--- 1/draft-ietf-roll-aodv-rpl-12.txt 2022-03-07 15:16:26.568147922 -0800 +++ 2/draft-ietf-roll-aodv-rpl-13.txt 2022-03-07 15:16:26.608148439 -0800 @@ -1,23 +1,23 @@ ROLL C.E. Perkins Internet-Draft Lupin Lodge Intended status: Standards Track S.V.R.Anand -Expires: 3 August 2022 Indian Institute of Science +Expires: 8 September 2022 Indian Institute of Science S. Anamalamudi SRM University-AP B. Liu Huawei Technologies - 30 January 2022 + 7 March 2022 Supporting Asymmetric Links in Low Power Networks: AODV-RPL - draft-ietf-roll-aodv-rpl-12 + draft-ietf-roll-aodv-rpl-13 Abstract Route discovery for symmetric and asymmetric Peer-to-Peer (P2P) traffic flows is a desirable feature in Low power and Lossy Networks (LLNs). For that purpose, this document specifies a reactive P2P route discovery mechanism for both hop-by-hop routing and source routing: Ad Hoc On-demand Distance Vector Routing (AODV) based RPL protocol (AODV-RPL). Paired Instances are used to construct directional paths, for cases where there are asymmetric links between @@ -31,90 +31,91 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on 3 August 2022. + This Internet-Draft will expire on 8 September 2022. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6 - 4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 6 + 4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 7 4.1. AODV-RPL RREQ Option . . . . . . . . . . . . . . . . . . 7 - 4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 8 + 4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 9 4.3. AODV-RPL Target Option . . . . . . . . . . . . . . . . . 10 - 5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 11 - 6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 13 - 6.1. Route Request Generation . . . . . . . . . . . . . . . . 13 + 5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 12 + 6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 14 + 6.1. Route Request Generation . . . . . . . . . . . . . . . . 14 6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 14 - 6.2.1. Step 1: RREQ reception and evaluation . . . . . . . . 14 + 6.2.1. Step 1: RREQ reception and evaluation . . . . . . . . 15 6.2.2. Step 2: TargNode and Intermediate Router determination . . . . . . . . . . . . . . . . . . . . 15 6.2.3. Step 3: Intermediate Router RREQ processing . . . . . 16 6.2.4. Step 4: Symmetric Route Processing at an Intermediate Router . . . . . . . . . . . . . . . . . . . . . . . 16 - 6.2.5. Step 5: RREQ propagation at an Intermediate Router . 16 + 6.2.5. Step 5: RREQ propagation at an Intermediate Router . 17 6.2.6. Step 6: RREQ reception at TargNode . . . . . . . . . 17 6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 17 - 6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 17 + 6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 18 6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 18 6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 18 6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 19 6.4.1. Step 1: Receiving and Evaluation . . . . . . . . . . 19 6.4.2. Step 2: OrigNode or Intermediate Router . . . . . . . 19 - 6.4.3. Step 3: Build Route to TargNode . . . . . . . . . . . 19 + 6.4.3. Step 3: Build Route to TargNode . . . . . . . . . . . 20 6.4.4. Step 4: RREP Propagation . . . . . . . . . . . . . . 20 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 20 8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 21 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 10. Security Considerations . . . . . . . . . . . . . . . . . . . 22 - 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 12.1. Normative References . . . . . . . . . . . . . . . . . . 23 - 12.2. Informative References . . . . . . . . . . . . . . . . . 23 + 12.2. Informative References . . . . . . . . . . . . . . . . . 24 Appendix A. Example: Using ETX/RSSI Values to determine value of S bit . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 - Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 26 - B.1. Changes from version 11 to version 12 . . . . . . . . . . 26 - B.2. Changes from version 10 to version 11 . . . . . . . . . . 27 - B.3. Changes from version 09 to version 10 . . . . . . . . . . 28 - B.4. Changes from version 08 to version 09 . . . . . . . . . . 