directions meet the requirements of data symmetrically, i.e., both directions meet the requirements of data
transmission. If the RREQ-DIO arrives over an interface that is not transmission. If the RREQ-DIO arrives over an interface that is not
known to be symmetric, or is known to be asymmetric, the S bit is set known to be symmetric or is known to be asymmetric, the S bit is set
to 0. If the S bit arrives already set to be '0', it is set to be to 0. If the S bit arrives already set to be 0, then it is set to be
'0' when the RREQ-DIO is propagated (Figure 5). For an asymmetric 0 when the RREQ-DIO is propagated (Figure 5). For an asymmetric
route, there is at least one hop which doesn't satisfy the Objective route, there is at least one hop that doesn't satisfy the Objective
Function. Based on the S bit received in RREQ-DIO, TargNode T Function. Based on the S bit received in RREQ-DIO, TargNode T
determines whether or not the route is symmetric before transmitting determines whether or not the route is symmetric before transmitting
the RREP-DIO message upstream towards the OrigNode O. the RREP-DIO message upstream towards the OrigNode O.
It is beyond the scope of this document to specify the criteria used It is beyond the scope of this document to specify the criteria used
when determining whether or not each link is symmetric. As an when determining whether or not each link is symmetric. As an
example, intermediate routers can use local information (e.g., bit example, intermediate routers can use local information (e.g., bit
rate, bandwidth, number of cells used in 6tisch [RFC9030]), a priori rate, bandwidth, number of cells used in 6tisch [RFC9030]), a priori
knowledge (e.g., link quality according to previous communication) or knowledge (e.g., link quality according to previous communication),
use averaging techniques as appropriate to the application. Other or averaging techniques as appropriate to the application. Other
link metric information can be acquired before AODV-RPL operation, by link metric information can be acquired before AODV-RPL operation, by
executing evaluation procedures; for instance test traffic can be executing evaluation procedures; for instance, test traffic can be
generated between nodes of the deployed network. During AODV-RPL generated between nodes of the deployed network. During AODV-RPL
operation, OAM techniques for evaluating link state (see [RFC7548], operation, Operations, Administration, and Maintenance (OAM)
[RFC7276], [co-ioam]) MAY be used (at regular intervals appropriate techniques for evaluating link state (see [RFC7548], [RFC7276], and
for the LLN). The evaluation procedures are out of scope for AODV- [co-ioam]) MAY be used (at regular intervals appropriate for the
RPL. For further information on this topic, see [Link_Asymmetry], LLN). The evaluation procedures are out of scope for AODV-RPL. For
further information on this topic, see [Link_Asymmetry],
[low-power-wireless], and [empirical-study]. [low-power-wireless], and [empirical-study].
Appendix A describes an example method using the upstream Expected Appendix A describes an example method using the upstream Expected
Number of Transmissions (ETX) and downstream Received Signal Strength Transmission Count (ETX) and downstream Received Signal Strength
Indicator (RSSI) to estimate whether the link is symmetric in terms Indicator (RSSI) to estimate whether the link is symmetric in terms
of link quality using an averaging technique. of link quality using an averaging technique.
BR BR
/----+----\ /----+----\
/ | \ / | \
/ | \ / | \
R R R R R R
/ \ | / \ / \ | / \
/ \ | / \ / \ | / \
skipping to change at page 17, line 8 skipping to change at line 701
<--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0--
>---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> >---- RREQ-Instance (Control: O-->T; Data: T-->O) ------->
<---- RREP-Instance (Control: T-->O; Data: O-->T) -------< <---- RREP-Instance (Control: T-->O; Data: O-->T) -------<
Figure 5: AODV-RPL with Asymmetric Paired Instances Figure 5: AODV-RPL with Asymmetric Paired Instances
As illustrated in Figure 5, an intermediate router determines the S As illustrated in Figure 5, an intermediate router determines the S
bit value that the RREQ-DIO should carry using link asymmetry bit value that the RREQ-DIO should carry using link asymmetry
detection methods as discussed earlier in this section. In many detection methods as discussed earlier in this section. In many
cases the intermediate router has already made the link asymmetry cases, the intermediate router has already made the link asymmetry
decision by the time RREQ-DIO arrives. decision by the time RREQ-DIO arrives.
See Appendix B for examples illustrating RREQ and RREP transmissions See Appendix B for examples illustrating RREQ and RREP transmissions
in some networks with symmetric and asymmetric links. in some networks with symmetric and asymmetric links.
6. AODV-RPL Operation 6. AODV-RPL Operation
6.1. Route Request Generation 6.1. Route Request Generation
The route discovery process is initiated when an application at the The route discovery process is initiated when an application at the
OrigNode has data to be transmitted to the TargNode, but does not OrigNode has data to be transmitted to the TargNode but does not have
have a route that satisfies the Objective Function for the target of a route that satisfies the Objective Function for the target of the
the application's data. In this case, the OrigNode builds a local application's data. In this case, the OrigNode builds a local
RPLInstance and a DODAG rooted at itself. Then it transmits a DIO RPLInstance and a DODAG rooted at itself. Then, it transmits a DIO
message containing exactly one RREQ option (see Section 4.1) to message containing exactly one RREQ option (see Section 4.1) to
multicast group all-AODV-RPL-nodes. The RREQ-DIO MUST contain at multicast group all-AODV-RPL-nodes. The RREQ-DIO MUST contain at
least one ART Option (see Section 4.3), which indicates the TargNode. least one ART option (see Section 4.3), which indicates the TargNode.
The S bit in RREQ-DIO sent out by the OrigNode is set to 1. The S bit in RREQ-DIO sent out by the OrigNode is set to 1.
Each node maintains a sequence number; the operation is specified in Each node maintains a sequence number; the operation is specified in
section 7.2 of [RFC6550]. When the OrigNode initiates a route Section 7.2 of [RFC6550]. When the OrigNode initiates a route
discovery process, it MUST increase its own sequence number to avoid discovery process, it MUST increase its own sequence number to avoid
conflicts with previously established routes. The sequence number is conflicts with previously established routes. The sequence number is
carried in the Orig SeqNo field of the RREQ option. carried in the Orig SeqNo field of the RREQ option.
The Target Prefix / Address in the ART Option can be a unicast IPv6 The Target Prefix / Address in the ART option can be a unicast IPv6
address or a prefix. The OrigNode can initiate the route discovery address or a prefix. The OrigNode can initiate the route discovery
process for multiple targets simultaneously by including multiple ART process for multiple targets simultaneously by including multiple ART
Options. Within a RREQ-DIO the Objective Function for the routes to options. Within a RREQ-DIO, the Objective Function for the routes to
different TargNodes MUST be the same. different TargNodes MUST be the same.
OrigNode can maintain different RPLInstances to discover routes with OrigNode can maintain different RPLInstances to discover routes with
different requirements to the same targets. Using the RPLInstanceID different requirements to the same targets. Using the RPLInstanceID
pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for
different RPLInstances can be generated. different RPLInstances can be generated.
The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If
the duration specified by the L field has elapsed, the OrigNode MUST the duration specified by the L field has elapsed, the OrigNode MUST
leave the DODAG and stop sending RREQ-DIOs in the related leave the DODAG and stop sending RREQ-DIOs in the related
RPLInstance. OrigNode needs to set L field such that the DODAG will RPLInstance. OrigNode needs to set the L field such that the DODAG
not prematurely timeout during data transfer with the TargNode. For will not prematurely timeout during data transfer with the TargNode.
setting this value, it has to consider factors such as Trickle timer, For setting this value, it has to consider factors such as the
TargNode hop distance, network size, link behavior, expected data Trickle timer, TargNode hop distance, network size, link behavior,
usage time, and so on. expected data usage time, and so on.
6.2. Receiving and Forwarding RREQ messages 6.2. Receiving and Forwarding RREQ Messages
6.2.1. Step 1: RREQ reception and evaluation 6.2.1. Step 1: RREQ Reception and Evaluation
When a router X receives a RREQ message over a link from a neighbor When a router X receives a RREQ message over a link from a neighbor
Y, X first determines whether or not the RREQ is valid. If so, X Y, X first determines whether or not the RREQ is valid. If so, X
then determines whether or not it has sufficient resources available then determines whether or not it has sufficient resources available
to maintain the RREQ-Instance and the value of the 'S' bit needed to to maintain the RREQ-Instance and the value of the S bit needed to
process an eventual RREP, if the RREP were to be received. If not, process an eventual RREP, if the RREP were to be received. If not,
then X MUST either free up sufficient resources (the means for this then X MUST either free up sufficient resources (the means for this
are beyond the scope of this document), or drop the packet and are beyond the scope of this document) or drop the packet and
discontinue processing of the RREQ. Otherwise, X next determines discontinue processing of the RREQ. Otherwise, X next determines
whether the RREQ advertises a usable route to OrigNode, by checking whether the RREQ advertises a usable route to OrigNode, by checking
whether the link to Y can be used to transmit packets to OrigNode. whether the link to Y can be used to transmit packets to OrigNode.
When H=0 in the incoming RREQ, the router MUST drop the RREQ-DIO if When H=0 in the incoming RREQ, the router MUST drop the RREQ-DIO if
one of its addresses is present in the Address Vector. When H=1 in one of its addresses is present in the Address Vector. When H=1 in
the incoming RREQ, the router MUST drop the RREQ message if Orig the incoming RREQ, the router MUST drop the RREQ message if the Orig
SeqNo field of the RREQ is older than the SeqNo value that X has SeqNo field of the RREQ is older than the SeqNo value that X has
stored for a route to OrigNode. Otherwise, the router determines stored for a route to OrigNode. Otherwise, the router determines
whether to propagate the RREQ-DIO. It does this by determining whether to propagate the RREQ-DIO. It does this by determining
whether or not a route to OrigNode using the upstream direction of whether or not a route to OrigNode using the upstream direction of
the incoming link satisfies the Objective Function (OF). In order to the incoming link satisfies the Objective Function (OF). In order to
evaluate the OF, the router first determines the maximum useful rank evaluate the OF, the router first determines the maximum useful rank
(MaxUsefulRank). If the router has previously joined the RREQ- (MaxUsefulRank). If the router has previously joined the RREQ-
Instance associated with the RREQ-DIO, then MaxUsefulRank is set to Instance associated with the RREQ-DIO, then MaxUsefulRank is set to
be the Rank value that was stored when the router processed the best be the Rank value that was stored when the router processed the best
previous RREQ for the DODAG with the given RREQ-Instance. Otherwise, previous RREQ for the DODAG with the given RREQ-Instance. Otherwise,
MaxUsefulRank is set to be RankLimit. If OF cannot be satisfied MaxUsefulRank is set to be RankLimit. If OF cannot be satisfied
(i.e., the Rank evaluates to a value greater than MaxUsefulRank) the (i.e., the Rank evaluates to a value greater than MaxUsefulRank), the
RREQ-DIO MUST be dropped, and the following steps are not processed. RREQ-DIO MUST be dropped, and the following steps are not processed.
