Mobile Ad hoc Networks Working Group C. Perkins Internet-Draft Futurewei Intended status: Standards Track S. Ratliff Expires: October 6, 2016 Idirect J. Dowdell Airbus Defence and Space L. Steenbrink HAW Hamburg, Dept. Informatik V. Mercieca Airbus Defence and Space April 4, 2016 Ad Hoc On-demand Distance Vector Version 2 (AODVv2) Routing draft-ietf-manet-aodvv2-14 Abstract The Ad Hoc On-demand Distance Vector Version 2 (AODVv2) routing protocol is intended for use by mobile routers in wireless, multihop networks. AODVv2 determines unicast routes among AODVv2 routers within the network in an on-demand fashion. 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 http://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 6, 2016. Copyright Notice Copyright (c) 2016 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 (http://trustee.ietf.org/license-info) in effect on the date of Perkins, et al. Expires October 6, 2016 [Page 1] Internet-Draft AODVv2 April 2016 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. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 9 4. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. InterfaceSet . . . . . . . . . . . . . . . . . . . . . . 11 4.2. Router Client Table . . . . . . . . . . . . . . . . . . . 11 4.3. Neighbor Table . . . . . . . . . . . . . . . . . . . . . 12 4.4. Sequence Numbers . . . . . . . . . . . . . . . . . . . . 12 4.5. Local Route Set . . . . . . . . . . . . . . . . . . . . . 13 4.6. Multicast Route Message Table . . . . . . . . . . . . . . 15 4.7. Route Error (RERR) Table . . . . . . . . . . . . . . . . 17 5. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. AODVv2 Protocol Operations . . . . . . . . . . . . . . . . . 19 6.1. Initialization . . . . . . . . . . . . . . . . . . . . . 19 6.2. Next Hop Monitoring . . . . . . . . . . . . . . . . . . . 20 6.3. Neighbor Table Update . . . . . . . . . . . . . . . . . . 21 6.4. Interaction with the Forwarding Plane . . . . . . . . . . 22 6.5. Message Transmission . . . . . . . . . . . . . . . . . . 24 6.6. Route Discovery, Retries and Buffering . . . . . . . . . 25 6.7. Processing Received Route Information . . . . . . . . . . 26 6.7.1. Evaluating Route Information . . . . . . . . . . . . 27 6.7.2. Applying Route Updates . . . . . . . . . . . . . . . 28 6.8. Suppressing Redundant Messages Using the Multicast Route Message Table . . . . . . . . . . . . . . . . . . . . . . 31 6.9. Suppressing Redundant Route Error Messages using the Route Error Table . . . . . . . . . . . . . . . . . . . . 33 6.10. Local Route Set Maintenance . . . . . . . . . . . . . . . 34 6.10.1. LocalRoute State Changes . . . . . . . . . . . . . . 34 6.10.2. Reporting Invalid Routes . . . . . . . . . . . . . . 36 7. AODVv2 Protocol Messages . . . . . . . . . . . . . . . . . . 37 7.1. Route Request (RREQ) Message . . . . . . . . . . . . . . 37 7.1.1. RREQ Generation . . . . . . . . . . . . . . . . . . . 38 7.1.2. RREQ Reception . . . . . . . . . . . . . . . . . . . 39 7.1.3. RREQ Regeneration . . . . . . . . . . . . . . . . . . 40 7.2. Route Reply (RREP) Message . . . . . . . . . . . . . . . 41 7.2.1. RREP Generation . . . . . . . . . . . . . . . . . . . 42 7.2.2. RREP Reception . . . . . . . . . . . . . . . . . . . 44 7.2.3. RREP Regeneration . . . . . . . . . . . . . . . . . . 45 7.3. Route Reply Acknowledgement (RREP_Ack) Message . . . . . 46 Perkins, et al. Expires October 6, 2016 [Page 2] Internet-Draft AODVv2 April 2016 7.3.1. RREP_Ack Generation . . . . . . . . . . . . . . . . . 46 7.3.2. RREP_Ack Reception . . . . . . . . . . . . . . . . . 47 7.4. Route Error (RERR) Message . . . . . . . . . . . . . . . 47 7.4.1. RERR Generation . . . . . . . . . . . . . . . . . . . 48 7.4.2. RERR Reception . . . . . . . . . . . . . . . . . . . 50 7.4.3. RERR Regeneration . . . . . . . . . . . . . . . . . . 51 8. RFC 5444 Representation . . . . . . . . . . . . . . . . . . . 52 8.1. Route Request Message Representation . . . . . . . . . . 53 8.1.1. Message Header . . . . . . . . . . . . . . . . . . . 53 8.1.2. Message TLV Block . . . . . . . . . . . . . . . . . . 53 8.1.3. Address Block . . . . . . . . . . . . . . . . . . . . 53 8.1.4. Address Block TLV Block . . . . . . . . . . . . . . . 53 8.2. Route Reply Message Representation . . . . . . . . . . . 54 8.2.1. Message Header . . . . . . . . . . . . . . . . . . . 54 8.2.2. Message TLV Block . . . . . . . . . . . . . . . . . . 54 8.2.3. Address Block . . . . . . . . . . . . . . . . . . . . 55 8.2.4. Address Block TLV Block . . . . . . . . . . . . . . . 55 8.3. Route Reply Acknowledgement Message Representation . . . 56 8.3.1. Message Header . . . . . . . . . . . . . . . . . . . 56 8.3.2. Message TLV Block . . . . . . . . . . . . . . . . . . 56 8.3.3. Address Block . . . . . . . . . . . . . . . . . . . . 56 8.3.4. Address Block TLV Block . . . . . . . . . . . . . . . 57 8.4. Route Error Message Representation . . . . . . . . . . . 57 8.4.1. Message Header . . . . . . . . . . . . . . . . . . . 57 8.4.2. Message TLV Block . . . . . . . . . . . . . . . . . . 57 8.4.3. Address Block . . . . . . . . . . . . . . . . . . . . 57 8.4.4. Address Block TLV Block . . . . . . . . . . . . . . . 58 9. Simple External Network Attachment . . . . . . . . . . . . . 58 10. Optional Features . . . . . . . . . . . . . . . . . . . . . . 59 10.1. Expanding Rings Multicast . . . . . . . . . . . . . . . 60 10.2. Precursor Lists . . . . . . . . . . . . . . . . . . . . 60 10.3. Intermediate RREP . . . . . . . . . . . . . . . . . . . 61 10.4. Message Aggregation Delay . . . . . . . . . . . . . . . 61 11. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 61 11.1. Timers . . . . . . . . . . . . . . . . . . . . . . . . . 62 11.2. Protocol Constants . . . . . . . . . . . . . . . . . . . 63 11.3. Local Settings . . . . . . . . . . . . . . . . . . . . . 64 11.4. Network-Wide Settings . . . . . . . . . . . . . . . . . 64 11.5. Optional Feature Settings . . . . . . . . . . . . . . . 64 11.6. MetricType Allocation . . . . . . . . . . . . . . . . . 65 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 65 12.1. RFC 5444 Message Types . . . . . . . . . . . . . . . . . 65 12.2. RFC 5444 Address Block TLV Types . . . . . . . . . . . . 