--- 1/draft-ietf-roll-aodv-rpl-08.txt 2021-02-02 15:14:16.014430859 -0800 +++ 2/draft-ietf-roll-aodv-rpl-09.txt 2021-02-02 15:14:16.178435145 -0800 @@ -1,26 +1,26 @@ ROLL S. Anamalamudi Internet-Draft SRM University-AP Intended status: Standards Track M. Zhang -Expires: November 8, 2020 Huawei Technologies +Expires: August 6, 2021 Huawei Technologies C. Perkins - Deep Blue Sky Networks + Lupin Lodge S.V.R.Anand Indian Institute of Science B. Liu Huawei Technologies - May 7, 2020 + February 2, 2021 - AODV based RPL Extensions for Supporting Asymmetric P2P Links in Low- - Power and Lossy Networks - draft-ietf-roll-aodv-rpl-08 + AODV based RPL Extensions for Supporting Asymmetric P2P Links in + Low-Power and Lossy Networks + draft-ietf-roll-aodv-rpl-09 Abstract Route discovery for symmetric and asymmetric Point-to-Point (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, in case some of the links between source and @@ -34,77 +34,78 @@ 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 November 8, 2020. + This Internet-Draft will expire on August 6, 2021. Copyright Notice - Copyright (c) 2020 IETF Trust and the persons identified as the + Copyright (c) 2021 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 5 + 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6 4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 6 4.1. AODV-RPL RREQ Option . . . . . . . . . . . . . . . . . . 6 4.2. AODV-RPL RREP Option . . . . . . . . . . . . . . . . . . 8 4.3. AODV-RPL Target Option . . . . . . . . . . . . . . . . . 10 5. Symmetric and Asymmetric Routes . . . . . . . . . . . . . . . 11 6. AODV-RPL Operation . . . . . . . . . . . . . . . . . . . . . 13 6.1. Route Request Generation . . . . . . . . . . . . . . . . 13 6.2. Receiving and Forwarding RREQ messages . . . . . . . . . 14 6.2.1. General Processing . . . . . . . . . . . . . . . . . 14 6.2.2. Additional Processing for Multiple Targets . . . . . 15 6.3. Generating Route Reply (RREP) at TargNode . . . . . . . . 16 6.3.1. RREP-DIO for Symmetric route . . . . . . . . . . . . 16 6.3.2. RREP-DIO for Asymmetric Route . . . . . . . . . . . . 16 6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 17 6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 17 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 19 8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 19 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 - 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 20 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 + 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 19 9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 20 10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 - 11. Link State Determination . . . . . . . . . . . . . . . . . . 21 - 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 - 12.1. Normative References . . . . . . . . . . . . . . . . . . 21 - 12.2. Informative References . . . . . . . . . . . . . . . . . 22 - Appendix A. Example: ETX/RSSI Values to select S bit . . . . . . 23 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 21 + 11.2. Informative References . . . . . . . . . . . . . . . . . 22 + Appendix A. Example: Using ETX/RSSI Values to determine value of + S bit . . . . . . . . . . . . . . . . . . . . . . . 23 Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 24 - B.1. Changes from version 07 to version 08 . . . . . . . . . . 24 - B.2. Changes from version 06 to version 07 . . . . . . . . . . 24 - B.3. Changes from version 05 to version 06 . . . . . . . . . . 25 - B.4. Changes from version 04 to version 05 . . . . . . . . . . 25 - B.5. Changes from version 03 to version 04 . . . . . . . . . . 25 - B.6. Changes from version 02 to version 03 . . . . . . . . . . 25 - Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 26 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 + B.1. Changes from version 08 to version 09 . . . . . . . . . . 24 + B.2. Changes from version 07 to version 08 . . . . . . . . . . 25 + B.3. Changes from version 06 to version 07 . . . . . . . . . . 26 + B.4. Changes from version 05 to version 06 . . . . . . . . . . 26 + B.5. Changes from version 04 to version 05 . . . . . . . . . . 26 + B.6. Changes from version 03 to version 04 . . . . . . . . . . 26 + B.7. Changes from version 02 to version 03 . . . . . . . . . . 27 + Appendix C. Contributors . . . . . . . . . . . . . . . . . . . . 