Otherwise, the router MUST join the RREQ-Instance and prepare to Otherwise, the router MUST join the RREQ-Instance and prepare to
propagate the RREQ-DIO, as follows. The upstream neighbor router propagate the RREQ-DIO, as follows. The upstream neighbor router
that transmitted the received RREQ-DIO is selected as the preferred that transmitted the received RREQ-DIO is selected as the preferred
parent in the RREQ-Instance. parent in the RREQ-Instance.
6.2.2. Step 2: TargNode and Intermediate Router determination 6.2.2. Step 2: TargNode and Intermediate Router Determination
After determining that a received RREQ provides a usable route to After determining that a received RREQ provides a usable route to
OrigNode, a router determines whether it is a TargNode, or a possible OrigNode, a router determines whether it is a TargNode, a possible
intermediate router between OrigNode and a TargNode, or both. The intermediate router between OrigNode and a TargNode, or both. The
router is a TargNode if it finds one of its own addresses in a Target router is a TargNode if it finds one of its own addresses in a Target
Option in the RREQ. After possibly propagating the RREQ according to option in the RREQ. After possibly propagating the RREQ according to
the procedures in Steps 3, 4, and 5, the TargNode generates a RREP as the procedures in Steps 3, 4, and 5, the TargNode generates a RREP as
specified in Section 6.3. If S=0, the determination of TargNode specified in Section 6.3. If S=0, the determination of TargNode
status and determination of a usable route to OrigNode is the same. status and determination of a usable route to OrigNode is the same.
If the OrigNode tries to reach multiple TargNodes in a single RREQ- If the OrigNode tries to reach multiple TargNodes in a single RREQ-
Instance, one of the TargNodes can be an intermediate router to other Instance, one of the TargNodes can be an intermediate router to other
TargNodes. In this case, before transmitting the RREQ-DIO to TargNodes. In this case, before transmitting the RREQ-DIO to
multicast group all-AODV-RPL-nodes, a TargNode MUST delete the Target multicast group all-AODV-RPL-nodes, a TargNode MUST delete the Target
Option encapsulating its own address, so that downstream routers with option encapsulating its own address, so that downstream routers with
higher Rank values do not try to create a route to this TargNode. higher Rank values do not try to create a route to this TargNode.
An intermediate router could receive several RREQ-DIOs from routers An intermediate router could receive several RREQ-DIOs from routers
with lower Rank values in the same RREQ-Instance with different lists with lower Rank values in the same RREQ-Instance with different lists
of Target Options. For the purposes of determining the intersection of Target options. For the purposes of determining the intersection
with previous incoming RREQ-DIOs, the intermediate router maintains a with previous incoming RREQ-DIOs, the intermediate router maintains a
record of the targets that have been requested for a given RREQ- record of the targets that have been requested for a given RREQ-
Instance. An incoming RREQ-DIO message having multiple ART Options Instance. An incoming RREQ-DIO message having multiple ART options
coming from a router with higher Rank than the Rank of the stored coming from a router with higher Rank than the Rank of the stored
targets is ignored. When transmitting the RREQ-DIO, the intersection targets is ignored. When transmitting the RREQ-DIO, the intersection
of all received lists MUST be included if it is nonempty after of all received lists MUST be included if it is nonempty after
TargNode has deleted the Target Option encapsulating its own address. TargNode has deleted the Target option encapsulating its own address.
If the intersection is empty, it means that all the targets have been If the intersection is empty, it means that all the targets have been
reached, and the router MUST NOT transmit any RREQ-DIO. Otherwise it reached, and the router MUST NOT transmit any RREQ-DIO. Otherwise,
proceeds to Section 6.2.3. it proceeds to Section 6.2.3.
For example, suppose two RREQ-DIOs are received with the same For example, suppose two RREQ-DIOs are received with the same
RPLInstance and OrigNode. Suppose further that the first RREQ has RPLInstance and OrigNode. Suppose further that the first RREQ has
(T1, T2) as the targets, and the second one has (T2, T4) as targets. (T1, T2) as the targets, and the second one has (T2, T4) as targets.
Then only T2 needs to be included in the generated RREQ-DIO. Then, only T2 needs to be included in the generated RREQ-DIO.
The reasoning for using the intersection of the lists in the RREQs is The reasoning for using the intersection of the lists in the RREQs is
as follows. When two or more RREQs are received with the same Orig as follows. When two or more RREQs are received with the same Orig
SeqNo, they were transmitted by OrigNode with the same destinations SeqNo, they were transmitted by OrigNode with the same destinations
and OF. When an intermediate node receives two RREQs with the same and OF. When an intermediate node receives two RREQs with the same
Orig SeqNo but different lists of destinations, that means that some Orig SeqNo but different lists of destinations, that means that some
intermediate nodes retransmitting the RREQs have already deleted intermediate nodes retransmitting the RREQs have already deleted
themselves from the list of destinations before they retransmitted themselves from the list of destinations before they retransmitted
the RREQ. Those deleted nodes are not be re-inserted back into the the RREQ. Those deleted nodes are not to be reinserted back into the
list of destinations. list of destinations.
6.2.3. Step 3: Intermediate Router RREQ processing 6.2.3. Step 3: Intermediate Router RREQ Processing
The intermediate router establishes itself as a viable node for a The intermediate router establishes itself as a viable node for a
route to OrigNode as follows. If the H bit is set to 1, for a hop- route to OrigNode as follows. If the H bit is set to 1, for a hop-
by-hop route, then the router MUST build or update its upward route by-hop route, then the router MUST build or update its upward route
entry towards OrigNode, which includes at least the following items: entry towards OrigNode, which includes at least the following items:
Source Address, RPLInstanceID, Destination Address, Next Hop, Source Address, RPLInstanceID, Destination Address, Next Hop,
Lifetime, and Sequence Number. The Destination Address and the Lifetime, and Sequence Number. The Destination Address and the
RPLInstanceID respectively can be learned from the DODAGID and the RPLInstanceID can be learned from the DODAGID and the RPLInstanceID
RPLInstanceID of the RREQ-DIO. The Source Address is the address of the RREQ-DIO, respectively. The Source Address is the address
used by the router to send data to the Next Hop, i.e., the preferred used by the router to send data to the Next Hop, i.e., the preferred
parent. The lifetime is set according to DODAG configuration (not parent. The lifetime is set according to DODAG configuration (not
the L field) and can be extended when the route is actually used. the L field) and can be extended when the route is actually used.
The Sequence Number represents the freshness of the route entry; it The Sequence Number represents the freshness of the route entry; it
is copied from the Orig SeqNo field of the RREQ option. A route is copied from the Orig SeqNo field of the RREQ option. A route
entry with the same source and destination address, same entry with the same source and destination address and the same
RPLInstanceID, but a stale Sequence Number (i.e., incoming sequence RPLInstanceID, but a stale Sequence Number (i.e., incoming sequence
number is less than the currently stored Sequence Number of the route number is less than the currently stored Sequence Number of the route
entry), MUST be deleted. entry), MUST be deleted.
6.2.4. Step 4: Symmetric Route Processing at an Intermediate Router 6.2.4. Step 4: Symmetric Route Processing at an Intermediate Router
If the S bit of the incoming RREQ-DIO is 0, then the route cannot be If the S bit of the incoming RREQ-DIO is 0, then the route cannot be
symmetric, and the S bit of the RREQ-DIO to be transmitted is set to symmetric, and the S bit of the RREQ-DIO to be transmitted is set to
0. Otherwise, the router MUST determine whether the downward (i.e., 0. Otherwise, the router MUST determine whether the downward
towards the TargNode) direction of the incoming link satisfies the direction (i.e., towards the TargNode) of the incoming link satisfies
OF. If so, the S bit of the RREQ-DIO to be transmitted is set to 1. the OF. If so, the S bit of the RREQ-DIO to be transmitted is set to
Otherwise the S bit of the RREQ-DIO to be transmitted is set to 0. 1. Otherwise, the S bit of the RREQ-DIO to be transmitted is set to
0.
When a router joins the RREQ-Instance, it also associates within its When a router joins the RREQ-Instance, it also associates within its
data structure for the RREQ-Instance the information about whether or data structure for the RREQ-Instance the information about whether or
not the RREQ-DIO to be transmitted has the S-bit set to 1. This not the RREQ-DIO to be transmitted has the S bit set to 1. This
information associated to RREQ-Instance is known as the S-bit of the information associated to RREQ-Instance is known as the S bit of the
RREQ-Instance. It will be used later during the RREP-DIO message RREQ-Instance. It will be used later during the RREP-DIO message
processing Section 6.3.2. processing (see Section 6.3.2).
Suppose a router has joined the RREQ-Instance, and H=0, and the S-bit Suppose a router has joined the RREQ-Instance, and H=0, and the S bit
of the RREQ-Instance is set to 1. In this case, the router MAY of the RREQ-Instance is set to 1. In this case, the router MAY
optionally include the Address Vector of the symmetric route back to optionally include the Address Vector of the symmetric route back to
OrigNode as part of the RREQ-Instance data. This is useful if the OrigNode as part of the RREQ-Instance data. This is useful if the
router later receives an RREP-DIO that is paired with the RREQ- router later receives an RREP-DIO that is paired with the RREQ-
Instance. If the router does NOT include the Address Vector, then it Instance. If the router does NOT include the Address Vector, then it
has to rely on multicast for the RREP. The multicast can impose a has to rely on multicast for the RREP. The multicast can impose a
substantial performance penalty. substantial performance penalty.
6.2.5. Step 5: RREQ propagation at an Intermediate Router 6.2.5. Step 5: RREQ Propagation at an Intermediate Router
If the router is an intermediate router, then it transmits the RREQ- If the router is an intermediate router, then it transmits the RREQ-
DIO to the multicast group all-AODV-RPL-nodes; if the H bit is set to DIO to the multicast group all-AODV-RPL-nodes; if the H bit is set to
0, the intermediate router MUST append the address of its interface 0, the intermediate router MUST append the address of its interface
receiving the RREQ-DIO into the address vector. If, in addition, the receiving the RREQ-DIO into the address vector. In addition, if the
address of the router's interface transmitting the RREQ-DIO is not address of the router's interface transmitting the RREQ-DIO is not
the same as the address of the interface receiving the RREQ-DIO, the the same as the address of the interface receiving the RREQ-DIO, the
router MUST also append the transmitting interface address into the router MUST also append the transmitting interface address into the
address vector. address vector.
6.2.6. Step 6: RREQ reception at TargNode 6.2.6. Step 6: RREQ Reception at TargNode
If the router is a TargNode and was already associated with the RREQ- If the router is a TargNode and was already associated with the RREQ-
Instance, it takes no further action and does not send an RREP-DIO. Instance, it takes no further action and does not send an RREP-DIO.
If TargNode is not already associated with the RREQ-Instance, it If TargNode is not already associated with the RREQ-Instance, it
prepares and transmits a RREP-DIO, possibly after waiting for prepares and transmits a RREP-DIO, possibly after waiting for
RREP_WAIT_TIME, as detailed in (Section 6.3). RREP_WAIT_TIME, as detailed in (Section 6.3).