66 12.3. ADDRESS_TYPE TLV Values . . . . . . . . . . . . . . . . 66 13. Security Considerations . . . . . . . . . . . . . . . . . . . 67 13.1. Availability . . . . . . . . . . . . . . . . . . . . . . 67 13.1.1. Denial of Service . . . . . . . . . . . . . . . . . 67 13.1.2. Malicious RERR messages . . . . . . . . . . . . . . 68 Perkins, et al. Expires October 6, 2016 [Page 3] Internet-Draft AODVv2 April 2016 13.1.3. False Confirmation of Link Bidirectionality . . . . 69 13.1.4. Message Deletion . . . . . . . . . . . . . . . . . . 70 13.2. Confidentiality . . . . . . . . . . . . . . . . . . . . 70 13.3. Integrity . . . . . . . . . . . . . . . . . . . . . . . 71 13.3.1. Message Insertion . . . . . . . . . . . . . . . . . 71 13.3.2. Message Modification - Man in the Middle . . . . . . 71 13.3.3. Replay Attacks . . . . . . . . . . . . . . . . . . . 72 13.4. Protection Mechanisms . . . . . . . . . . . . . . . . . 72 13.4.1. Confidentiality and Authentication . . . . . . . . . 72 13.4.2. Integrity and Trust using ICVs . . . . . . . . . . . 72 13.4.3. Replay Protection using Timestamps . . . . . . . . . 73 13.4.4. Application to AODVv2 . . . . . . . . . . . . . . . 73 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 75 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 76 15.1. Normative References . . . . . . . . . . . . . . . . . . 76 15.2. Informative References . . . . . . . . . . . . . . . . . 77 Appendix A. AODVv2 Draft Updates . . . . . . . . . . . . . . . . 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 79 1. Overview The Ad hoc On-Demand Distance Vector Version 2 (AODVv2) protocol enables dynamic, self-starting, multihop routing between participating mobile nodes wishing to establish and maintain an ad hoc network. The basic operations of the AODVv2 protocol are route discovery and route maintenance. AODVv2 does not require nodes to maintain routes to destinations that are not in active communication. AODVv2 allows mobile nodes to respond to link breakages and changes in network topology in a timely manner. The operation of AODVv2 is loop-free, and by avoiding the Bellman-Ford "counting to infinity" problem offers quick convergence when the ad hoc network topology changes (typically, when a node moves in the network). When links break, AODVv2 causes the affected set of nodes to be notified so that they are able to invalidate the routes using the lost link. One distinguishing feature of AODVv2 is its use of a destination sequence number for each route entry. The destination sequence number is created by the destination to be included along with any route information it sends to requesting nodes. Using destination sequence numbers ensures loop freedom and is simple to program. Given the choice between two routes to a destination, a requesting node is required to select the one with the greatest sequence number. Compared to AODV [RFC3561], AODVv2 makes some features optional, notably intermediate route replies, expanding ring search, and precursor lists. Hello messages and local repair have been removed. AODVv2 provides a mechanism for the use of multiple metric types. Message formats have been updated and made compliant with [RFC5444]. Perkins, et al. Expires October 6, 2016 [Page 4] Internet-Draft AODVv2 April 2016 AODVv2 control messages are defined as sets of data, which are mapped to message elements using the Generalized MANET Packet/Message Format defined in [RFC5444] and sent using the parameters in [RFC5498]. Verification of link bidirectionality has been substantially improved, and additional refinements made for route timeouts and state management. Although AODVv2 is closely related to AODV [RFC3561], and shares some features of DSR [RFC4728], AODVv2 is not interoperable with either of those protocols. Compared to AODV, AODVv2 makes some features optional, notably intermediate route replies, expanding ring search, and precursor lists. Hello messages and local repair have been removed. AODVv2 provides a mechanism for the use of multiple metric types. Message formats have been updated and made compliant with [RFC5444]. AODVv2 control messages are defined as sets of data, which are mapped to messages using the Generalized MANET Packet/Message Format defined in [RFC5444] and sent using the parameters in [RFC5498]. The basic operations of the AODVv2 protocol are route discovery and route maintenance. An AODVv2 router is configured to perform route discovery on behalf of a configured set of IP addresses known as Router Clients. Route discovery is performed when an AODVv2 router needs to forward an IP packet from one of its Router Clients, but does not have a valid route to the packet's destination. AODVv2 routers use Route Request (RREQ) and Route Reply (RREP) messages to carry route information between the originator of the route discovery and the router responsible for the target, establishing a route to both endpoints on all intermediate routers. A metric value is included to represent the cost of the route contained within the message. AODVv2 uses sequence numbers to identify stale routing information, and compares route metric values to determine if advertised routes could form loops. Route maintenance includes confirming bidirectionality of links to next hop AODVv2 routers, issuing Route Error (RERR) messages, reacting to received Route Error messages, and extending and enforcing route timeouts. The on-demand nature of AODVv2 requires signals to be exchanged between AODVv2 and the forwarding plane. These signals indicate when: a packet is to be forwarded, in order to initiate route discovery; packet forwarding fails, in order to initiate route error reporting; a packet is successfully forwarded, for route maintenance. Perkins, et al. Expires October 6, 2016 [Page 5] Internet-Draft AODVv2 April 2016 Security for authentication of AODVv2 routers and encryption of control messages is accomplished using the TIMESTAMP and ICV TLVs defined in [RFC7182]. 