--- 1/draft-ietf-roll-aodv-rpl-07.txt 2020-05-07 10:13:56.900291254 -0700 +++ 2/draft-ietf-roll-aodv-rpl-08.txt 2020-05-07 10:13:56.956292680 -0700 @@ -1,198 +1,165 @@ ROLL S. Anamalamudi Internet-Draft SRM University-AP Intended status: Standards Track M. Zhang -Expires: October 14, 2019 Huawei Technologies +Expires: November 8, 2020 Huawei Technologies C. Perkins - Futurewei + Deep Blue Sky Networks S.V.R.Anand Indian Institute of Science B. Liu Huawei Technologies - April 12, 2019 + May 7, 2020 - Asymmetric AODV-P2P-RPL in Low-Power and Lossy Networks (LLNs) - draft-ietf-roll-aodv-rpl-07 + AODV based RPL Extensions for Supporting Asymmetric P2P Links in Low- + Power and Lossy Networks + draft-ietf-roll-aodv-rpl-08 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. Paired Instances are used to construct directional paths, - in case some of the links between source and target node are - asymmetric. + protocol (AODV-RPL). Paired Instances are used to construct + directional paths, in case some of the links between source and + target node are asymmetric. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 October 14, 2019. + This Internet-Draft will expire on November 8, 2020. Copyright Notice - Copyright (c) 2019 IETF Trust and the persons identified as the + Copyright (c) 2020 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 6 - 4. AODV-RPL DIO Options . . . . . . . . . . . . . . . . . . . . 7 - 4.1. AODV-RPL DIO RREQ Option . . . . . . . . . . . . . . . . 7 - 4.2. AODV-RPL DIO RREP Option . . . . . . . . . . . . . . . . 9 - 4.3. AODV-RPL DIO Target Option . . . . . . . . . . . . . . . 10 + 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 3. Overview of AODV-RPL . . . . . . . . . . . . . . . . . . . . 5 + 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 . . . . . . . . . . . . . . . . 16 + 6.3.3. RPLInstanceID Pairing . . . . . . . . . . . . . . . . 17 6.4. Receiving and Forwarding Route Reply . . . . . . . . . . 17 - 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 18 + 7. Gratuitous RREP . . . . . . . . . . . . . . . . . . . . . . . 19 8. Operation of Trickle Timer . . . . . . . . . . . . . . . . . 19 - 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 - 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 19 - 9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 19 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 + 9.1. New Mode of Operation: AODV-RPL . . . . . . . . . . . . . 20 + 9.2. AODV-RPL Options: RREQ, RREP, and Target . . . . . . . . 20 10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 - 11. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 21 - 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 - 13.1. Normative References . . . . . . . . . . . . . . . . . . 21 - 13.2. Informative References . . . . . . . . . . . . . . . . . 22 + 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 Appendix B. Changelog . . . . . . . . . . . . . . . . . . . . . 24 - B.1. Changes from version 06 to version 07 . . . . . . . . . . 24 - B.2. Changes from version 05 to version 06 . . . . . . . . . . 24 - B.3. Changes from version 04 to version 05 . . . . . . . . . . 24 - B.4. Changes from version 03 to version 04 . . . . . . . . . . 24 - B.5. Changes from version 02 to version 03 . . . . . . . . . . 25 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 + 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 1. Introduction - RPL[RFC6550] (Routing Protocol for LLNs (Low-Power and Lossy - Networks)) is a 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 traverse a common ancestor in storing mode. Such - P2P traffic is thereby likely to traverse longer routes and may - suffer severe congestion near the DAG root (for more information see - [RFC6997], [RFC6998]). - - To discover better paths for P2P traffic flows in RPL, P2P-RPL - [RFC6997] specifies a temporary DODAG where the source acts as a - temporary root. The source initiates DIOs encapsulating the P2P - Route Discovery option (P2P-RDO) with an address vector for both hop- - by-hop mode (H=1) and source routing mode (H=0). Subsequently, each - intermediate router adds its IP address and multicasts the P2P mode - DIOs, until the message reaches the Target Node, which then sends the - "Discovery Reply" object. P2P-RPL is efficient for source routing, - but much less efficient for hop-by-hop routing due to the extra - address vector overhead. However, for symmetric links, when the P2P - mode DIO message is being multicast from the source hop-by-hop, - receiving nodes can infer a next hop towards the source. When the - Target Node subsequently replies to the source along the established - forward route, receiving nodes determine the next hop towards the - Target Node. For hop-by-hop routes (H=1) over symmetric links, this - would allow efficient use of routing tables for P2P-RDO messages - instead of the "Address Vector". - - RPL and P2P-RPL both specify the use of a single DODAG in networks of - symmetric links, where the two directions of a link MUST both satisfy - the constraints of the objective