<?xmlversion="1.0" encoding="US-ASCII"?> <!-- This template is for creating an Internet Draft using xml2rfc, which is available here: http://xml.resource.org.version='1.0' encoding='UTF-8'?> <!DOCTYPE rfcSYSTEM "rfc2629.dtd"[ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]>--> <!-- For a complete list and description of processing instructions (PIs), please see http://xml.resource.org/authoring/README.html. --> <!-- Below are generally applicable Processing Instructions (PIs) that most I-Ds might want to use. (Here they are set differently than their defaults in xml2rfc v1.32) --> <?rfc strict="yes" ?> <!-- give errors regarding ID-nits and DTD validation --> <!-- control the table of contents (ToC) --> <?rfc toc="yes"?> <!-- generate a ToC --> <?rfc tocdepth="4"?> <!-- the number of levels of subsections in ToC. default: 3 --> <!-- control references --> <?rfc symrefs="yes"?> <!-- use symbolic references tags, i.e, [RFC2119] instead of [1] --> <?rfc sortrefs="yes" ?> <!-- sort the reference entries alphabetically --> <!-- control vertical white space (using these PIs as follows is recommended by the RFC Editor) --> <?rfc compact="yes" ?> <!-- do not start each main section on a new page --> <?rfc subcompact="no" ?> <!-- keep one blank line between list items --> <!-- end of list of popular I-D processing instructions --><rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std" docName="draft-ietf-roll-aodv-rpl-20" number="9854" updates="" obsoletes="" ipr="trust200902" submissionType="IETF" consensus="true"xmlns:xi="http://www.w3.org/2001/XInclude"> <!-- category values: std, bcp, info, exp, and historic http://umeeting.huawei.com/Portal/business.action?BMECID=1474233&BMETimestamp=1426658395147 ipr values: full3667, noModification3667, noDerivatives3667 you can add the attributes updates="NNNN" and obsoletes="NNNN" they will automatically be output with "(if approved)" --> <!-- ***** FRONT MATTER ***** --> <!-- TODO: -->tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3" xml:lang="en"> <front><!-- The abbreviated title is used in the page header - it is only necessary if the full title is longer than 39 characters --><titleabbrev="AODV-RPL"> Supporting Asymmetric Links in Low Power Networks: AODV-RPL </title> <!-- add 'role="editor"' belowabbrev="AODV-RPL">AODV-RPL: The Routing Protocol forthe editors if appropriate --> <!-- Another author who claims to be an editor -->Low-Power and Lossy Networks (RPL) Based on Ad Hoc On-Demand Distance Vector (AODV) Routing</title> <seriesInfo name="RFC" value="9854"/> <author fullname="Charles E. Perkins" initials="C.E." surname="Perkins"> <organization>Blue Meadow Networks</organization> <address> <postal><street/><city>Saratoga</city><region/><region>CA</region> <code>95070</code> <country>UnitedStates</country>States of America</country> </postal><phone/><email>charliep@lupinlodge.com</email><!-- uri and facsimile elements may also be added --></address> </author> <authorfullname="S.V.Rfullname="S.V.R. Anand"initials="" surname="S.V.R.Anand">initials="S.V.R." surname="Anand"> <organization>Indian Institute of Science</organization> <address> <postal><street></street> <!-- Reorder these if your country does things differently --><city>Bangalore</city><region/><code>560012</code> <country>India</country> </postal><phone/><email>anandsvr@iisc.ac.in</email><!-- uri and facsimile elements may also be added --></address> </author> <author fullname="Satish Anamalamudi" initials="S." surname="Anamalamudi"> <organization>SRM University-AP</organization> <address> <postal> <street>Amaravati Campus</street><!-- Reorder these if your country does things differently --><city>Amaravati, Andhra Pradesh</city><region/><code>522 502</code> <country>India</country> </postal><phone/><email>satishnaidu80@gmail.com</email><!-- uri and facsimile elements may also be added --></address> </author> <author fullname="Bing Liu" initials="B." surname="Liu"> <organization>Huawei Technologies</organization> <address> <postal> <street>No. 156 BeiqingRd. Haidian District</street> <!-- Reorder these if your country does things differently -->Rd.</street> <cityarea>Haidian District</cityarea> <city>Beijing</city><region/><code>100095</code> <country>China</country> </postal><phone/><email>remy.liubing@huawei.com</email> </address> </author> <dateyear=""/> <!-- If the month and year are both specified and are the current ones, xml2rfc will fill in the current day for you. If only the current year is specified, xml2rfc will fill in the current day and month for you. If the year is not the current one, it is necessary to specify at least a month (xml2rfc assumes day="1" if not specified for the purpose of calculating the expiry date). With drafts it is normally sufficient to specify just the year. --> <!-- Meta-data Declarations --> <area>Internet</area> <workgroup>ROLL</workgroup> <!-- WG name at the upperleft corner of the doc; IETF is fine for individual submissions. If this element is not present, the default is "Network Working Group", which is used by the RFC Editor as a nod to the history of the IETF. --> <keyword>AODV, Peer-to-Peeryear="2025" month="September"/> <area>RTG</area> <workgroup>roll</workgroup> <keyword>AODV</keyword> <keyword>Peer-to-Peer RouteDiscovery, Asymmetric</keyword> <!-- Keywords will be incorporated into HTML output files in a meta tag but they have no effect on text or nroff output. If you submit your draft to the RFC Editor, the keywords will be used for the search engine. -->Discovery</keyword> <keyword>Asymmetric</keyword> <abstract><t> Route<t>Route discovery for symmetric and asymmetric Peer-to-Peer (P2P) traffic flows is a desirable feature inLow powerLow-Power and Lossy Networks (LLNs). For that purpose, this document specifies AODV-RPL -- the Routing Protocol for Low-Power and Lossy Networks (RPL) based on Ad hoc On-demand Distance Vector (AODV) routing. AODV-RPL is a reactive P2P route discovery mechanism for both hop-by-hop routes and sourcerouting: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL protocol (AODV-RPL).routing. PairedInstancesinstances are used to construct directionalpaths,paths for cases where there are asymmetric links between source and target nodes. </t> </abstract> </front> <middle> <sectionanchor="Introduction" title="Introduction">anchor="Introduction"> <name>Introduction</name> <t> The Routing Protocol for Low-Power and Lossy Networks (RPL) <xref target="RFC6550"/> is an IPv6 distance vector routing protocol designed to support multiple traffic flows through a root-based Destination-Oriented Directed Acyclic Graph (DODAG). Typically,<!-- Gunter Van de Velde 2/11/2025, 8:36 PM -->a router does not have routing information for destinations attached to most other routers. Consequently, for traffic between routers within the DODAG (i.e.,Peer-to-Peer (P2P) traffic)P2P traffic), data packets either have to traverse the root in non-storingmode,mode or traverse a common ancestor in storing mode. Such P2P traffic is thereby likely to traverse longer routes and may suffer severe congestion near the root (for moreinformationinformation, see <xref target="RFC6687"/>, <xref target="RFC6997"/>, <xref target="RFC6998"/>, and <xref target="RFC9010"/>). The network environment that is considered in this document is assumed to be the same as that described inSection 1 of<xreftarget="RFC6550"/>.target="RFC6550" sectionFormat="of" section="1"/>. Each radio interface/link and the associated address should be treated as an independent intermediate router. Such routers have differentlinkslinks, and the rules forthelink symmetry apply independently for each of these. </t> <t> The route discovery process in AODV-RPL is modeled on the analogouspeer-to-peerP2P procedure specified in AODV <xref target="RFC3561"/>. The on-demand property of AODV route discovery is useful for the needs of routing in RPL-based LLNs when routes are needed but aren't yet established.Peer-to-peerP2P routing is desirable to discover shorter routes,andespecially when it is desired to avoid directing additional traffic through a root or gateway node of the network. It may happen that some routes need to be established proactively when known beforehand and when AODV-RPL's route discovery process introduces unwanted delayat the timewhen the application is launched. </t> <t> AODV terminology has been adapted for use with AODV-RPL messages, namelyRREQ"RREQ" forRoute Request,"Route Request", andRREP"RREP" forRoute Reply."Route Reply". AODV-RPL currently omits some features compared to AODV -- in particular, flaggingRoute Errors, "blacklisting"route errors, blocking the use of unidirectional links(<xref target="RFC3561"/>),<xref target="RFC3561"/>, multihoming, and handling unnumbered interfaces. </t><t> AODV-RPL<t>AODV-RPL reuses and extends the core RPL functionality to support routes with bidirectional asymmetric links. It retains RPL's DODAG formation, RPL Instance and the associated Objective Function (OF) (defined in <xref target="RFC6551"/>),trickleTrickle timers, and support for storing and non-storing modes. AODV-RPL adds the basic messages RREQ and RREP as part of the RPL DODAG Information Object (DIO) control message, which go in separate (paired) RPLinstances.Instances. AODV-RPL does not utilize the Destination Advertisement Object (DAO) control message of RPL. <!-- The P2P routes do not have to go through the tree root. I don't remember what are the point-to-multipoint routes under discussion here. --> AODV-RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) with three newOptionsoptions for the DIO message, dedicated todiscoverdiscovering P2P routes. These P2P routes may differ from routes discoverable bynative RPL.RPL <xref target="RFC6550"/>. Since AODV-RPL uses newly definedOptionsoptions and a newly allocated multicast group (see <xref target="iana"/>), there is no conflict with P2P-RPL <xref target="RFC6997"/>, a previous document using the same MOP. AODV-RPL can be operated whether or not P2P-RPL ornativeRPL <xref target="RFC6550"/> isrunning otherwise.also running. AODV-RPL could be used for networks in which routes are needed withObjective FunctionsOFs that cannot be satisfied by routes that are constrained to traverse the root of the network or other common ancestors. P2P routes often require fewer hops and therefore consume less resources than routes that traverse the root or other common ancestors. Similar in cost to base RPL <xref target="RFC6550"/>, the cost will depend on many <!-- From Anand: The real cost depends on many factors such as the proximity of the OrigNode and TargNodes, Gratuitous RREP, lifetime of the P2P routes, distribution of symmetric/asymmetric P2P links, number of Targets given in AODV-RPL Target (ART) Option, H-bit value, RREP_WAIT_TIME and so on. --> factors such as the proximity of the OrigNode and TargNodes and distribution of symmetric/asymmetric P2P links. Experience with AODV <xref target="aodv-tot"/> suggests that AODV-RPL will often find routes with improvedrankRank compared to routes constrained to traverse a common ancestor of the source and destination nodes. <!-- However, there does not seem to be much value in maintaining two routing protocols even if they are compatible. --> </t> </section><!-- End of section "Introduction" --><sectionanchor="terms" title="Terminology">anchor="terms"> <name>Terminology</name> <t> The key words"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY","<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", "<bcp14>MAY</bcp14>", and"OPTIONAL""<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described inBCP 14BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shown here. </t> <t> AODV-RPL reuses names for messages and data structures, including Rank,DODAGDODAG, and DODAGID, as defined in RPL <xref target="RFC6550"/>. </t><t><list style="hanging"> <t hangText="AODV"><vspace /> Ad Hoc On-demand<t>This document also uses the following terms:</t> <dl newline="true" spacing="normal"> <dt>AODV</dt> <dd>Ad hoc On-Demand Distance VectorRouting<xreftarget="RFC3561"/>.</t>target="RFC3561"/>.</dd> <!-- /* Murray Kucherawy: does not appear anywhere else in the document. */ <t hangText="AODV-RPL Instance"><vspace /> Either the RREQ-Instance or RREP-Instance</t> --><t hangText="ART option"><vspace /><dt>ART option</dt> <dd>The AODV-RPL Targetoption: a targetoption defined in thisdocument.</t> <t hangText="Asymmetric Route"><vspace /> Thedocument.</dd> <dt>Asymmetric route</dt> <dd>The route from the OrigNode to the TargNode can traverse different nodes than the route from the TargNode to the OrigNode. An asymmetric route may result from the asymmetry of links, such that only one direction of the series of links satisfies theObjective FunctionOF during route discovery. <!-- CEP: Need to check this!! But the RREQ *still* has to store the reverse route... If the OrigNode doesn't require an upward route towards itself, the route is also considered as asymmetric. --></t> <t hangText="Bi-directional Asymmetric Link"><vspace /> A</dd> <dt>Bidirectional asymmetric link</dt> <dd>A link that can be used in both directions but with different linkcharacteristics. </t> <t hangText="DIO"><vspace /> DODAGcharacteristics.</dd> <dt>DIO</dt> <dd>DODAG Information Object (as defined in <xreftarget="RFC6550"/>) </t> <t hangText="DODAGtarget="RFC6550"/>).</dd> <dt>DODAG RREQ-Instance (or simplyRREQ-Instance)"><vspace />RREQ-Instance)</dt> <dd>An RPL Instance built using the DIO with RREQ option; used for transmission of control messages from OrigNode to TargNode, thus enabling data transmission from TargNode toOrigNode. </t> <t hangText="DODAGOrigNode.</dd> <dt>DODAG RREP-Instance (or simplyRREP-Instance)"><vspace />RREP-Instance)</dt> <dd>An RPL Instance built using the DIO with RREP option; used for transmission of control messages from TargNode toOrigNodeOrigNode, thus enabling data transmission from OrigNode to TargNode.</t> <t hangText="Downward Direction"><vspace /> The</dd> <dt>Downward direction</dt> <dd>The direction from the OrigNode to theTargNode.</t> <t hangText="Downward Route"><vspace /> ATargNode.</dd> <dt>Downward route</dt> <dd>A route in the downwarddirection. </t> <t hangText="hop-by-hop route"><vspace /> Adirection.