6.3. Generating Route Reply (RREP) at TargNode 6.3. Generating Route Reply (RREP) at TargNode
When a TargNode receives a RREQ message over a link from a neighbor When a TargNode receives a RREQ message over a link from a neighbor
Y, TargNode first follows the procedures in Section 6.2. If the link Y, TargNode first follows the procedures in Section 6.2. If the link
to Y can be used to transmit packets to OrigNode, TargNode generates to Y can be used to transmit packets to OrigNode, TargNode generates
a RREP according to the steps below. Otherwise TargNode drops the a RREP according to the steps below. Otherwise, TargNode drops the
RREQ and does not generate a RREP. RREQ and does not generate a RREP.
If the L field is not 0, the TargNode MAY delay transmitting the If the L field is not 0, the TargNode MAY delay transmitting the
RREP-DIO for duration RREP_WAIT_TIME to await a route with a lower RREP-DIO for the duration RREP_WAIT_TIME to await a route with a
Rank. The value of RREP_WAIT_TIME is set by default to 1/4 of the lower Rank. The value of RREP_WAIT_TIME is set by default to 1/4 of
duration determined by the L field. For L == 0, RREP_WAIT_TIME is the duration determined by the L field. For L == 0, RREP_WAIT_TIME
set by default to 0. Depending upon the application, RREP_WAIT_TIME is set by default to 0. Depending upon the application,
may be set to other values. Smaller values enable quicker formation RREP_WAIT_TIME may be set to other values. Smaller values enable
for the P2P route. Larger values enable formation of P2P routes with quicker formation for the P2P route. Larger values enable formation
better Rank values. of P2P routes with better Rank values.
The address of the OrigNode MUST be encapsulated in the ART Option The address of the OrigNode MUST be encapsulated in the ART option
and included in this RREP-DIO message along with the SeqNo of and included in this RREP-DIO message along with the SeqNo of
TargNode. TargNode.
6.3.1. RREP-DIO for Symmetric route 6.3.1. RREP-DIO for Symmetric Route
If the RREQ-Instance corresponding to the RREQ-DIO that arrived at If the RREQ-Instance corresponding to the RREQ-DIO that arrived at
TargNode has the S bit set to 1, there is a symmetric route both of TargNode has the S bit set to 1, there is a symmetric route, both of
whose directions satisfy the Objective Function. Other RREQ-DIOs whose directions satisfy the Objective Function. Other RREQ-DIOs
might later provide better upward routes. The method of selection might later provide better upward routes. The method of selection
between a qualified symmetric route and an asymmetric route that between a qualified symmetric route and an asymmetric route that
might have better performance is implementation-specific and out of might have better performance is implementation specific and out of
scope. scope.
For a symmetric route, the RREP-DIO message is unicast to the next For a symmetric route, the RREP-DIO message is unicast to the next
hop according to the Address Vector (H=0) or the route entry (H=1); hop according to the Address Vector (H=0) or the route entry (H=1);
the DODAG in RREP-Instance does not need to be built. The the DODAG in RREP-Instance does not need to be built. The
RPLInstanceID in the RREP-Instance is paired as defined in RPLInstanceID in the RREP-Instance is paired as defined in
Section 6.3.3. In case the H bit is set to 0, the address vector Section 6.3.3. If the H bit is set to 0, the address vector from the
from the RREQ-DIO MUST be included in the RREP-DIO. RREQ-DIO MUST be included in the RREP-DIO.
6.3.2. RREP-DIO for Asymmetric Route 6.3.2. RREP-DIO for Asymmetric Route
When a RREQ-DIO arrives at a TargNode with the S bit set to 0, the When a RREQ-DIO arrives at a TargNode with the S bit set to 0, the
TargNode MUST build a DODAG in the RREP-Instance corresponding to the TargNode MUST build a DODAG in the RREP-Instance corresponding to the
RREQ-DIO rooted at itself, in order to provide OrigNode with a RREQ-DIO rooted at itself, in order to provide OrigNode with a
downstream route to the TargNode. The RREP-DIO message is downstream route to the TargNode. The RREP-DIO message is
transmitted to multicast group all-AODV-RPL-nodes. transmitted to multicast group all-AODV-RPL-nodes.
6.3.3. RPLInstanceID Pairing 6.3.3. RPLInstanceID Pairing
Since the RPLInstanceID is assigned locally (i.e., there is no Since the RPLInstanceID is assigned locally (i.e., there is no
coordination between routers in the assignment of RPLInstanceID), the coordination between routers in the assignment of RPLInstanceID), the
tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely
identify a discovered route. It is possible that multiple route identify a discovered route. It is possible that multiple route
discoveries with dissimilar Objective Functions are initiated discoveries with dissimilar Objective Functions are initiated
simultaneously. Thus between the same pair of OrigNode and TargNode, simultaneously. Thus, between the same pair of OrigNode and
there can be multiple AODV-RPL route discovery instances. So that TargNode, there can be multiple AODV-RPL route discovery instances.
OrigNode and Targnode can avoid any mismatch, they MUST pair the So that OrigNode and TargNode can avoid any mismatch, they MUST pair
RREQ-Instance and the RREP-Instance in the same route discovery by the RREQ-Instance and the RREP-Instance in the same route discovery
using the RPLInstanceID. by using the RPLInstanceID.
When preparing the RREP-DIO, a TargNode could find the RPLInstanceID When preparing the RREP-DIO, a TargNode could find the RPLInstanceID
candidate for the RREP-Instance is already occupied by another RPL candidate for the RREP-Instance is already occupied by another RPL
Instance from an earlier route discovery operation which is still Instance from an earlier route discovery operation that is still
active. This unlikely case might happen if two distinct OrigNodes active. This unlikely case might happen if two distinct OrigNodes
need routes to the same TargNode, and they happen to use the same need routes to the same TargNode, and they happen to use the same
RPLInstanceID for RREQ-Instance. In such cases, the RPLInstanceID of RPLInstanceID for RREQ-Instance. In such cases, the RPLInstanceID of
an already active RREP-Instance MUST NOT be used again for assigning an already active RREP-Instance MUST NOT be used again for assigning
RPLInstanceID for the later RREP-Instance. If the same RPLInstanceID RPLInstanceID for the later RREP-Instance. If the same RPLInstanceID
were re-used for two distinct DODAGs originated with the same DODAGID were reused for two distinct DODAGs originated with the same DODAGID
(TargNode address), intermediate routers could not distinguish (TargNode address), intermediate routers could not distinguish
between these DODAGs (and their associated Objective Functions). between these DODAGs (and their associated Objective Functions).
Instead, the RPLInstanceID MUST be replaced by another value so that Instead, the RPLInstanceID MUST be replaced by another value so that
the two RREP-instances can be distinguished. In the RREP-DIO option, the two RREP-Instances can be distinguished. In the RREP-DIO option,
the Delta field of the RREP-DIO message (Figure 2) indicates the the Delta field of the RREP-DIO message (Figure 2) indicates the
value that TargNode adds to the RPLInstanceID in the RREQ-DIO that it value that TargNode adds to the RPLInstanceID in the RREQ-DIO that it
received, to obtain the value of the RPLInstanceID it uses in the received, to obtain the value of the RPLInstanceID it uses in the
RREP-DIO message. 0 indicates that the RREQ-InstanceID has the same RREP-DIO message. 0 indicates that the RREQ-InstanceID has the same
value as the RPLInstanceID of the RREP message. When the new value as the RPLInstanceID of the RREP message. When the new
RPLInstanceID after incrementation exceeds 255, it rolls over RPLInstanceID after incrementation exceeds 255, it rolls over
starting at 0. For example, if the RREQ-InstanceID is 252, and starting at 0. For example, if the RREQ-InstanceID is 252 and
incremented by 6, the new RPLInstanceID will be 2. Related incremented by 6, the new RPLInstanceID will be 2. Related
operations can be found in Section 6.4. RPLInstanceID collisions do operations can be found in Section 6.4. RPLInstanceID collisions do
not occur across RREQ-DIOs; the DODAGID equals the OrigNode address not occur across RREQ-DIOs; the DODAGID equals the OrigNode address
and is sufficient to disambiguate between DODAGs. and is sufficient to disambiguate between DODAGs.
6.4. Receiving and Forwarding Route Reply 6.4. Receiving and Forwarding Route Reply
Upon receiving a RREP-DIO, a router which already belongs to the Upon receiving a RREP-DIO, a router that already belongs to the RREP-
RREP-Instance SHOULD drop the RREP-DIO. Otherwise the router Instance SHOULD drop the RREP-DIO. Otherwise, the router performs
performs the steps in the following subsections. the steps in the following subsections.
6.4.1. Step 1: Receiving and Evaluation 6.4.1. Step 1: Receiving and Evaluation
If the Objective Function is not satisfied, the router MUST NOT join If the Objective Function is not satisfied, the router MUST NOT join
the DODAG; the router MUST discard the RREP-DIO, and does not execute the DODAG; the router MUST discard the RREP-DIO and does not execute
the remaining steps in this section. An Intermediate Router MUST the remaining steps in this section. An Intermediate Router MUST
discard a RREP if one of its addresses is present in the Address discard a RREP if one of its addresses is present in the Address
Vector, and does not execute the remaining steps in this section. Vector and does not execute the remaining steps in this section.
If the S bit of the associated RREQ-Instance is set to 1, the router If the S bit of the associated RREQ-Instance is set to 1, the router
MUST proceed to Section 6.4.2. MUST proceed to Section 6.4.2.
If the S-bit of the RREQ-Instance is set to 0, the router MUST If the S bit of the RREQ-Instance is set to 0, the router MUST
determine whether the downward direction of the link (towards the determine whether the downward direction of the link (towards the
TargNode) over which the RREP-DIO is received satisfies the Objective TargNode) over which the RREP-DIO is received satisfies the Objective
Function, and the router's Rank would not exceed the RankLimit. If Function and whether the router's Rank would not exceed the
so, the router joins the DODAG of the RREP-Instance. The router that RankLimit. If so, the router joins the DODAG of the RREP-Instance.
transmitted the received RREP-DIO is selected as the preferred The router that transmitted the received RREP-DIO is selected as the
parent. Afterwards, other RREP-DIO messages can be received; AODV- preferred parent. Afterwards, other RREP-DIO messages can be
RPL does not specify any action to be taken in such cases. received; AODV-RPL does not specify any action to be taken in such
cases.
6.4.2. Step 2: OrigNode or Intermediate Router 6.4.2. Step 2: OrigNode or Intermediate Router
The router updates its stored value of the TargNode's sequence number The router updates its stored value of the TargNode's sequence number
according to the value provided in the ART option. The router next according to the value provided in the ART option. The router next
checks if one of its addresses is included in the ART Option. If so, checks if one of its addresses is included in the ART option. If so,
this router is the OrigNode of the route discovery. Otherwise, it is this router is the OrigNode of the route discovery. Otherwise, it is
an intermediate router. an intermediate router.