27 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 1. Introduction RPL [RFC6550] (Routing Protocol for Low-Power and Lossy Networks) 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., Point-to-Point (P2P) traffic) data packets either have to traverse the root in non-storing mode, or @@ -118,27 +119,28 @@ route discovery is natural for the needs of peer-to-peer routing in RPL-based LLNs. AODV terminology has been adapted for use with AODV- RPL messages, namely RREQ for Route Request, and RREP for Route Reply. AODV-RPL currently omits some features compared to AODV -- in particular, flagging Route Errors, blacklisting unidirectional links, multihoming, and handling unnumbered interfaces. AODV-RPL reuses and provides a natural extension to the core RPL functionality to support routes with birectional asymmetric links. It retains RPL's DODAG formation, RPL Instance and the associated - Objective Function, trickle timers, and support for storing and non- - storing modes. AODV adds basic messages RREQ and RREP as part of RPL - DIO (DODAG Information Object) control messages, and does not utilize - the DAO message of RPL. AODV-RPL specifies a new MOP running in a - seperate instance dedicating to discover P2P routes, which may differ - from the P2MP routes discoverable by native RPL. AODV-RPL can be - operated whether or not native RPL is running otherwise. + Objective Function (defined in [RFC6551]), trickle timers, and + support for storing and non-storing modes. AODV adds basic messages + RREQ and RREP as part of RPL DIO (DODAG Information Object) control + messages, and does not utilize the DAO message of RPL. AODV-RPL + specifies a new MOP running in a separate instance dedicated to + discover P2P routes, which may differ from the P2MP routes + discoverable by native RPL. AODV-RPL can be operated whether or not + native RPL is running otherwise. 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 @@ -195,25 +197,27 @@ P2P Point-to-Point -- in other words, not constrained a priori to traverse a common ancestor. reactive routing Same as "on-demand" routing. RREQ-DIO message An AODV-RPL MOP 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]. RREP-DIO message An AODV-RPL MOP DIO message containing the RREP option. The RPLInstanceID in RREP-DIO is typically paired to the one in the - associated RREQ-DIO message. + associated RREQ-DIO message. 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. TargNode The IPv6 router (Target Node) for which OrigNode requires a route @@ -321,23 +325,21 @@ the OrigNode and the TargNode. Once the time is reached, a node MUST leave the DAG and stop sending or receiving any more DIOs for the temporary DODAG. * 0x00: No time limit imposed. * 0x01: 16 seconds * 0x02: 64 seconds * 0x03: 256 seconds L is independent from the route lifetime, which is defined in the - DODAG configuration option. 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. + DODAG configuration option. MaxRank 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 @@ -422,40 +424,40 @@ 4.3. AODV-RPL Target Option The AODV-RPL Target (ART) Option is based on the Target Option in core RPL [RFC6550]. The Flags field is replaced by the Destination Sequence Number of the TargNode and the Prefix Length field is reduced to 7 bits so that the value is limited to be no greater than 127. A RREQ-DIO message MUST carry at least one ART Option. A RREP-DIO message MUST carry exactly one ART Option. Otherwise, the message - SHOULD be dropped. + MUST be dropped. OrigNode can include multiple TargNode addresses via multiple AODV- RPL Target Options in the RREQ-DIO, for routes that share the same requirement on metrics. This reduces the cost to building only one DODAG. 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 |r|Prefix Length| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + | | Target Prefix / Address (Variable Length) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 3: Target option format for AODV-RPL MOP + Figure 3: ART Option format for AODV-RPL MOP Option Type TBD4 Option Length Length of the option in octets excluding the Type and Length fields Dest SeqNo @@ -477,28 +479,29 @@ The Prefix Length field contains the number of valid leading bits in the prefix. The length of the field is the least number of octets that can contain all of the bits of the Prefix, in other words Floor((7+(Prefix Length))/8) octets. The remaining bits in the Target Prefix / Address field after the prefix length (if any) MUST be set to zero on transmission and MUST be ignored on receipt. 