29 - B.5. Changes from version 07 to version 08 . . . . . . . . . . 29 - B.6. Changes from version 06 to version 07 . . . . . . . . . . 30 - B.7. Changes from version 05 to version 06 . . . . . . . . . . 30 - B.8. Changes from version 04 to version 05 . . . . . . . . . . 30 - B.9. Changes from version 03 to version 04 . . . . . . . . . . 30 - B.10. Changes from version 02 to version 03 . . . . . . . . . . 31 - Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 31 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 + Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 27 + B.1. Changes from version 12 to version 13 . . . . . . . . . . 27 + B.2. Changes from version 11 to version 12 . . . . . . . . . . 28 + B.3. Changes from version 10 to version 11 . . . . . . . . . . 28 + B.4. Changes from version 09 to version 10 . . . . . . . . . . 29 + B.5. Changes from version 08 to version 09 . . . . . . . . . . 30 + B.6. Changes from version 07 to version 08 . . . . . . . . . . 30 + B.7. Changes from version 06 to version 07 . . . . . . . . . . 31 + B.8. Changes from version 05 to version 06 . . . . . . . . . . 31 + B.9. Changes from version 04 to version 05 . . . . . . . . . . 31 + B.10. Changes from version 03 to version 04 . . . . . . . . . . 32 + B.11. Changes from version 02 to version 03 . . . . . . . . . . 32 + Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 32 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 1. Introduction Routing Protocol for Low-Power and Lossy Networks (RPL) [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, a router does not have routing information for most other routers. Consequently, for traffic between routers within the DODAG (i.e., Peer-to-Peer (P2P) traffic) data packets either have to traverse the root in non-storing mode, or @@ -140,22 +141,26 @@ (defined in [RFC6551]), trickle timers, and support for storing and non-storing modes. AODV-RPL adds basic messages RREQ and RREP as part of RPL DODAG Information Object (DIO) control message, which go in separate (paired) RPL instances. AODV-RPL does not utilize the Destination Advertisement Object (DAO) control message of RPL. AODV- RPL uses the "P2P Route Discovery Mode of Operation" (MOP == 4) with three new Options for the DIO message, dedicated to discover P2P routes. These P2P routes may differ from routes discoverable by native RPL. Since AODV-RPL uses newly defined Options, there is no conflict with P2P-RPL [RFC6997], a previous document using the same - MOP. AODV-RPL can be operated whether or not native RPL is running - otherwise. + MOP. AODV-RPL can be operated whether or not P2P-RPL or native RPL + is running otherwise. For many networks AODV-RPL could be a + replacement for RPL, since it can find better routes at very moderate + extra cost. Consequently, it is unlikely that RPL would be needed in + a network that is running AODV-RPL, even though it would be possible + to run both protocols at the same time. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. AODV-RPL reuses names for messages and data structures, including @@ -173,26 +178,26 @@ Bi-directional Asymmetric Link A link that can be used in both directions but with different link characteristics. DIO DODAG Information Object DODAG RREQ-Instance (or simply RREQ-Instance) RPL Instance built using the DIO with RREQ option; used for - control message transmission from OrigNode to TargNode, thus + transmission of control messages from OrigNode to TargNode, thus enabling data transmission from TargNode to OrigNode. DODAG RREP-Instance (or simply RREP-Instance) RPL Instance built using the DIO with RREP option; used for - control message transmission from TargNode to OrigNode thus + transmission of control messages from TargNode to OrigNode thus enabling data transmission from OrigNode to TargNode. Downward Direction The direction from the OrigNode to the TargNode. Downward Route A route in the downward direction. hop-by-hop routing Routing when each router stores routing information about the next @@ -214,25 +219,31 @@ traverse a common ancestor. reactive routing Same as "on-demand" routing. RREQ-DIO message 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 [RFC6550]. + RREQ-InstanceID + The RPLInstanceID for the RREQ-Instance. This term is used to + indicate the value of the RPLInstanceID