6.4.3. Step 3: Build Route to TargNode 6.4.3. Step 3: Build Route to TargNode
If the H bit is set to 1, then the router (OrigNode or intermediate) If the H bit is set to 1, then the router (OrigNode or intermediate)
MUST build a downward route entry towards TargNode which includes at MUST build a downward route entry towards TargNode that includes at
least the following items: OrigNode Address, RPLInstanceID, TargNode least the following items: OrigNode Address, RPLInstanceID, TargNode
Address as destination, Next Hop, Lifetime and Sequence Number. For Address as destination, Next Hop, Lifetime, and Sequence Number. For
a symmetric route, the Next Hop in the route entry is the router from a symmetric route, the Next Hop in the route entry is the router from
which the RREP-DIO is received. For an asymmetric route, the Next which the RREP-DIO is received. For an asymmetric route, the Next
Hop is the preferred parent in the DODAG of RREP-Instance. The Hop is the preferred parent in the DODAG of RREP-Instance. The
RPLInstanceID in the route entry MUST be the RREQ-InstanceID (i.e., RPLInstanceID in the route entry MUST be the RREQ-InstanceID (i.e.,
after subtracting the Delta field value from the value of the after subtracting the Delta field value from the value of the
RPLInstanceID). The source address is learned from the ART Option, RPLInstanceID). The source address is learned from the ART option,
and the destination address is learned from the DODAGID. The and the destination address is learned from the DODAGID. The
lifetime is set according to DODAG configuration (i.e., not the L lifetime is set according to DODAG configuration (i.e., not the L
field) and can be extended when the route is actually used. The field) and can be extended when the route is actually used. The
sequence number represents the freshness of the route entry, and is sequence number represents the freshness of the route entry and is
copied from the Dest SeqNo field of the ART option of the RREP-DIO. copied from the Dest SeqNo field of the ART option of the RREP-DIO.
A route entry with same source and destination address, same A route entry with the same source and destination address and the
RPLInstanceID, but stale sequence number MUST be deleted. same RPLInstanceID, but a stale sequence number, MUST be deleted.
6.4.4. Step 4: RREP Propagation 6.4.4. Step 4: RREP Propagation
If the receiver is the OrigNode, it can start transmitting the If the receiver is the OrigNode, it can start transmitting the
application data to TargNode along the path as provided in RREP- application data to TargNode along the path as provided in RREP-
Instance, and processing for the RREP-DIO is complete. Otherwise, Instance, and processing for the RREP-DIO is complete. Otherwise,
the RREP will be propagated towards OrigNode. If H=0, the the RREP will be propagated towards OrigNode. If H=0, the
intermediate router MUST include the address of the interface intermediate router MUST include the address of the interface
receiving the RREP-DIO into the address vector. If H=1, according to receiving the RREP-DIO into the address vector. If H=1, according to
the previous step the intermediate router has set up a route entry the previous step, the intermediate router has set up a route entry
for TargNode. If the intermediate router has a route to OrigNode, it for TargNode. If the intermediate router has a route to OrigNode, it
uses that route to unicast the RREP-DIO to OrigNode. Otherwise, in uses that route to unicast the RREP-DIO to OrigNode. Otherwise, in
case of a symmetric route, the RREP-DIO message is unicast to the the case of a symmetric route, the RREP-DIO message is unicast to the
Next Hop according to the address vector in the RREP-DIO (H=0) or the Next Hop according to the address vector in the RREP-DIO (H=0) or the
local route entry (H=1). Otherwise, in case of an asymmetric route, local route entry (H=1). Otherwise, in the case of an asymmetric
the intermediate router transmits the RREP-DIO to multicast group route, the intermediate router transmits the RREP-DIO to multicast
all-AODV-RPL-nodes. The RPLInstanceID in the transmitted RREP-DIO is group all-AODV-RPL-nodes. The RPLInstanceID in the transmitted RREP-
the same as the value in the received RREP-DIO. DIO is the same as the value in the received RREP-DIO.
7. Gratuitous RREP 7. Gratuitous RREP
In some cases, an Intermediate router that receives a RREQ-DIO In some cases, an Intermediate router that receives a RREQ-DIO
message MAY unicast a "Gratuitous" RREP-DIO message back to OrigNode message MAY unicast a Gratuitous RREP-DIO (G-RREP-DIO) message back
before continuing the transmission of the RREQ-DIO towards TargNode. to OrigNode before continuing the transmission of the RREQ-DIO
The Gratuitous RREP allows the OrigNode to start transmitting data to towards TargNode. The Gratuitous RREP (G-RREP) allows the OrigNode
TargNode sooner. The G bit of the RREP option is provided to to start transmitting data to TargNode sooner. The G bit of the RREP
distinguish the Gratuitous RREP-DIO (G=1) sent by the Intermediate option is provided to distinguish the G-RREP-DIO (G=1) sent by the
router from the RREP-DIO sent by TargNode (G=0). Intermediate router from the RREP-DIO sent by TargNode (G=0).
The gratuitous RREP-DIO MAY be sent out when the Intermediate router The G-RREP-DIO MAY be sent out when the Intermediate router receives
receives a RREQ-DIO for a TargNode, and the router has a pair of a RREQ-DIO for a TargNode and the router has a pair of downward and
downward and upward routes to the TargNode which also satisfy the upward routes to the TargNode that also satisfy the Objective
Objective Function and for which the destination sequence number is Function and for which the destination sequence number is at least as
at least as large as the sequence number in the RREQ-DIO message. large as the sequence number in the RREQ-DIO message. After
After unicasting the Gratuitous RREP to the OrigNode, the unicasting the G-RREP to the OrigNode, the Intermediate router then
Intermediate router then unicasts the RREQ towards TargNode, so that unicasts the RREQ towards TargNode, so that TargNode will have the
TargNode will have the advertised route towards OrigNode along with advertised route towards OrigNode along with the RREQ-InstanceID for
the RREQ-InstanceID for the RREQ-Instance. An upstream intermediate the RREQ-Instance. An upstream intermediate router that receives
router that receives such a G-RREP MUST also generate a G-RREP and such a G-RREP MUST also generate a G-RREP and send it further
send it further upstream towards OrigNode. upstream towards OrigNode.
In case of source routing, the intermediate router MUST include the In case of source routing, the intermediate router MUST include the
address vector between the OrigNode and itself in the Gratuitous address vector between the OrigNode and itself in the G-RREP. It
RREP. It also includes the address vector in the unicast RREQ-DIO also includes the address vector in the unicast RREQ-DIO towards
towards TargNode. Upon reception of the unicast RREQ-DIO, the TargNode. Upon reception of the unicast RREQ-DIO, the TargNode will
TargNode will have a route address vector from itself to the have a route address vector from itself to the OrigNode. Then, the
OrigNode. Then the router MUST include the address vector from the router MUST include the address vector from the TargNode to the
TargNode to the router itself in the gratuitous RREP-DIO to be router itself in the G-RREP-DIO to be transmitted.
transmitted.
For establishing hop-by-hop routes, the intermediate router MUST For establishing hop-by-hop routes, the intermediate router MUST
unicast the received RREQ-DIO to the Next Hop on the route. The Next unicast the received RREQ-DIO to the Next Hop on the route. The Next
Hop router along the route MUST build new route entries with the Hop router along the route MUST build new route entries with the
related RPLInstanceID and DODAGID in the downward direction. This related RPLInstanceID and DODAGID in the downward direction. This
process repeats at each node until the RREQ-DIO arrives at the process repeats at each node until the RREQ-DIO arrives at the
TargNode. Then the TargNode and each router along the path towards TargNode. Then, the TargNode and each router along the path towards
OrigNode MUST unicast the RREP-DIO hop-by-hop towards OrigNode as OrigNode MUST unicast the RREP-DIO hop-by-hop towards OrigNode as
specified in Section 6.3. specified in Section 6.3.
8. Operation of Trickle Timer 8. Operation of Trickle Timer
RREQ-Instance/RREP-Instance multicast uses trickle timer operations RREQ-Instance/RREP-Instance multicast uses Trickle timer operations
[RFC6206] to control RREQ-DIO and RREP-DIO transmissions. The [RFC6206] to control RREQ-DIO and RREP-DIO transmissions. The
Trickle control of these DIO transmissions follows the procedures Trickle control of these DIO transmissions follows the procedures
described in the Section 8.3 of [RFC6550] entitled "DIO described in Section 8.3 of [RFC6550] entitled "DIO Transmission".
Transmission". If the route is symmetric, the RREP DIO does not need If the route is symmetric, the RREP-DIO does not need the Trickle
the Trickle timer mechanism. timer mechanism.
9. IANA Considerations 9. IANA Considerations
Note to RFC editor: AODV-RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4),
with new options as specified in this document. This document has
The sentence "The parenthesized numbers are only suggestions." is to been added as an additional reference for "P2P Route Discovery Mode
be removed prior publication. of Operation" in the "Mode of Operation" registry within the "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group.
A Subregistry in this section refers to a named sub-registry of the IANA has assigned the three new AODV-RPL options described in Table 1
"Routing Protocol for Low Power and Lossy Networks (RPL)" registry. in the "RPL Control Message Options" registry within the "Routing
Protocol for Low Power and Lossy Networks (RPL)" registry group.
AODV-RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) +=======+=============+===========+
with new Options as specified in this document. Please cite AODV-RPL | Value | Meaning | Reference |
and this document as one of the protocols using MOP 4. +=======+=============+===========+
| 0x0B | RREQ Option | RFC 9854 |
+-------+-------------+-----------+
| 0x0C | RREP Option | RFC 9854 |
+-------+-------------+-----------+
| 0x0D | ART Option | RFC 9854 |
+-------+-------------+-----------+
IANA is asked to assign three new AODV-RPL options "RREQ", "RREP" and Table 1: AODV-RPL Options
"ART", as described in Figure 6 from the "RPL Control Message
Options" Subregistry. The parenthesized numbers are only
suggestions.
+-------------+------------------------+---------------+ IANA has allocated the permanent multicast address with link-local
| Value | Meaning | Reference | scope in Table 2 for nodes implementing this specification. This
+-------------+------------------------+---------------+ allocation has been made in the "Local Network Control Block
| TBD2 (0x0B) | RREQ Option | This document | (224.0.0.0 - 224.0.0.255 (224.0.0/24))" registry within the "IPv4
+-------------+------------------------+---------------+ Multicast Address Space Registry" registry group.
| TBD3 (0x0C) | RREP Option | This document |
+-------------+------------------------+---------------+
| TBD4 (0x0D) | ART Option | This document |
+-------------+------------------------+---------------+
Figure 6: AODV-RPL Options +=============+====================+============+
| Address(es) | Description | References |
+=============+====================+============+
| 224.0.0.69 | all-AODV-RPL-nodes | RFC 9854 |
+-------------+--------------------+------------+
IANA is requested to allocate a new permanent multicast address with Table 2: Permanent Multicast Address with
link-local scope called all-AODV-RPL-nodes for nodes implementing Link-Local Scope
this specification from the "Local Network Control Block (224.0.0.0 -
224.0.0.255 (224.0.0/24))" registry in the "IPv4 Multicast Address
Space Registry" group.