5. Symmetric and Asymmetric Routes - In Figure 4 and Figure 5, BR is the Border Router, O is the OrigNode, - R is an intermediate router, and T is the TargNode. If the RREQ-DIO - arrives over an interface that is known to be symmetric, and the S - bit is set to 1, then it remains as 1, as illustrated in Figure 4. - If an intermediate router sends out RREQ-DIO with the S bit set to 1, - then all the one-hop links on the route from the OrigNode O to this - router meet the requirements of route discovery, and the route can be - used symmetrically. + Links are considered symmetric until additional information is + collected. In Figure 4 and Figure 5, BR is the Border Router, O is + the OrigNode, R is an intermediate router, and T is the TargNode. If + the RREQ-DIO arrives over an interface that is known to be symmetric, + and the S bit is set to 1, then it remains as 1, as illustrated in + Figure 4. If an intermediate router sends out RREQ-DIO with the S + bit set to 1, then all the one-hop links on the route from the + OrigNode O to this router meet the requirements of route discovery, + and the route can be used symmetrically. BR /----+----\ / | \ / | \ R R R _/ \ | / \ / \ | / \ / \ | / \ R -------- R --- R ----- R -------- R @@ -522,30 +525,36 @@ RREQ-DIO arrives over an interface that is not known to be symmetric, or is known to be asymmetric, the S bit is set to 0. If the S bit arrives already set to be '0', it is set to be '0' on retransmission (Figure 5). For an asymmetric route, there is at least one hop which doesn't satisfy the Objective Function. 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. The criteria used to determine whether or not each link is symmetric - is beyond the scope of the document, and may be implementation- - specific. For instance, intermediate routers can use local - information (e.g., bit rate, bandwidth, number of cells used in - 6tisch), a priori knowledge (e.g. link quality according to previous - communication) or use averaging techniques as appropriate to the - application. + is beyond the scope of the document. For instance, intermediate + routers can use local information (e.g., bit rate, bandwidth, number + of cells used in 6tisch), a priori knowledge (e.g. link quality + according to previous communication) or use averaging techniques as + appropriate to the application. Other link metric information can be + acquired before AODV-RPL operation, by executing evaluation + procedures; for instance test traffic can be generated between nodes + of the deployed network. During AODV-RPL operation, OAM techniques + for evaluating link state (see([RFC7548], [RFC7276], [co-ioam]) MAY + be used (at regular intervals appropriate for the LLN). The + evaluation procedures are out of scope for AODV-RPL. - Appendix A describes an example method using the ETX and RSSI to - estimate whether the link is symmetric in terms of link quality is - given in using an averaging technique. + Appendix A describes an example method using the upstream Expected + Number of Transmissions" (ETX) and downstream Received Signal + Strength Indicator (RSSI) to estimate whether the link is symmetric + in terms of link quality is given in using an averaging technique. BR /----+----\ / | \ / | \ R R R / \ | / \ / \ | / \ / \ | / \ R --------- R --- R ---- R --------- R @@ -584,21 +593,21 @@ conflicts with previously established routes. The sequence number is carried in the Orig SeqNo field of the RREQ option. The address in the ART Option can be a unicast IPv6 address or a prefix. The OrigNode can initiate the route discovery process for multiple targets simultaneously by including multiple ART Options, and within a RREQ-DIO the requirements for the routes to different TargNodes MUST be the same. OrigNode can maintain different RPLInstances to discover routes with - different requirements to the same targets. Using the InstanceID + 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 distinguished. The transmission of RREQ-DIO obeys the Trickle timer [RFC6206]. If the duration specified by the L bit has elapsed, the OrigNode MUST leave the DODAG and stop sending RREQ-DIOs in the related RPLInstance. 