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]. In addition, this document uses terminology from [RFC5444], and defines the following terms: AddressList A list of IP addresses as used in AODVv2 messages. AckReq Used in a Route Reply message to indicate the IP address of the router from which a Route Reply Acknowledgement is expected. AdvRte A route advertised in an incoming route message. AODVv2 Router An IP addressable device in the ad hoc network that performs the AODVv2 protocol operations specified in this document. CurrentTime The current time as maintained by the AODVv2 router. ENAR (External Network Access Router) An AODVv2 router with an interface to an external, non-AODVv2 network. InterfaceSet The set of all network interfaces supporting AODVv2. Invalid route A route that cannot be used for forwarding but still contains useful sequence number information. LocalRoute An entry in the Local Route Set as defined in Section 4.5. MANET A Mobile Ad Hoc Network as defined in [RFC2501]. MetricType The metric type for a metric value included in a message. Perkins, et al. Expires October 6, 2016 [Page 6] Internet-Draft AODVv2 April 2016 MetricTypeList A list of metric types associated with the addresses in the AddressList of a Route Error message. Neighbor An AODVv2 router from which an RREQ or RREP message has been received. Neighbors exchange routing information and verify bidirectionality of the link to a neighbor before installing a route via that neighbor into the Local Route Set. OrigAddr The source IP address of the IP packet triggering route discovery. OrigMetric The metric value associated with the route to OrigAddr (and any other addresses included in the given prefix length). OrigPrefixLen The prefix length, in bits, configured in the Router Client entry which includes OrigAddr. OrigSeqNum The sequence number of the AODVv2 router which originated the Route Request on behalf of OrigAddr. PktSource The source address of the IP packet which triggered a Route Error message. PrefixLengthList A list of routing prefix lengths associated with the addresses in the AddressList of a message. Reactive Performed only in reaction to specific events. In AODVv2, routes are requested only when data packets need to be forwarded. In this document, "reactive" is synonymous with "on-demand". RERR (Route Error) The AODVv2 message type used to indicate that an AODVv2 router does not have a valid LocalRoute toward one or more particular destinations. RERR_Gen (RERR Generating Router) The AODVv2 router generating a Route Error message. RerrMsg (RERR Message) A Route Error (RERR) message. Perkins, et al. Expires October 6, 2016 [Page 7] Internet-Draft AODVv2 April 2016 Routable Unicast IP Address A routable unicast IP address is a unicast IP address that is scoped sufficiently to be forwarded by a router. Globally-scoped unicast IP addresses and Unique Local Addresses (ULAs) [RFC4193] are examples of routable unicast IP addresses. Router Client An address or address range configured on an AODVv2 router, on behalf of which that router will initiate and respond to route discoveries. These addresses may be used by the AODVv2 router itself or by non-routing devices that are reachable without traversing another AODVv2 router. RREP (Route Reply) The AODVv2 message type used to reply to a Route Request message. RREP_Gen (RREP Generating Router) The AODVv2 router that generates the Route Reply message, i.e., the router configured with TargAddr as a Router Client. RREQ (Route Request) The AODVv2 message type used to discover a route to TargAddr and distribute information about a route to OrigAddr. RREQ_Gen (RREQ Generating Router) The AODVv2 router that generates the Route Request message, i.e., the router configured with OrigAddr as a Router Client. RteMsg (Route Message) A Route Request (RREQ) or Route Reply (RREP) message. SeqNum The sequence number maintained by an AODVv2 router to indicate freshness of route information. SeqNumList A list of sequence numbers associated with the addresses in the AddressList of a message. TargAddr The target address of a route request, i.e., the destination address of the IP packet triggering route discovery. TargMetric The metric value associated with the route to TargAddr (and any other addresses included in the given prefix length). TargPrefixLen Perkins, et al. Expires October 6, 2016 [Page 8] Internet-Draft AODVv2 April 2016 The prefix length, in bits, configured in the Router Client entry which includes TargAddr. TargSeqNum The sequence number of the AODVv2 router which originated the Route Reply on behalf of TargAddr. Unreachable Address An address reported in a Route Error message, either the address on a LocalRoute which became Invalid, or the destination address of an IP packet that could not be forwarded because a valid LocalRoute to the destination is not known, and will not be requested. Upstream In the direction from destination to source (from TargAddr to OrigAddr). ValidityTime The length of time the route described by the message is offered. Valid route A route that can be used for forwarding, which has been confirmed as having a bidirectional link to the next hop, and has not timed out or been made invalid by a route error. This document uses the notational conventions in Table 1 to simplify the text. +-----------------------+------------------------------------+ | Notation | Meaning | +-----------------------+------------------------------------+ | Route[Address] | A route toward Address | | Route[Address].Field | A field in a route toward Address | | RteMsg.Field | A field in either RREQ or RREP | +-----------------------+------------------------------------+ Table 1: Notational Conventions 3. Applicability Statement The AODVv2 routing protocol is a reactive routing protocol. A reactive protocol only sends messages to discover a route when there is data to send on that route. Therefore, a reactive routing protocol requires certain interactions with the forwarding plane (for example, to indicate when a packet is to be forwarded, in order to initiate route discovery). The set of signals exchanged between AODVv2 and the forwarding plane are discussed in Section 6.4. Perkins, et al. Expires October 6, 2016 [Page 9] Internet-Draft AODVv2 April 2016 AODVv2 is designed for stub or disconnected mobile ad hoc networks, i.e., non-transit networks or those not connected to the internet. AODVv2 can, however, be configured to perform gateway functions when attached to external networks, as discussed in Section 