function. This disallows the use of - asymmetric links which are qualified in one direction. But, - application-specific routing requirements as defined in IETF ROLL - Working Group [RFC5548], [RFC5673], [RFC5826] and [RFC5867] may be - satisfied by routing paths using bidirectional asymmetric links. For - this purpose, [I-D.thubert-roll-asymlink] described bidirectional - asymmetric links for RPL [RFC6550] with Paired DODAGs, for which the - DAG root (DODAGID) is common for two Instances. This can satisfy - application-specific routing requirements for bidirectional - asymmetric links in core RPL [RFC6550]. Using P2P-RPL twice with - Paired DODAGs, on the other hand, requires two roots: one for the - source and another for the target node due to temporary DODAG - formation. For networks composed of bidirectional asymmetric links - (see Section 5), AODV-RPL specifies P2P route discovery, utilizing - RPL with a new MoP. AODV-RPL makes use of two multicast messages to - discover possibly asymmetric routes. This provides higher route - diversity and can find suitable routes that might otherwise go - undetected by RPL. AODV-RPL eliminates the need for address vector - overhead in hop-by-hop mode. This significantly reduces the control - packet size, which is important for Constrained LLN networks. Both - discovered routes (upward and downward) meet the application specific - metrics and constraints that are defined in the Objective Function - for each Instance [RFC6552]. On the other hand, the point-to-point - nature of routes discovered by AODV-RPL can reduce interference near - the root nodes and also provide routes with fewer hops, likely - improving performance in the network. + 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 + traverse a common ancestor in storing mode. Such P2P traffic is + thereby likely to traverse longer routes and may suffer severe + congestion near the DAG root (for more information see [RFC6997], + [RFC6998]). The route discovery process in AODV-RPL is modeled on the analogous procedure specified in AODV [RFC3561]. The on-demand nature of AODV 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. + 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 - [RFC2119], [RFC8174]. This document uses the following terms: + "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 Ad Hoc On-demand Distance Vector Routing[RFC3561]. AODV-RPL Instance Either the RREQ-Instance or RREP-Instance Asymmetric Route 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 fulfills the constraints - in route discovery. + only one direction of the series of links satisfies the Objective + Function during route discovery. 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 @@ -226,25 +193,25 @@ and TargNode. 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 + An AODV-RPL MOP DIO message containing the RREQ option. The RPLInstanceID in RREQ-DIO is assigned locally by the OrigNode. RREP-DIO message - An AODV-RPL MoP DIO message containing the RREP option. The + 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. 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. @@ -260,73 +227,76 @@ ART option AODV-RPL Target option: a target option defined in this document. 3. Overview of AODV-RPL With AODV-RPL, routes from OrigNode to TargNode within the LLN network are established "on-demand". In other words, the route discovery mechanism in AODV-RPL is invoked reactively when OrigNode has data for delivery to the TargNode but existing routes do not - satisfy the application's requirements. The routes discovered by - AODV-RPL are not constrained to traverse a common ancestor. Unlike - RPL [RFC6550] and P2P-RPL [RFC6997], 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 to TargNode, and another from TargNode to OrigNode. - When possible, AODV-RPL also enables symmetric route discovery along - Paired DODAGs (see Section 5). + satisfy the application's requirements. AODV-RPL is thus functional + without requiring the use of RPL or any other routing protocol. + + 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 + to TargNode, and another from TargNode to OrigNode. When possible, + AODV-RPL also enables symmetric route discovery along Paired DODAGs + (see Section 5). In AODV-RPL, routes are discovered by first forming a temporary DAG rooted at the OrigNode. Paired DODAGs (Instances) are constructed - according to the AODV-RPL Mode of Operation (MoP) during route + according to the AODV-RPL Mode of Operation (MOP) 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 Paired DODAGs based on - the rank as calculated from the DIO message. Henceforth in this + the Rank as calculated from the DIO message. Henceforth in this document, the RREQ-DIO message means the AODV-RPL mode DIO message from OrigNode to TargNode, containing the RREQ option (see Section 4.1). Similarly, the RREP-DIO message means the AODV-RPL mode DIO message from TargNode to OrigNode, containing the RREP option (see 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 DIO RREQ Option +4.1. AODV-RPL RREQ Option OrigNode sets its IPv6 address