10. Security Considerations 10. Security Considerations
The security considerations for the operation of AODV-RPL are similar The security considerations for the operation of AODV-RPL are similar
to those for the operation of RPL (as described in Section 19 of the to those for the operation of RPL (as described in Section 19 of the
RPL specification [RFC6550]). Sections 6.1 and 10 of [RFC6550] RPL specification [RFC6550]). Sections 6.1 and 10 of [RFC6550]
describe RPL's optional security framework, which AODV-RPL relies on describe RPL's optional security framework, which AODV-RPL relies on
to provide data confidentiality, authentication, replay protection, to provide data confidentiality, authentication, replay protection,
and delay protection services. Additional analysis for the security and delay protection services. Additional analysis for the security
threats to RPL can be found in [RFC7416]. threats to RPL can be found in [RFC7416].
skipping to change at page 26, line 44 skipping to change at line 1160
discovery only if it can support the security configuration in use discovery only if it can support the security configuration in use
(see Section 6.1 of [RFC6550]), which also specifies the key in use. (see Section 6.1 of [RFC6550]), which also specifies the key in use.
It does not matter whether the key is preinstalled or dynamically It does not matter whether the key is preinstalled or dynamically
acquired. The router must have the key in use before it can join the acquired. The router must have the key in use before it can join the
DAG being created for secure route discovery. DAG being created for secure route discovery.
If a rogue router knows the key for the security configuration in If a rogue router knows the key for the security configuration in
use, it can join the secure AODV-RPL route discovery and cause use, it can join the secure AODV-RPL route discovery and cause
various types of damage. Such a rogue router could advertise false various types of damage. Such a rogue router could advertise false
information in its DIOs in order to include itself in the discovered information in its DIOs in order to include itself in the discovered
route(s). It could generate bogus RREQ-DIO, and RREP-DIO messages route(s). It could generate bogus RREQ-DIO and RREP-DIO messages
carrying bad routes or maliciously modify genuine RREP-DIO messages carrying bad routes or maliciously modify genuine RREP-DIO messages
it receives. A rogue router acting as the OrigNode could launch it receives. A rogue router acting as the OrigNode could launch
denial-of-service attacks against the LLN deployment by initiating denial-of-service attacks against the LLN deployment by initiating
fake AODV-RPL route discoveries. When rogue routers might be fake AODV-RPL route discoveries. When rogue routers might be
present, RPL's preinstalled mode of operation, where the key to use present, RPL's preinstalled mode of operation, where the key to use
for route discovery is preinstalled, SHOULD be used. for route discovery is preinstalled, SHOULD be used.
When a RREQ-DIO message uses the source routing option by setting the When a RREQ-DIO message uses the source routing option by setting the
H bit to 0, a rogue router may populate the Address Vector field with H bit to 0, a rogue router may populate the Address Vector field with
a set of addresses that may result in the RREP-DIO traveling in a a set of addresses that may result in the RREP-DIO traveling in a
routing loop. routing loop.
If a rogue router is able to forge a gratuitous RREP, it could mount If a rogue router is able to forge a G-RREP, it could mount denial-
denial-of-service attacks. of-service attacks.
11. Acknowledgements
The authors thank Pascal Thubert, Rahul Jadhav, and Lijo Thomas for
their support and valuable inputs. The authors specially thank
Lavanya H.M for implementing AODV-RPl in Contiki and conducting
extensive simulation studies.
The authors would like to acknowledge the review, feedback and
comments from the following people, in alphabetical order: Roman
Danyliw, Lars Eggert, Benjamin Kaduk, Tero Kivinen, Erik Kline,
Murray Kucherawy, Warren Kumari, Francesca Palombini, Alvaro Retana,
Ines Robles, John Scudder, Meral Shirazipour, Peter Van der Stok,
Eric Vyncke, and Robert Wilton.
12. References 11. References
12.1. 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>.
[RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
"The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206, "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
March 2011, <https://www.rfc-editor.org/info/rfc6206>. March 2011, <https://www.rfc-editor.org/info/rfc6206>.
skipping to change at page 28, line 9 skipping to change at line 1206
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551, in Low-Power and Lossy Networks", RFC 6551,
DOI 10.17487/RFC6551, March 2012, DOI 10.17487/RFC6551, March 2012,
<https://www.rfc-editor.org/info/rfc6551>. <https://www.rfc-editor.org/info/rfc6551>.
[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>.
12.2. Informative References 11.2. Informative References
[aodv-tot] Perkins, C.E. and E.M. Royer, "Ad-hoc On-demand Distance [aodv-tot] Perkins, C.E. and E.M. Royer, "Ad-hoc On-demand Distance
Vector Routing", Proceedings WMCSA'99. Second IEEE Vector Routing", Proceedings WMCSA'99. Second IEEE
Workshop on Mobile Computing Systems and Applications , Workshop on Mobile Computing Systems and Applications, pp.
February 1999. 90-100, February 1999.
[co-ioam] Rashmi Ballamajalu, Anand, S.V.R., and Malati Hegde, "Co- [co-ioam] Ballamajalu, R., Anand, S.V.R., and M. Hegde, "Co-iOAM:
iOAM: In-situ Telemetry Metadata Transport for Resource In-situ Telemetry Metadata Transport for Resource
Constrained Networks within IETF Standards Framework", Constrained Networks within IETF Standards Framework",
2018 10th International Conference on Communication 2018 10th International Conference on Communication
Systems & Networks (COMSNETS) pp.573-576, January 2018. Systems & Networks (COMSNETS), pp. 573-576, January 2018.
[contiki] Contiki contributors, "The Contiki Open Source OS for the [contiki] "The Contiki Open Source OS for the Internet of Things
Internet of Things (Contiki Version 2.7)", November 2013, (Contiki Version 2.7)", commit 7635906, November 2013,
<https://github.com/contiki-os/contiki>. <https://github.com/contiki-os/contiki>.
[Contiki-ng] [Contiki-ng]
Contiki-NG contributors, "Contiki-NG: The OS for Next "Contiki-NG: The OS for Next Generation IoT Devices
Generation IoT Devices (Contiki-NG Version 4.6)", December (Contiki-NG Version 4.6)", commit 3b0bc6a, December 2020,
2020, <https://github.com/contiki-ng/contiki-ng>. <https://github.com/contiki-ng/contiki-ng>.
[cooja] Contiki/Cooja contributors, "Cooja Simulator for Wireless [cooja] "Cooja Simulator for Wireless Sensor Networks (Contiki/
Sensor Networks (Contiki/Cooja Version 2.7)", November Cooja Version 2.7)", commit 7635906, November 2013,
2013, <https://github.com/contiki- <https://github.com/contiki-os/contiki/tree/master/tools/
os/contiki/tree/master/tools/cooja>. cooja>.
[empirical-study] [empirical-study]
Prasant Misra, Nadeem Ahmed, and Sanjay Jha, "An empirical Misra, P., Ahmed, N., and S. Jha, "An empirical study of
study of asymmetry in low-power wireless links", IEEE asymmetry in low-power wireless links", IEEE
Communications Magazine (Volume: 50, Issue: 7), July 2012. Communications Magazine, vol. 50, no. 7, pp. 137-146, July
2012.
[Link_Asymmetry] [Link_Asymmetry]
Lifeng Sang, Anish Arora, and Hongwei Zhang, "On Link Sang, L., Arora, A., and H. Zhang, "On Link Asymmetry and
Asymmetry and One-way Estimation in Wireless Sensor One-way Estimation in Wireless Sensor Networks", ACM
Networks", ACM Transactions on Sensor Networks, Volume 6 Transactions on Sensor Networks, vol. 6, no. 2, pp. 1-25,
Issue 2 pp.1-25, February 2010, DOI 10.1145/1689239.1689242, March 2010,
<https://doi.org/10.1145/1689239.1689242>. <https://doi.org/10.1145/1689239.1689242>.
[low-power-wireless] [low-power-wireless]
Kannan Srinivasan, Prabal Dutta, Arsalan Tavakoli, and Srinivasan, K., Dutta, P., Tavakoli, A., and P. Levis, "An
Philip Levis, "An empirical study of low-power wireless", empirical study of low-power wireless", ACM Transactions
ACM Transactions on Sensor Networks (Volume 6 Issue 2 on Sensor Networks, vol. 6, no. 2, pp. 1-49,
pp.1-49), February 2010, DOI 10.1145/1689239.1689246, March 2010,
<https://doi.org/10.1145/1689239.1689246>. <https://doi.org/10.1145/1689239.1689246>.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561, Demand Distance Vector (AODV) Routing", RFC 3561,
DOI 10.17487/RFC3561, July 2003, DOI 10.17487/RFC3561, July 2003,
<https://www.rfc-editor.org/info/rfc3561>. <https://www.rfc-editor.org/info/rfc3561>.
[RFC6687] Tripathi, J., Ed., de Oliveira, J., Ed., and JP. Vasseur, [RFC6687] Tripathi, J., Ed., de Oliveira, J., Ed., and JP. Vasseur,
Ed., "Performance Evaluation of the Routing Protocol for Ed., "Performance Evaluation of the Routing Protocol for
Low-Power and Lossy Networks (RPL)", RFC 6687, Low-Power and Lossy Networks (RPL)", RFC 6687,
skipping to change at page 30, line 5 skipping to change at line 1293
and M. Richardson, Ed., "A Security Threat Analysis for and M. Richardson, Ed., "A Security Threat Analysis for
the Routing Protocol for Low-Power and Lossy Networks the Routing Protocol for Low-Power and Lossy Networks
(RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015,
<https://www.rfc-editor.org/info/rfc7416>. <https://www.rfc-editor.org/info/rfc7416>.
[RFC7548] Ersue, M., Ed., Romascanu, D., Schoenwaelder, J., and A. [RFC7548] Ersue, M., Ed., Romascanu, D., Schoenwaelder, J., and A.
Sehgal, "Management of Networks with Constrained Devices: Sehgal, "Management of Networks with Constrained Devices:
Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015, Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015,
<https://www.rfc-editor.org/info/rfc7548>. <https://www.rfc-editor.org/info/rfc7548>.
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, DOI 10.17487/RFC7991, December 2016,
<https://www.rfc-editor.org/info/rfc7991>.
[RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL [RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL
(Routing Protocol for Low-Power and Lossy Networks) (Routing Protocol for Low-Power and Lossy Networks)
Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021, Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021,
<https://www.rfc-editor.org/info/rfc9010>. <https://www.rfc-editor.org/info/rfc9010>.
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time- [RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)", Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021, RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>. <https://www.rfc-editor.org/info/rfc9030>.
Appendix A. Example: Using ETX/RSSI Values to determine value of S bit Appendix A. Example: Using ETX/RSSI Values to Determine Value of S Bit
The combination of Received Signal Strength Indication(downstream) The combination of the downstream Received Signal Strength Indicator
(RSSI) and Expected Number of Transmissions(upstream) (ETX) has been (RSSI) and the upstream Expected Transmission Count (ETX) has been
tested to determine whether a link is symmetric or asymmetric at tested to determine whether a link is symmetric or asymmetric at
intermediate routers. We present two methods to obtain an ETX value intermediate routers. We present two methods to obtain an ETX value
from RSSI measurement. from RSSI measurement.