as provided by OrigNode in + the RREQ message. The RPLInstanceID in the RREP message along + with the Delta value determines the associated RREQ-InstanceID. + RREP-DIO message A DIO message containing the RREP option. OrigNode pairs the RPLInstanceID in RREP-DIO to the one in the associated RREQ-DIO - message as described in Section 6.3.2. The RREP-DIO message has a - secure variant as noted in [RFC6550]. + message (i.e., the RREQ-InstanceID) as described in Section 6.3.2. + The RREP-DIO message has a secure variant as noted in [RFC6550]. Source routing A mechanism by which the source supplies the complete route towards the target node along with each data packet [RFC6550]. Symmetric route The upstream and downstream routes traverse the same routers and over the same links. TargNode @@ -266,39 +277,40 @@ symmetric routes are possible (see Section 5). In AODV-RPL, routes are discovered by first forming a temporary 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 to TargNode whereas the RREP-Instance is formed by route control messages from TargNode to OrigNode. Intermediate routers join the DODAGs based on the Rank [RFC6550] as calculated from the DIO message. Henceforth in this document, "RREQ-DIO message" means the - DIO message from OrigNode to TargNode, containing the RREQ option as - specified in Section 4.1. Similarly, "RREP-DIO message" means the - DIO message from TargNode to OrigNode, containing the RREP option as - specified in Section 4.2. 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. + DIO message from OrigNode toward TargNode, containing the RREQ option + as specified in Section 4.1. Similarly, "RREP-DIO message" means the + DIO message from TargNode toward OrigNode, containing the RREP option + as specified in Section 4.2. 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. 4. AODV-RPL DIO Options + 4.1. AODV-RPL RREQ Option OrigNode selects one of its IPv6 addresses and sets it in the DODAGID field of the RREQ-DIO message. Exactly one RREQ option MUST be present in a RREQ-DIO message, otherwise the message MUST be dropped. 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 | MaxRank | + | Option Type | Option Length |S|H|X| Compr | L | RankLimit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Orig SeqNo | | +-+-+-+-+-+-+-+-+ | | | | | | Address Vector (Optional, Variable Length) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -333,61 +345,62 @@ with the IPv6 address in the DODAGID. This field is only used in source routing mode (H=0). In hop-by-hop mode (H=1), this field MUST be set to zero and ignored upon reception. L 2-bit unsigned integer determining the length of time 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 node MUST leave the RREQ-Instance and stop sending or receiving any more DIOs for the RREQ-Instance. This naturally depends on the - node's ability to keep track of the time. L is independent from - the route lifetime, which is defined in the DODAG configuration - option. + node's ability to keep track of time. Once a node leaves an RREQ- + Instance, it MUST NOT rejoin the same RREQ-Instance. L is + independent from the route lifetime, which is defined in the DODAG + configuration option. * 0x00: No time limit imposed. * 0x01: 16 seconds * 0x02: 64 seconds * 0x03: 256 seconds - MaxRank + RankLimit This field indicates the upper limit on the integer portion of the Rank (calculated using the DAGRank() macro defined in [RFC6550]). A value of 0 in this field indicates the limit is infinity. Orig SeqNo Sequence Number of OrigNode. See Section 6.1. Address Vector 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 Compr field. TargNode can join the RREQ instance at a Rank whose integer portion - is less than or equal to the MaxRank. Other nodes MUST NOT join a - RREQ instance if its own Rank would be equal to or higher than - MaxRank. A router MUST discard a received RREQ if the integer part - of the advertised Rank equals or exceeds the MaxRank limit. + is less than or equal to the RankLimit. Any other node MUST NOT join + a RREQ instance if its own Rank would be equal to or higher than + RankLimit. A router MUST discard a received RREQ if the integer part + of the advertised Rank equals or exceeds the RankLimit. 