</dd> <dt>Hop-by-hop route</dt> <dd>A route for which each router along the routing path stores routing information about the next hop. A hop-by-hop route is created using RPL's "storingmode".</t> <t hangText="OF"><vspace /> An Objectivemode".</dd> <dt>OF</dt> <dd>Objective Functionas(as defined in <xreftarget="RFC6550"/>. </t> <t hangText="OrigNode"><vspace /> Thetarget="RFC6550"/>).</dd> <dt>OrigNode</dt> <dd>The IPv6 router(Originating Node)(originating node) initiating the AODV-RPL route discovery to obtain a route to TargNode.</t> <t hangText="Paired DODAGs"><vspace /> Two</dd> <dt>Paired DODAGs</dt> <dd>Two DODAGs for a single route discovery process between OrigNode andTargNode.</t> <t hangText="P2P"><vspace /> Peer-to-Peer -- inTargNode.</dd> <dt>P2P</dt> <dd>Peer-to-Peer (in other words, not constrained a priori to traverse a commonancestor. </t> <t hangText="REJOIN_REENABLE"><vspace /> Theancestor).</dd> <dt>REJOIN_REENABLE</dt> <dd>The duration during which a node is prohibited from joining a DODAG with a particular RREQ-InstanceID, after it has left a DODAG with the same RREQ-InstanceID. The default value of REJOIN_REENABLE is 15minutes.</t> <t hangText="RREQ"><vspace /> A RREQ-DIO message. </t> <t hangText="RREQ-DIO message"><vspace /> Aminutes.</dd> <dt>RREQ</dt> <dd>Route Request.</dd> <dt>RREQ-DIO message</dt> <dd>A DIO message containing the RREQ option. The RPLInstanceID in RREQ-DIO is assigned locally by the OrigNode. The RREQ-DIO message has a secure variant as noted in <xreftarget="RFC6550"/>. </t> <t hangText="RREQ-InstanceID"><vspace /> Thetarget="RFC6550"/>.</dd> <dt>RREQ-InstanceID</dt> <dd>The RPLInstanceID for the RREQ-Instance. The RREQ-InstanceID is formed as the ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr), where Orig_RPLInstanceID is the local RPLInstanceID allocated byOrigNode,OrigNode and OrigNode-IPaddr is an IP address of OrigNode. The RREQ-InstanceID uniquely identifies the RREQ-Instance.</t> <t hangText="RREP"><vspace /> A RREP-DIO message. </t> <t hangText="RREP-DIO message"><vspace /> A</dd> <dt>RREP</dt> <dd>Route Reply.</dd> <dt>RREP-DIO message</dt> <dd>A DIO message containing the RREP option. OrigNode pairs the RPLInstanceID in RREP-DIO to the one in the associated RREQ-DIO message (i.e., the RREQ-InstanceID) as described in <xref target="asymmetricrrep"/>. The RREP-DIO message has a secure variant as noted in <xreftarget="RFC6550"/>. </t> <t hangText="RREP-InstanceID"><vspace />target="RFC6550"/>.</dd> <dt>RREP-InstanceID</dt> <dd> The RPLInstanceID for the RREP-Instance. The RREP-InstanceID is formed as the ordered pair (Targ_RPLInstanceID, TargNode-IPaddr), where Targ_RPLInstanceID is the local RPLInstanceID allocated byTargNode,TargNode and TargNode-IPaddr is an IP address of TargNode. The RREP-InstanceID uniquely identifies the RREP-Instance. The RPLInstanceID in the RREP message along with the Delta value indicates the associated RREQ-InstanceID. The InstanceIDs are matched by the mechanism explained in <xreftarget="instancepairing"/> </t> <t hangText="Source routing"><vspace /> Atarget="instancepairing"/>.</dd> <dt>Source routing</dt> <dd>A mechanism by which the source supplies a vector of addresses towards the destination node along with each data packet <xreftarget="RFC6550"/>. </t> <t hangText="Symmetric route"><vspace /> Thetarget="RFC6550"/>.</dd> <dt>Symmetric route</dt> <dd>The upstream and downstream routes traverse the same routers and over the samelinks. </t> <!-- CEP: pagination :-( --> <t hangText="TargNode"><vspace /> Thelinks.</dd> <dt>TargNode</dt> <dd>The IPv6 router(Target Node)(target node) for which OrigNode requires a route and initiatesRoute Discoveryroute discovery within the LLN.</t> <t hangText="Upward Direction"><vspace /> The</dd> <dt>Upward direction</dt> <dd>The direction from the TargNode to theOrigNode.</t> <t hangText="Upward Route"><vspace /> AOrigNode.</dd> <dt>Upward route</dt> <dd>A route in the upwarddirection. </t> </list></t>direction.</dd> </dl> </section><!-- End<section> <name>Overview ofsection "Terminology" --> <section title="Overview of AODV-RPL">AODV-RPL</name> <t> With AODV-RPL, routes from OrigNode to TargNode within the LLN do not become established until they are needed. The route discovery mechanism in AODV-RPL is invoked when OrigNode has data for delivery to a TargNode, but existing routes do not satisfy the application's requirements. For thisreasonreason, AODV-RPL is considered to be an example of an "on-demand" routingprotocols.protocol. Such protocols are also known as "reactive" routing protocols since their operations are 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 protocol. </t> <t> The routes discovered by AODV-RPL are not constrained to traverse a common ancestor. AODV-RPL can enable asymmetric communication paths in networks with bidirectional asymmetric links. For this purpose, AODV-RPL enables discovery of two routes: namely, one from OrigNode toTargNode,TargNode and another from TargNode to OrigNode. AODV-RPL also enables discovery of symmetric routes alongPairedpaired DODAGs, when symmetric routes are possible (see <xref target="channel"/>). </t> <t> In AODV-RPL, routes are discovered by first forming a temporaryDAGDirected Acyclic Graph (DAG) rooted at the OrigNode. Paired DODAGs (Instances) are constructed during route formation between the OrigNode and TargNode. The RREQ-Instance is formed by route control messages from OrigNode toTargNodeTargNode, whereas the RREP-Instance is formed by route control messages from TargNode to OrigNode. The route discovered in the RREQ-Instance is used for transmitting data from TargNode to OrigNode, and the route discovered in RREP-Instance is used for transmitting data from OrigNode to TargNode. </t> <t> Intermediate routers join the DODAGs based on the Rank <xref target="RFC6550"/> as calculated from the DIO messages. AODV-RPL uses the same notion ofrankRank as defined inRFC6550: "The<xref target="RFC6550"/>:</t> <blockquote>The Rank is the expression of a relative position within a DODAG Version with regard to neighbors, and it is not necessarily a good indication or a proper expression of a distance or a path cost to theroot." Theroot.</blockquote> <t>The Rank measurements provided in AODV messages do not indicate a distance or a path cost to the root. </t> <t> Henceforth in this document, "RREQ-DIO message" means the DIO message from OrigNode toward TargNode, containing the RREQ option as specified in <xref target="RREQmsg"/>. The RREQ-InstanceID is formed as the ordered pair (Orig_RPLInstanceID, OrigNode-IPaddr), where Orig_RPLInstanceID is the local RPLInstanceID allocated byOrigNode,OrigNode 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 whenever that node receives a data packet with Source Address == OrigNode-IPaddr and IPv6 RPL Option having the RPLInstanceID == Orig_RPLInstanceID. The'D'D bit of the RPLInstanceID field is set to 0 to indicate that the source address of the IPv6 packet is the DODAGID. </t> <t> Similarly, "RREP-DIO message" means the DIO message from TargNode toward OrigNode, containing the RREP option as specified in <xref target="RREPmsg"/>. The RREP-InstanceID is formed as the ordered pair (Targ_RPLInstanceID, TargNode-IPaddr), where Targ_RPLInstanceID is the local RPLInstanceID allocated byTargNode,TargNode and TargNode-IPaddr is the IP address of TargNode. A node receiving the RREP-DIO can use the RREP-InstanceID to identify the proper OF whenever that node receives a data packet with Source Address == TargNode-IPaddr and IPv6 RPL Option having the RPLInstanceID == Targ_RPLInstanceID along with'D'D == 0 as above. </t> </section><!-- End of section "Overview of AODV-RPL" --><sectionanchor="Options" title="AODV-RPLanchor="Options"> <name>AODV-RPL DIOOptions">Options</name> <sectionanchor="RREQmsg" title="AODV-RPLanchor="RREQmsg"> <name>AODV-RPL RREQOption">Option</name> <t> OrigNode selects one of its IPv6 addresses and sets it in the DODAGID<!-- CEP: SHOULD changed to MUST by request of Alvaro Retana. -->field of the RREQ-DIO message. The address scope of the selected<!-- Gunter Van de Velde 2/11/2025, 8:36 PM -->addressMUST<bcp14>MUST</bcp14> encompass the domain where the route is built (e.g, not link-local);otherwiseotherwise, the route discovery will fail. Exactly one RREQ optionMUST<bcp14>MUST</bcp14> be present inaan RREQ-DIOmessage, otherwisemessage; otherwise, the messageMUST<bcp14>MUST</bcp14> be dropped. </t> <figureanchor="figRREQ" title="Formatanchor="figRREQ"> <name>Format for AODV-RPL RREQOption">Option</name> <artwork align="center"><![CDATA[ 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length |S|H|X| Compr | L | RankLimit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Orig SeqNo | | +-+-+-+-+-+-+-+-+ | | | | Address Vector (Optional, Variable Length) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . .. ]]></artwork>.]]></artwork> </figure>OrigNode<t>OrigNode supplies the following information in the RREQ option: </t><t><list style="hanging"> <t hangText="Option Type"><vspace /> 8-bit<dl newline="true" spacing="normal"> <dt>Option Type</dt> <dd>8-bit unsigned integer specifying the type of the option(TBD2)</t> <t hangText="Option Length"><vspace /> 8-bit(0x0B).</dd> <dt>Option Length</dt> <dd>8-bit unsigned integer specifying the length of the option in octets, excluding the Option Type and Option Length fields.VariableIt is variable due to the presence of theaddress vectorAddress Vector and the number of octets elided according to the Comprvalue.</t> <t hangText="S"><vspace /> Symmetricvalue.</dd> <dt>S</dt> <dd>Symmetric bit indicating a symmetric route from the OrigNode to the router transmitting this RREQ-DIO. See <xreftarget="channel"/>.</t> <t hangText="H"><vspace /> Settarget="channel"/>.</dd> <dt>H</dt> <dd>Set to one for a hop-by-hop route. Set to zero for a source route. This flag controls both the downstream route and upstreamroute. </t> <t hangText="X"><vspace /> Reserved; MUSTroute.</dd> <dt>X</dt> <dd>Reserved. This field <bcp14>MUST</bcp14> be initialized to zero and ignored uponreception.</t> <t hangText="Compr"><vspace /> 4-bitreception.</dd> <dt>Compr</dt> <dd>4-bit unsigned integer. When Compr is nonzero, exactly that number of prefix octetsMUST<bcp14>MUST</bcp14> be elided from each address before storing it in the Address Vector. The octets elided are shared 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 fieldMUST<bcp14>MUST</bcp14> be set to zero and ignored uponreception.</t>reception.</dd> <!-- CEP: Shouldn't we allow address compression for the Target Option? --><t hangText="L"><vspace /> <?rfc subcompact="yes" ?> 2-bit<dt>L</dt> <dd> <t>2-bit unsigned integer determining the time duration that a node is able to belong to the RREQ-Instance (a temporary DAG including the OrigNode and the TargNode). Once the time is reached, a nodeSHOULD<bcp14>SHOULD</bcp14> leave the RREQ-Instance and stop sending or receiving any more DIOs for the RREQ-Instance;otherwiseotherwise, memory and network resources are likely to be consumed unnecessarily. This naturally depends on the node's ability to keep track of time. Once a node leaves an RREQ-Instance, itMUST NOT<bcp14>MUST NOT</bcp14> rejoin the same RREQ-Instance for at least the time interval specified by the configuration variable REJOIN_REENABLE.<list style="symbols"> <t>0x00: No time limit imposed. </t> <t>0x01: 16 seconds </t> <t>0x02: 64 seconds </t> <t>0x03: 256 seconds </t> </list> <?rfc subcompact="no" ?>L is independent from the route lifetime, which is defined in the DODAG configuration option. </t> <ul spacing="compact"> <li> <t>0x00: No time limit imposed</t> </li> <li> <t>0x01: 16 seconds</t> </li> <li> <t>0x02: 64 seconds</t> </li> <li> <t>0x03: 256 seconds</t> </li> </ul> <t> <!-- The route entries in hop-by-hop routing and states of source routing can still be maintained even after the node no longer maintains DAG connectivity or messaging. --> <!-- according to email to the list, 12/27/2020 --> </t><t hangText="RankLimit"><vspace /> 8-bit</dd> <dt>RankLimit</dt> <dd>8-bit unsigned integer specifying the upper limit on the integer portion of the Rank (calculated using the DAGRank() macro defined in <xref target="RFC6550"/>). A value of 0 in this field indicates the limit isinfinity. </t> <t hangText="Orig SeqNo"><vspace /> 8-bitinfinity.</dd> <dt>Orig SeqNo</dt> <dd>8-bit unsigned integer specifying thesequenceSequence Number of OrigNode. See <xreftarget="rreq"/>. </t> <t hangText="Address Vector"><vspace /> Atarget="rreq"/>.</dd> <dt>Address Vector</dt> <dd>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. The prefix of each address is elided according to the Comprfield.</t> </list> </t> <t> TargNodefield.</dd> </dl> <t>TargNode can join theRREQ instanceRREQ-Instance at a Rank whose integer portion is less than or equal to the RankLimit. Any other nodeMUST NOT<bcp14>MUST NOT</bcp14> joina RREQ instancean RREQ-Instance if its own Rank would be equal to or higher than the RankLimit. A routerMUST<bcp14>MUST</bcp14> discard a received RREQ if the integer part of the advertised Rank equals or exceeds theRankLimit. </t> <t> </t>RankLimit.</t> </section><!-- End of section "RREQ Message" --><sectionanchor="RREPmsg" title="AODV-RPLanchor="RREPmsg"> <name>AODV-RPL RREPOption">Option</name> <t> TargNode sets one of its IPv6 addresses in the DODAGID <!-- CEP: SHOULD changed to MUST, by request of Alvaro Retana. --> field of the RREP-DIO message. The address scope of the selected address must encompass the domain where the route is built (e.g, not link-local). Exactly one RREP optionMUST<bcp14>MUST</bcp14> be present inaan RREP-DIO message,otherwiseotherwise, the messageMUST<bcp14>MUST</bcp14> be dropped. TargNode supplies the following information in the RREP option: </t> <figureanchor="figRREP" title="Formatanchor="figRREP"> <name>Format for AODV-RPL RREPoption">Option</name> <artwork align="center"><![CDATA[ 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length |G|H|X| Compr | L | RankLimit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Delta |X X| | +-+-+-+-+-+-+-+-+ | | | | | | Address Vector (Optional, Variable Length) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . .. ]]></artwork>.]]