in the DODAGID field of the RREQ-DIO - message. A RREQ-DIO message MUST carry exactly one RREQ option. + message. A RREQ-DIO message MUST carry exactly one RREQ option, + otherwise it SHOULD 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Type | Option Length |S|H|X| Compr | L | MaxRank | + | Option Type | Option Length |S|H|X| Compr | L | MaxRank | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Orig SeqNo | | +-+-+-+-+-+-+-+-+ | | | | | | Address Vector (Optional, Variable Length) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 1: DIO RREQ option format for AODV-RPL MoP + Figure 1: Format for AODV-RPL RREQ Option OrigNode supplies the following information in the RREQ option: - Type - The type assigned to the RREQ option (see Section 9.2). + Option Type + TBD2 Option Length The length of the option in octets, excluding the Type and Length fields. Variable due to the presence of the address vector and the number of octets elided according to the Compr value. S Symmetric bit indicating a symmetric route from the OrigNode to the router transmitting this RREQ-DIO. @@ -339,162 +309,156 @@ Reserved. Compr 4-bit unsigned integer. Number of prefix octets that are elided from 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 field MUST be set to zero and ignored upon reception. L - 2-bit unsigned integer determining the duration that a node is able to belong to the temporary DAG in RREQ-Instance, including 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. The definition for the "L" bit is similar to - that found in [RFC6997], except that the values are adjusted to - enable arbitrarily long route lifetime. + 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 DAG expires. + after the node no longer maintains DAG connectivity or messaging. MaxRank This field indicates the upper limit on the integer portion of the - rank (calculated using the DAGRank() macro defined in [RFC6550]). + 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, defined similarly as in AODV - [RFC3561]. + 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. + 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. - A node MUST NOT join a RREQ instance if its own rank would equal to - or higher than MaxRank. Targnode can join the RREQ instance at a - rank whose integer portion is equal to the MaxRank. A router MUST - discard a received RREQ if the integer part of the advertised rank - equals or exceeds the MaxRank limit. This definition of MaxRank is - the same as that found in [RFC6997]. + TargNode can join the RREQ instance at a Rank whose integer portion + is 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. -4.2. AODV-RPL DIO RREP Option +4.2. AODV-RPL RREP Option TargNode sets its IPv6 address in the DODAGID field of the RREP-DIO - message. A RREP-DIO message MUST carry exactly one RREP option. - TargNode supplies the following information in the RREP option: + message. A RREP-DIO message MUST carry exactly one RREP option, + otherwise the message SHOULD 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Type | Option Length |G|H|X| Compr | L | MaxRank | + | Option Type | Option Length |G|H|X| Compr | L | MaxRank | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Shift |Rsv| | +-+-+-+-+-+-+-+-+ | | | | | | Address Vector (Optional, Variable Length) | . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Figure 2: DIO RREP option format for AODV-RPL MoP + Figure 2: Format for AODV-RPL RREP option - Type - The type assigned to the RREP option (see Section 9.2) + Option Type + TBD3 Option Length The length of the option in octets, excluding the Type and Length fields. Variable due to the presence of the address vector and the number of octets elided according to the Compr value. G Gratuitous route (see Section 7). H Requests either source routing (H=0) or hop-by-hop (H=1) for the - downstream route. It MUST be set to be the same as the 'H' bit in + downstream route. It MUST be set to be the same as the H bit in RREQ option. X Reserved. Compr 4-bit unsigned integer. Same definition as in RREQ option. L 2-bit unsigned integer defined as in RREQ option. 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 + 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 InstanceID (see Section 6.3.3); 0 indicates that the - original InstanceID is used. + original RPLInstanceID (see Section 6.3.3); 0 indicates that the + original RPLInstanceID is used. Rsv 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 - route that 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. + Only present when the H bit is set to 0. For an asymmetric route, + the Address Vector represents the IPv6 addresses of the route that + 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. -4.3. AODV-RPL DIO Target Option +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. + message MUST carry exactly one ART Option. Otherwise, the message + SHOULD be dropped. OrigNode can include multiple TargNode addresses via multiple AODV- RPL Target Options in the RREQ-DIO, for routes that share the same - constraints. This reduces the cost to