4.2. AODV-RPL RREP Option TargNode sets one of its IPv6 addresses in the DODAGID field of the RREP-DIO message. Exactly one RREP option MUST be present in a RREP- DIO message, otherwise the message MUST be dropped. TargNode supplies the following information in the RREP option: 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 | MaxRank | + | Option Type | Option Length |G|H|X| Compr | L | RankLimit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Shift |X X| | + | Delta |X X| | +-+-+-+-+-+-+-+-+ | | | | | | Address Vector (Optional, Variable Length) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Format for AODV-RPL RREP option @@ -411,29 +424,30 @@ Reserved; MUST be initialized to zero and ignored upon reception. Compr 4-bit unsigned integer. Same definition as in RREQ option. L 2-bit unsigned integer defined as in RREQ option. The lifetime of the RREP-Instance MUST be shorter than the lifetime of the RREQ- Instance to which it is paired. - MaxRank - Similarly to MaxRank in the RREQ message, this field indicates the - upper limit on the integer portion of the Rank. A value of 0 in - this field indicates the limit is infinity. + RankLimit + Similarly to RankLimit in the RREQ message, this field indicates + the upper limit on the integer portion of the Rank. A value of 0 + in this field indicates the limit is infinity. - Shift - 6-bit unsigned integer. This field is used to recover the - original RPLInstanceID (see Section 6.3.3); 0 indicates that the - original RPLInstanceID is used. + Delta + 6-bit unsigned integer. This field is used to recover the RREQ- + InstanceID (see Section 6.3.3); 0 indicates that the RREQ- + InstanceID has the same value as the RPLInstanceID of the RREP + message. X X Reserved; MUST be initialized to zero and ignored upon reception. Address Vector Only present when the H bit is set to 0. For an asymmetric route, the Address Vector represents the IPv6 addresses of the path through the network the RREP-DIO has passed. For a symmetric route, it is the Address Vector when the RREQ-DIO arrives at the TargNode, unchanged during the transmission to the OrigNode. @@ -631,46 +644,47 @@ different requirements to the same targets. Using the RPLInstanceID pairing mechanism (see Section 6.3.3), route replies (RREP-DIOs) for different RPLInstances can be generated. The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If the length of time specified by the L field has elapsed, the OrigNode MUST leave the DODAG and stop sending RREQ-DIOs in the related RPLInstance. 6.2. Receiving and Forwarding RREQ messages - 6.2.1. Step 1: RREQ reception and evaluation When a router X receives a RREQ message over a link from a neighbor - Y, X determines whether or not the RREQ is valid. If so, then X - determines whether the RREQ advertises a usable route to OrigNode, by - checking whether the link to Y can be used to tramsmit packets to - OrigNode. + Y, X first determines whether or not the RREQ is valid. If so, X + then determines whether or not it has sufficient resources available + to maintain the state needed to process an eventual RREP if the RREP + were to be received. If not, then X MUST 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 tramsmit packets to OrigNode. When H=0 in the incoming RREQ, the router MUST drop the RREQ-DIO if one of its addresses is present in the Address Vector. When H=1 in the incoming RREQ, the router MUST drop the RREQ message if 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 useful rank - (MaxUseRank). If the router has previously joined the RREQ-Instance - associated with the RREQ-DIO, then MaxUseRank 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, - MaxUseRank is set to be MaxRank. If OF cannot be satisfied (i.e., - the Rank evaluates to a value greater than MaxUseRank) the RREQ-DIO - MUST be dropped, and the following steps are not processed. - + (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 than MaxUsefulRank) the + RREQ-DIO MUST be dropped, and the following steps are not processed. Otherwise, the router MUST 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. 