></artwork> </figure><list style="hanging"> <t hangText="Option Type"><vspace /> 8-bit<dl newline="true" spacing="normal"> <dt>Option Type</dt> <dd>8-bit unsigned integer specifying the type of the option(TBD3)</t> <t hangText="Option Length"><vspace /> 8-bit(0x0C).</dd> <dt>Option Length</dt> <dd>8-bit unsigned integer specifying the length of the option in octets, excluding the Option Type and Option Length fields.VariableIt is variable due to the presence of theaddress vectorAddress Vector and the number of octets elided according to the Comprvalue.</t> <t hangText="G"><vspace /> Gratuitousvalue.</dd> <dt>G</dt> <dd>Gratuitous RREP (see <xreftarget="G-RREP"/>).</t> <t hangText="H"><vspace /> Thetarget="G-RREP"/>).</dd> <dt>H</dt> <dd>The H bit in the RREP optionMUST<bcp14>MUST</bcp14> be set to be the same as the H bit in the RREQ option. It requests either source routing (H=0) or hop-by-hop (H=1) for the downstreamroute.</t> <t hangText="X"><vspace /> 1-bitroute.</dd> <dt>X</dt> <dd>1-bit Reservedfield; MUSTfield. This field <bcp14>MUST</bcp14> be initialized to zero and ignored uponreception.</t> <t hangText="Compr"><vspace /> 4-bitreception.</dd> <dt>Compr</dt> <dd>4-bit unsigned integer.SameThis field has the same definition as in the RREQoption. </t> <t hangText="L"><vspace /> 2-bitoption.</dd> <dt>L</dt> <dd>2-bit unsigned integer defined as in the RREQ option. The lifetime of the RREP-InstanceSHOULD<bcp14>SHOULD</bcp14> be no greater than the lifetime of the RREQ-Instance to which it is paired, so that the memory required to store the RREP-Instance can be reclaimed when no longerneeded.</t> <t hangText="RankLimit"><vspace /> 8-bitneeded.</dd> <dt>RankLimit</dt> <dd>8-bit unsigned integer specifying the upper limit on the integer portion of the Rank, similarly to RankLimit in the RREQ message. A value of 0 in this field indicates the limit isinfinity. </t>infinity.</dd> <!-- CEP: is 7 bits O.K. for RankLimit? --><t hangText="Delta"><vspace /> 6-bit<dt>Delta</dt> <dd>6-bit unsigned integer. TargNode uses the Delta field so that nodes receiving its RREP message can identify the RREQ-InstanceID of the RREQ message that triggered the transmission of the RREP (see <xreftarget="instancepairing"/>). </t> <t hangText="X X"><vspace /> 2-bittarget="instancepairing"/>).</dd> <dt>X X</dt> <dd>2-bit Reservedfield; MUSTfield. This field <bcp14>MUST</bcp14> be initialized to zero and ignored uponreception.</t> <t hangText="Address Vector"><vspace />reception.</dd> <dt>Address Vector</dt> <dd> 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 route, the Address Vector represents the IPv6 addresses of the path through the network the RREP-DIO has passed. In contrast, for a symmetric route, it is the Address Vector when the RREQ-DIO arrives at the TargNode, unchanged during the transmission to the OrigNode.</t> </list> </t></dd> </dl> <!-- /* Make the following into an XML comment */ [A] It is technically feasible to have partially active DODAG pair. Having this condition lets graceful shutdown of the current route discovery instance initiated by OrigNode. It marks the end of DODAG pairing as RREQ and RREP Instances can be treated as belonging to the same route discovery. The resources held by the intermediate nodes is released, and OrigNode can start reusing the same RPLInstanceID in the RREQ for its new route discovery. Having RREQ-Instance lifetime thus enables this. --> </section><!-- End of section "AODV-RPL RREP Option" --><sectionanchor="artop" title="AODV-RPLanchor="artop"> <name>AODV-RPL TargetOption">Option</name> <t> The AODV-RPL Target (ART)Optionoption is based on the TargetOptionoption in the core RPL specification <xref target="RFC6550"/>. The Flags field is replaced by the Destination Sequence Number of theTargNodeTargNode, and the Prefix Length field is reduced to 7 bits so that the value is limited to be no greater than 127. </t> <t> A RREQ-DIO messageMUST<bcp14>MUST</bcp14> carry at least one ARTOption.option. A RREP-DIO messageMUST<bcp14>MUST</bcp14> carry exactly one ARTOption.option. Otherwise, the messageMUST<bcp14>MUST</bcp14> be dropped. <!-- CEP: Is it needed for RREPs with symmetric routes? --> </t> <t> OrigNode can include multiple TargNode addresses via multipleAODV-RPL Target OptionsART options in the RREQ-DIO, for routes that share the same requirement on metrics. This reduces the cost to building only one DODAG for multiple targets. </t><t><figureanchor="figTarg" title="ARTanchor="figTarg"> <name>ART OptionformatFormat forAODV-RPL">AODV-RPL</name> <artwork align="center"><![CDATA[ 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Length | Dest SeqNo |X|Prefix Length| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + | | Target Prefix / Address (Variable Length) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . .. ]]></artwork>.]]></artwork> </figure><list style="hanging"> <t hangText="Option Type"> <vspace /> 8-bit<dl newline="true" spacing="normal"> <dt>Option Type</dt> <dd>8-bit unsigned integer specifying the type of the option(TBD4) </t> <t hangText="Option Length"> <vspace /> 8-bit(0x0D).</dd> <dt>Option Length</dt> <dd>8-bit unsigned integer specifying the length of the option inoctetsoctets, excluding the Option Type and Option Lengthfields. </t> <t hangText="Dest SeqNo"> <vspace /></t> <t> 8-bitfields.</dd> <dt>Dest SeqNo</dt> <dd>8-bit unsigned integer. In RREQ-DIO, if nonzero, it is the Sequence Number for the last route that OrigNode stored to the TargNode for which a route is desired. In RREP-DIO, it is thedestination sequence numberDestination Sequence Number associated to the route. Zero is used if there is no known information about thesequence numberSequence Number ofTargNode,TargNode and not usedotherwise. </t> <t hangText="X"> <vspace /> A one-bit reservedotherwise.</dd> <dt>X</dt> <dd>1-bit Reserved field. This fieldMUST<bcp14>MUST</bcp14> be initialized to zero by the sender andMUST<bcp14>MUST</bcp14> be ignored by thereceiver. </t> <t hangText="Prefix Length"> <vspace /> 7-bitreceiver.</dd> <dt>Prefix Length</dt> <dd>7-bit unsigned integer. The Prefix Length field contains the number of valid leading bits in the prefix. If Prefix Length is 0, then the value in the Target Prefix / Address field represents an IPv6 address, not aprefix. </t> <t hangText="Targetprefix.</dd> <dt>Target Prefix /Address"> <vspace /> (variable-length field) AnAddress</dt> <dd>A variable-length field with an IPv6 destination address or prefix. The length of the Target Prefix / Address field is the least number of octets that can represent all of the bits of the Prefix, in otherwordswords, Ceil(Prefix Length/8) octets. When Prefix Length is not equal to 8*Ceil(Prefix Length/8) and nonzero, the Target Prefix / Address field will contain some initial bits that are not part of the Target Prefix. Those initial bits (if any)MUST<bcp14>MUST</bcp14> be set to zero on transmission andMUST<bcp14>MUST</bcp14> be ignored on receipt. If Prefix Length is zero, the Address field is 128 bits.</t> </list> </t></dd> </dl> </section><!-- End of section "AODV-RPL Target Option" --></section><!-- End of section "AODV-RPL Options" --><sectionanchor="channel" title="Symmetricanchor="channel"> <name>Symmetric and AsymmetricRoutes">Routes</name> <t> Links are considered symmetric until indication to the contrary is received. In Figures <xreftarget="figSymm-a"/>target="figSymm-a" format="counter"/> and <xreftarget="figSymm-b"/>,target="figSymm-b" format="counter"/>, BR is the Border Router, O is the OrigNode, each R is an intermediate router, and T is the TargNode. Inthis example,these examples, the use of BR is only for illustrative purposes; AODV does not depend on the use of border routers for its operation. If the RREQ-DIO arrives over an interface that is known to besymmetric,symmetric and the S bit is set to 1, then it remains as 1, as illustrated in <xref target="figSymm-a"/>. If an intermediate router sends out RREQ-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 discovery, and the route can be used symmetrically. </t><t><figure anchor="figSymm-a" title="AODV-RPL<figure anchor="figSymm-a"> <name>AODV-RPL with SymmetricInstances">Instances</name> <artwork align="center"><![CDATA[ BR /----+----\ / | \ / | \ R R R _/ \ | / \ / \ | / \ / \ | / \ R -------- R --- R ----- R -------- R / \ <--S=1--> / \ <--S=1--> / \ <--S=1--> \ / \ / <--S=1--> / \ / \ / \ O ---------- R ------ R------ R ----- R ----------- T / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ R ----- R ----------- R ----- R ----- R ----- R ---- R----- R >---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> <---- RREP-Instance (Control: T-->O; Data: O-->T) -------< ]]></artwork></figure></t></figure> <t> Upon receivingaan RREQ-DIO with the S bit set to 1, a node determines whether the link over which it was received can be used symmetrically, i.e., both directions meet the requirements of data transmission. If the RREQ-DIO arrives over an interface that is not known to besymmetric,symmetric or is known to be asymmetric, the S bit is set to 0. If the S bit arrives already set to be'0',0, then it is set to be'0'0 when the RREQ-DIO is propagated (<xref target="figSymm-b"/>). For an asymmetric route, there is at least one hopwhichthat doesn't satisfy theObjective Function.OF. Based on the S bit received in RREQ-DIO, TargNode T determines whether or not the route is symmetric before transmitting the RREP-DIO message upstream towards the OrigNode O. </t> <t> It is beyond the scope of this document to specify the criteria used when determining whether or not each link is symmetric. As an example, intermediate routers can use local information (e.g., bit rate, bandwidth, number of cells used in6tisch6TiSCH <xref target="RFC9030"/>), a priori knowledge (e.g., link quality according to previouscommunication)communication), oruseaveraging techniques as appropriate to the application. Other link metric information can be acquired before AODV-RPL operation, by executing evaluation procedures; forinstanceinstance, test traffic can be generated between nodes of the deployed network. During AODV-RPL operation,OAMOperations, Administration, and Maintenance (OAM) techniques for evaluating link state (see <xref target="RFC7548"/>, <xref target="RFC7276"/>, and <xref target="co-ioam"/>)MAY<bcp14>MAY</bcp14> be used (at regular intervals appropriate for the LLN). The evaluation procedures are out of scope for AODV-RPL. For further information on this topic, see <xref target="Link_Asymmetry"/>, <xref target="low-power-wireless"/>, and <xref target="empirical-study"/>. </t> <t> <xref target="appendix-a"/> describes an example method using the upstream ExpectedNumber of TransmissionsTransmission Count (ETX) and downstream Received Signal Strength Indicator (RSSI) to estimate whether the link is symmetric in terms of link quality using an averaging technique. </t> <figureanchor="figSymm-b" title="AODV-RPLanchor="figSymm-b"> <name>AODV-RPL with Asymmetric PairedInstances">Instances</name> <artwork align="center"><![CDATA[ BR /----+----\ / | \ / | \ R R R / \ | / \ / \ | / \ / \ | / \ R --------- R --- R ---- R --------- R / \ --S=1--> / \ --S=0--> / \ --S=1--> \ / \ / --S=0--> / \ / \ / \ O ---------- R ------ R------ R ----- R ----------- T / \ / \ / \ / \ / <--S=0-- / \ / \ / <--S=0-- / \ / \ / \ / \ R ----- R ----------- R ----- R ----- R ----- R ---- R----- R <--S=0-- <--S=0-- <--S=0-- <--S=0-- <--S=0-- >---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> <---- RREP-Instance (Control: T-->O; Data: O-->T) -------<]]></artwork> </figure> <t> As illustrated in <xref target="figSymm-b"/>, an intermediate router determines the S bit value that the RREQ-DIO should carry using link asymmetry detection methods as discussed earlier in this section. In manycasescases, the intermediate router has already made the link asymmetry decision by the time RREQ-DIO arrives. </t> <t> See <xref target="Examples"/> for examples illustrating RREQ and RREP transmissions in some networks with symmetric and asymmetric links. </t> </section><!-- End of section "Symmetric and Asymmetric Routes" --> <section anchor="aodvrplop" title="AODV-RPL Operation"><sectionanchor="rreq" title="Route Request Generation">anchor="aodvrplop"> <name>AODV-RPL Operation</name> <section anchor="rreq"> <name>Generating RREQ</name> <t> The route discovery process is initiated when an application at the OrigNode has data to be transmitted to theTargNode,TargNode but does not have a route that satisfies theObjective FunctionOF for the target of the application's data. In this case, the OrigNode builds a localRPLInstanceRPL Instance and a DODAG rooted at itself.ThenThen, it transmits a DIO message containing exactly one RREQ option (see <xref target="RREQmsg"/>) to multicast group all-AODV-RPL-nodes. The RREQ-DIOMUST<bcp14>MUST</bcp14> contain at least one ARTOptionoption (see <xref target="artop"/>), which indicates the TargNode. <!-- CEP: or network prefix containing the TargNode. --> The S bit in RREQ-DIO sent out by the OrigNode is set to 1. </t> <t> Each node maintains asequence number;Sequence Number; the operation is specified insection 7.2 of<xreftarget="RFC6550"/>.target="RFC6550" sectionFormat="of" section="7.2"/>. When the OrigNode initiates a route discovery process, itMUST<bcp14>MUST</bcp14> increase its ownsequence numberSequence Number to avoid conflicts with previously established routes. Thesequence numberSequence Number is carried in the Orig SeqNo field of the RREQ option. </t> <t> The Target Prefix / Address in the ARTOptionoption can be a unicast IPv6 address or a prefix. The OrigNode can initiate the route discovery process for multiple targets simultaneously by including multiple ARTOptions.options. Withina RREQ-DIOan RREQ-DIO, theObjective FunctionOF for the routes to different TargNodesMUST<bcp14>MUST</bcp14> be the same. </t> <t> OrigNode can maintain differentRPLInstancesRPL Instances to discover routes with different requirements to the same targets. Using the RPLInstanceID pairing mechanism (see <xref target="instancepairing"/>), route replies (RREP-DIOs) for differentRPLInstancesRPL Instances can be generated. </t> <t> The transmission of RREQ-DIO obeys the Trickle timer <xref target="RFC6206"/>. If the duration specified by the L field has elapsed, the OrigNodeMUST<bcp14>MUST</bcp14> leave the DODAG and stop sending RREQ-DIOs in the relatedRPLInstance.RPL Instance. OrigNode needs to set the L field such that the DODAG will not prematurely timeout during data transfer with the TargNode. For setting this value, it has to consider factors such as the Trickle timer, TargNode hop distance, network size, link behavior, expected data usage time, and so on. </t> </section> <!