6.2. Receiving and Forwarding RREQ messages @@ -612,76 +621,75 @@ Step 1: If the S bit in the received RREQ-DIO is set to 1, the router MUST determine whether each direction of the link (by which the RREQ- DIO is received) satisfies the Objective Function. In case that the downward (i.e. towards the TargNode) direction of the link does not satisfy the Objective Function, the link can't be used symmetrically, thus the S bit of the RREQ-DIO to be sent out MUST be set as 0. If the S bit in the received RREQ-DIO is set to 0, - the router MUST only check into the upward direction (towards the + the router MUST determine into the upward direction (towards the OrigNode) of the link. If the upward direction of the link can satisfy the Objective - Function (defined in [RFC6551]), and the router's Rank would not - exceed the MaxUseRank limit, the router joins the DODAG of the - RREQ-Instance. The router that transmitted the received RREQ-DIO - is selected as the preferred parent. Otherwise, if the Objective - Function is not satisfied or the MaxUseRank limit is exceeded, the - router MUST discard the received RREQ-DIO and MUST NOT join the - DODAG. + Function, and the router's Rank would not exceed the MaxUseRank + limit, the router joins the DODAG of the RREQ-Instance. The + router that transmitted the received RREQ-DIO is selected as the + preferred parent. Otherwise, if the Objective Function is not + satisfied or the MaxUseRank limit is exceeded, the router MUST + discard the received RREQ-DIO and MUST NOT join the DODAG. Step 2: Then the router checks if one of its addresses is included in one of the ART Options. If so, this router is one of the TargNodes. Otherwise, it is an intermediate router. Step 3: If the H bit is set to 1, then the router (TargNode or intermediate) MUST build an upward route entry towards OrigNode - which MUST include at least the following items: Source Address, - InstanceID, Destination Address, Next Hop, Lifetime, and Sequence - Number. The Destination Address and the InstanceID respectively - can be learned from the DODAGID and the RPLInstanceID of the RREQ- - DIO, and the Source Address is the address used by the local - router to send data to the OrigNode. The Next Hop is the + which includes at least the following items: Source Address, + RPLInstanceID, Destination Address, Next Hop, Lifetime, and + Sequence Number. The Destination Address and the RPLInstanceID + respectively can be learned from the DODAGID and the RPLInstanceID + of the RREQ-DIO, and the Source Address is the address used by the + local router to send data to the OrigNode. The Next Hop is the preferred parent. The lifetime is set according to DODAG configuration (i.e., not the L bit) and can be extended when the route is actually used. The sequence number represents the freshness of the route entry, and it is copied from the Orig SeqNo field of the RREQ option. A route entry with the same source and - destination address, same InstanceID, but stale sequence number, - MUST be deleted. + destination address, same RPLInstanceID, but stale sequence + number, MUST be deleted. Step 4: If the router is an intermediate router, then it transmits a RREQ- DIO via link-local multicast; if the H bit is set to 0, the intermediate router MUST include the address of the interface - receiving the RREQ-DIO into the address vector.. Otherwise, if - the router (i.e., TargNode) was not already associated with the - RREQ-Instance, it prepares 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. + receiving the RREQ-DIO into the address vector. Otherwise, if the + router (i.e., TargNode) was not already associated with the RREQ- + Instance, it prepares 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. 6.2.2. Additional Processing for Multiple Targets If the OrigNode tries to reach multiple TargNodes in a single RREQ- Instance, one of the TargNodes can be an intermediate router to the others, therefore it MUST continue sending RREQ-DIO to reach other targets. In this case, before rebroadcasting the RREQ-DIO, a TargNode MUST delete the Target Option encapsulating its own address, so that downstream routers with higher Rank values do not try to - create a route to this TargetNode. + create a route to this TargNode. An intermediate router could receive several RREQ-DIOs from routers with lower Rank values in the same RREQ-Instance but have different lists of Target Options. When rebroadcasting the RREQ-DIO, the intersection of these lists MUST be included. For example, suppose two RREQ-DIOs are received with the same RPLInstance and OrigNode. Suppose further that the first RREQ has (T1, T2) as the targets, and the second one has (T2, T4) as targets. Then only T2 needs to be included in the generated RREQ-DIO. If the intersection is empty, it @@ -749,90 +757,87 @@ When preparing the RREP-DIO, a TargNode could find the RPLInstanceID to be used for the RREP-Instance is already occupied by another RPL Instance from an earlier route discovery operation which is still active. In other