6.2.2. Step 2: TargNode and Intermediate Router determination After determining that a received RREQ provides a usable route to OrigNode, a router determines whether it is a TargNode, or a possible intermediate router between OrigNode and a TargNode, or both. The @@ -747,25 +761,25 @@ 6.2.5. Step 5: RREQ propagation at an Intermediate Router If the router is an intermediate router, then it transmits the RREQ- DIO to the multicast group all-RPL-nodes; if the H bit is set to 0, the intermediate router MUST append the address of its interface receiving the RREQ-DIO into the address vector. 6.2.6. Step 6: RREQ reception at TargNode - If the router is a TargNode and it was not already associated with - the RREQ-Instance, it prepares and transmits a RREP-DIO - (Section 6.3). If, on the other hand, TargNode was already - associated with the RREQ-Instance, it takes no further action and - does not send an RREP-DIO. + 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 transmits a RREP-DIO, possibly after waiting for + RREP_WAIT_TIME, as detailed in (Section 6.3). 6.3. Generating Route Reply (RREP) at TargNode When a TargNode receives a RREQ message over a link from a neighbor Y, TargNode first follows the procedures in Section 6.2. If the link to Y can be used to tramsmit packets to OrigNode, TargNode generates a RREP according to the steps below. Otherwise TargNode drops the RREQ and does not generate a RREP. If the L field is not 0, the TargNode MAY delay transmitting the @@ -817,33 +831,34 @@ there can be multiple AODV-RPL route discovery instances. So that OrigNode and Targnode can avoid any mismatch, they MUST pair the RREQ-Instance and the RREP-Instance in the same route discovery by using the RPLInstanceID. 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 operation which 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 original - RPLInstanceID of an already active RREP-Instance MUST NOT be used - again for assigning RPLInstanceID for the later RREP-Instance. - Reusing the same RPLInstanceID for two distinct DODAGs originated - with the same DODAGID (TargNode address) would prevent intermediate - routers to distinguish between these DODAGs (and their associated - Objective Functions). Instead, the RPLInstanceID MUST be replaced by - another value so that the two RREP-instances can be distinguished. - In RREP-DIO option, the Shift field of the RREP-DIO message(Figure 2) - indicates the shift to be applied to original RPLInstanceID to obtain - the replacement RPLInstanceID. When the new RPLInstanceID after - shifting exceeds 255, it rolls over starting at 0. For example, if - the original RPLInstanceID is 252, and shifted by 6, the new + RPLInstanceID for RREQ-Instance. In such cases, the RPLInstanceID of + an already active RREP-Instance MUST NOT be used again for assigning + RPLInstanceID for the later RREP-Instance. Reusing the same + RPLInstanceID for two distinct DODAGs originated with the same + DODAGID (TargNode address) would prevent intermediate routers from + distinguishing between these DODAGs (and their associated Objective + Functions). Instead, the RPLInstanceID MUST be replaced by another + value so that the two RREP-instances can be distinguished. In the + RREP-DIO option, the Delta field of the RREP-DIO message (Figure 2) + indicates the increment to be applied to the pre-existing + RPLInstanceID to obtain the value of the RPLInstanceID that is used + in the RREP-DIO message. When the new RPLInstanceID after + incrementation exceeds 255, it rolls over starting at 0. For + example, if the RREQ-InstanceID is 252, and incremented by 6, the new RPLInstanceID will be 2. Related operations can be found in Section 6.4. RPLInstanceID collisions do not occur across RREQ-DIOs; the DODAGID equals the OrigNode address and is sufficient to disambiguate between DODAGs. 6.4. Receiving and Forwarding Route Reply Upon receiving a RREP-DIO, a router which already belongs to the RREP-Instance SHOULD drop the DIO. Otherwise the router performs the steps in the following subsections. @@ -855,87 +870,88 @@ the remaining steps in this section. An Intermediate Router MUST discard a RREP if one of its addresses is present in the Address Vector, and does not execute the remaining steps in this section. If the S bit of the associated RREQ-Instance is set to 1, the router MUST proceed to Section 6.2.2. If the S-bit of the RREQ-Instance is set to 0, the router MUST determine whether the downward direction of the link (towards the TargNode) over which the RREP-DIO is received satisfies the Objective - Function, and the router's Rank would not exceed the MaxRank limit. - If so, the router joins the DODAG of the RREP-Instance. The router - that transmitted the received RREP-DIO is selected as the preferred + Function, and the router's Rank would not exceed the RankLimit. If + so, 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. 