-- CEP: The Trickle timer eliminates the need for RREQ_WAIT_TIME? --> <sectionanchor="process_rreq" title="Receivinganchor="process_rreq"> <name>Receiving and Forwarding RREQmessages">Messages</name> <sectionanchor="rreq_step1" title="Stepanchor="rreq_step1"> <name>Step 1: RREQreceptionReception andevaluation">Evaluation</name> <!-- CEP: descriptive text, might decide to include it somewhere. An intermediate router X receives a RREQ message a neighbor Y. If X can use the incoming link to transmit a packet to OrigNode by way of Y, X will propagate the RREQ message in hopes of eventually providing Targnode with a route towards OrigNode. In that case, X could use Y as the first hop of its own route towards OrigNode, but very likely X does not otherwise need a route to OrigNode. X determines whether it can use the incoming link to transmit a packet to OrigNode by determining whether or not the upstream direction of the incoming link satisfies the OF. When TargNode receives a RREQ, and the upstream direction of the incoming link satisfies the OF, TargNode has a route to OrigNode via the neighbor Y that transmitted the RREQ. If in addition the S bit is set in the OrigNode, and if the downstream direction of the incoming link is suitable for TargNode to receive packets from that neighbor Y, then the entire path traversed by the RREQ is symmetric and OrigNode can use that path to send packets to TargNode. In order to provide that routing information (about a viable path to TargNode) to OrigNode, TargNode unicasts a RREP back to Y. --><t> When<t>When a router X receivesaan RREQ message over a link from a neighbor Y, X first determines whether or not the RREQ is valid. Ifso,valid, X then determines whether or not it has sufficient resources available to maintain the RREQ-Instance and the value of the'S'S bit needed to process an eventual RREP, if the RREP were to be received. Ifnot,not valid, then XMUST<bcp14>MUST</bcp14> either free up sufficient resources (the means for this are beyond the scope of this document), or drop the packet and discontinue processing of the RREQ. Otherwise, X next determines whether the RREQ advertises a usable route to OrigNode, by checking whether the link to Y can be used to transmit packets to OrigNode. </t> <t> When H=0 in the incoming RREQ, the routerMUST<bcp14>MUST</bcp14> drop the RREQ-DIO if one of its addresses is present in the Address Vector. When H=1 in the incoming RREQ, the routerMUST<bcp14>MUST</bcp14> drop the RREQ message if the Orig SeqNo field of the RREQ is older than the SeqNo value that X has stored for a route to OrigNode. Otherwise, the router determines whether to propagate the RREQ-DIO. It does this by determining whether or not a route to OrigNode using the upstream direction of the incoming link satisfies the Objective Function (OF). In order to evaluate the OF, the router first determines the maximum usefulrankRank (MaxUsefulRank). If the router has previously joined the RREQ-Instance associated with the RREQ-DIO, then MaxUsefulRank is set to be the Rank value that was stored when the router processed the best previous RREQ for the DODAG with the given RREQ-Instance. Otherwise, MaxUsefulRank is set to be RankLimit. If OF cannot be satisfied (i.e., the Rank evaluates to a value greater thanMaxUsefulRank)MaxUsefulRank), the RREQ-DIOMUST<bcp14>MUST</bcp14> be dropped, and the following steps are not processed. Otherwise, the routerMUST<bcp14>MUST</bcp14> join the RREQ-Instance and prepare to propagate the RREQ-DIO, as follows. The upstream neighbor router that transmitted the received RREQ-DIO is selected as the preferred parent in the RREQ-Instance. </t></section><!--End of section "Step 1: RREQ reception and evaluation"--></section> <sectionanchor="rreq_step2" title="Stepanchor="rreq_step2"> <name>Step 2: TargNode and Intermediate Routerdetermination">Determination</name> <t> <!-- Kaduk comment 16 --> After determining that a received RREQ provides a usable route to OrigNode, a router determines whether it is a TargNode,ora possible intermediate router between OrigNode and a TargNode, or both. The router is a TargNode if it finds one of its own addresses in a TargetOptionoption in the RREQ. After possibly propagating the RREQ according to the procedures in Steps 3, 4, and 5, the TargNode generatesaan RREP as specified in <xref target="gen-rrep"/>. If S=0, the determination of TargNode status and determination of a usable route to OrigNode is the same. </t> <t> If the OrigNode tries to reach multiple TargNodes in a single RREQ-Instance, one of the TargNodes can be an intermediate router to other TargNodes. In this case, before transmitting the RREQ-DIO to multicast group all-AODV-RPL-nodes, a TargNodeMUST<bcp14>MUST</bcp14> delete the TargetOptionoption encapsulating its own address, so that downstream routers with higher Rank values do not try to create a route to this TargNode. </t> <t> An intermediate router could receive several RREQ-DIOs from routers with lower Rank values in the same RREQ-Instance with different lists of TargetOptions.options. For the purposes of determining the intersection with previous incoming RREQ-DIOs, the intermediate router maintains a record of the targets that have been requested for a given RREQ-Instance. An incoming RREQ-DIO message having multiple ARTOptionsoptions coming from a router with higher Rank than the Rank of the stored targets is ignored. When transmitting the RREQ-DIO, the intersection of all received listsMUST<bcp14>MUST</bcp14> be included if it is nonempty after TargNode has deleted the TargetOptionoption encapsulating its own address. If the intersection is empty, it means that all the targets have been reached, and the routerMUST NOT<bcp14>MUST NOT</bcp14> transmit any RREQ-DIO.OtherwiseOtherwise, it proceeds to <xref target="rreq_step3"/>. </t> <t> For example, suppose two RREQ-DIOs are received with the sameRPLInstanceRPL Instance and OrigNode. Suppose further that the first RREQ has (T1, T2) as the targets, and the second one has (T2, T4) as targets.ThenThen, only T2 needs to be included in the generated RREQ-DIO. </t> <t> 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 SeqNo, they were transmitted by OrigNode with the same destinations and OF. When an intermediate node receives two RREQs with the same Orig SeqNo but different lists of destinations, that means that some intermediate nodes retransmitting the RREQs have already deleted themselves from the list of destinations before they retransmitted the RREQ. Those deleted nodes are not to bere-insertedreinserted back into the list of destinations. </t></section><!--End of section "Step 2: TargNode and Intermediate Router determination"--></section> <sectionanchor="rreq_step3" title="Stepanchor="rreq_step3"> <name>Step 3: Intermediate Router RREQprocessing">Processing</name> <t> 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-by-hop route, then the routerMUST<bcp14>MUST</bcp14> build or update its upward route entry towards OrigNode, which includes at least the following items: Source Address, RPLInstanceID, Destination Address, Next Hop, Lifetime, and Sequence Number. <!-- CEP TODO: What is the Destination Address, if not OrigNode? --> The Destination Address and the RPLInstanceIDrespectivelycan be learned from the DODAGID and the RPLInstanceID of theRREQ-DIO.RREQ-DIO, respectively. The Source Address is the address 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 the L field) and can be extended when the route is actually used. The Sequence Number represents the freshness of the route entry; it is copied from the Orig SeqNo field of the RREQ option. A route entry with the same source and destinationaddress,address and the same RPLInstanceID, but a stale Sequence Number (i.e., incomingsequence numberSequence Number is less than the currently stored Sequence Number of the route entry),MUST<bcp14>MUST</bcp14> be deleted. <!-- CEP TODO: Need to specify that the information from the existing RREQ updates the route entry? What happens if the existing route entry has a newer SeqNo than the RREQ? Proposal: intermediate router updates the RREQ with its newer SeqNo. --> </t> </section><!--End of section "Step 3: Intermediate Router RREQ processing"--><sectionanchor="rreq_step4" title="Stepanchor="rreq_step4"> <name>Step 4: Symmetric Route Processing at an IntermediateRouter">Router</name> <t> 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 0. Otherwise, the routerMUST<bcp14>MUST</bcp14> determine whether the downward direction (i.e., towards the TargNode)directionof the incoming link satisfies the OF. Ifso,it does, the S bit of the RREQ-DIO to be transmitted is set to 1.OtherwiseOtherwise, the S bit of the RREQ-DIO to be transmitted is set to 0. </t> <t> When a router joins the RREQ-Instance, it also associates within its data structure for the RREQ-Instance the information about whether or not the RREQ-DIO to be transmitted has theS-bitS bit set to 1. This information associated to RREQ-Instance is known as theS-bitS bit of the RREQ-Instance. It will be used later during the RREP-DIO message processing (see <xreftarget="asymmetricrrep"/>.target="asymmetricrrep"/>). <!-- for RPLInstance pairing as described in <xref target="forwardRREP"/>. CEP TODO: check language about pairing. --> </t><t> Suppose<t>Suppose a router has joined the RREQ-Instance,and H=0,the H bit is set to 0, and theS-bitS bit of the RREQ-Instance is set to 1. In this case, the routerMAY<bcp14>MAY</bcp14> optionally include the Address Vector of the symmetric route back to 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-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 substantial performance penalty. </t></section><!-- End of section "Step 4: Symmetric Route Processing at an Intermediate Router" --></section> <sectionanchor="rreq_step5" title="Stepanchor="rreq_step5"> <name>Step 5: RREQpropagationPropagation at an IntermediateRouter">Router</name> <t> 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 0, the intermediate routerMUST<bcp14>MUST</bcp14> append the address of its interface receiving the RREQ-DIO into theaddress vector. If, inAddress Vector. In addition, if the 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 routerMUST<bcp14>MUST</bcp14> also append the transmitting interface address into theaddress vector.Address Vector. </t></section><!-- End of section "Step 5: RREQ propagation at an Intermediate Router" --></section> <sectionanchor="rreq_step6" title="Stepanchor="rreq_step6"> <name>Step 6: RREQreceptionReception atTargNode">TargNode</name> <t> 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. If TargNode is not already associated with the RREQ-Instance, it prepares and transmitsaan RREP-DIO, possibly after waiting for RREP_WAIT_TIME, as detailed in (<xref target="gen-rrep"/>). </t></section><!--End of section "Step 6: RREQ reception at TargNode"--> </section><!--End of section "Receiving and Forwarding Route Request"--></section> </section> <sectionanchor="gen-rrep" title="Generating Route Reply (RREP)anchor="gen-rrep"> <name>Generating RREP atTargNode">TargNode</name> <t> When a TargNode receivesaan RREQ message over a link from a neighbor Y, TargNode first follows the procedures in <xref target="process_rreq"/>. If the link to Y can be used to transmit packets to OrigNode, TargNode generatesaan RREP according tothe steps below. OtherwiseSections <xref format="counter" target="rrepsymmetric"/> and <xref target="asymmetricrrep" format="counter"/>. Otherwise, TargNode drops the RREQ and does not generateaan RREP. </t> <t> If the L field is not 0, the TargNodeMAY<bcp14>MAY</bcp14> delay transmitting the RREP-DIO for the duration RREP_WAIT_TIME to await a route with a lower Rank. The value of RREP_WAIT_TIME is set by default to 1/4 of the duration determined by the L field. For L == 0, RREP_WAIT_TIME is set by default to 0. Depending upon the application, RREP_WAIT_TIME may be set to other values. Smaller values enable quicker formation for the P2P route. Larger values enable formation of P2P routes with better Rank values. </t> <t> The address of the OrigNodeMUST<bcp14>MUST</bcp14> be encapsulated in the ARTOptionoption and included in this RREP-DIO message along with the SeqNo of TargNode. </t> <sectionanchor="rrepsymmetric" title="RREP-DIOanchor="rrepsymmetric"> <name>RREP-DIO for Symmetricroute">Route</name> <t> If the RREQ-Instance corresponding to the RREQ-DIO that arrived at TargNode has the S bit set to 1, there is a symmetricrouteroute, both of whose directions satisfy theObjective Function.OF. Other RREQ-DIOs might later provide better upward routes. The method of selection between a qualified symmetric route and an asymmetric route that might have better performance isimplementation-specificimplementation specific and out of scope. <!-- CEP: Our comment to John Scudder: If L is zero, RREP_WAIT_TIME should be set to the lifetime of the DODAG. The text above effectively has: If L is zero, RREP_WAIT_TIME should be set to zero. It seems to me that it is better if the node doesn't wait. --> </t> <!-- CEP: The RREP ART has OrigNode address but the SeqNo of TargNode. The SeqNo of OrigNode is not present! --> <t> For a symmetric route, the RREP-DIO message is unicast to thenext hopNext 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 RPLInstanceID in the RREP-Instance is paired as defined in <xref target="instancepairing"/>.In caseIf the H bit is set to 0, theaddress vectorAddress Vector from the RREQ-DIOMUST<bcp14>MUST</bcp14> be included in the RREP-DIO. </t> </section><!