Method 1: In the first method, we constructed a table measuring RSSI Method 1: In the first method, we constructed a table measuring RSSI
vs ETX using the Cooja simulation [cooja] setup in the Contiki OS versus ETX using the Cooja simulation [cooja] setup in the Contiki
environment[contiki]. We used Contiki-2.7 running 6LoWPAN/RPL OS environment [contiki]. We used Contiki-2.7 running the
protocol stack for the simulations. For approximating the number 6LoWPAN/RPL protocol stack for the simulations. For approximating
of packet drops based on the RSSI values, we implemented simple the number of packet drops based on the RSSI values, we
logic that drops transmitted packets with certain pre-defined implemented simple logic that drops transmitted packets with
ratios before handing over the packets to the receiver. The certain predefined ratios before handing over the packets to the
packet drop ratio is implemented as a table lookup of RSSI ranges receiver. The packet drop ratio is implemented as a table lookup
mapping to different packet drop ratios with lower RSSI ranges of RSSI ranges mapping to different packet drop ratios with lower
resulting in higher values. While this table has been defined for RSSI ranges resulting in higher values. While this table has been
the purpose of capturing the overall link behavior, it is highly defined for the purpose of capturing the overall link behavior, in
recommended to conduct physical radio measurement experiments, in general, it is highly recommended to conduct physical radio
general. By keeping the receiving node at different distances, we measurement experiments. By keeping the receiving node at
let the packets experience different packet drops as per the different distances, we let the packets experience different
described method. The ETX value computation is done by another packet drops as per the described method. The ETX value
module which is part of RPL Objective Function implementation. computation is done by another module that is part of RPL
Since ETX value is reflective of the extent of packet drops, it Objective Function implementation. Since the ETX value is
allowed us to prepare a useful ETX vs RSSI table. ETX versus RSSI reflective of the extent of packet drops, it allowed us to prepare
values obtained in this way may be used as explained below: a useful ETX versus RSSI table. ETX versus RSSI values obtained
in this way may be used as explained below:
Source -------> NodeA -------> NodeB -----> Destination Source -------> NodeA -------> NodeB -----> Destination
Figure 7: Communication link from Source to Destination Figure 6: Communication Link from Source to Destination
+=========================+========================================+ +=========================+=======================+
| RSSI at NodeA for NodeB | Expected ETX at NodeA for NodeB->NodeA | | RSSI at NodeA for NodeB | Expected ETX at NodeA |
+=========================+========================================+ | | for NodeB->NodeA |
| > -60 | 150 | +=========================+=======================+
+-------------------------+----------------------------------------+ | > -60 | 150 |
| -70 to -60 | 192 | +-------------------------+-----------------------+
+-------------------------+----------------------------------------+ | -70 to -60 | 192 |
| -80 to -70 | 226 | +-------------------------+-----------------------+
+-------------------------+----------------------------------------+ | -80 to -70 | 226 |
| -90 to -80 | 662 | +-------------------------+-----------------------+
+-------------------------+----------------------------------------+ | -90 to -80 | 662 |
| -100 to -90 | 3840 | +-------------------------+-----------------------+
+-------------------------+----------------------------------------+ | -100 to -90 | 3840 |
+-------------------------+-----------------------+
Table 1: Selection of S bit based on Expected ETX value Table 3: Selection of S Bit Based on Expected
ETX Value
Method 2: One could also make use of the function Method 2: One could also make use of the function
guess_etx_from_rssi() defined in the 6LoWPAN/RPL protocol stack of guess_etx_from_rssi() defined in the 6LoWPAN/RPL protocol stack of
Contiki-ng OS [Contiki-ng] to obtain RSSI-ETX mapping. This Contiki-ng OS [Contiki-ng] to obtain RSSI-ETX mapping. This
function outputs ETX value ranging between 128 and 3840 for -60 <= function outputs an ETX value ranging between 128 and 3840 for -60
rssi <= -89. The function description is beyond the scope of this <= rssi <= -89. The function description is beyond the scope of
document. this document.
We tested the operations in this specification by making the We tested the operations in this specification by making the
following experiment, using the above parameters. In our experiment, following experiment, using the above parameters. In our experiment,
a communication link is considered as symmetric if the ETX value of a communication link is considered as symmetric if the ETX value of
NodeA->NodeB and NodeB->NodeA (see Figure 7) are within, say, a 1:3 NodeA->NodeB and NodeB->NodeA (see Figure 6) are within, say, a 1:3
ratio. This ratio should be understood as determining the link's ratio. This ratio should be understood as determining the link's
symmetric/asymmetric nature. NodeA can typically know the ETX value symmetric/asymmetric nature. NodeA can typically know the ETX value
in the direction of NodeA -> NodeB but it has no direct way of in the direction of NodeA->NodeB, but it has no direct way of knowing
knowing the value of ETX from NodeB->NodeA. Using physical testbed the value of ETX from NodeB->NodeA. Using physical testbed
experiments and realistic wireless channel propagation models, one experiments and realistic wireless channel propagation models, one
can determine a relationship between RSSI and ETX representable as an can determine a relationship between RSSI and ETX representable as an
expression or a mapping table. Such a relationship in turn can be expression or a mapping table. Such a relationship, in turn, can be
used to estimate ETX value at nodeA for link NodeB--->NodeA from the used to estimate the ETX value at NodeA for link NodeB->NodeA from
received RSSI from NodeB. Whenever nodeA determines that the link the received RSSI from NodeB. Whenever NodeA determines that the
towards the nodeB is bi-directional asymmetric then the S bit is set link towards the NodeB is bidirectional asymmetric, then the S bit is
to 0. Afterwards, the link from NodeA to Destination remains set to 0. Afterwards, the link from NodeA to Destination remains
designated as asymmetric and the S bit remains set to 0. designated as asymmetric, and the S bit remains set to 0.
Determination of asymmetry versus bidirectionality remains a topic of Determination of asymmetry versus bidirectionality remains a topic of
lively discussion in the IETF. lively discussion in the IETF.
Appendix B. Some Example AODV-RPL Message Flows Appendix B. Some Example AODV-RPL Message Flows
This appendix provides some example message flows showing RREQ and This appendix provides some example message flows showing RREQ and
RREP establishing symmetric and asymmetric routes. Also, examples RREP establishing symmetric and asymmetric routes. Also, examples
for the use of RREP_WAIT and G-RREP are included. In the examples, for the use of RREP_WAIT and G-RREP are included. In the examples,
router (O) is to be understood as performing the role of OrigNode. router (O) is to be understood as performing the role of OrigNode.
Router (T) is to be understood as performing the role of TargNode. Router (T) is to be understood as performing the role of TargNode.
Routers (R) are intermediate routers that are performing AODV-RPL Routers (R) are intermediate routers that are performing AODV-RPL
functions in order to discover one or more suitable routes between functions in order to discover one or more suitable routes between
(O) and (T). (O) and (T).
B.1. Example control message flows in symmetric and asymmetric networks B.1. Example Control Message Flows in Symmetric and Asymmetric Networks
In the following diagram, RREQ messages are multicast from router (O) In the following diagram, RREQ messages are multicast from router (O)
in order to discover routes to and from router (T). The RREQ control in order to discover routes to and from router (T). The RREQ control
messages flow outward from (O). Each router along the way messages flow outward from (O). Each router along the way
establishes a single RREQ-Instance identified by RREQ-InstanceID even establishes a single RREQ-Instance identified by RREQ-InstanceID even
if multiple RREQs are received with the same RREQ-InstanceID. In the if multiple RREQs are received with the same RREQ-InstanceID. In the
top half of the diagram, the routers are able to offer a symmetric top half of the diagram, the routers are able to offer a symmetric
route at each hop of the path from (O) to (T). When (T) receives a route at each hop of the path from (O) to (T). When (T) receives a
RREQ, it is then able to transmit data packets to (O). Router (T) RREQ, it is then able to transmit data packets to (O). Router (T)
then prepares to send a RREP along the symmetric path that would then prepares to send a RREP along the symmetric path that would
skipping to change at page 32, line 44 skipping to change at line 1420
| v | v
(O) --------->(R) --------->(R)-------->(T) (O) --------->(R) --------->(R)-------->(T)
/ \ RREQ RREQ RREQ ^ / \ RREQ RREQ RREQ ^
| \ (S=1) (S=0) (S=0) | | \ (S=1) (S=0) (S=0) |
| \ / | \ /
RREQ | \ RREQ (S=1) RREQ (S=0) RREQ | \ RREQ (S=1) RREQ (S=0)
(S=0) | \ / (S=0) | \ /
v \ RREQ (S=0) / v \ RREQ (S=0) /
(R) ---->(R)------>(R)----.....--->(R) (R) ---->(R)------>(R)----.....--->(R)
Figure 8: AODV-RPL RREQ message flow example when symmetric path Figure 7: AODV-RPL RREQ Message Flow Example When Symmetric Path
available Available
In the following diagram which results from the above RREQ message In the following diagram, which results from the above RREQ message
transmission, a symmetric route is available from (T) to router (O) transmission, a symmetric route is available from (T) to router (O)
via the routers in the top half of the diagram. RREP messages are via the routers in the top half of the diagram. RREP messages are
sent via unicast along the symmetric route. Since the RREP message sent via unicast along the symmetric route. Since the RREP message
is transmitted via unicast, no RREP messages are sent by router (T) is transmitted via unicast, no RREP messages are sent by router (T)
to the routers in the bottom half of the diagram. to the routers in the bottom half of the diagram.
(R)<------RREP----- (R)<------RREP----- (R) (R)<------RREP----- (R)<------RREP----- (R)
| ^ | ^
| | | |
RREP RREP RREP RREP
skipping to change at page 33, line 27 skipping to change at line 1445
v | v |
(O) ----------(R) ----------(R) --------(T) (O) ----------(R) ----------(R) --------(T)
/ \ | / \ |
| \ | | \ |
| \ (no RREP messages sent) / | \ (no RREP messages sent) /
| \ / | \ /
| \ / | \ /
| \ / | \ /
(R) -----(R)-------(R)----.....----(R) (R) -----(R)-------(R)----.....----(R)
Figure 9: AODV-RPL RREP message flow example when symmetric path Figure 8: AODV-RPL RREP Message Flow Example When Symmetric Path
available Available
In the following diagram, RREQ messages are multicast from router (O) In the following diagram, RREQ messages are multicast from router (O)
in order to discover routes to and from router (T) as before. As in order to discover routes to and from router (T) as before. As
shown, no symmetric route is available from (O) to (T). shown, no symmetric route is available from (O) to (T).