6.4.2. Step 2: OrigNode or Intermediate Router The router updates its stored value of the TargNode's sequence number according to the value provided in the ART option. The router next checks if one of its addresses is included in the ART Option. If so, this router is the OrigNode of the route discovery. Otherwise, it is an intermediate router. 6.4.3. Step 3: Build Route to TargNode If the H bit is set to 1, then the router (OrigNode or intermediate) MUST build a downward route entry towards TargNode which includes at least the following items: OrigNode Address, RPLInstanceID, TargNode Address as destination, Next Hop, Lifetime 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 entry MUST be the original RPLInstanceID - (after subtracting the Shift field value). The source address is - learned from the ART 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. The sequence number represents the freshness - of the route entry, and is copied from the Dest SeqNo field of the - ART option of the RREP-DIO. A route entry with same source and - destination address, same RPLInstanceID, but stale sequence number - (i.e., incoming sequence number is less than the currently stored - sequence number of the route entry), MUST be deleted. + RPLInstanceID in the route entry MUST 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 ART 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. The + sequence number represents the freshness of the route entry, and is + copied from the Dest SeqNo field of the ART option of the RREP-DIO. + A route entry with same source and destination address, same + RPLInstanceID, but stale sequence number (i.e., incoming sequence + number is less than the currently stored sequence number of the route + entry), MUST be deleted. 6.4.4. Step 4: RREP Propagation 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 router MUST include the address of the interface receiving the RREP-DIO into the address vector. If H=1, according to the last step 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 case of a symmetric route, the RREP-DIO message is unicast to the Next Hop according to the address vector in the RREP-DIO (H=0) or the - local route entry (H=1). Otherwise In case of an asymmetric route, + local route entry (H=1). Otherwise, in case of an asymmetric route, the intermediate router transmits the RREP-DIO to multicast group all-RPL-nodes. The RPLInstanceID in the transmitted RREP-DIO is the same as the value in the received RREP-DIO. 7. Gratuitous RREP In some cases, an Intermediate router that receives a RREQ-DIO message MAY transmit a "Gratuitous" RREP-DIO message back to OrigNode instead of continuing to multicast the RREQ-DIO towards TargNode. The intermediate router effectively builds the RREP-Instance on behalf of the actual TargNode. The G bit of the RREP option is provided to distinguish the Gratuitous RREP-DIO (G=1) sent by the Intermediate router from the RREP-DIO sent by TargNode (G=0). The gratuitous RREP-DIO MAY be sent out when an intermediate router receives a RREQ-DIO for a TargNode, and the router has a pair of downward and upward routes to the TargNode which also satisfy the Objective Function and for which the destination sequence number is - at least as large. + at least as large as the sequence number in the RREQ-DIO message. In case of source routing, the intermediate router MUST unicast the received RREQ-DIO to TargNode including the address vector between the OrigNode and the router. Thus the TargNode can have a complete upward route address vector from itself to the OrigNode. Then the router MUST include the address vector from the TargNode to the router itself in the gratuitous RREP-DIO to be transmitted. In case of hop-by-hop routing, the intermediate router MUST unicast the received RREQ-DIO to the Next Hop on the route. The Next Hop @@ -943,25 +959,26 @@ RPLInstanceID and DODAGID in the downward direction. The above process will happen recursively until the RREQ-DIO arrives at the TargNode. Then the TargNode MUST unicast recursively the RREP-DIO hop-by-hop to the intermediate router, and the routers along the route SHOULD build new route entries in the upward direction. Upon receiving the unicast RREP-DIO, the intermediate router sends the gratuitous RREP-DIO to the OrigNode as defined in Section 6.3. 