-- end section title="RREP-DIO for Symmetric route" --><sectionanchor="asymmetricrrep" title="RREP-DIOanchor="asymmetricrrep"> <name>RREP-DIO for AsymmetricRoute">Route</name> <t> Whenaan RREQ-DIO arrives at a TargNode with the S bit set to 0, the TargNodeMUST<bcp14>MUST</bcp14> build a DODAG in the RREP-Instance corresponding to the RREQ-DIO rooted at itself, in order to provide OrigNode with a downstream route to the TargNode. The RREP-DIO message is transmitted to multicast group all-AODV-RPL-nodes. </t> </section> <sectionanchor="instancepairing" title="RPLInstanceID Pairing">anchor="instancepairing"> <name>RPLInstanceID Pairing</name> <t> Since the RPLInstanceID is assigned locally (i.e., there is no coordination between routers in the assignment of RPLInstanceID), the tuple (OrigNode, TargNode, RPLInstanceID) is needed to uniquely identify a discovered route. It is possible that multiple route discoveries with dissimilarObjective FunctionsOFs are initiated simultaneously.ThusThus, between the same pair of OrigNode and TargNode, there can be multiple AODV-RPL route discovery instances. So that OrigNode andTargnodeTargNode can avoid any mismatch, theyMUST<bcp14>MUST</bcp14> pair the RREQ-Instance and the RREP-Instance in the same route discovery by using the RPLInstanceID. </t> <t> When preparing the RREP-DIO, a TargNode could find the RPLInstanceID candidate for the RREP-Instance is already occupied by another RPL Instance from an earlier route discovery operationwhichthat is still active. This unlikely case might happen if two distinct OrigNodes need routes to the same TargNode, and they happen to use the same RPLInstanceID for RREQ-Instance. In such cases, the RPLInstanceID of an already active RREP-InstanceMUST NOT<bcp14>MUST NOT</bcp14> be used again for assigning RPLInstanceID for the later RREP-Instance. If the same RPLInstanceID werere-usedreused for two distinct DODAGs originated with the same DODAGID (TargNode address), intermediate routers could not distinguish between these DODAGs (and their associatedObjective Functions).OFs). Instead, the RPLInstanceIDMUST<bcp14>MUST</bcp14> be replaced by another value so that the twoRREP-instancesRREP-Instances can be distinguished. In the RREP-DIO option, the Delta field of the RREP-DIO message (<xref target="figRREP"/>) indicates the 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 RREP-DIO message. 0 indicates that the RREQ-InstanceID has the same value as the RPLInstanceID of the RREP message. <!-- How many bits is the RPLInstanceID?? --> When the new RPLInstanceID after incrementation exceeds 255, it rolls over starting at 0. For example, if the RREQ-InstanceID is252,252 and incremented by 6, the new RPLInstanceID will be 2. Related operations can be found in <xref target="forwardRREP"/>. RPLInstanceID collisions do not occur across RREQ-DIOs; the DODAGID equals the OrigNode address and is sufficient to disambiguate between DODAGs. <!-- TODO: Could say something about only 6 bits needed for Delta field. --> </t> </section><!-- end section title="RREP-DIO for Asymmetric Route" --></section><!-- End of section "Generating Route Reply at TargNode" --><sectionanchor="forwardRREP" title="Receivinganchor="forwardRREP"> <name>Receiving and ForwardingRoute Reply">RREP</name> <t> Upon receivingaan RREP-DIO, a routerwhichthat already belongs to the RREP-InstanceSHOULD<bcp14>SHOULD</bcp14> drop the RREP-DIO.OtherwiseOtherwise, the router performs the steps in the following subsections. </t> <sectionanchor="rrep_step1" title="Stepanchor="rrep_step1"> <name>Step 1: Receiving andEvaluation">Evaluation</name> <t> If theObjective FunctionOF is not satisfied, the routerMUST NOT<bcp14>MUST NOT</bcp14> join the DODAG; the routerMUST<bcp14>MUST</bcp14> discard theRREP-DIO,RREP-DIO and does not execute the remaining steps in this section. AnIntermediate Router MUSTintermediate router <bcp14>MUST</bcp14> discardaan RREP if one of its addresses is present in the AddressVector,Vector and does not execute the remaining steps in this section. </t> <t> If the S bit of the associated RREQ-Instance is set to 1, the routerMUST<bcp14>MUST</bcp14> proceed to <xref target="rrep_step2"/>. </t> <t> If theS-bitS bit of the RREQ-Instance is set to 0, the routerMUST<bcp14>MUST</bcp14> determine whether the downward direction of the link (towards the TargNode) over which the RREP-DIO is received satisfies theObjective Function,OF and whether the router's Rank would not exceed the RankLimit. Ifso,these are true, the router joins the DODAG of the RREP-Instance. The router that transmitted the received RREP-DIO is selected as the preferred parent. Afterwards, other RREP-DIO messages can be received; AODV-RPL does not specify any action to be taken in such cases. <!-- CEP: delete this as suggested by Alvaro. How to maintain the parent set, select the preferred parent, and update the router's Rank obeys the core RPL and the OFs defined in ROLL WG. --> </t></section><!--End of section "Step 1: Receiving and Evaluation"--></section> <sectionanchor="rrep_step2" title="Stepanchor="rrep_step2"> <name>Step 2: OrigNode or IntermediateRouter"> <t> TheRouter</name> <t>The router updates its stored value of the TargNode'ssequence numberSequence Number according to the value provided in the ART option. The router next checks if one of its addresses is included in the ARTOption.option. Ifso,it is included, this router is the OrigNode of the route discovery. Otherwise, it is an intermediaterouter. </t> </section><!--End of section "Step 2: OrigNode or Intermediate Router"-->router.</t> </section> <sectionanchor="rrep_step3" title="Stepanchor="rrep_step3"> <name>Step 3: Build Route toTargNode">TargNode</name> <t> If the H bit is set to 1, then the router (OrigNode or intermediate)MUST<bcp14>MUST</bcp14> build a downward route entry towards TargNodewhichthat includes at least the following items: OrigNode Address, RPLInstanceID, TargNode Address as destination, Next Hop,LifetimeLifetime, and Sequence Number. For 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 Hop is the preferred parent in the DODAG of RREP-Instance. The RPLInstanceID in the route entryMUST<bcp14>MUST</bcp14> be the RREQ-InstanceID (i.e., after subtracting the Delta field value from the value of the RPLInstanceID). The source address is learned from the ARTOption,option, and the destination address is learned from the DODAGID. The lifetime is set according to DODAG configuration (i.e., not the L field) and can be extended when the route is actually used. Thesequence numberSequence Number represents the freshness of the routeentry,entry and is copied from the Dest SeqNo field of the ART option of the RREP-DIO. A route entry with the same source and destinationaddress,address and the same RPLInstanceID, but a stalesequence number MUSTSequence Number, <bcp14>MUST</bcp14> be deleted. </t></section><!--End of section "Step 3: Build Route to TargNode"--></section> <sectionanchor="rrep_step4" title="Stepanchor="rrep_step4"> <name>Step 4: RREPPropagation">Propagation</name> <t> If the receiver is the OrigNode, it can start transmitting the application data to TargNode along the path as provided in RREP-Instance, and processing for the RREP-DIO is complete. Otherwise, the RREP will be propagated towards OrigNode. If H=0, the intermediate routerMUST<bcp14>MUST</bcp14> include the address of the interface receiving the RREP-DIO into theaddress vector.Address Vector. If H=1, according to the previousstepstep, the intermediate router has set up a route entry for TargNode. If the intermediate router has a route to OrigNode, it uses that route to unicast the RREP-DIO to OrigNode. Otherwise, in the case of a symmetric route, the RREP-DIO message is unicast to the Next Hop according to theaddress vectorAddress Vector in the RREP-DIO (H=0) or the local route entry (H=1). Otherwise, in the case of an asymmetric route, the intermediate router transmits the RREP-DIO to multicast group all-AODV-RPL-nodes. The RPLInstanceID in the transmitted RREP-DIO is the same as the value in the received RREP-DIO. </t></section><!--End of section "Step 4: RREP Propagation"--></section> <!-- CEP: Alternatively, could forward if better Rank value. Or maybe only forward for symmetric routes? --> </section><!--End of section "Receiving and Forwarding Route Reply"--></section><!-- End of section "AODV-RPL operation" --><sectionanchor="G-RREP" title="Gratuitous RREP">anchor="G-RREP"> <name>Gratuitous RREP</name> <t> In some cases, anIntermediateintermediate router that receivesaan RREQ-DIO messageMAY<bcp14>MAY</bcp14> unicast a"Gratuitous"Gratuitous RREP-DIO (G-RREP-DIO) message back to OrigNode before continuing the transmission of the RREQ-DIO towards TargNode. The Gratuitous RREP (G-RREP) allows the OrigNode to start transmitting data to TargNode sooner. The G bit of the RREP option is provided to distinguish theGratuitous RREP-DIOG-RREP-DIO (G=1) sent by theIntermediateintermediate router from the RREP-DIO sent by TargNode (G=0). </t> <t> Thegratuitous RREP-DIO MAYG-RREP-DIO <bcp14>MAY</bcp14> be sent out when theIntermediateintermediate router receivesaan RREQ-DIO for aTargNode,TargNode and the router has a pair of downward and upward routes to the TargNodewhichthat also satisfy theObjective FunctionOF and for which thedestination sequence numberDestination Sequence Number is at least as large as thesequence numberSequence Number in the RREQ-DIO message. After unicasting theGratuitous RREPG-RREP to the OrigNode, theIntermediateintermediate router then unicasts the RREQ towards TargNode, so that TargNode will have the advertised route towards OrigNode along with the RREQ-InstanceID for the RREQ-Instance. An upstream intermediate router that receives such a G-RREPMUST<bcp14>MUST</bcp14> also generate a G-RREP and send it further upstream towards OrigNode. </t> <t> In case of source routing, the intermediate routerMUST<bcp14>MUST</bcp14> include theaddress vectorAddress Vector between the OrigNode and itself in theGratuitous RREP.G-RREP. It also includes theaddress vectorAddress Vector in the unicast RREQ-DIO towards TargNode. Upon reception of the unicast RREQ-DIO, the TargNode will have a routeaddress vectorAddress Vector from itself to the OrigNode.ThenThen, the routerMUST<bcp14>MUST</bcp14> include theaddress vectorAddress Vector from the TargNode to the router itself in thegratuitous RREP-DIOG-RREP-DIO to be transmitted. </t> <t> For establishing hop-by-hop routes, the intermediate routerMUST<bcp14>MUST</bcp14> unicast the received RREQ-DIO to the Next Hop on the route. The Next Hop router along the routeMUST<bcp14>MUST</bcp14> build new route entries with the related RPLInstanceID and DODAGID in the downward direction. This process repeats at each node until the RREQ-DIO arrives at the TargNode.ThenThen, the TargNode and each router along the path towards OrigNodeMUST<bcp14>MUST</bcp14> unicast the RREP-DIO hop-by-hop towards OrigNode as specified in <xref target="gen-rrep"/>. </t> </section><!-- End of section "Gratuitous RREP" --><sectionanchor="trickle" title="Operationanchor="trickle"> <name>Operation of TrickleTimer">Timer</name> <t> <!-- Anand: No need to borrow text from RFC6997. We can reuse trickle timer and DIO transmission procedure in RFC6550. --> RREQ-Instance/RREP-Instance multicast usestrickleTrickle timer operations <xref target="RFC6206"/> to control RREQ-DIO and RREP-DIO transmissions. The Trickle control of these DIO transmissions follows the procedures described inthe Section 8.3 of<xreftarget="RFC6550"/>target="RFC6550" sectionFormat="of" section="8.3"/> entitled "DIO Transmission". If the route is symmetric, theRREP DIORREP-DIO does not need the Trickle timer mechanism. </t> </section><!-- End of section "Operation of Trickle Timer" --><sectionanchor="iana" title="IANA Considerations"> <t> Note to RFC editor: </t> <t> The sentence "The parenthesized numbers are only suggestions." is to be removed prior publication. </t> <t> A Subregistry in this section refers to a named sub-registry of the "Routing Protocol for Low Power and Lossy Networks (RPL)" registry. </t>anchor="iana"> <name>IANA Considerations</name> <t> AODV-RPL uses the "P2P Route Discovery Mode of Operation" (MOP ==4)4), with newOptionsoptions as specified in this document.Please cite AODV-RPL and thisThis document has been added asonean additional reference for "P2P Route Discovery Mode of Operation" in theprotocols using MOP 4."Mode of Operation" registry within the "Routing Protocol for Low Power and Lossy Networks (RPL)" registry group. </t> <t> IANAis asked to assignhas assigned the three new AODV-RPL options"RREQ", "RREP" and "ART", asdescribed in <xref target="ianaOpts"/>fromin the "RPL Control Message Options"Subregistry. The parenthesized numbers are only suggestions. <figure anchor="ianaOpts" title="AODV-RPL Options"> <artwork align="center"><![CDATA[ +-------------+------------------------+---------------+ | Value | Meaning | Reference | +-------------+------------------------+---------------+ | TBD2 (0x0B) | RREQ Option | This document | +-------------+------------------------+---------------+ | TBD3 (0x0C) | RREP Option | This document | +-------------+------------------------+---------------+ | TBD4 (0x0D) | ART Option | This document | +-------------+------------------------+---------------+ ]]></artwork> </figure></t>registry within the "Routing Protocol for Low Power and Lossy Networks (RPL)" registry group. </t> <table anchor="ianaOpts"> <name>AODV-RPL Options</name> <thead> <tr> <th>Value</th> <th>Meaning</th> <th>Reference</th> </tr> </thead> <tbody> <tr> <td>0x0B</td> <td>RREQ</td> <td>RFC 9854</td> </tr> <tr> <td>0x0C</td> <td>RREP</td> <td>RFC 9854</td> </tr> <tr> <td>0x0D</td> <td>ART</td> <td>RFC 9854</td> </tr> </tbody> </table> <t><!-- To resolve Roman Danyliw's comment 2/17/2025, 9:52 AM -->IANAis requested to allocate a newhas allocated the permanent multicast address with link-local scopecalled all-AODV-RPL-nodesin <xref target="ianaMultiAddress"/> for nodes implementing thisspecification fromspecification. This allocation has been made in the "Local Network Control Block (224.0.0.0 - 224.0.0.255 (224.0.0/24))" registryinwithin the "IPv4 Multicast Address Space Registry" registry group. </t></section> <!