building only one DODAG. - Furthermore, a single Target Option can be used for different - TargNode addresses if they share the same prefix; in that case the - use of the destination sequence number is not defined in this - document. + 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Type | Option Length | Dest SeqNo |r|Prefix Length| + | 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: Target option format for AODV-RPL MOP - Type - The type assigned to the ART Option + Option Type + TBD4 Option Length Length of the option in octets excluding the Type and Length fields Dest SeqNo In RREQ-DIO, if nonzero, it is the last known Sequence Number for TargNode for which a route is desired. In RREP-DIO, it is the destination sequence number associated to the route. @@ -504,34 +468,37 @@ by the sender and MUST be ignored by the receiver. Prefix Length 7-bit unsigned integer. Number of valid leading bits in the IPv6 Prefix. If Prefix Length is 0, then the value in the Target Prefix / Address field represents an IPv6 address, not a prefix. Target Prefix / Address (variable-length field) An IPv6 destination address or prefix. The Prefix Length field contains the number of valid leading bits - in the prefix. The 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. + 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' + 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. + 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 @@ -542,35 +509,35 @@ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ / \ R ----- R ----------- R ----- R ----- R ----- R ---- R----- R >---- RREQ-Instance (Control: O-->T; Data: T-->O) -------> <---- RREP-Instance (Control: T-->O; Data: O-->T) -------< Figure 4: AODV-RPL with Symmetric Paired Instances - Upon receiving a RREQ-DIO with the 'S' bit set to 1, a node - determines whether this one-hop link can be used symmetrically, i.e., - both the two directions meet the requirements of data transmission. - If the RREQ-DIO arrives over an interface that is not known to be - symmetric, or is known to be asymmetric, the 'S' bit is set to 0. If - the 'S' bit arrives already set to be '0', it is set to be '0' on - retransmission (Figure 5). Therefore, for asymmetric route, there is - at least one hop which doesn't fulfill the constraints in the two - directions. Based on the 'S' bit received in RREQ-DIO, the TargNode - T determines whether or not the route is symmetric before - transmitting the RREP-DIO message upstream towards the OrigNode O. + Upon receiving a RREQ-DIO with the S bit set to 1, a node determines + whether this one-hop link can be used symmetrically, i.e., both the + two directions meet the requirements of data transmission. If the + RREQ-DIO arrives over an interface that is not known to be symmetric, + or is known to be asymmetric, the S bit is set 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 MAY use local + 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. 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. BR @@ -596,599 +563,643 @@ <---- RREP-Instance (Control: T-->O; Data: O-->T) -------< Figure 5: AODV-RPL with Asymmetric Paired Instances 6. AODV-RPL Operation 6.1. Route Request Generation The route discovery process is initiated when an application at the OrigNode has data to be transmitted to the TargNode, but does not - have a route for the target that fulfills the requirements of the - data transmission. In this case, the OrigNode builds a local + have a route that satisfies the Objective Function for the target of + the data transmission. In this case, the OrigNode builds a local RPLInstance and a DODAG rooted at itself. Then it transmits a DIO message containing exactly one RREQ option (see Section 4.1) via link-local multicast. The DIO MUST contain at least one ART Option - (see Section 4.3). The 'S' bit in RREQ-DIO sent out by the OrigNode - is set to 1. + (see Section 4.3). The S bit in RREQ-DIO sent out by the OrigNode is + set to 1. - Each node maintains a sequence number, which rolls over like a - lollipop counter [Perlman83]; refer to section 7.2 of [RFC6550] for - detailed operation. When the OrigNode initiates a route discovery - process, it MUST increase its own sequence number to avoid conflicts - with previously established routes. The sequence number is carried - in the OrigSeqNo field of the RREQ option. + Each node maintains a sequence number; the operation is specified in + section 7.2 of [RFC6550]. When the OrigNode initiates a route + discovery process, it MUST increase its own sequence number to avoid + 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 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. If the - duration specified by the "L" bit has elapsed, the OrigNode MUST + 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 6.2.1. General Processing - Upon receiving a RREQ-DIO, a router which does not belong to the - RREQ-instance goes through the following steps: + Upon receiving a RREQ-DIO, a router goes through the steps below. If + the router does not belong to the RREQ-Instance, then the maximum + useful rank (MaxUseRank) is MaxRank. Otherwise, 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. Step 1: - If the 'S' bit in the received RREQ-DIO is set to 1, the router - MUST check the two directions of the link by which the RREQ-DIO is - received. In case that the downward (i.e. towards the TargNode) - direction of the link can't fulfill the requirements, 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 only checks into the upward - direction (towards the OrigNode) of the link. + 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 + OrigNode) of the link. - If the upward direction of the link can fulfill the requirements - indicated in the constraint option, and the router's rank would - not exceed the MaxRank limit, the router joins the DODAG of the + 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. Later, other RREQ-DIO - messages might be received. 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. In case that the - constraint or the MaxRank limit is not fulfilled, the router MUST - discard the received RREQ-DIO and MUST NOT join the DODAG. + 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 the upward route entry accordingly. The - route entry MUST include at least the following items: Source - Address, InstanceID, Destination Address, Next Hop, Lifetime, and - Sequence Number. The Destination Address and the InstanceID can - be respectively learned from the DODAGID and the RPLInstanceID of - the RREQ-DIO, and the Source Address is copied from the ART - Option. The next hop is the preferred parent. The lifetime is - set according to DODAG configuration and can be extended when the + 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 + 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 same source and + field of the RREQ option. A route entry with the same source and destination address, same InstanceID, but stale sequence number, - SHOULD be deleted. - - If the 'H' bit is set to 0, an intermediate router MUST include - the address of the interface receiving the RREQ-DIO into the - address vector. + MUST be deleted. Step 4: - An intermediate router transmits a RREQ-DIO via link-local - multicast. TargNode prepares a RREP-DIO. + 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. 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 SHOULD continue sending RREQ-DIO to reach other + 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 ranks do not try to create a - route to this TargetNode. + so that downstream routers with higher Rank values do not try to + create a route to this TargetNode. An intermediate router could receive several RREQ-DIOs from routers - with lower ranks in the same RREQ-instance but have different lists - of Target Options. When rebroadcasting the RREQ-DIO, the - intersection of these lists SHOULD be included. For example, suppose + 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 - means that all the targets have been reached, and the router SHOULD - NOT send out any RREQ-DIO. Any RREQ-DIO message with different ART - Options coming from a router with higher rank is ignored. + means that all the targets have been reached, and the router MUST NOT + send out any RREQ-DIO. 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 + associated with the RREQ-Instance. Any RREQ-DIO message with + different ART Options coming from a router with higher Rank is + ignored. 6.3. Generating Route Reply (RREP) at TargNode 6.3.1. RREP-DIO for Symmetric route - If a RREQ-DIO arrives at TargNode with the 'S' bit set to 1, there is - a symmetric route along which both directions can fulfill the - requirements. Other RREQ-DIOs might later provide asymmetric upward + If a RREQ-DIO arrives at TargNode with the S bit set to 1, there is a + symmetric route along which both directions satisfy the Objective + Function. Other RREQ-DIOs might later provide asymmetric upward routes (i.e. S=0). Selection between a qualified symmetric route and an asymmetric route that might have better performance is - implementation-specific and out of scope. If the implementation uses - the symmetric route, the TargNode MAY delay transmitting the RREP-DIO - for duration RREP_WAIT_TIME to await a better symmetric route. + implementation-specific and out of scope. If the implementation + selects the symmetric route, and the L bit is not 0, the TargNode MAY + delay transmitting the RREP-DIO for duration RREP_WAIT_TIME to await + a symmetric route with a lower Rank. The value of RREP_WAIT_TIME is + set by default to 1/4 of the time duration determined by the L bit. For a symmetric route, the RREP-DIO message is unicast to the next hop according to the accumulated address vector (H=0) or the route entry (H=1). Thus the DODAG in RREP-Instance does not need to be built. The RPLInstanceID in the RREP-Instance is paired as defined - in Section 6.3.3. In case the 'H' bit is set to 0, the address - vector received in the RREQ-DIO MUST be included in the RREP-DIO. - TargNode increments its current sequence number and uses the - incremented result in the Dest SeqNo in the ART option of the RREQ- - DIO. The address of the OrigNode MUST be encapsulated in the ART - Option and included in this RREP-DIO message. + in Section 6.3.3. In case the H bit is set to 0, the address vector + received in the RREQ-DIO MUST be included in the RREP-DIO. TargNode + increments its current sequence number and uses the incremented + result in the Dest SeqNo in the ART option of the RREQ-DIO. The + address of the OrigNode MUST be encapsulated in the ART Option and + included in this RREP-DIO message. 