9. AODVv2 handles a wide variety of mobility and traffic patterns by determining routes on-demand. In networks with a large number of routers, AODVv2 is best suited for relatively sparse traffic scenarios where each router forwards IP packets to a small percentage of other AODVv2 routers in the network. In this case fewer routes are needed, and therefore less control traffic is produced. Data packets may be buffered until a route to their destination is available, as described in Section 6.6. AODVv2 provides for message integrity and security against replay attacks by using integrity check values, timestamps and sequence numbers, as described in Section 13. If security associations can be established, encryption can be used for AODVv2 messages to ensure that only trusted routers participate in routing operations. Since the route discovery process aims for a route to be established in both directions along the same path, uni-directional links are not suitable. AODVv2 will detect and exclude those links from route discovery. The route discovered is optimised for the requesting router, and the return path may not be the optimal route. AODVv2 is applicable to memory constrained devices, since only a little routing state is maintained in each AODVv2 router. AODVv2 routes that are not needed for forwarding data do not need to be maintained. On routers unable to store persistent AODVv2 state, recovery can impose a performance penalty (e.g., in case of AODVv2 router reboot), since if a router loses its sequence number, there is a delay before the router can resume full operations. This is described in Section 6.1. AODVv2 supports routers with multiple interfaces and multiple IP addresses per interface. A router may also use the same IP address on multiple interfaces. AODVv2 requires only that each interface configured for AODVv2 has at least one unicast IP address. Address assignment procedures are out of scope for AODVv2. AODVv2 supports Router Clients with multiple interfaces, as long as each interface is configured with its own unicast IP address. Multi- homing of a Router Client IP address is not supported by AODVv2, and therefore an IP address SHOULD NOT be configured as a Router Client on more than one AODVv2 router at any one time. Perkins, et al. Expires October 6, 2016 [Page 10] Internet-Draft AODVv2 April 2016 The routing algorithm in AODVv2 MAY be operated at layers other than the network layer, using layer-appropriate addresses. 4. Data Structures 4.1. InterfaceSet The InterfaceSet is a conceptual data structure which contains information about all interfaces available to AODVv2. Each element in the InterfaceSet MUST contain the following: Interface.Id An identifier that is unique in node-local scope and that allows the AODVv2 implementation to identify exactly one local network interface. If multiple interfaces of the AODVv2 router are configured for use by AODVv2, they MUST be configured in the InterfaceSet. Otherwise the InterfaceSet MAY be empty. 4.2. Router Client Table An AODVv2 router provides route discovery services for its own local applications and for other non-routing devices that are reachable without traversing another AODVv2 router. The addresses used by these devices, and the AODVv2 router itself, are configured in the Router Client Table. An AODVv2 router will only originate Route Request and Route Reply messages on behalf of configured Router Client addresses. Router Client Table entries MUST contain: RouterClient.IPAddress An IP address or the start of an address range that requires route discovery services from the AODVv2 router. RouterClient.PrefixLength The length, in bits, of the routing prefix associated with the RouterClient.IPAddress. If a prefix length is included, the AODVv2 router MUST provide connectivity for all addresses within that prefix. RouterClient.Cost The cost associated with reaching this address or address range. A Router Client address MUST NOT be served by more than one AODVv2 router at any one time. To shift responsibility for a Router Client Perkins, et al. Expires October 6, 2016 [Page 11] Internet-Draft AODVv2 April 2016 to a different AODVv2 router, correct AODVv2 routing behavior MUST be observed; The AODVv2 router adding the Router Client MUST wait for any existing routing information about this Router Client to be purged from the network, i.e., at least MAX_SEQNUM_LIFETIME since the last SeqNum update on the router which is removing this Router Client. 4.3. Neighbor Table A Neighbor Table MUST be maintained with information about neighboring AODVv2 routers. Neighbor Table entries are stored when AODVv2 messages are received. If the Neighbor is chosen as a next hop on an installed route, the link to the Neighbor MUST be tested for bidirectionality and the result stored in this table. A route will only be considered valid when the link is confirmed to be bidirectional. Neighbor Table entries MUST contain: Neighbor.IPAddress An IP address of the neighboring router, learned from the source IP address of a received route message. Neighbor.State Indicates whether the link to the neighbor is bidirectional. There are three possible states: Confirmed, Unknown, and Blacklisted. Unknown is the initial state. Confirmed indicates that the link to the neighbor has been confirmed as bidirectional. Blacklisted indicates that the link to the neighbor is uni- directional. Section 6.2 discusses how to monitor link bidirectionality. Neighbor.ResetTime When the value of Neighbor.State is Blacklisted, this indicates the time at which the value of Neighbor.State will revert to Unknown. By default this value is calculated at the time the router is blacklisted and is equal to CurrentTime + MAX_BLACKLIST_TIME. When the value of Neighbor.State is not Blacklisted, this time is set to INFINITY_TIME. Neighbor.Interface The interface on which the link to the neighbor was established. 