-- End of section "IANA Considerations" --> <section anchor="sec" title="Security Considerations"> <t> The<table anchor="ianaMultiAddress"> <name>Permanent Multicast Address with Link-Local Scope</name> <thead> <tr> <th>Address(es)</th> <th>Description</th> <th>References</th> </tr> </thead> <tbody> <tr> <td>224.0.0.69</td> <td>all-AODV-RPL-nodes</td> <td>RFC 9854</td> </tr> </tbody> </table> </section> <section anchor="sec"> <name>Security Considerations</name> <t>The security considerations for the operation of AODV-RPL are similar to those for the operation of RPL (as described in Section19<xref target="RFC6550" sectionFormat="bare" section="19"/> of the RPL specification <xref target="RFC6550"/>). Sections6.1<xref target="RFC6550" sectionFormat="bare" section="6.1"/> and10<xref target="RFC6550" sectionFormat="bare" section="10"/> of <xref target="RFC6550"/> describe RPL's optional security framework, which AODV-RPL relies on to provide data confidentiality, authentication, replay protection, and delay protection services. Additional analysis for the security threats to RPL can be found in <xreftarget="RFC7416"/>. </t> <t> Atarget="RFC7416"/>.</t> <t>A router can join a temporary DAG created for a secure AODV-RPL route discovery only if it can support the security configuration in use (seeSection 6.1 of<xreftarget="RFC6550"/>),target="RFC6550" sectionFormat="of" section="6.1"/>), which also specifies the key in use. 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 DAG being created for secure routediscovery. </t> <t> Ifdiscovery.</t> <t>If a rogue router knows the key for the security configuration in use, it can join the secure AODV-RPL route discovery and cause various types of damage. Such a rogue router could advertise false information in its DIOs in order to include itself in the discovered route(s). It could generate bogusRREQ-DIO,RREQ-DIO and RREP-DIO messages carrying bad routes or maliciously modify genuine RREP-DIO messages it receives. A rogue router acting as the OrigNode could launch denial-of-service attacks against the LLN deployment by initiating fake AODV-RPL route discoveries. When rogue routers might be present, RPL's preinstalled mode of operation, where the key to use for route discovery is preinstalled,SHOULD<bcp14>SHOULD</bcp14> be used. <!-- CEP: commented out upon request by Alvaro Retana. ....... but maybe something should be said without making a mandate. If a future IETF document specifies the authenticated mode of operation as described in <xref target="RFC6550"/>, then future AODV-RPL implementations SHOULD use the authenticated mode of operation. --> </t> <t> Whenaan 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 a set of addresses that may result in the RREP-DIO traveling in a routing loop. </t> <t> If a rogue router is able to forge agratuitous RREP,G-RREP, it could mount denial-of-service attacks. </t> </section><!-- End of section "Security Considerations" --> <section title="Acknowledgements"> <t> 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. </t> <t> 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. </t> </section></middle> <back><!-- *****BACK MATTER ***** --> <!-- References split into informative and normative --> <!-- There are 2 ways to insert reference entries from the citation libraries: 1. define an ENTITY at the top, and use "ampersand character" RFC2629; here (as shown) 2. simply use a PI "less than character"?rfc include="reference.RFC.2119.xml"?> here (for I-Ds: include="reference.I-D.narten-iana-considerations-rfc2434bis.xml") Both are cited textually in the same manner: by using xref elements. If you use the PI option, xml2rfc will, by default, try to find included files in the same directory as the including file. You can also define the XML_LIBRARY environment variable with a value containing a set of directories to search. These can be either in the local filing system or remote ones accessed by http (http://domain/dir/... ).--> <references title="Normative References"><references> <name>References</name> <references> <name>Normative References</name> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/><!-- <?rfc include='reference.RFC.2119'?> <?rfc include='reference.RFC.5095'?> <?rfc include='reference.RFC.6206'?> <xi:include href="http://xml2rfc.tools.ietf.org/public/rfc/ bibxml/reference.RFC.6206"/> <xi:include href="http://bib.ietf.org/public/rfc/ bibxml/reference.RFC.6206"/> <?rfc xi:include href="http://bib.ietf.org/public/rfc/ bibxml/reference.RFC.6206"/> --><xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6206.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6550.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6551.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> </references><references title="Informative References"><references> <name>Informative References</name> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3561.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6687.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6997.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6998.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7416.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7548.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7276.xml"/> <xi:includehref="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7991.xml"/> <xi:includehref="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9010.xml"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9030.xml"/> <!-- Co-iOAM paper Reference R. Ballamajalu, S. V. R. Anand and M. Hegde, "Co-iOAM: In-situ telemetry metadata transport for resource constrained networks within IETF standards framework," 2018 10th International Conference on Communication Systems & Networks (COMSNETS), Bengaluru, 2018, pp. 573-576. doi: 10.1109/COMSNETS.2018.8328276 --> <referenceanchor="co-ioam">anchor="co-ioam" target="https://ieeexplore.ieee.org/document/8328276"> <front> <title> Co-iOAM: In-situ Telemetry Metadata Transport for Resource Constrained Networks within IETF Standards Framework </title> <author fullname="Rashmi Ballamajalu"initials="" surname="Rashmi Ballamajalu">initials="R." surname="Ballamajalu"> <organization> </organization> <address> </address> </author> <author fullname="S.V.R. Anand" initials="S.V.R." surname="Anand"> <organization> </organization> <address> </address> </author> <author fullname="Malati Hegde"initials="" surname="Malati Hegde">initials="M." surname="Hegde"> <organization> </organization> <address> </address> </author> <date month="Jan"year="2018" />year="2018"/> </front><seriesInfo name="2018<refcontent>2018 10th International Conference on Communication Systems & Networks(COMSNETS)" value="pp.573-576"/>(COMSNETS), pp. 573-576</refcontent> <seriesInfo name="DOI" value="10.1109/COMSNETS.2018.8328276"/> </reference> <referenceanchor="aodv-tot"> <!-- DOI: 10.1109/MCSA.1999.749281 -->anchor="aodv-tot" target="https://ieeexplore.ieee.org/document/749281"> <front> <title> Ad-hoc On-demand Distance Vector Routing </title> <author fullname="C.E. Perkins" initials="C.E." surname="Perkins"><organization> Advanced<organization>Advanced Development Group, Sun MicroSystems Laboratories, Inc., Menlo Park, CA,USA </organization>USA</organization> <address> </address> </author> <author fullname="E.M. Royer" initials="E.M." surname="Royer"><organization> Advanced<organization>Advanced Development Group, Sun MicroSystems Laboratories, Inc., Menlo Park, CA,USA </organization>USA</organization> <address> </address> </author> <date month="Feb"year="1999" />year="1999"/> </front><seriesInfo name="Proceedings<refcontent>Proceedings WMCSA'99. Second IEEE Workshop on Mobile Computing Systems andApplications" value="" />Applications, pp. 90-100</refcontent> <seriesInfo name="DOI" value="10.1109/MCSA.1999.749281"/> </reference> <!-- [cooja] --> <reference anchor="cooja" target="https://github.com/contiki-os/contiki/tree/master/tools/cooja"> <front> <title> Cooja Simulator for Wireless Sensor Networks (Contiki/Cooja Version 2.7) </title><author fullname="Contiki/Cooja contributors" initials="" surname="Contiki/Cooja contributors"> <organization> </organization> <address> </address> </author><author/> <date month="Nov" year="2013"/> </front> <refcontent>commit 7635906</refcontent> </reference> <!-- [contiki] --> <reference anchor="contiki" target="https://github.com/contiki-os/contiki"> <front> <title> The Contiki Open Source OS for the Internet of Things (Contiki Version 2.7) </title><author fullname="Contiki contributors" initials="" surname="Contiki contributors"> <organization> </organization> <address> </address> </author><author/> <date month="Nov"year="2013" />year="2013"/> </front> <refcontent>commit 7635906</refcontent> </reference> <!-- [Contiki-ng] --> <reference anchor="Contiki-ng" target="https://github.com/contiki-ng/contiki-ng"> <front> <title> Contiki-NG: The OS for Next Generation IoT Devices (Contiki-NG Version 4.6) </title><author fullname="Contiki-NG contributors" initials="" surname="Contiki-NG contributors"> <organization> </organization> <address> </address> </author><author/> <date month="Dec"year="2020" />year="2020"/> </front> <refcontent>commit 3b0bc6a</refcontent> </reference> <!-- [Link_Asymmetry] --> <reference anchor="Link_Asymmetry" target="https://doi.org/10.1145/1689239.1689242"> <front> <title> On Link Asymmetry and One-way Estimation in Wireless Sensor Networks </title> <author fullname="Lifeng Sang"initials="" surname="Lifeng Sang">initials="L." surname="Sang"> <organization> </organization> <address> </address> </author> <author fullname="Anish Arora"initials="" surname="Anish Arora">initials="A." surname="Arora"> <organization> </organization> <address> </address> </author> <author fullname="Hongwei Zhang"initials="" surname="Hongwei Zhang">initials="H." surname="Zhang"> <organization> </organization> <address> </address> </author> <datemonth="Feb" year="2010" />month="March" year="2010"/> </front><seriesInfo name="ACM<refcontent>ACM Transactions on Sensor Networks,Volume 6 Issue 2" value="pp.1-25"/>vol. 6, no. 2, pp. 1-25</refcontent> <seriesInfo name="DOI" value="10.1145/1689239.1689242"/> </reference> <!-- [low-power-wireless] --> <reference anchor="low-power-wireless" target="https://doi.org/10.1145/1689239.1689246"> <front> <title> An empirical study of low-power wireless </title> <author fullname="Kannan Srinivasan"initials="" surname="Kannan Srinivasan">initials="K." surname="Srinivasan"> <organization> </organization> <address> </address> </author> <author fullname="Prabal Dutta"initials="" surname="Prabal Dutta">initials="P." surname="Dutta"> <organization> </organization> <address> </address> </author> <author fullname="Arsalan Tavakoli"initials="" surname="Arsalan Tavakoli">initials="A." surname="Tavakoli"> <organization> </organization> <address> </address> </author> <author fullname="Philip Levis"initials="" surname="Philip Levis">initials="P" surname="Levis"> <organization> </organization> <address> </address> </author> <datemonth="Feb" year="2010" />month="March" year="2010"/> </front><seriesInfo name="ACM<refcontent>ACM Transactions on SensorNetworks" value="(Volume 6 Issue 2 pp.1-49)"/>Networks, vol. 6, no. 2, pp. 1-49</refcontent> <seriesInfo name="DOI" value="10.1145/1689239.1689246"/> </reference> <referenceanchor="empirical-study">anchor="empirical-study" target="https://ieeexplore.ieee.org/document/6231290"> <front> <title> An empirical study of asymmetry in low-power wireless links </title> <author fullname="Prasant Misra"initials="" surname="Prasant Misra">initials="P." surname="Misra"> <organization> </organization> <address> </address> </author> <author fullname="Nadeem Ahmed"initials="" surname="Nadeem Ahmed">initials="N." surname="Ahmed"> <organization> </organization> <address> </address> </author> <author fullname="Sanjay Jha"initials="" surname="Sanjay Jha">initials="S." surname="Jha"> <organization> </organization> <address> </address> </author> <datemonth="Jul" year="2012" />month="July" year="2012"/> </front><seriesInfo name="IEEE<refcontent>IEEE CommunicationsMagazine" value="(Volume:Magazine, vol. 50,Issue: 7)"/>no. 7, pp. 137-146</refcontent> <seriesInfo name="DOI" value="10.1109/MCOM.2012.6231290"/> </reference> </references> </references> <sectionanchor="appendix-a" title="Example:anchor="appendix-a"> <name>Example: Using ETX/RSSI Values todetermine valueDetermine Value of Sbit"> <t> TheBit</name> <t>The combination of the downstream Received Signal StrengthIndication(downstream)Indicator (RSSI) and the upstream ExpectedNumber of Transmissions(upstream)Transmission Count (ETX) has been tested to determine whether a link is symmetric or asymmetric at intermediate routers. We present two methods to obtain an ETX value from RSSImeasurement. </t>measurement.