(R) ---RREQ(S=0)--->(R) ---RREQ(S=0)--->(R) (R) ---RREQ(S=0)--->(R) ---RREQ(S=0)--->(R)
^ | ^ |
| | | |
RREQ(S=1) RREQ(S=0) RREQ(S=1) RREQ(S=0)
| | | |
| v | v
(O) --------->(R) --------->(R)-------->(T) (O) --------->(R) --------->(R)-------->(T)
^ \ RREQ RREQ RREQ | \ ^ \ RREQ RREQ RREQ | \
| \ (S=1) (S=0) (S=0) | | | \ (S=1) (S=0) (S=0) | |
| \ / | | \ / |
| RREQ (S=1) RREQ (S=0) / (R) | RREQ (S=1) RREQ (S=0) / (R)
| \ / | | \ / |
| \ RREQ (S=0) / / | \ RREQ (S=0) / /
(R) ---->(R)------>(R)----.....----->(R)--- (R) ---->(R)------>(R)----.....----->(R)---
Figure 10: AODV-RPL RREQ message flow when symmetric path unavailable Figure 9: AODV-RPL RREQ Message Flow When Symmetric Path Unavailable
Upon receiving the RREQ in Figure 10, Router (T) then prepares to Upon receiving the RREQ in Figure 9, router (T) then prepares to send
send a RREP that would enable router (O) to send packets to router a RREP that would enable router (O) to send packets to router (T).
(T). In Figure 10, since no symmetric route is available from (T) to In Figure 9, since no symmetric route is available from (T) to router
router (O), RREP messages are sent via multicast to all neighboring (O), RREP messages are sent via multicast to all neighboring routers.
routers.
(R)<------RREP----- (R)<------RREP----- (R) (R)<------RREP----- (R)<------RREP----- (R)
| | | |
| | | |
RREP RREP RREP RREP
| | | |
| | | |
v v v v
(O)<--------- (R)<--------- (R)<------- (T) (O)<--------- (R)<--------- (R)<------- (T)
^ \ RREP RREP RREP | \ ^ \ RREP RREP RREP | \
| \ | |RREP | \ | |RREP
| \ / | | \ / |
RREP | \ RREP RREP / (R) RREP | \ RREP RREP / (R)
| \ / | | \ / |
| \ / / | \ / /
(R)<----- (R)<----- (R)<---.....---- (R)< - RREP (R)<----- (R)<----- (R)<---.....---- (R)< - RREP
RREP RREP RREP RREP RREP RREP
Figure 11: AODV-RPL RREQ and RREP Instances for Asymmetric Links Figure 10: AODV-RPL RREQ and RREP Instances for Asymmetric Links
B.2. Example RREP_WAIT handling B.2. Example RREP_WAIT Handling
In Figure 12, the first RREQ arrives at (T). This triggers TargNode In Figure 11, the first RREQ arrives at (T). This triggers TargNode
to start RREP_WAIT_TIME timer. to start the RREP_WAIT_TIME timer.
(O) --------->(R) --------->(R)-------->(T) (O) --------->(R) --------->(R)-------->(T)
RREQ RREQ RREQ RREQ RREQ RREQ
(S=1) (S=0) (S=0) (S=1) (S=0) (S=0)
Figure 12: TargNode starts RREP_WAIT Figure 11: TargNode Starts RREP_WAIT
In Figure 13, another RREQ arrives before RREP_WAIT_TIME timer is In Figure 12, another RREQ arrives before the RREP_WAIT_TIME timer is
expired. It could be preferable compared the previously received expired. It could be preferable compared the previously received
RREP that caused the RREP_WAIT_TIME timer to be set. RREP that caused the RREP_WAIT_TIME timer to be set.
(O) (T) (O) (T)
/ \ ^ / \ ^
| \ | | \ |
| \ / | \ /
RREQ | \ RREQ (S=1) RREQ (S=0) RREQ | \ RREQ (S=1) RREQ (S=0)
(S=0) | \ / (S=0) | \ /
v \ RREQ (S=0) / v \ RREQ (S=0) /
(R) ---->(R)------>(R)----.....--->(R) (R) ---->(R)------>(R)----.....--->(R)
Figure 13: Waiting TargNode receives preferable RREQ Figure 12: Waiting TargNode Receives Preferable RREQ
In Figure 14, the RREP_WAIT_TIME timer expires. TargNode selects the In Figure 13, the RREP_WAIT_TIME timer expires. TargNode selects the
path with S=1. path with S=1.
(R) ---RREQ(S=1)--->(R) ---RREQ(S=1)--->(R) (R) ---RREQ(S=1)--->(R) ---RREQ(S=1)--->(R)
^ | ^ |
| | | |
RREQ(S=1) RREQ(S=1) RREQ(S=1) RREQ(S=1)
| | | |
| v | v
(O) (T) (O) (T)
Figure 14: RREP_WAIT expires at TargNode Figure 13: RREP_WAIT Expires at TargNode
B.3. Example G-RREP handling B.3. Example G-RREP Handling
In Figure 15, R* has upward and downward routes to TargNode (T) that In Figure 14, R* has upward and downward routes to TargNode (T) that
satisfies OF of RPL Instance originated by OrigNode (O) and satisfy the OF of the RPL Instance originated by OrigNode (O), and
destination sequence number is at least as large as the sequence the destination sequence number is at least as large as the sequence
number in the RREQ message. number in the RREQ message.
(R) ---RREQ(S=1)--->(R) ---RREQ(S=0)--->(R) (R) ---RREQ(S=1)--->(R) ---RREQ(S=0)--->(R)
^ | ^ |
| | | |
RREQ(S=1) RREQ(S=0) RREQ(S=1) RREQ(S=0)
| | | |
| v | v
(O) --------->(R) --------->(R)-------->(T) (O) --------->(R) --------->(R)-------->(T)
/ \ RREQ RREQ RREQ ^ / \ RREQ RREQ RREQ ^
| \ (S=1) (S=0) (S=0) | | \ (S=1) (S=0) (S=0) |
| \ / | \ /
RREQ | \ RREQ (S=1) / RREQ | \ RREQ (S=1) /
(S=0) | \ / (S=0) | \ /
v \ v v \ v
(R) ---->(R*)<------>(R)<----....--->(R) (R) ---->(R*)<------>(R)<----....--->(R)
Figure 15: RREP triggers G-RREP at Intermediate Node Figure 14: RREP Triggers G-RREP at Intermediate Node
In Figure 16, R* transmits the G-RREP DIO back to OrigNode (O) and In Figure 15, R* transmits the G-RREP-DIO back to OrigNode (O) and
forwards the incoming RREQ towards (T). forwards the incoming RREQ towards (T).
(O) (T) (O) (T)
\ ^ \ ^
\ | \ |
\ (RREQ) / \ (RREQ) /
\ G-RREP DIO / \ G-RREP-DIO /
\ / \ /
\ (RREQ) (RREQ) / \ (RREQ) (RREQ) /
(R*)------>(R)----....--->(R) (R*)------>(R)----....--->(R)
Figure 16: Intermediate Node initiates G-RREP Figure 15: Intermediate Node Initiates G-RREP
Appendix C. Changelog
Note to the RFC Editor: please remove this section before
publication.
C.1. Changes from version 19 to version 20
* Changed Option Format drawings to avoid suggesting that the Option
Length is a multiple of 4 bytes for AODV-RPL options.
* Deleted the terms "on-demand routing" and "reactive routing" from
the Terminology list. In the overview, explained those two terms
as an illustration for the protocol design goals.
* In Section 9, to improve readability, explicitly named the "Local
Network Control Block (224.0.0.0 - 224.0.0.255 (224.0.0/24))"
registry in the "IPv4 Multicast Address Space Registry" as the
relevant registries.
* Changed "must" to "MUST", so that "the selected address MUST
encompass the domain where the route is built".
* Inserted language allowing a node X to free up sufficient
resources for a particular RREQ instead of dropping it, when
resources are not already available upon reception of that RREQ.
* New author's address, minor editorial.
C.2. Changes from version 18 to version 19
* Observed the difference in address ordering in the Address Vector,
depending on whether or not the RREP is returning a symmetric
route. Specified that the prefix of each address is elided
according to the Compr field.
* Added length specification for byte-sized message fields, which
had previously relied on implicit length specification from the
message's packet format diagram.
* Added clarifying language for handling of initial zero bits in
some cases for the Target Prefix / Address field.
* Updated specification regarding the need for a router to ensure
the availability of RREQ state information when processing a
corresponding RREP.
* Replaced GRREP by G-RREP when describing Gratuitous RREP.
* Updated affiliations for Charles Perkins, Abdur Rashid Sangi and
email address for S.V.R. Anand.
* Corrected misspellings, typos.
C.3. Changes from version 17 to version 18
* Replaced "on-demand nature of AODV route discovery is natural" by
"on-demand property of AODV route discovery is useful" in
Section 1.
* In Section 6.2.4, instead of describing an option to "associate
the Address Vector of the symmetric route ..." to the RREQ-
Instance, reformulated the description as an option to "include
the Address Vector of the symmetric route ..." as part of the
RREQ-Instance in Section 6.2.4.
* Changed from v2-style RFC citations to using Xinclude as specified
in [RFC7991].
C.4. Changes from version 16 to version 17
* Added new Terminology definitions for RREQ, RREP, OF.
* Added clarifying detail about some kinds of improved routes
discoverable by AODV-RPL.
* Added forward reference explaining how RREP-InstanceID is matched
with the proper RREQ-InstanceID.
* Added explanation about the function of the 'D' bit of the
RPLInstanceID.
* Provided detail about why a node should leave the RREQ-Instance
after the specified amount of time.
* Specified that "An upstream intermediate router that receives such
a G-RREP MUST also generate a G-RREP and send it further upstream
towards OrigNode."
* Added more illustrative diagrams in new Appendix B. Example
diagrams show control message flows for RREQ and for RREP in cases
when symmetric route is either available or not available. The
use of RREP_WAIT and G-RREP is also illustrated in other new
diagrams.
* Included the reasoning for using intersections of RREQ target
lists in Section 6.2.2.
* Various editorial improvements and clarifications.
C.5. Changes from version 15 to version 16
* Modified language to be more explicit about when AODV-RPL is
likely to produce preferable routes compared to routing protocols
that are constrained to traverse common ancestors.
* Added explanation that the way AODV-RPL uses the Rank function
does not express a distance or a path cost to the root.
* Added a citation suggesting AODV-RPL's likely improvements in
routing costs.
C.6. Changes from version 14 to version 15
* Clarified that AODV-RPL treats the addresses of multiple
interfaces on the same router as the addresses of independent
routers.
* Added details about cases when proactive route establishment is
preferable to AODV-RPL's reactive route establishment.
* Various editorial stylistic improvements.
* Added citations about techniques that can be used for evaluating a
link's state.
* Clarified that the determination of TargNode status and
determination of a usable route to OrigNode does not depend on
whether or not S == 0.
* Clarified that AODV-RPL does not specify any action to be taken
when multiple RREP-DIO messages are received and the S-bit of the
RREQ-Instance is 0.
C.7. Changes from version 13 to version 14
* Provided more details about scenarios naturally supporting the
choice of AODV-RPL as a routing protocol
* Added new informative references [RFC6687], [RFC9010]) that
describe the value provided by peer-to-peer routing.