words, it might happen that two distinct OrigNodes need routes to the same TargNode, and they happen to use the same RPLInstanceID for RREQ-Instance. In this case, the occupied RPLInstanceID MUST NOT be used again. Then the second RPLInstanceID MUST be shifted into another integer so that the two RREP-instances can be distinguished. In RREP option, the Shift field indicates the shift to be applied to original RPLInstanceID. When the new - InstanceID after shifting exceeds 63, it rolls over starting at 0. - For example, the original InstanceID is 60, and shifted by 6, the new - InstanceID will be 2. Related operations can be found in + RPLInstanceID after shifting exceeds 63, it rolls over starting at 0. + For example, the original RPLInstanceID is 60, and shifted by 6, the + new RPLInstanceID will be 2. Related operations can be found in Section 6.4. 6.4. Receiving and Forwarding Route Reply Upon receiving a RREP-DIO, a router which does not belong to the RREQ-Instance goes through the following steps: Step 1: If the S bit is set to 1, the router MUST proceed to step 2. - If the S bit of the RREP-DIO is set to 0, the router MUST check - the downward direction of the link (towards the TargNode) over - which the RREP-DIO is received. If the downward direction of the - link can satisfy the Objective Function, and the router's Rank - would not exceed the MaxRank limit, 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. + If the S bit of the RREP-DIO 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 parent. Afterwards, other RREP-DIO + messages can be received. If the Objective Function is not satisfied, the router MUST NOT join the DODAG; the router MUST discard the RREQ-DIO, and does not execute the remaining steps in this section. Step 2: 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. Step 3: If the H bit is set to 1, then the router (OrigNode or - intermediate) MUST build a downward route entry. The route entry - MUST include at least the following items: OrigNode Address, - InstanceID, TargNode Address as destination, Next Hop, Lifetime + 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 RREQ-Instance. The InstanceID in the route entry + the DODAG of RREQ-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 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 InstanceID, - but stale sequence number, SHOULD be deleted. - - If the H bit is set to 0, for an asymmetric route, an intermediate - router MUST include the address of the interface receiving the - RREP-DIO into the address vector; for a symmetric route, there is - nothing to do in this step. + lifetime is set according to DODAG configuration (i.e., not the L + bit) 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, MUST be deleted. Step 4: 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, - in case of an asymmetric route, the intermediate router transmits - the RREP-DIO via link-local multicast. 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). The RPLInstanceID in the transmitted RREP-DIO is the - same as the value in the received RREP-DIO. The local knowledge - for the TargNode's sequence number SHOULD be updated. + in case of an asymmetric route, the intermediate router MUST + include the address of the interface receiving the RREP-DIO into + the address vector, and then transmit the RREP-DIO via link-local + multicast. 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). The RPLInstanceID + in the transmitted RREP-DIO is the same as the value in the + received RREP-DIO. The local knowledge for the TargNode's + sequence number SHOULD be updated. Upon receiving a RREP-DIO, a router which already belongs to the RREQ-Instance SHOULD drop the 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 @@ -870,114 +875,97 @@ transmissions. The Trickle control of these DIO transmissions follow the procedures described in the Section 8.3 of [RFC6550] entitled "DIO Transmission". 