8. Operation of Trickle Timer - The trickle timer operation to control RREQ-Instance/RREP-Instance - multicast uses [RFC6206] to control RREQ-DIO and RREP-DIO - transmissions. The Trickle control of these DIO transmissions follow - the procedures described in the Section 8.3 of [RFC6550] entitled - "DIO Transmission". + RREQ-Instance/RREP-Instance multicast uses trickle timer operations + [RFC6206] to control RREQ-DIO and RREP-DIO transmissions. The + Trickle control of these DIO transmissions follows the procedures + described in the Section 8.3 of [RFC6550] entitled "DIO + Transmission". If the route is symmetric, the RREP DIO does not need + the Trickle timer mechanism. 9. IANA Considerations Note to RFC editor: The sentence "The parenthesized numbers are only suggestions." is to be removed prior publication. A Subregistry in this section refers to a named sub-registry of the "Routing Protocol for Low Power and Lossy Networks (RPL)" registry. @@ -1194,26 +1212,53 @@ knowing the value of ETX from 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 a relationship in turn can be used to estimate ETX value at nodeA for link NodeB--->NodeA from the received RSSI from NodeB. Whenever nodeA determines that the link towards the nodeB is bi-directional asymmetric then the S bit is set to 0. Afterwards, the link from NodeA to Destination remains designated as asymmetric and the S bit remains set to 0. + Determination of asymmetry versus bidirectionality remains a topic of + lively discussion in the IETF. + Appendix B. Changelog Note to the RFC Editor: please remove this section before publication. -B.1. Changes from version 11 to version 12 +B.1. Changes from version 12 to version 13 + + * Changed name of "Shift" field to be the "Delta" field. + + * Specified that if a node does not have resources, it MUST drop the + RREQ. + + * Changed name of MaxUseRank to MaxUsefulRank. + + * Revised a sentence that was not clear about when a TargNode can + delay transmission of the RREP in response to a RREQ. + + * Provided advice about running AODV-RPL at same time as P2P-RPL or + native RPL. + + * Small reorganization and enlargement of the description of Trickle + time operation in Section 8. + + * Added definition for "RREQ-InstanceID" to Terminology section. + + * Specified that once a node leaves an RREQ-Instance, it MUST NOT + rejoin the same RREQ-Instance. + +B.2. Changes from version 11 to version 12 + * Defined RREP_WAIT_TIME for asymmetric as well as symmetric handling of RREP-DIO. * Clarifed link-local multicast transmission to use link-local multicast group all-RPL nodes. * Identified some security threats more explicitly. * Specified that the pairing between RREQ-DIO and RREP-DIO happens at OrigNode and TargNode. Intermediate routers do not necessarily @@ -1227,21 +1272,21 @@ Operation" (MOP == 4), instead of requesting the allocation of a new MOP. Clarified that there is no conflict with [RFC6997]. * Fixed several important typos and improved language in numerous places. * Reorganized the steps in the specification for handling RREQ and RREP at an intermediate router, to more closely follow the order of processing actions to be taken by the router. -B.2. Changes from version 10 to version 11 +B.3. Changes from version 10 to version 11 * Numerous editorial improvements. * Replace Floor((7+(Prefix Length))/8) by Ceil(Prefix Length/8) for simplicity and ease of understanding. * Use "L field" instead of "L bit" since L is a two-bit field. * Improved the procedures in section 6.2.1. @@ -1268,48 +1313,48 @@ * Added mandates for reserved fields, and replaces some ambiguous language phraseology by mandates. * Replaced "retransmit" terminology by more correct "propagate" terminology. * Added text about determining link symmetry near Figure 5. * Mandated checking the Address Vector to avoid routing loops. - * Improved specification