4.4. Sequence Numbers Sequence numbers enable AODVv2 routers to determine the temporal order of route discovery messages, identifying stale routing information so that it can be discarded. The sequence number Perkins, et al. Expires October 6, 2016 [Page 12] Internet-Draft AODVv2 April 2016 fulfills the same roles as the "Destination Sequence Number" of DSDV [Perkins94], and the AODV Sequence Number in [RFC3561]. Each AODVv2 router in the network MUST maintain its own sequence number. All RREQ and RREP messages created by an AODVv2 router include the router's sequence number, reported as a 16-bit unsigned integer. Each AODVv2 router MUST ensure that its sequence number is strictly increasing, and that it is incremented by one (1) whenever an RREQ or RREP is created, except when the sequence number is 65,535 (the maximum value of a 16-bit unsigned integer), in which case it MUST be reset to one (1). The value zero (0) is reserved to indicate that the sequence number is unknown. An AODVv2 router MUST only attach its own sequence number to information about a route to one of its configured Router Clients, all route messages regenerated by other routers retain the originator's sequence number. Tod determine staleness, the previously stored sequence number associated with the originator, is subtracted from the incoming sequence number. The result of the subtraction is to be interpreted as a signed 16-bit integer, and if less than zero, the information in the new AODVv2 message is stale and MUST be discarded. This, along with the processes in Section 6.7.1, ensures loop freedom. An AODVv2 router SHOULD maintain its sequence number in persistent storage. If the sequence number is lost, the router MUST follow the procedure in Section 6.1 to safely resume routing operations with a new sequence number. 4.5. Local Route Set All AODVv2 routers MUST maintain a Local Route Set, containing information about routes learned from AODVv2 route messages. The Local Route Set is stored separately from the forwarding plane's routing table (referred to as Routing Information Base (RIB)), which may be updated by other routing protocols operating on the AODVv2 router as well. The Routing Information Base is updated using information from the Local Route Set. Alternatively, implementations MAY choose to modify the Routing Information Base directly. Routes learned from AODVv2 route messages are referred to in this document as LocalRoutes, and MUST contain the following information: LocalRoute.Address An address, which, when combined with LocalRoute.PrefixLength, describes the set of destination addresses this route includes. Perkins, et al. Expires October 6, 2016 [Page 13] Internet-Draft AODVv2 April 2016 LocalRoute.PrefixLength The prefix length, in bits, associated with LocalRoute.Address. LocalRoute.SeqNum The sequence number associated with LocalRoute.Address, obtained from the last route message that successfully updated this entry. LocalRoute.NextHop The source IP address of the IP packet containing the AODVv2 message advertising the route to LocalRoute.Address, i.e. an IP address of the AODVv2 router used for the next hop on the path toward LocalRoute.Address. LocalRoute.NextHopInterface The interface used to send IP packets toward LocalRoute.Address. LocalRoute.LastUsed If this route is installed in the Routing Information Base, the time it was last used to forward an IP packet. LocalRoute.LastSeqNumUpdate The time LocalRoute.SeqNum was last updated. LocalRoute.ExpirationTime The time at which this LocalRoute MUST be marked as Invalid. An AODVv2 router MAY be offered a route for a limited time. In this case, the route is referred to as a timed route. If a route is not timed, LocalRoute.ExpirationTime is INFINITY_TIME. LocalRoute.MetricType The type of metric associated with this route. LocalRoute.Metric The cost of the route toward LocalRoute.Address expressed in units consistent with LocalRoute.MetricType. LocalRoute.State The last known state (Unconfirmed, Idle, Active, or Invalid) of the route. LocalRoute.Precursors (optional feature) A list of upstream neighbors using the route (see Section 10.2). There are four possible states for a LocalRoute: Unconfirmed A route learned from a Route Request message, which has not yet been confirmed as bidirectional. It MUST NOT be used for Perkins, et al. Expires October 6, 2016 [Page 14] Internet-Draft AODVv2 April 2016 forwarding IP packets, and therefore it is not referred to as a valid route. This state only applies to routes learned through RREQ messages. Idle A route which has been learned from a route message, and has also been confirmed, but has not been used in the last ACTIVE_INTERVAL. It is able to be used for forwarding IP packets, and therefore it is referred to as a valid route. Active A route which has been learned from a route message, and has also been confirmed, and has been used in the last ACTIVE_INTERVAL. It is able to be used for forwarding IP packets, and therefore it is referred to as a valid route. Invalid A route which has expired or been lost. It MUST NOT be used for forwarding IP packets, and therefore it is not referred to as a valid route. Invalid routes contain sequence number information which allows incoming information to be assessed for freshness. When the Local Route Set is stored separately from the Routing Information Base, routes are added to the Routing Information Base when LocalRoute.State is valid (set to Active or Idle), and removed from the Routing Information Base when LocalRoute.State becomes Invalid. Changes to LocalRoute state are detailed in Section 6.10.1. Multiple valid routes for the same address and prefix length but for different metric types may exist in the Local Route Set, but the decision of which of these routes to install in the Routing Information Base to use for forwarding is outside the scope of AODVv2. 