9. IANA Considerations 9.1. New Mode of Operation: AODV-RPL IANA is asked to assign a new Mode of Operation, named "AODV-RPL" for Point-to-Point(P2P) hop-by-hop routing from the "Mode of Operation" - Registry [RFC6550]. + Registry. The parenthesized number 5 is only a suggestion. +-------------+---------------+---------------+ | Value | Description | Reference | +-------------+---------------+---------------+ | TBD1 (5) | AODV-RPL | This document | +-------------+---------------+---------------+ Figure 6: Mode of Operation 9.2. AODV-RPL Options: RREQ, RREP, and Target IANA is asked to assign three new AODV-RPL options "RREQ", "RREP" and "ART", as described in Figure 7 from the "RPL Control Message - Options" Registry [RFC6550]. + Options" Registry. The parenthesized numbers are only suggestions. +-------------+------------------------+---------------+ | Value | Meaning | Reference | +-------------+------------------------+---------------+ - | TBD2 (0x0A) | RREQ Option | This document | + | TBD2 (0x0B) | RREQ Option | This document | +-------------+------------------------+---------------+ - | TBD3 (0x0B) | RREP Option | This document | + | TBD3 (0x0C) | RREP Option | This document | +-------------+------------------------+---------------+ - | TBD4 (0x0C) | ART Option | This document | + | TBD4 (0x0D) | ART Option | This document | +-------------+------------------------+---------------+ Figure 7: AODV-RPL Options 10. Security Considerations In general, the security considerations for the operation of AODV-RPL are similar to those for the operation of RPL (as described in Section 19 of the RPL specification [RFC6550]). Sections 6.1 and 10 of [RFC6550] describe RPL's security framework, which provides data confidentiality, authentication, replay protection, and delay - protection services. + protection services. Additional analysis for the security threats to + RPL can be found in [RFC7416]. 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, 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 a secure P2P-RPL route discovery. 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 bogus 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. In this type of scenario, RPL's - authenticated mode of operation, where a node can obtain the key to - use for a P2P-RPL route discovery only after proper authentication, - SHOULD be used. - - When RREQ-DIO message uses source routing option with 'H' set to 0, - some of the security concerns that led to the deprecation of Type 0 - routing headers [RFC5095] may apply. To avoid the possibility of a - RREP-DIO message traveling in a routing loop, if one of its addresses - are present as part of the Source Route listed inside the message, - the Intermediate Router MUST NOT forward the message. - -11. Link State Determination + preinstalled mode of operation, where the key to use for a P2P-RPL + route discovery is preinstalled, SHOULD be used. If a future IETF + document specifies the authenticated mode of operation as described + in [RFC6550], then future AODV-RPL implementations SHOULD use the + authenticated mode of operation. - This document specifies that links are considered symmetric until - additional information is collected. Other link metric information - can be acquired before AODV-RPL operation, by executing evaluation - procedures; for instance test traffic can be generated between nodes - of the deployed network. During AODV-RPL operation, OAM techniques - for evaluating link state (see([RFC7548], [RFC7276], [co-ioam]) MAY - be used (at regular intervals appropriate for the LLN). The - evaluation procedures are out of scope for AODV-RPL. + When a RREQ-DIO message uses the source routing option by setting the + H bit to 0, a rogue router may populate the Address Vector field with + a set of addresses that may result in the RREP-DIO traveling in a + routing loop. The TargNode MUST NOT generate a RREP if one of its + addresses is present in the Address Vector. An Intermediate Router + MUST NOT forward a RREP if one of its addresses is present in the + Address Vector. -12. References +11. References -12.1. Normative References +11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . - [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- - Demand Distance Vector (AODV) Routing", RFC 3561, - DOI 10.17487/RFC3561, July 2003, - . - - [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation - of Type 0 Routing Headers in IPv6", RFC 5095, - DOI 10.17487/RFC5095, December 2007, - . - [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206, March 2011, . [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. Alexander, "RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks", RFC 6550, DOI 10.17487/RFC6550, March 2012, . @@ -987,188 +975,268 @@ in Low-Power and Lossy Networks", RFC 6551, DOI 10.17487/RFC6551, March 2012, . [RFC6998] Goyal, M., Ed., Baccelli, E., Brandt, A., and J. Martocci, "A Mechanism to Measure the Routing Metrics along a Point- to-Point Route in a Low-Power and Lossy Network", RFC 6998, DOI 10.17487/RFC6998, August 2013, . + [RFC7416] Tsao, T., Alexander, R., Dohler, M., Daza, V., Lozano, A., + and