for use of the Shift value in + * Improved specification for use of the Delta value in Section 6.3.3. * Corrected the wrong use of RREQ-Instance to be RREP-Instance. * Referred to Subregistry values instead of Registry values in Section 9. * Sharpened language in Section 10, eliminated misleading use of capitalization in the words "Security Configuration". * Added acknowledgements and contributors. -B.3. Changes from version 09 to version 10 +B.4. Changes from version 09 to version 10 * Changed the title for brevity and to remove acronyms. * Added "Note to the RFC Editor" in Section 9. * Expanded DAO and P2MP in Section 1. * Reclassified [RFC6998] and [RFC7416] as Informational. * SHOULD changed to MUST in Section 4.1 and Section 4.2. * Several editorial improvements and clarifications. -B.4. Changes from version 08 to version 09 +B.5. Changes from version 08 to version 09 * Removed section "Link State Determination" and put some of the relevant material into Section 5. * Cited security section of [RFC6550] as part of the RREP-DIO message description in Section 2. * SHOULD has been changed to MUST in Section 4.2. * Expanded the terms ETX and RSSI in Section 5. @@ -1322,21 +1367,21 @@ operation. * Appendix A has been mostly re-written to describe methods to determine whether or not the S bit should be set to 1. * For consistency, adjusted several mandates from SHOULD to MUST and from SHOULD NOT to MUST NOT. * Numerous editorial improvements and clarifications. -B.5. Changes from version 07 to version 08 +B.6. Changes from version 07 to version 08 * Instead of describing the need for routes to "fulfill the requirements", specify that routes need to "satisfy the Objective Function". * Removed all normative dependencies on [RFC6997] * Rewrote Section 10 to avoid duplication of language in cited specifications. @@ -1356,70 +1401,70 @@ * Specified behavior upon reception of a RREQ-DIO or RREP-DIO message for an already existing DODAGID (e.g, Section 6.4). * Fixed numerous language issues in IANA Considerations Section 9. * For consistency, adjusted several mandates from SHOULD to MUST and from SHOULD NOT to MUST NOT. * Numerous editorial improvements and clarifications. -B.6. Changes from version 06 to version 07 +B.7. Changes from version 06 to version 07 * Added definitions for all fields of the ART option (see Section 4.3). Modified definition of Prefix Length to prohibit Prefix Length values greater than 127. * Modified the language from [RFC6550] Target Option definition so that the trailing zero bits of the Prefix Length are no longer described as "reserved". * Reclassified [RFC3561] and [RFC6998] as Informative. * Added citation for [RFC8174] to Terminology section. -B.7. Changes from version 05 to version 06 +B.8. Changes from version 05 to version 06 * Added Security Considerations based on the security mechanisms defined in [RFC6550]. * Clarified the nature of improvements due to P2P route discovery versus bidirectional asymmetric route discovery. * Editorial improvements and corrections. -B.8. Changes from version 04 to version 05 +B.9. Changes from version 04 to version 05 * Add description for sequence number operations. * Extend the residence duration L in section 4.1. * Change AODV-RPL Target option to ART option. -B.9. Changes from version 03 to version 04 +B.10. Changes from version 03 to version 04 * Updated RREP option format. Remove the T bit in RREP option. * Using the same RPLInstanceID for RREQ and RREP, no need to update [RFC6550]. - * Explanation of Shift field in RREP. + * Explanation of Delta field in RREP. * Multiple target options handling during transmission. -B.10. Changes from version 02 to version 03 +B.11. Changes from version 02 to version 03 * Include the support for source routing. * Import some features from [RFC6997], e.g., choice between hop-by- hop and source routing, the L field which determines the duration - of residence in the DAG, MaxRank, etc. + of residence in the DAG, RankLimit, etc. * Define new target option for AODV-RPL, including the Destination Sequence Number in it. Move the TargNode address in RREQ option and the OrigNode address in RREP option into ADOV-RPL Target Option. * Support route discovery for multiple targets in one RREQ-DIO. * New RPLInstanceID pairing mechanism.