4.6. Multicast Route Message Table A route message (RteMsg) is either a Route Request or Route Reply message. RREQ messages are multicast by default and regenerated multiple times, and RREP messages will be multicast when the link to the next router is not known to be bidirectional. Multiple similar route messages might be received by any one router during one route discovery attempt. The AODVv2 router does not need to regenerate or respond to every one of these messages. The Multicast Route Message Table is a conceptual table which contains information about previously received multicast route Perkins, et al. Expires October 6, 2016 [Page 15] Internet-Draft AODVv2 April 2016 messages, so that incoming route messages can be compared with previously received messages to determine if the incoming information is redundant or stale, and the router can avoid sending redundant control traffic. Multicast Route Message Table entries MUST contain the following information: RteMsg.MessageType Either RREQ or RREP. RteMsg.OrigAddr The source address of the IP packet triggering the route request. RteMsg.OrigPrefixLen The prefix length associated with RteMsg.OrigAddr, originally from the Router Client entry on RREQ_Gen which includes RteMsg.OrigAddr. RteMsg.TargAddr The destination address of the IP packet triggering the route request. RteMsg.TargPrefixLen The prefix length associated with RteMsg.TargAddr, originally from the Router Client entry on RREP_Gen which includes RteMsg.TargAddr. If RteMsg is a RREQ, RteMsg.TargPrefixLen MUST equal address length. RteMsg.OrigSeqNum The sequence number associated with the route to OrigAddr, if RteMsg is an RREQ. RteMsg.TargSeqNum The sequence number associated with the route to TargAddr, if RteMsg is an RREP. RteMsg.MetricType The metric type of the route requested. RteMsg.Metric The metric value received in the RteMsg. RteMsg.Timestamp The last time this Multicast Route Message Table entry was updated. RteMsg.RemoveTime Perkins, et al. Expires October 6, 2016 [Page 16] Internet-Draft AODVv2 April 2016 The time at which this entry MUST be removed from the Multicast Route Message Table. This is set to CurrentTime + MAX_SEQNUM_LIFETIME, whenever the sequence number of this entry (RteMsg.OrigSeqNum for an RREQ, or RteMsg.TargSeqNum for an RREP) is updated. RteMsg.AckReqAddr The address from which a RREP_Ack is expected, if RteMsg is a RREP that contains an AckReq. The Multicast Route Message Table is maintained so that no two entries have the same MessageType, OrigAddr, TargAddr, and MetricType. See Section 6.8 for details about updating this table. 4.7. Route Error (RERR) Table Each sent RERR message SHOULD be recorded in a conceptual table called the Route Error (RERR) Table. Each entry contains the following information: RerrMsg.Timeout The time after which the entry SHOULD be deleted. RerrMsg.AddressList The AddressList of the RERR to be recorded. RerrMsg.PktSource: The PktSource of the RERR to be recorded, if any. See section Section 6.9 for instructions on how to update the table. 5. Metrics Metrics measure a cost or quality associated with a route or a link, e.g., latency, delay, financial cost, energy, etc. Metric values are reported in Route Request and Route Reply messages. In Route Request messages, the metric describes the cost of the route from OrigAddr (and any other addresses included in the prefix length of RREQ_Gen's Router Client entry for OrigAddr) to the router sending the Route Request. For RREQ_Gen, this is the cost associated with the Router Client entry which includes OrigAddr. For routers which regenerate the RREQ, this is the cost from OrigAddr to the regenerating router, combining the metric value from the received RREQ message with knowledge of the link cost from the sender to the receiver, i.e., the incoming link cost. This updated route cost is included when regenerating the Route Request message, and used to install a route back toward OrigAddr. Perkins, et al. Expires October 6, 2016 [Page 17] Internet-Draft AODVv2 April 2016 Similarly, in Route Reply messages, the metric reflects the cost of the route from TargAddr (and any other addresses included in the prefix length of RREP_Gen's Router Client entry for TargAddr) to the router sending the Route Reply. For RREP_Gen, this is the cost associated with the Router Client entry which includes TargAddr. For routers which regenerate the RREP, this is the cost from TargAddr to the regenerating router, combining the metric value from the received RREP message with knowledge of the link cost from the sender to the receiver, i.e., the incoming link cost. This updated route cost is included when regenerating the Route Reply message, and used to install a route back toward TargAddr. Assuming link metrics are symmetric, the cost of the routes installed in the Local Route Set at each router will be correct. While this assumption is not always correct, calculating incoming/outgoing metric data is outside of scope of this document. The route discovered is optimised for the requesting router, and the return path may not be the optimal route. AODVv2 enables the use of multiple metric types. Each route discovery attempt indicates the metric type which is requested for the route. Only one metric type MUST be used in each route discovery attempt. For each MetricType, AODVv2 requires: o A MetricType number, to indicate the metric type of a route. MetricType numbers allocated are detailed in Section 11.6. o A maximum value, denoted MAX_METRIC[MetricType]. This MUST always be the maximum expressible metric value of type MetricType. Field lengths associated with metric values are found in Section 11.6. If the cost of a route exceeds MAX_METRIC[MetricType], the route is ignored. o A function for incoming link cost, denoted Cost(L). Using incoming link costs means that the route learned has a path optimized for the direction from OrigAddr to TargAddr. o A function for route cost, denoted Cost(R). o A function to analyze routes for potential loops based on metric information, denoted LoopFree(R1, R2). LoopFree verifies that a route R2 is not a sub-section of another route R1. An AODVv2 router invokes LoopFree() as part of the process in Section 6.7.1, when an advertised route (R1) and an existing LocalRoute (R2) have the same destination address, metric type, and sequence number. LoopFree returns FALSE to indicate that an advertised route is not Perkins, et al. Expires October 6, 2016 [Page 18] Internet-Draft AODVv2 April 2016 to be used to update a stored LocalRoute, as it may cause a routing loop. In the case where the existing LocalRoute is Invalid, it is possible that the advertised route includes the existing LocalRoute and came from a router which did not yet receive notification of the route becoming Invalid, so the advertised route should not be used to update the Local Route Set, in case it forms a loop to a broken route. AODVv2 currently supports cost metrics where Cost(R) is strictly increasing, by defining: o Cost(R) := Sum of Cost(L) of each link in the route o LoopFree(R1, R2) := ( Cost(R1) <= Cost(R2) ) Implementers MAY consider other metric types, but the definitions of Cost and LoopFree functions for such types are undefined, and interoperability issues need to be considered. 