M. Richardson, Ed., "A Security Threat Analysis for + the Routing Protocol for Low-Power and Lossy Networks + (RPLs)", RFC 7416, DOI 10.17487/RFC7416, January 2015, + . + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . -12.2. Informative References +11.2. Informative References - [co-ioam] Ballamajalu, Rashmi., S.V.R., Anand., and Malati. Hegde, + [co-ioam] Ballamajalu, Rashmi., S.V.R., Anand., and Malati 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) pp.573-576, Jan 2018. + [contiki] Contiki contributors, "The Contiki Open Source OS for the + Internet of Things (Contiki Version 2.7)", Nov 2013, + . + + [Contiki-ng] + Contiki-NG contributors, "Contiki-NG: The OS for Next + Generation IoT Devices (Contiki-NG Version 4.6)", Dec + 2020, . + + [cooja] Contiki/Cooja contributors, "Cooja Simulator for Wireless + Sensor Networks (Contiki/Cooja Version 2.7)", Nov 2013, + . + + [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- + Demand Distance Vector (AODV) Routing", RFC 3561, + DOI 10.17487/RFC3561, July 2003, + . + [RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and J. Martocci, "Reactive Discovery of Point-to-Point Routes in Low-Power and Lossy Networks", RFC 6997, DOI 10.17487/RFC6997, August 2013, . [RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y. Weingarten, "An Overview of Operations, Administration, and Maintenance (OAM) Tools", RFC 7276, DOI 10.17487/RFC7276, June 2014, . [RFC7548] Ersue, M., Ed., Romascanu, D., Schoenwaelder, J., and A. Sehgal, "Management of Networks with Constrained Devices: Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015, . -Appendix A. Example: ETX/RSSI Values to select S bit +Appendix A. Example: Using ETX/RSSI Values to determine value of S bit The combination of Received Signal Strength Indication(downstream) (RSSI) and Expected Number of Transmissions(upstream)" (ETX) has been tested to determine whether a link is symmetric or asymmetric at - intermediate nodes. ETX and RSSI values may be used in conjunction - as explained below: + intermediate nodes. We present two methods to obtain an ETX value + from RSSI measurement. + + Method 1: In the first method, we constructed a table measuring RSSI + vs ETX using the Cooja simulation [cooja] setup in the Contiki OS + environment[contiki]. We used Contiki-2.7 running 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 certain pre-defined + 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, it is highly + recommended to conduct physical radio measurement experiments, in + general. 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 + module which is part of RPL Objective Function implementation. + Since ETX value is reflective of the extent of pakcet drops, it + allowed us to prepare a useful ETX vs RSSI table. ETX versus RSSI + values obtained in this way may be used as explained below: Source---------->NodeA---------->NodeB------->Destination Figure 8: Communication link from Source to Destination +-------------------------+----------------------------------------+ | RSSI at NodeA for NodeB | Expected ETX at NodeA for NodeB->NodeA | +-------------------------+----------------------------------------+ | > -60 | 150 | | -70 to -60 | 192 | | -80 to -70 | 226 | | -90 to -80 | 662 | - | -100 to -90 | 993 | + | -100 to -90 | 3840 | +-------------------------+----------------------------------------+ Table 1: Selection of S bit based on Expected ETX value + Method 2: One could also make use of the function + guess_etx_from_rssi() defined in the 6LoWPAN/RPL protocol stack of + Contiki-ng OS [Contiki-ng] to obtain RSSI-ETX mapping. This + function outputs ETX value ranging between 128 and 3840 for -60 <= + rssi <= -89. The function description is beyond the scope of this + document. + 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 of NodeA->NodeB and NodeB->NodeA (see Figure 8) 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 of NodeA -> NodeB but it has no direct way of 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. Later on, the link from NodeA to Destination is asymmetric - with S bit remains set to 0. + to 0. Afterwards, the link from NodeA to Destination remains + designated as asymmetric and the S bit remains set to 0. Appendix B. Changelog Note to the RFC Editor: please remove this section before publication. -B.1. Changes from version 07 to version 08 +B.1. Changes from version 08 to version 09 + + o Removed section "Link State Determination" and put some of the + relevant material into Section 5. + + o Cited security section of [RFC6550] as part of the RREP-DIO + message description in Section 2. + + o SHOULD has been changed to MUST in Section 4.2. + + o Expanded the terms ETX and RSSI in Section 5. + + o Section 6.4 has been expanded to provide a more precise + explanation of the handling of route reply. + + o Added [RFC7416] in the Security Considerations (Section 10) for + RPL security threats. Cited [RFC6550] for authenticated mode of + operation. + + o Appendix A has been mostly re-written to describe methods to + determine whether or not the 'S' bit should be set to 1. + + o For consistency, adjusted several mandates from SHOULD to MUST and + from SHOULD NOT to MUST NOT. + + o Numerous editorial improvements and clarifications. + +B.2. Changes from version 07 to version 08 o Instead of describing the need for routes to "fulfill the requirements", specify that routes need to "satisfy the Objective Function". o Removed all normative dependencies on [RFC6997] o Rewrote Section 10 to avoid duplication of language in cited specifications. - o Added Section 11 with text and citations to more fully describe - how implementations determine whether links are symmetric. + o Added a new section "Link State Determination" with text and + citations to more fully describe how implementations determine + whether links are symmetric. o Modified text comparing AODV-RPL to other protocols to emphasize the need for AODV-RPL instead of the problems with the other protocols. o Clarified that AODV-RPL uses some of the base RPL specification but does not require an instance of RPL to run. o Improved capitalization, quotation, and spelling variations. o Specified behavior upon reception of a RREQ-DIO or RREP-DIO message for an already existing DODAGID (e.g, Section 6.4). o Fixed numerous language issues in IANA Considerations Section 9. o For consistency, adjusted several mandates from SHOULD to MUST and from SHOULD NOT to MUST NOT. - o Numerous editorial improvements and clarificaions. + o Numerous editorial improvements and clarifications. -B.2. Changes from version 06 to version 07 +B.3. Changes from version 06 to version 07 o 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. o Modified the language from [RFC6550] Target Option definition so that the trailing zero bits of the Prefix Length are no longer described as "reserved". o Reclassified [RFC3561] and [RFC6998] as Informative. o Added citation for [RFC8174] to Terminology section. -B.3. Changes from version 05 to version 06 +B.4. Changes from version 05 to version 06 o Added Security Considerations based on the security mechanisms defined in [RFC6550]. o Clarified the nature of improvements due to P2P route discovery versus bidirectional asymmetric route discovery. o Editorial improvements and corrections. -B.4. Changes from version 04 to version 05 +B.5. Changes from version 04 to version 05 o Add description for sequence number operations. o Extend the residence duration L in section 4.1. o Change AODV-RPL Target option to ART option. -B.5. Changes from version 03 to version 04 +B.6. Changes from version 03 to version 04 o Updated RREP option format. Remove the T bit in RREP option. o Using the same RPLInstanceID for RREQ and RREP, no need to update [RFC6550]. o Explanation of Shift field in RREP. o Multiple target options handling during transmission. -B.6. Changes from version 02 to version 03 +B.7. Changes from version 02 to version 03 o Include the support for source routing. o Import some features from [RFC6997], e.g., choice between hop-by- hop and source routing, the L bit which determines the duration of residence in the DAG, MaxRank, etc. o 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. o Support route discovery for multiple targets in one RREQ-DIO. - o New InstanceID pairing mechanism. + o New RPLInstanceID pairing mechanism. Appendix C. Contributors Abdur Rashid Sangi Huaiyin Institute of Technology No.89 North Beijing Road, Qinghe District Huaian 223001 P.R. China Email: sangi_bahrian@yahoo.com @@ -1182,31 +1250,31 @@ Email: satishnaidu80@gmail.com Mingui Zhang Huawei Technologies No. 156 Beiqing Rd. Haidian District Beijing 100095 China Email: zhangmingui@huawei.com - Charles E. Perkins - Deep Blue Sky Networks + Lupin Lodge Saratoga 95070 United States Email: charliep@computer.org + S.V.R Anand Indian Institute of Science Bangalore 560012 India - Email: anand@ece.iisc.ernet.in + Email: anandsvr@iisc.ac.in Bing Liu Huawei Technologies No. 156 Beiqing Rd. Haidian District Beijing 100095 China Email: remy.liubing@huawei.com