</t> <dl newline="false" spacing="normal"> <dt>Method 1:</dt> <dd> <t><list style="hanging"> <t hangText="Method 1:">In the first method, we constructed a table measuring RSSIvsversus ETX using the Cooja simulation <xref target="cooja"/> setup in the Contiki OSenvironment<xrefenvironment <xref target="contiki"/>. We used Contiki-2.7 running the 6LoWPAN/RPL protocol stack for the simulations. For approximating the number of packet drops based on the RSSI values, we implemented simple logic that drops transmitted packets with certainpre-definedpredefined ratios before handing over the packets to the receiver. The packet drop ratio is implemented as a table lookup of RSSI ranges mapping to different packet drop ratios with lower RSSI ranges resulting in higher values. While this table has been defined for the purpose of capturing the overall link behavior, in general, it is highly recommended to conduct physical radio measurementexperiments, in general.experiments. By keeping the receiving node at different distances, we let the packets experience different packet drops as per the described method. The ETX value computation is done by another modulewhichthat is part of RPLObjective FunctionOF implementation. Since the ETX value is reflective of the extent of packet drops, it allowed us to prepare a useful table correlating ETXvsand RSSItable.values (see <xref target="table_ETX_RSSI"/>). ETXversusand RSSI values obtained in this way may be used as explainedbelow:below:</t> <figureanchor="commlink" title="Communication linkanchor="commlink"> <name>Communication Link from Source toDestination"> <artwork> <![CDATA[SourceDestination</name> <artwork><![CDATA[ Source -------> NodeA -------> NodeB ----->Destination]]> </artwork>Destination]]></artwork> </figure></t> </list> </t> <texttable anchor="table_ETX_RSSI" title="Selection<table anchor="table_ETX_RSSI"> <name>Selection of Sbit basedBit Based on Expected ETXvalue"> <ttcol align='center'>RSSIValue</name> <thead> <tr> <th align="center">RSSI at NodeA forNodeB</ttcol> <ttcol align='center'>ExpectedNodeB</th> <th align="center">Expected ETX at NodeA forNodeB->NodeA</ttcol> <c>> -60</c> <c>150</c> <c>-70 to -60</c> <c>192</c> <c>-80 to -70</c> <c>226</c> <c>-90 to -80</c> <c>662</c> <c>-100 to -90</c> <c>3840</c> </texttable> <t> <list style="hanging"> <t hangText="Method 2:">OneNodeB->NodeA</th> </tr> </thead> <tbody> <tr> <td align="center">> -60</td> <td align="center">150</td> </tr> <tr> <td align="center">-70 to -60</td> <td align="center">192</td> </tr> <tr> <td align="center">-80 to -70</td> <td align="center">226</td> </tr> <tr> <td align="center">-90 to -80</td> <td align="center">662</td> </tr> <tr> <td align="center">-100 to -90</td> <td align="center">3840</td> </tr> </tbody> </table> </dd> <dt>Method 2:</dt> <dd>One could also make use of the function guess_etx_from_rssi() defined in the 6LoWPAN/RPL protocol stack of Contiki-ng OS <xref target="Contiki-ng"/> to obtain RSSI-ETX mapping. This function outputs an ETX value ranging between 128 and 3840 for -60 <= rssi <= -89. The function description is beyond the scope of this document.</t> </list> </t></dd> </dl> <t> We tested the operations in this specification by making the following experiment, using the above parameters. In our experiment, a communication link is considered as symmetric if the ETX value ofNodeA->NodeBNodeA->NodeB andNodeB->NodeANodeB->NodeA (see <xref target="commlink"/>) are within, say, a 1:3 ratio. This ratio should be understood as determining the link's symmetric/asymmetric nature. NodeA can typically know the ETX value in the direction ofNodeA -> NodeBNodeA->NodeB, but it has no direct way of knowing the value of ETX fromNodeB->NodeA.NodeB->NodeA. Using physical testbed experiments and realistic wireless channel propagation models, one can determine a relationship between RSSI and ETX representable as an expression or a mapping table. Such arelationshiprelationship, inturnturn, can be used to estimate the ETX value atnodeANodeA for linkNodeB--->NodeANodeB->NodeA from the received RSSI from NodeB. WhenevernodeANodeA determines that the link towards thenodeBNodeB isbi-directional asymmetricbidirectional asymmetric, then the S bit is set to 0. Afterwards, the link from NodeA to Destination remains designated asasymmetricasymmetric, and the S bit remains set to 0. </t><t> Determination<t>Determination of asymmetry versus bidirectionality remains a topic of lively discussion in the IETF. <!-- https://github.com/roll-wg/dao-projection/issues/11 --> </t> </section> <sectionanchor="Examples" title="Someanchor="Examples"> <name>Some Example AODV-RPL MessageFlows">Flows</name> <t> This appendix provides some example message flows showing RREQ and RREP establishing symmetric and asymmetric routes. Also, 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 (T) is to be understood as performing the role of TargNode. Routers (R) are intermediate routers that are performing AODV-RPL functions in order to discover one or more suitable routes between (O) and (T). </t> <sectionanchor="Asymmetric-examples" title="Example control message flowsanchor="Asymmetric-examples"> <name>Example Control Message Flows insymmetricSymmetric andasymmetric networks">Asymmetric Networks</name> <t> In the following diagram, RREQ messages are multicast from router (O) in order to discover routes to and from router (T). The RREQ control messages flow outward from (O). Each router along the way establishes a single RREQ-Instance identified by RREQ-InstanceID even 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 route at each hop of the path from (O) to (T). When (T) receivesaan RREQ, it is then able to transmit data packets to (O). Router (T) then prepares to sendaan RREP along the symmetric path that would enable router (O) to send packets to router (T). </t> <figureanchor="figSymm-RREQ_flow" title="AODV-RPLanchor="figSymm-RREQ_flow"> <name>AODV-RPL RREQmessage flow example when symmetric path available">Message Flow Example When Symmetric Path Available</name> <artwork align="center"><![CDATA[ (R) ---RREQ(S=1)--->(R) ---RREQ(S=1)--->(R) ^ | | | RREQ(S=1) RREQ(S=1) | | | v (O) --------->(R) --------->(R)-------->(T) / \ RREQ RREQ RREQ ^ | \ (S=1) (S=0) (S=0) | | \ / RREQ | \ RREQ (S=1) RREQ (S=0) (S=0) | \ / v \ RREQ (S=0) / (R)---->(R)------>(R)----.....--->(R) ]]></artwork>---->(R)------>(R)----.....--->(R)]]></artwork> </figure></t><t> In the followingdiagramdiagram, which results from the above RREQ message transmission, a symmetric route is available from (T) to router (O) via the routers in the top half of the diagram. RREP messages are sent via unicast along the symmetric route. Since the RREP message is transmitted via unicast, no RREP messages are sent by router (T) to the routers in the bottom half of the diagram. </t> <figureanchor="figSymm-RREP_flow" title="AODV-RPLanchor="figSymm-RREP_flow"> <name>AODV-RPL RREPmessage flow example when symmetric path available">Message Flow Example When Symmetric Path Available</name> <artwork align="center"><![CDATA[ (R)<------RREP----- (R)<------RREP----- (R) | ^ | | RREP RREP | | v | (O) ----------(R) ----------(R) --------(T) / \ | | \ | | \ (no RREP messages sent) / | \ / | \ / | \ / (R)-----(R)-------(R)----.....----(R) ]]></artwork>-----(R)-------(R)----.....----(R)]]></artwork> </figure></t><t> In the following diagram, RREQ messages are multicast from router (O) in order to discover routes to and from router (T) as before. As shown, no symmetric route is available from (O) to (T). </t> <figureanchor="figAsymm-RREQ_flow" title="AODV-RPLanchor="figAsymm-RREQ_flow"> <name>AODV-RPL RREQmessage flow when symmetric path unavailable">Message Flow When Symmetric Path Unavailable</name> <artwork align="center"><![CDATA[ (R) ---RREQ(S=0)--->(R) ---RREQ(S=0)--->(R) ^ | | | RREQ(S=1) RREQ(S=0) | | | v (O) --------->(R) --------->(R)-------->(T) ^ \ RREQ RREQ RREQ | \ | \ (S=1) (S=0) (S=0) | | | \ / | | RREQ (S=1) RREQ (S=0) / (R) | \ / | | \ RREQ (S=0) / / (R)---->(R)------>(R)----.....----->(R)--- ]]></artwork>---->(R)------>(R)----.....----->(R)---]]></artwork> </figure></t><t> Upon receiving the RREQ in <xref target="figAsymm-RREQ_flow"/>,Routerrouter (T) then prepares to sendaan RREP that would enable router (O) to send packets to router (T). In <xref target="figAsymm-RREQ_flow"/>, since no symmetric route is available from (T) to router (O), RREP messages are sent via multicast to all neighboring routers. </t> <figureanchor="figAsymm-RREP_flow" title="AODV-RPLanchor="figAsymm-RREP_flow"> <name>AODV-RPL RREQ andRREP InstancesRREP-Instances for AsymmetricLinks">Links</name> <artwork align="center"><![CDATA[ (R)<------RREP----- (R)<------RREP----- (R) | | | | RREP RREP | | | | v v (O)<--------- (R)<--------- (R)<------- (T) ^ \ RREP RREP RREP | \ | \ | |RREP | \ / | RREP | \ RREP RREP / (R) | \ / | | \ / / (R)<----- (R)<----- (R)<---.....---- (R)< - RREP RREP RREPRREP ]]></artwork>RREP]]></artwork> </figure></t></section><!-- End of section "Example control message flows . . ." --><sectionanchor="RREP_WAIT-example" title="Exampleanchor="RREP_WAIT-example"> <name>Example RREP_WAIThandling">Handling</name> <t> In <xref target="fig-RREP_WAIT-a"/>, the first RREQ arrives at (T). This triggers TargNode to start the RREP_WAIT_TIME timer. </t> <figureanchor="fig-RREP_WAIT-a" title="TargNode starts RREP_WAIT">anchor="fig-RREP_WAIT-a"> <name>TargNode Starts RREP_WAIT</name> <artwork align="center"><![CDATA[ (O) --------->(R) --------->(R)-------->(T) RREQ RREQ RREQ (S=1) (S=0)(S=0) ]]></artwork>(S=0)]]></artwork> </figure></t><t> In <xref target="fig-RREP_WAIT-b"/>, another RREQ arrives before the RREP_WAIT_TIME timer is expired. It could be preferable compared the previously received RREP that caused the RREP_WAIT_TIME timer to be set. </t> <figureanchor="fig-RREP_WAIT-b" title="Waitinganchor="fig-RREP_WAIT-b"> <name>Waiting TargNodereceives preferable RREQ">Receives Preferable RREQ</name> <artwork align="center"><![CDATA[ (O) (T) / \ ^ | \ | | \ / RREQ | \ RREQ (S=1) RREQ (S=0) (S=0) | \ / v \ RREQ (S=0) / (R)---->(R)------>(R)----.....--->(R) ]]></artwork>---->(R)------>(R)----.....--->(R)]]></artwork> </figure></t><t> In <xref target="fig-RREP_WAIT-c"/>, the RREP_WAIT_TIME timer expires. TargNode selects the path with S=1. </t> <figureanchor="fig-RREP_WAIT-c" title="RREP_WAIT expiresanchor="fig-RREP_WAIT-c"> <name>RREP_WAIT Expires atTargNode">TargNode</name> <artwork align="center"><![CDATA[ (R) ---RREQ(S=1)--->(R) ---RREQ(S=1)--->(R) ^ | | | RREQ(S=1) RREQ(S=1) | | | v (O)(T) ]]></artwork>(T)]]></artwork> </figure></t></section><!-- End of section "Example RREP_WAIT handling" --><sectionanchor="G-RREP-example" title="Exampleanchor="G-RREP-example"> <name>Example G-RREPhandling"> <t> InHandling</name> <t>In <xref target="fig-G-RREP-a"/>, R* has upward and downward routes to TargNode (T) thatsatisfiessatisfy the OF of the RPL Instance originated by OrigNode(O)(O), anddestination sequence numberthe Destination Sequence Number is at least as large as thesequence numberSequence Number in the RREQmessage.message.</t> <figureanchor="fig-G-RREP-a" title="RREP triggersanchor="fig-G-RREP-a"> <name>RREP Triggers G-RREP at IntermediateNode">Node</name> <artwork align="center"><![CDATA[ (R) ---RREQ(S=1)--->(R) ---RREQ(S=0)--->(R) ^ | | | RREQ(S=1) RREQ(S=0) | | | v (O) --------->(R) --------->(R)-------->(T) / \ RREQ RREQ RREQ ^ | \ (S=1) (S=0) (S=0) | | \ / RREQ | \ RREQ (S=1) / (S=0) | \ / v \ v (R)---->(R*)<------>(R)<----....--->(R) ]]></artwork>---->(R*)<------>(R)<----....--->(R)]]></artwork> </figure></t><t> In <xref target="fig-G-RREP-b"/>, R* transmits theG-RREP DIOG-RREP-DIO back to OrigNode (O) and forwards the incoming RREQ towards (T). </t> <figureanchor="fig-G-RREP-b" title="Intermediateanchor="fig-G-RREP-b"> <name>Intermediate Nodeinitiates G-RREP">Initiates G-RREP</name> <artwork align="center"><![CDATA[ (O) (T) \ ^ \ | \ (RREQ) / \G-RREP DIOG-RREP-DIO / \ / \ (RREQ) (RREQ) /(R*)------>(R)----....--->(R) ]]></artwork>(R*)------>(R)----....--->(R)]]></artwork> </figure></t></section><!-- End of section "Example G-RREP handling" --></section><!-- End of section "Some Example AODV-RPL Message Flows" --> <section anchor="appendix-c" title="Changelog"> <t> Note to the RFC Editor: please remove this section before publication. </t><sectiontitle="Changes from version 19 to version 20"> <t> <!-- In response to non-blocking AD comments, end of Feb. 2025 --> <list style="symbols"> <t> <!-- Gunter Van de Velde 2/11/2025, 8:36 PM --> Changed Option Format drawings to avoid suggesting that the Option Length is a multiple of 4 bytes for AODV-RPL options. </t> <t> <!-- Murray Kucherawy 2/20/2025, 12:53 AM --> 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. </t> <t> <!-- Roman Danyliw 2/17/2025, 9:52 AM --> 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. </t> <t> <!-- Gunter Van de Velde 2/11/2025, 8:36 PM --> Changed "must" to "MUST", so that "the selected address MUST encompass the domain where the route is built". </t> <t> <!-- John Scudder 3/1/2025, 12:12 PM --> 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. </t> <t> New author's address, minor editorial. </t> </list> </t> </section> <section title="Changes from version 18 to version 19"> <t> <list style="symbols"> <t> 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. </t> <t> Added length specification for byte-sized message fields, which had previously relied on implicit length specification from the message's packet format diagram. </t> <t> Added clarifying language for handling of initial zero bits in some cases for the Target Prefix / Address field. </t> <t> Updated specification regarding the need for a router to ensure the availability of RREQ state information when processing a corresponding RREP. </t> <t> Replaced GRREP by G-RREP when describing Gratuitous RREP. </t> <t> Updated affiliations for Charles Perkins, Abdur Rashid Sangi and email address for S.V.R. Anand. </t> <t> Corrected misspellings, typos. </t> </list> </t> </section> <section title="Changes from version 17 to version 18"> <t> <list style="symbols"> <t> Replaced "on-demand nature of AODV route discovery is natural" by "on-demand property of AODV route discovery is useful" in <xref target="Introduction"/>. </t> <t> In <xref target="rreq_step4"/>, 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 <xref target="rreq_step4"/>. </t> <t> Changed from v2-style RFC citations to using Xinclude as specified in <xref target="RFC7991"/>. </t> </list> </t> </section> <section title="Changes from version 16 to version 17"> <t> <list style="symbols"> <t> Added new Terminology definitions for RREQ, RREP, OF. </t> <t> Added clarifying detail about some kinds of improved routes discoverable by AODV-RPL. </t> <t> Added forward reference explaining how RREP-InstanceID is matched with the proper RREQ-InstanceID. </t> <t> Added explanation about the function of the 'D' bit of the RPLInstanceID. </t> <t> Provided detail about why a node should leave the RREQ-Instance after the specified amount of time. </t> <t> 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." </t> <t> Added more illustrative diagrams in new <xref target="Examples"/>. Example diagrams show control message flowsnumbered="false"> <name>Acknowledgements</name> <t>The authors thank <contact fullname="Pascal Thubert"/>, <contact fullname="Rahul Jadhav"/>, and <contact