6. AODVv2 Protocol Operations The AODVv2 protocol's operations include managing sequence numbers, monitoring next hop AODVv2 routers on discovered routes and updating the Neighbor Table, performing route discovery and dealing with requests from other routers, processing incoming route information and updating the Local Route Set, updating the Multicast Route Message Table and suppressing redundant messages, and reporting broken routes. These processes are discussed in detail in the following sections. 6.1. Initialization During initialization where an AODVv2 router does not have information about its previous sequence number, or if its sequence number is lost at any point, the router resets its sequence number to one (1). However, other AODVv2 routers may still hold sequence number information that this router previously issued. Since sequence number information is removed if there has been no update to the sequence number in MAX_SEQNUM_LIFETIME, the initializing router MUST wait for MAX_SEQNUM_LIFETIME before it creates any messages containing its new sequence number. It can then be sure that the information it sends will not be considered stale. During this wait period, the router is permitted to do the following: o Process information in a received RREQ or RREP message to learn a route to the originator or target of that route discovery Perkins, et al. Expires October 6, 2016 [Page 19] Internet-Draft AODVv2 April 2016 o Regenerate a received RREQ or RREP o Send an RREP_Ack o Maintain valid routes in the Local Route Set o Create, process and regenerate RERR messages 6.2. Next Hop Monitoring To ensure AODVv2 routers Routers do not establish routes over uni- directional links, AODVv2 routers MUST verify that the link to the next hop router is bidirectional before marking a route as valid in the Local Route Set. AODVv2 provides a mechanism for testing bidirectional connectivity during route discovery, and blacklisting routers where bidirectional connectivity is not available. If a route discovery is retried by RREQ_Gen, the blacklisted routers can be excluded from the process, and a different route can be discovered. Further, a route is not to be used for forwarding until the bidirectionality of the link to the next hop is confirmed. AODVv2 routers do not need to monitor bidirectionality for links to neighboring routers which are not used as next hops on routes in the Local Route Set. o Bidirectional connectivity to upstream routers is tested by requesting acknowledgement of RREP messages by including an AckReq, which MUST be answered by sending an RREP_Ack. Receipt of an RREP_Ack within RREP_Ack_SENT_TIMEOUT proves that bidirectional connectivity exists. Otherwise, a link is determined to be unidirectional. All AODVv2 routers MUST support this process, which is explained in Section 7.2 and Section 7.3. o For the downstream router, receipt of an RREP message containing the route to TargAddr is confirmation of bidirectionality , since an RREP message is a reply to a RREQ message which previously crossed the link in the opposite direction. To assist with next hop monitoring, a Neighbor Table (Section 4.3) is maintained. When an RREQ or RREP is received, search for an entry in the Neighbor Table where all of the following conditions are met: o Neighbor.IPAddress == IP address from which the RREQ or RREP was received o Neighbor.Interface == Interface on which the RREQ or RREP was received. Perkins, et al. Expires October 6, 2016 [Page 20] Internet-Draft AODVv2 April 2016 If such an entry does not exist, a new entry is created as described in Section 6.3. While the value of Neighbor.State is Unknown, acknowledgement of RREP messages sent to that neighbor MUST be requested. If an acknowledgement is not received within the timeout period, the neighbor MUST have Neighbor.State set to Blacklisted. If an acknowledgement is received within the timeout period, Neighbor.State is set to Confirmed. While the value of Neighbor.State is Confirmed, the request for an acknowledgement of any other RREP message is unnecessary. When routers perform other operations such as those from the list below, these MAY be used as additional indications of connectivity: o NHDP HELLO Messages [RFC6130] o Route timeout o Lower layer triggers, e.g. message reception or link status notifications o TCP timeouts o Promiscuous listening o Other monitoring mechanisms or heuristics If such an external process signals that the link to a neighbor is bidirectional, the AODVv2 router MAY update the matching Neighbor Table entry by changing the value of Neighbor.State to Confirmed, e.g. receipt of a Neighborhood Discovery Protocol HELLO message with the receiving router listed as a neighbor. If an external process signals that a link is not bidirectional, the the value of Neighbor.State MAY be changed to Blacklisted, e.g. notification of a TCP timeout. 6.3. Neighbor Table Update On receipt of an RREQ or RREP message, the Neighbor Table MUST be checked for an entry with Neighbor.IPAddress which matches the source IP address of a packet containing the AODVv2 message. If no matching entry is found, a new entry is created. A new Neighbor Table entry is created as follows: o Neighbor.IPAddress := Source IP address of the received route message o Neighbor.State := Unknown Perkins, et al. Expires October 6, 2016 [Page 21] Internet-Draft AODVv2 April 2016 o Neighbor.ResetTime := INFINITY_TIME o Neighbor.Interface := Interface on which the RREQ or RREP was received. MUST equal Interface.Id of one of the entries in the InterfaceSet (see Section 4.1). If the message is one of the following: o an RREP which answers a RREQ sent within RREQ_WAIT_TIME over the same interface as Neighbor.Interface o an RREP_Ack which answers a RREP sent within RREP_Ack_SENT_TIMEOUT over the same interface as Neighbor.Interface the link to the neighbor is bidirectional and the Neighbor Table entry is updated as follows: o Neighbor.State := Confirmed o Neighbor.ResetTime := INFINITY_TIME If an RREP_Ack is not received within RREP_Ack_SENT_TIMEOUT, the link is considered to be uni-directional and the Neighbor Table entry is updated as follows: o Neighbor.State := Blacklisted o Neighbor.ResetTime := CurrentTime + MAX_BLACKLIST_TIME When the Neighbor.ResetTime is reached, the Neighbor Table entry is updated as follows: o Neighbor.State := Unknown When a link to a neighbor is determined to be broken, the Neighbor Table entry SHOULD be removed. Route requests from neighbors with Neighbor.State set to Blacklisted are ignored to avoid persistent IP packet loss or protocol failures. Neighbor.ResetTime allows the neighbor to again be allowed to participate in route discoveries after MAX_BLACKLIST_TIME, in case the link between the routers has become bidirectional. 