6.3.2. RREP-DIO for Asymmetric Route - When a RREQ-DIO arrives at a TargNode with the 'S' bit set to 0, the + When a RREQ-DIO arrives at a TargNode with the S bit set to 0, the TargNode MUST build a DODAG in the RREP-Instance rooted at itself in order to discover the downstream route from the OrigNode to the TargNode. The RREP-DIO message MUST be re-transmitted via link-local - multicast until the OrigNode is reached or MaxRank is exceeded. + multicast until the OrigNode is reached or MaxRank is exceeded. The + TargNode MAY delay transmitting the RREP-DIO for 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 time duration + determined by the L bit. The settings of the fields in RREP option and ART option are the same - as for the symmetric route, except for the 'S' bit. + as for the symmetric route, except for the S bit. 6.3.3. RPLInstanceID Pairing 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. The upper layer applications may have - different requirements and they can initiate the route discoveries + identify a discovered route. It is possible that multiple route + discoveries with dissimilar Objective Functions are initiated simultaneously. Thus between the same pair of OrigNode and TargNode, - there can be multiple AODV-RPL instances. To avoid any mismatch, the - RREQ-Instance and the RREP-Instance in the same route discovery MUST - be paired somehow, e.g. using the RPLInstanceID. + there can be multiple AODV-RPL route discovery instances. To avoid + any mismatch, the RREQ-Instance and the RREP-Instance in the same + route discovery MUST be paired using the RPLInstanceID. 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 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: + RREQ-Instance goes through the following steps: Step 1: - If the 'S' bit is set to 1, the router proceeds to step 2. + 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 + 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 fulfill the requirements indicated in the constraint - option, 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. 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. + 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 constraints are not fulfilled, the router MUST NOT join the - DODAG; the router MUST discard the RREQ-DIO, and does not execute - the remaining steps in this section. + 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 + If the H bit is set to 1, then the router (OrigNode or intermediate) MUST build a downward route entry. The route entry - SHOULD include at least the following items: OrigNode Address, + MUST include at least the following items: OrigNode Address, InstanceID, TargNode Address as destination, Next Hop, Lifetime - and Sequence Number. For a symmetric route, the next hop in the + 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 + For an asymmetric route, the Next Hop is the preferred parent in the DODAG of RREQ-Instance. The InstanceID 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. + 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. 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 + 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 - behalf of the actual TargNode. The 'G' bit of the RREP option is + 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 node from the RREP-DIO sent by TargNode (G=0). - The gratuitous RREP-DIO can be sent out when an intermediate router R - receives a RREQ-DIO for a TargNode T, and R happens to have a more - recent (larger destination sequence number) pair of downward and - upward routes to T which also fulfill the requirements. + The gratuitous RREP-DIO can be sent out when an intermediate router + receives a RREQ-DIO for a TargNode, and the router has a more recent + (larger destination sequence number) pair of downward and upward + routes to the TargNode which also satisfy the Objective Function. - In case of source routing, the intermediate router R MUST unicast the - received RREQ-DIO to TargNode T including the address vector between - the OrigNode O and the router R. Thus T can have a complete upward - route address vector from itself to O. Then R MUST send out the - gratuitous RREP-DIO including the address vector from R to T. + 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 send out the gratuitous RREP-DIO including the address + vector from the router itself to the TargNode. - In case of hop-by-hop routing, R MUST unicast the received RREQ-DIO - hop-by-hop to T. The routers along the route SHOULD build new route - entries with the related RPLInstanceID and DODAGID in the downward - direction. Then T MUST unicast the RREP-DIO hop-by-hop to R, and the - routers along the route SHOULD build new route entries in the upward - direction. Upon receiving the unicast RREP-DIO, R sends the + 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 + router along the route MUST build new route entries with the related + 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 is similar to that in P2P-RPL [RFC6997]. + 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". 