* Requested IANA to allocate a new multicast group to enable clean
separation of AODV-RPL operation from previous routing protocols
in the RPL family.
* Cited [RFC6550] as the origination of the definition of DIO
* Defined "hop-by-hop route" as a route created using RPL's storing
mode.
* Defined new configuration variable REJOIN_REENABLE.
* Improved definition for RREQ-InstanceID. Created analogous
definition for RREP-InstanceID=(RPLInstanceID, TargNode_IPaddr)
* Improved definition of source routing
* Clarified that the Border Router (BR) in Figure 4 does not imply
that AODV does not a require a BR as a protocol entity.
* Provided more guidelines about factors to be considered by
OrigNode when selecting a value for the 'L' field.
* Described the disadvantage of not keeping track of the Address
Vector in the RREQ-Instance.
* Specified that in non-storing mode an intermediate node has to
record the IP addresses of both incoming and outgoing interfaces
into the Address Vector, when those interfaces have different IP
addresses.
* Added three informative references to describe relevant details
about evaluating link asymmetry.
* Clarified details about Gratuitous RREP.
C.8. Changes from version 12 to version 13
* Changed name of "Shift" field to be the "Delta" field.
* Specified that if a node does not have resources, it MUST drop the
RREQ.
* Changed name of MaxUseRank to MaxUsefulRank.
* Revised a sentence that was not clear about when a TargNode can
delay transmission of the RREP in response to a RREQ.
* Provided advice about running AODV-RPL at same time as P2P-RPL or
native RPL.
* Small reorganization and enlargement of the description of Trickle
time operation in Section 8.
* Added definition for "RREQ-InstanceID" to Terminology section.
* Specified that once a node leaves an RREQ-Instance, it MUST NOT
rejoin the same RREQ-Instance.
C.9. Changes from version 11 to version 12
* Defined RREP_WAIT_TIME for asymmetric as well as symmetric
handling of RREP-DIO.
* Clarified link-local multicast transmission to use link-local
multicast group all-RPL nodes.
* Identified some security threats more explicitly.
* Specified that the pairing between RREQ-DIO and RREP-DIO happens
at OrigNode and TargNode. Intermediate routers do not necessarily
maintain the pairing.
* When RREQ-DIO is received with H=0 and S=1, specified that
intermediate routers MAY store symmetric Address Vector
information for possible use when a matching RREP-DIO is received.
* Specified that AODV-RPL uses the "P2P Route Discovery Mode of
Operation" (MOP == 4), instead of requesting the allocation of a
new MOP. Clarified that there is no conflict with [RFC6997].
* Fixed several important typos and improved language in numerous
places.
* Reorganized the steps in the specification for handling RREQ and
RREP at an intermediate router, to more closely follow the order
of processing actions to be taken by the router.
C.10. Changes from version 10 to version 11
* Numerous editorial improvements.
* Replace Floor((7+(Prefix Length))/8) by Ceil(Prefix Length/8) for
simplicity and ease of understanding.
* Use "L field" instead of "L bit" since L is a two-bit field.
* Improved the procedures in section 6.2.1.
* Define the S bit of the data structure a router uses to represent
whether or not the RREQ instance is for a symmetric or an
asymmetric route. This replaces text in the document that was a
holdover from earlier versions in which the RREP had an S bit for
that purpose.
* Quote terminology from AODV that has been identified as possibly
originating in language reflecting various kinds of bias against
certain cultures.
* Clarified the relationship of AODV-RPL to RPL.
* Eliminated the "Point-to-Point" terminology to avoid suggesting
only a single link.
* Modified certain passages to better reflect the possibility that a
router might have multiple IP addresses.
* "Rsv" replaced by "X X" for reserved field.
* Added mandates for reserved fields, and replaces some ambiguous
language phraseology by mandates.
* Replaced "retransmit" terminology by more correct "propagate"
terminology.
* Added text about determining link symmetry near Figure 5.
* Mandated checking the Address Vector to avoid routing loops.
* Improved specification for use of the Delta value in
Section 6.3.3.
* Corrected the wrong use of RREQ-Instance to be RREP-Instance.
* Referred to Subregistry values instead of Registry values in
Section 9.
* Sharpened language in Section 10, eliminated misleading use of
capitalization in the words "Security Configuration".
* Added acknowledgements and contributors.
C.11. Changes from version 09 to version 10
* Changed the title for brevity and to remove acronyms.
* Added "Note to the RFC Editor" in Section 9.
* Expanded DAO and P2MP in Section 1.
* Reclassified [RFC6998] and [RFC7416] as Informational.
* SHOULD changed to MUST in Section 4.1 and Section 4.2.
* Several editorial improvements and clarifications.
C.12. Changes from version 08 to version 09
* Removed section "Link State Determination" and put some of the
relevant material into Section 5.
* Cited security section of [RFC6550] as part of the RREP-DIO
message description in Section 2.
* SHOULD has been changed to MUST in Section 4.2.
* Expanded the terms ETX and RSSI in Section 5.
* Section 6.4 has been expanded to provide a more precise
explanation of the handling of route reply.
* Added [RFC7416] in the Security Considerations (Section 10) for
RPL security threats. Cited [RFC6550] for authenticated mode of
operation.
* Appendix A has been mostly re-written to describe methods to
determine whether or not the S bit should be set to 1.
* For consistency, adjusted several mandates from SHOULD to MUST and
from SHOULD NOT to MUST NOT.
* Numerous editorial improvements and clarifications.
C.13. Changes from version 07 to version 08
* Instead of describing the need for routes to "fulfill the
requirements", specify that routes need to "satisfy the Objective
Function".
* Removed all normative dependencies on [RFC6997]
* Rewrote Section 10 to avoid duplication of language in cited
specifications.
* Added a new section "Link State Determination" with text and
citations to more fully describe how implementations determine
whether links are symmetric.
* Modified text comparing AODV-RPL to other protocols to emphasize
the need for AODV-RPL instead of the problems with the other
protocols.
* Clarified that AODV-RPL uses some of the base RPL specification
but does not require an instance of RPL to run.
* Improved capitalization, quotation, and spelling variations.
* Specified behavior upon reception of a RREQ-DIO or RREP-DIO
message for an already existing DODAGID (e.g, Section 6.4).
* Fixed numerous language issues in IANA Considerations Section 9.
* For consistency, adjusted several mandates from SHOULD to MUST and
from SHOULD NOT to MUST NOT.
* Numerous editorial improvements and clarifications.
C.14. Changes from version 06 to version 07
* Added definitions for all fields of the ART option (see
Section 4.3). Modified definition of Prefix Length to prohibit
Prefix Length values greater than 127.
* Modified the language from [RFC6550] Target Option definition so
that the trailing zero bits of the Prefix Length are no longer
described as "reserved".
* Reclassified [RFC3561] and [RFC6998] as Informative.
* Added citation for [RFC8174] to Terminology section.
C.15. Changes from version 05 to version 06
* Added Security Considerations based on the security mechanisms
defined in [RFC6550].
* Clarified the nature of improvements due to P2P route discovery
versus bidirectional asymmetric route discovery.
* Editorial improvements and corrections.
C.16. Changes from version 04 to version 05
* Add description for sequence number operations.
* Extend the residence duration L in section 4.1.
* Change AODV-RPL Target option to ART option.
C.17. Changes from version 03 to version 04
* Updated RREP option format. Remove the T bit in RREP option.
* Using the same RPLInstanceID for RREQ and RREP, no need to update
[RFC6550].
* Explanation of Delta field in RREP.
* Multiple target options handling during transmission.
C.18. Changes from version 02 to version 03
* Include the support for source routing.
* Import some features from [RFC6997], e.g., choice between hop-by-
hop and source routing, the L field which determines the duration
of residence in the DAG, RankLimit, etc.
* Define new target option for AODV-RPL, including the Destination
Sequence Number in it. Move the TargNode address in RREQ option
and the OrigNode address in RREP option into ADOV-RPL Target
Option.
* Support route discovery for multiple targets in one RREQ-DIO.
* New RPLInstanceID pairing mechanism.
Appendix D. Contributors
Abdur Rashid Sangi
Wenzhou-Kean University
88 Daxue Rd, Ouhai,
Wenzhou, Zhejiang Province
P.R. China 325060
Kean University
1000 Morris Avenue
Union, New Jersey 07083
USA
Email: sangi_bahrian@yahoo.com
Malati Hegde
Indian Institute of Science
Bangalore 560012
India Acknowledgements
Email: malati@iisc.ac.in The authors thank Pascal Thubert, Rahul Jadhav, and Lijo Thomas for
their support and valuable input. The authors specially thank
Lavanya H.M. for implementing AODV-RPL in Contiki and conducting
extensive simulation studies.
Mingui Zhang The authors would like to acknowledge the reviews, feedback, and
comments from the following people, in alphabetical order: Roman
Danyliw, Lars Eggert, Benjamin Kaduk, Tero Kivinen, Erik Kline,
Murray Kucherawy, Warren Kumari, Francesca Palombini, Alvaro Retana,
Ines Robles, John Scudder, Meral Shirazipour, Peter Van der Stok,
Éric Vyncke, and Robert Wilton.
Huawei Technologies Contributors
No. 156 Beiqing Rd. Haidian District
Beijing 100095 Abdur Rashid Sangi
Wenzhou-Kean University
88 Daxue Rd, Ouhai
Wenzhou
Zhejiang Province, 325060
Kean University
1000 Morris Avenue
Union, New Jersey 07083
United States of America
P.R. China
Email: sangi_bahrian@yahoo.com
P.R. China Malati Hegde
Indian Institute of Science
Bangalore 560012
India
Email: malati@iisc.ac.in
Email: zhangmingui@huawei.com Mingui Zhang
Huawei Technologies
No. 156 Beiqing Rd.
Haidian District
Beijing
100095
P.R. China
Email: zhangmingui@huawei.com
Authors' Addresses Authors' Addresses
Charles E. Perkins Charles E. Perkins
Blue Meadow Networks Blue Meadow Networks
Saratoga, 95070 Saratoga, CA 95070
United States United States of America
Email: charliep@lupinlodge.com Email: charliep@lupinlodge.com
S.V.R Anand S.V.R. Anand
Indian Institute of Science Indian Institute of Science
Bangalore 560012 Bangalore 560012
India India
Email: anandsvr@iisc.ac.in Email: anandsvr@iisc.ac.in
Satish Anamalamudi Satish Anamalamudi
SRM University-AP SRM University-AP
Amaravati Campus Amaravati Campus
Amaravati, Andhra Pradesh 522 502 Amaravati, Andhra Pradesh 522 502
India India
Email: satishnaidu80@gmail.com Email: satishnaidu80@gmail.com
Bing Liu Bing Liu
Huawei Technologies Huawei Technologies
No. 156 Beiqing Rd. Haidian District No. 156 Beiqing Rd.
Haidian District
Beijing Beijing
100095 100095
China China
Email: remy.liubing@huawei.com Email: remy.liubing@huawei.com
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