fullname="Lijo Thomas"/> forRREQtheir support andfor RREP in cases when symmetric route is either available or not available.valuable input. Theuse of RREP_WAIT and G-RREP is also illustrated in other new diagrams. </t> <t> Included the reasoning for using intersections of RREQ target lists in <xref target="rreq_step2"/>. </t> <t> Various editorial improvements and clarifications. </t> </list> </t> </section> <section title="Changes from version 15 to version 16"> <t> <list style="symbols"> <t> 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. </t> <t> Added explanation that the way AODV-RPL uses the Rank function does not express a distance or a path cost to the root. </t> <t> Added a citation suggesting AODV-RPL's likely improvements in routing costs. </t> </list> </t> </section> <section title="Changes from version 14 to version 15"> <t> <list style="symbols"> <t> Clarified that AODV-RPL treats the addresses of multiple interfaces on the same router as the addresses of independent routers. </t> <t> Added details about cases when proactive route establishment is preferable to AODV-RPL's reactive route establishment. </t> <t> Various editorial stylistic improvements. </t> <t> Added citations about techniques that can be used for evaluating a link's state. </t> <t> Clarified that the determination of TargNode status and determination of a usable route to OrigNode does not depend on whether or not S == 0. </t> <t> 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. </t> </list> </t> </section> <section title="Changes from version 13 to version 14"> <t> <list style="symbols"> <t> Provided more details about scenarios naturally supporting the choice of AODV-RPL as a routing protocol </t> <t> Added new informative references <xref target="RFC6687"/>, <xref target="RFC9010"/>) that describe the value provided by peer-to-peer routing. </t> <t> Requested IANA to allocate a new multicast group to enable clean separation of AODV-RPL operation from previous routing protocols in the RPL family. </t> <t> Cited <xref target="RFC6550"/> as the origination of the definition of DIO </t> <t> Defined "hop-by-hop route" as a route created using RPL's storing mode. </t> <t> Defined new configuration variable REJOIN_REENABLE. </t> <t> Improved definition for RREQ-InstanceID. Created analogous definition for RREP-InstanceID=(RPLInstanceID, TargNode_IPaddr) </t> <t> Improved definition of source routing </t> <t> Clarified that the Border Router (BR) in <xref target="figSymm-a"/> does not imply that AODV does not a require a BR as a protocol entity. </t> <t> Provided more guidelines about factors to be considered by OrigNode when selecting a value for the 'L' field. </t> <t> Described the disadvantage of not keeping track of the Address Vector in the RREQ-Instance. </t> <t> 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. </t> <t> Added three informative references to describe relevant details about evaluating link asymmetry. </t> <t> Clarified details about Gratuitous RREP. </t> </list> </t> </section> <section title="Changes from version 12 to version 13"> <t> <list style="symbols"> <t> Changed name of "Shift" field to be the "Delta" field. </t> <t> Specified that if a node does not have resources, it MUST drop the RREQ. </t> <t> Changed name of MaxUseRank to MaxUsefulRank. </t> <t> Revised a sentence that was not clear about when a TargNode can delay transmission of the RREP in response to a RREQ. </t> <t> Provided advice about running AODV-RPL at same time as P2P-RPL or native RPL. </t> <t> Small reorganization and enlargement of the description of Trickle time operation in <xref target="trickle"/>. </t> <t> Added definition for "RREQ-InstanceID" to Terminology section. </t> <t> Specified that once a node leaves an RREQ-Instance, it MUST NOT rejoin the same RREQ-Instance. </t> </list> </t> </section> <section title="Changes from version 11 to version 12"> <t> <list style="symbols"> <t> Defined RREP_WAIT_TIME for asymmetric as well as symmetric handling of RREP-DIO. </t> <t> Clarified link-local multicast transmission to use link-local multicast group all-RPL nodes. </t> <t> Identified some security threats more explicitly. </t> <t> Specified that the pairing between RREQ-DIO and RREP-DIO happens at OrigNode and TargNode. Intermediate routers do not necessarily maintain the pairing. </t> <t> 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. </t> <t> 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 <xref target="RFC6997"/>. </t> <t> Fixed several important typos and improved language in numerous places. </t> <t> 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. </t> </list> </t> </section> <section title="Changes from version 10 to version 11"> <t> <list style="symbols"> <t> Numerous editorial improvements. </t> <t> Replace Floor((7+(Prefix Length))/8) by Ceil(Prefix Length/8) for simplicity and ease of understanding. </t> <t> Use "L field" instead of "L bit" since L is a two-bit field. </t> <t> Improved the procedures in section 6.2.1. </t> <t> 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. </t> <t> Quote terminology from AODV that has been identified as possibly originating in language reflecting various kinds of bias against certain cultures. </t> <t> Clarified the relationship of AODV-RPL to RPL. </t> <t> Eliminated the "Point-to-Point" terminology to avoid suggesting only a single link. </t> <t> Modified certain passages to better reflect the possibility that a router might have multiple IP addresses. </t> <t> "Rsv" replaced by "X X" for reserved field. </t> <t> Added mandates for reserved fields, and replaces some ambiguous language phraseology by mandates. </t> <t> Replaced "retransmit" terminology by more correct "propagate" terminology. </t> <t> Added text about determining link symmetry near <xref target="figSymm-b"/>. </t> <t> Mandated checking the Address Vector to avoid routing loops. </t> <t> Improved specification for use of the Delta value in <xref target="instancepairing"/>. </t> <t> Corrected the wrong use of RREQ-Instance to be RREP-Instance. </t> <t> Referred to Subregistry values instead of Registry values in <xref target="iana"/>. </t> <t> Sharpened language in <xref target="sec"/>, eliminated misleading use of capitalization in the words "Security Configuration". </t> <t> Added acknowledgements and contributors. </t> </list> </t> </section> <section title="Changes from version 09 to version 10"> <t> <list style="symbols"> <t> Changed the title for brevity and to remove acronyms. </t> <t> Added "Note to the RFC Editor" in <xref target="iana"/>. </t> <t> Expanded DAO and P2MP in <xref target="Introduction"/>. </t> <t> Reclassified <xref target="RFC6998"/> and <xref target="RFC7416"/> as Informational. </t> <t> SHOULD changed to MUST in <xref target="RREQmsg"/> and <xref target="RREPmsg"/>. </t> <t> Several editorial improvements and clarifications. </t> </list> </t> </section> <section title="Changes from version 08 to version 09"> <t> <list style="symbols"> <t> Removed section "Link State Determination" and put some of the relevant material into <xref target="channel"/>. </t> <t> Cited security section of <xref target="RFC6550"/> as part of the RREP-DIO message description in <xref target="terms"/>. </t> <t> SHOULD has been changed to MUST in <xref target="RREPmsg"/>. </t> <t> Expanded the terms ETX and RSSI in <xref target="channel"/>. </t> <t> <xref target="forwardRREP"/> has been expanded to provide a more precise explanation of the handling of route reply. </t> <t> Added <xref target="RFC7416"/> in the Security Considerations (<xref target="sec"/>) for RPL security threats. Cited <xref target="RFC6550"/> for authenticated mode of operation. </t> <t> Appendix A has been mostly re-written to describe methods to determine whether or not the S bit should be set to 1. </t> <t> For consistency, adjusted several mandates from SHOULD to MUST and from SHOULD NOT to MUST NOT. </t> <t> Numerous editorial improvements and clarifications. </t> </list> </t> </section> <section title="Changes from version 07 to version 08"> <t> <list style="symbols"> <t> Instead of describing the need for routes to "fulfill the requirements", specify that routes need to "satisfy the Objective Function". </t> <t> Removed all normative dependencies on <xref target="RFC6997"/> </t> <t> Rewrote <xref target="sec"/> to avoid duplication of language in cited specifications. </t> <t> Added a new section "Link State Determination" <!-- <xref target="linkstate"/> --> with text and citations to more fully describe how implementations determine whether links are symmetric. </t> <t> Modified text comparing AODV-RPL to other protocols to emphasize the needauthors specially thank <contact fullname="Lavanya H.M."/> for implementing AODV-RPLinstead of the problems with the other protocols. </t> <t> Clarified that AODV-RPL uses some of the base RPL specification but does not require an instance of RPL to run. </t> <t> Improved capitalization, quotation, and spelling variations. </t> <t> Specified behavior upon reception of a RREQ-DIO or RREP-DIO message for an already existing DODAGID (e.g, <xref target="forwardRREP"/>). </t> <t> Fixed numerous language issuesinIANA Considerations <xref target="iana"/>. </t> <t> For consistency, adjusted several mandates from SHOULD to MUST and from SHOULD NOT to MUST NOT. </t> <t> Numerous editorial improvements and clarifications. </t> </list> </t> </section> <section title="Changes from version 06 to version 07"> <t> <list style="symbols"> <t> Added definitions for all fields of the ART option (see <xref target="artop"/>). Modified definition of Prefix Length to prohibit Prefix Length values greater than 127. </t> <t> Modified the language from <xref target="RFC6550"/> Target Option definition so that the trailing zero bits of the Prefix Length are no longer described as "reserved". </t> <t> Reclassified <xref target="RFC3561"/> and <xref target="RFC6998"/> as Informative. </t> <t> Added citation for <xref target="RFC8174"/> to Terminology section. </t> </list> </t> </section> <section title="Changes from version 05 to version 06"> <t> <list style="symbols"> <t> Added Security Considerations based on the security mechanisms defined in <xref target="RFC6550"/>. </t> <t> Clarified the nature of improvements due to P2P route discovery versus bidirectional asymmetric route discovery. </t> <t> Editorial improvementsContiki andcorrections. </t> </list> </t> </section> <section title="Changes from version 04 to version 05"> <t> <list style="symbols"> <t> Add description for sequence number operations. </t> <t> Extend the residence duration L in section 4.1. </t>conducting extensive simulation studies.</t> <t>Change AODV-RPL Target option to ART option. </t> </list> </t> </section> <section title="Changes from version 03The authors would like toversion 04"> <t> <list style="symbols"> <t> Updated RREP option format. Remove the T bit in RREP option. </t> <t> Usingacknowledge thesame RPLInstanceID for RREQreviews, feedback, andRREP, no need to update <xref target="RFC6550"/>. </t> <t> Explanation of Delta field in RREP. </t> <t> Multiple target options handling during transmission. </t> </list> </t> </section> <section title="Changescomments fromversion 02 to version 03"> <t> <list style="symbols"> <t> Includethesupport for source routing. </t> <t> Import some features from <xref target="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. </t> <t> 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. </t> <t> Support route discovery for multiple targetsfollowing people, inone RREQ-DIO. </t> <t> New RPLInstanceID pairing mechanism. </t> </list> </t> </section>alphabetical order: <contact fullname="Roman Danyliw"/>, <contact fullname="Lars Eggert"/>, <contact fullname="Benjamin Kaduk"/>, <contact fullname="Tero Kivinen"/>, <contact fullname="Erik Kline"/>, <contact fullname="Murray Kucherawy"/>, <contact fullname="Warren Kumari"/>, <contact fullname="Francesca Palombini"/>, <contact fullname="Alvaro Retana"/>, <contact fullname="Ines Robles"/>, <contact fullname="John Scudder"/>, <contact fullname="Meral Shirazipour"/>, <contact fullname="Peter Van der Stok"/>, <contact fullname="Éric Vyncke"/>, and <contact fullname="Robert Wilton"/>.</t> </section> <sectiontitle="Contributors"> <t><list> <t> Abdurnumbered="false"> <name>Contributors</name> <contact fullname="Abdur RashidSangi<vspace /> Wenzhou-Kean University<vspace /> 88Sangi"> <organization>Wenzhou-Kean University</organization> <address> <postal> <postalLine>88 Daxue Rd,Ouhai,<vspace /> Wenzhou, Zhejiang Province<vspace /> P.R. China 325060<vspace /> Kean University<vspace /> 1000Ouhai</postalLine> <postalLine>Wenzhou</postalLine> <postalLine>Zhejiang Province, 325060</postalLine> <postalLine>P.R. China</postalLine> <postalLine>Kean University</postalLine> <postalLine>1000 MorrisAvenue<vspace /> Union,Avenue</postalLine> <postalLine>Union, New Jersey07083<vspace /> USA<vspace /> Email: sangi_bahrian@yahoo.com</t> <t> Malati Hegde<vspace /> Indian07083</postalLine> <postalLine>United States of America</postalLine> </postal> <email>sangi_bahrian@yahoo.com</email> </address> </contact> <contact fullname="Malati Hegde"> <organization>Indian Institute ofScience<vspace /> Bangalore 560012<vspace /> India <vspace /> Email: malati@iisc.ac.in</t> <t> Mingui Zhang<vspace /> Huawei Technologies<vspace /> No. 156 Beiqing Rd. Haidian District<vspace /> Beijing 100095<vspace /> P.R. China<vspace /> Email: zhangmingui@huawei.com</t> <!-- <authorScience</organization> <address> <postal> <city>Bangalore</city><code>560012</code> <country>India</country> </postal> <email>malati@iisc.ac.in</email> </address> </contact> <contact fullname="MinguiZhang" initials="M." surname="Zhang">Zhang"> <organization>Huawei Technologies</organization> <address> <postal> <street>No. 156 BeiqingRd. Haidian District</street> <city>Beijing</city> <region/> <code>100095</code> <country>China</country>Rd.</street> <cityarea>Haidian District</cityarea> <city>Beijing</city><code>100095</code> <country>P.R. China</country> </postal><phone/><email>zhangmingui@huawei.com</email> </address></author> --> </list></t></contact> </section> </back> </rfc>