9. IANA Considerations 9.1. New Mode of Operation: AODV-RPL - IANA is required to assign a new Mode of Operation, named "AODV-RPL" - for Point-to-Point(P2P) hop-by-hop routing under the RPL registry. - The value of TBD1 is assigned from the "Mode of Operation" space - [RFC6550]. + 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]. +-------------+---------------+---------------+ | Value | Description | Reference | +-------------+---------------+---------------+ | TBD1 (5) | AODV-RPL | This document | +-------------+---------------+---------------+ Figure 6: Mode of Operation 9.2. AODV-RPL Options: RREQ, RREP, and Target - Three entries are required for new AODV-RPL options "RREQ", "RREP" - and "ART" with values of TBD2 (0x0A), TBD3 (0x0B) and TBD4 (0x0C) - from the "RPL Control Message Options" space [RFC6550]. + 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]. +-------------+------------------------+---------------+ | Value | Meaning | Reference | +-------------+------------------------+---------------+ | TBD2 (0x0A) | RREQ Option | This document | +-------------+------------------------+---------------+ | TBD3 (0x0B) | RREP Option | This document | +-------------+------------------------+---------------+ - | TBD3 (0x0C) | ART Option | This document | + | TBD4 (0x0C) | ART Option | This document | +-------------+------------------------+---------------+ Figure 7: AODV-RPL Options 10. Security Considerations - The security mechanisms defined in section 10 of [RFC6550] and - section 11 of [RFC6997] can also be applied to the control messages - defined in this specification. The RREQ-DIO and RREP-DIO both have a - secure variant, which provide integrity and replay protection as well - as optional confidentiality and delay protection. - - AODV-RPL can operate in the three security modes defined in - [RFC6550]. AODV-RPL messages SHOULD use a security mode at least as - strong as the security mode used in RPL. - - o Unsecured. In this mode, RREQ-DIO and RREP-DIO are used without - any security fields as defined in section 6.1 of [RFC6550]. The - control messages can be protected by other security mechanisms, - e.g. link-layer security. This mode SHOULD NOT be used when RPL - is using Preinstalled mode or Authenticated mode (see below). - - o Preinstalled. In this mode, AODV-RPL uses secure RREQ-DIO and - RREP-DIO messages, and a node wishing to join a secured network - will have been pre-configured with a shared key. A node can use - that key to join the AODV-RPL DODAG as a host or a router. - Unsecured messages MUST be dropped. This mode SHOULD NOT be used - when RPL is using Authenticated mode. + 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. - o Authenticated. In this mode, besides the preinstalled shared key, - a node MUST obtain a second key from a key authority. The - interaction between a node and the key authority is out of scope - for this specification. Authenticated mode may be useful, for - instance, to protect against a malicious rogue router advertising - false information in RREQ-DIO or RREP-DIO to include itself in the - discovered route. This mode would also prevent a malicious router - from initiating route discovery operations or launching denial-of- - service attacks to impair the performance of the LLN. AODV-RPL - can use the keys established with the Authenticated mode RPL - instance. Once a router or a host has been authenticated in the - RPL instance, it can join the AODV-RPL instance without any - further authentication. The authentication in AODV-RPL can also - be independent to RPL if, before joining the AODV-RPL instance, - the node obtains another key from the key authority. + 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. -11. Future Work + 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. - There has been some discussion about how to determine the initial - state of a link after an AODV-RPL-based network has begun operation. - The current draft operates as if the links are symmetric until - additional metric information is collected. The means for making - link metric information is considered out of scope for AODV-RPL. In - the future, RREQ and RREP messages could be equipped with new fields - for use in verifying link metrics. In particular, it is possible to - identify unidirectional links; an RREQ received across a - unidirectional link has to be dropped, since the destination node - cannot make use of the received DODAG to route packets back to the - source node that originated the route discovery operation. This is - roughly the same as considering a unidirectional link to present an - infinite cost metric that automatically disqualifies it for use in - the reverse direction. + 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. -12. Contributors +11. Link State Determination - Abdur Rashid Sangi - Huaiyin Institute of Technology - No.89 North Beijing Road, Qinghe District - Huaian 223001 - P.R. China - Email: sangi_bahrian@yahoo.com + 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. -13. References +12. References -13.1. Normative References +12.1. 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, . - [RFC6552] Thubert, P., Ed., "Objective Function Zero for the Routing - Protocol for Low-Power and Lossy Networks (RPL)", - RFC 6552, DOI 10.17487/RFC6552, March 2012, - . + [RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N., + and D. Barthel, "Routing Metrics Used for Path Calculation + 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, + . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . -13.2. Informative References - - [I-D.thubert-roll-asymlink] - Thubert, P., "RPL adaptation for asymmetrical links", - draft-thubert-roll-asymlink-02 (work in progress), - December 2011. - - [Perlman83] - Perlman, R., "Fault-Tolerant Broadcast of Routing - Information", December 1983. - - [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, - . - - [RFC5548] Dohler, M., Ed., Watteyne, T., Ed., Winter, T., Ed., and - D. Barthel, Ed., "Routing Requirements for Urban Low-Power - and Lossy Networks", RFC 5548, DOI 10.17487/RFC5548, May - 2009, . - - [RFC5673] Pister, K., Ed., Thubert, P., Ed., Dwars, S., and T. - Phinney, "Industrial Routing Requirements in Low-Power and - Lossy Networks", RFC 5673, DOI 10.17487/RFC5673, October - 2009, . - - [RFC5826] Brandt, A., Buron, J., and G. Porcu, "Home Automation - Routing Requirements in Low-Power and Lossy Networks", - RFC 5826, DOI 10.17487/RFC5826, April 2010, - . +12.2. Informative References - [RFC5867] Martocci, J., Ed., De Mil, P., Riou, N., and W. Vermeylen, - "Building Automation Routing Requirements in Low-Power and - Lossy Networks", RFC 5867, DOI 10.17487/RFC5867, June - 2010, . + [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. [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, . - [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, - . + [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 - We have tested the combination of "RSSI(downstream)" and "ETX - (upstream)" to determine whether the link is symmetric or asymmetric - at the intermediate nodes. The example of how the ETX and RSSI - values are used in conjuction is explained below: + 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: 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 | +-------------------------+----------------------------------------+ - Table 1: Selection of 'S' bit based on Expected ETX value + Table 1: Selection of S bit based on Expected ETX value 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, say, within 1:3 - ratio. This ratio should be taken as a notional metric for deciding - link symmetric/asymmetric nature, and precise definition of the ratio - is beyond the scope of the draft. In general, NodeA can only 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 "S=0". Later on, the link from - NodeA to Destination is asymmetric with "S" bit remains to "0". + 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. Appendix B. Changelog -B.1. Changes from version 06 to version 07 + Note to the RFC Editor: please remove this section before + publication. + +B.1. 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 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. + +B.2. 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 RFC 3561 and RFC 6998 as Informative. + o Reclassified [RFC3561] and [RFC6998] as Informative. - o Added citation to RFC 8174 to Terminology section. + o Added citation for [RFC8174] to Terminology section. -B.2. Changes from version 05 to version 06 +B.3. Changes from version 05 to version 06 o Added Security Considerations based on the security mechanisms - defined in RFC 6550. + 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.3. Changes from version 04 to version 05 +B.4. 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.4. Changes from version 03 to version 04 +B.5. Changes from version 03 to version 04 - o Updated RREP option format. Remove the 'T' bit in RREP option. + 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.5. Changes from version 02 to version 03 +B.6. 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. + 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. +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 + Authors' Addresses Satish Anamalamudi SRM University-AP Amaravati Campus Amaravati, Andhra Pradesh 522 502 India Email: satishnaidu80@gmail.com Mingui Zhang Huawei Technologies No. 156 Beiqing Rd. Haidian District Beijing 100095 China Email: zhangmingui@huawei.com Charles E. Perkins - Futurewei - 2330 Central Expressway - Santa Clara 95050 + Deep Blue Sky Networks + 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