6.4. Interaction with the Forwarding Plane The signals descried in the following are conceptual signals, and can be implemented in various ways. Conformant implementations of AODVv2 are not mandated to implement the forwarding plane separately from Perkins, et al. Expires October 6, 2016 [Page 22] Internet-Draft AODVv2 April 2016 the control plane or data plane; these signals and interactions are identified simply as assistance for implementers who may find them useful. AODVv2 requires signals from the forwarding plane: o A packet cannot be forwarded because a route is unavailable: AODVv2 needs to know the source and destination IP addresses of the packet. If the source of the packet is configured as a Router Client, the router should initiate route discovery to the destination. If it is not a Router Client, the router should create a Route Error message. o A packet is to be forwarded: AODVv2 needs to check the state of the route to ensure it is still valid. o Packet forwarding succeeds: AODVv2 needs to update the record of when a route was last used to forward a packet. o Packet forwarding failure occurs: AODVv2 needs to create a Route Error message. AODVv2 needs to send signals to the forwarding plane: o A route discovery is in progress: buffering might be configured for packets requiring a route, while route discovery is attempted. o A route discovery failed: any buffered packets requiring that route should be discarded, and the source of the packet should be notified that the destination is unreachable (using an ICMP Destination Unreachable message). Route discovery fails if an RREQ cannot be generated because the control message generation limit has been reached, or if an RREP is not received within RREQ_WAIT_TIME (see Section 6.6). o A route discovery is not permitted: any buffered packets requiring that route should be discarded. A route discovery will not be attempted if the source address of the packet needing a route is not configured as a Router Client. o A route discovery succeeded: install a corresponding route into the Routing Information Base and begin transmitting any buffered packets. o A route has been made invalid: remove the corresponding route from the Routing Information Base. Perkins, et al. Expires October 6, 2016 [Page 23] Internet-Draft AODVv2 April 2016 o A route has been updated: update the corresponding route in the Routing Information Base. 6.5. Message Transmission AODVv2 sends [RFC5444] formatted messages using the parameters for port number and IP protocol specified in [RFC5498]. Mapping of AODVv2 data to [RFC5444] messages is detailed in Section 8. AODVv2 multicast messages are sent to the link-local multicast address LL- MANET-Routers [RFC5498]. All AODVv2 routers MUST subscribe to LL- MANET-Routers on all AODVv2 interfaces [RFC5498] to receive AODVv2 messages. Note that multicast messages MAY be sent via unicast. For example, this may occur for certain link-types (non-broadcast media), for manually configured router adjacencies, or in order to improve robustness. When multiple interfaces are available, an AODVv2 router transmitting a multicast message to LL-MANET-Routers MUST send the message on all interfaces that have been configured for AODVv2 operation, as given in the InterfaceSet (Section 4.1). To avoid congestion, each AODVv2 router's rate of message generation SHOULD be limited (CONTROL_TRAFFIC_LIMIT) and administratively configurable. Messages SHOULD NOT be sent more frequently than one message per (1 / CONTROL_TRAFFIC_LIMIT)th of a second. If this threshold is reached, messages MUST be sent based on their priority: o Highest priority SHOULD be given to RREP_Ack messages. This allows links between routers to be confirmed as bidirectional and avoids undesired blacklisting of next hop routers. o Second priority SHOULD be given to RERR messages for undeliverable IP packets. This avoids repeated forwarding of packets over broken routes that are still in use by other routers. o Third priority SHOULD be given to RREP messages in order that RREQs do not time out. o Fourth priority SHOULD be given to RREQ messages. o Fifth priority SHOULD be given to RERR messages for newly invalidated routes. o Lowest priority SHOULD be given to RERR messages generated in response to RREP messages which cannot be regenerated. In this case the route request will be retried at a later point. Perkins, et al. Expires October 6, 2016 [Page 24] Internet-Draft AODVv2 April 2016 6.6. Route Discovery, Retries and Buffering AODVv2's RREQ and RREP messages are used for route discovery. RREQ messages are multicast to solicit an RREP, whereas RREP are unicast where possible. The constants used inSection 6.7.1 this section are defined in Section 11. When an AODVv2 router needs to forward an IP packet (with source address OrigAddr and destination address TargAddr) from one of its Router Clients, it needs a route to TargAddr in its Routing Information Base. If no route exists, the AODVv2 router generates (RREQ_Gen) and multicasts a Route Request message (RREQ), on all configured interfaces, containing OrigAddr and TargAddr. The procedure for this is described in Section 7.1.1. Each generated RREQ results in an increment to the router's sequence number. The AODVv2 router generating an RREQ is referred to as RREQ_Gen. Buffering might be configured for IP packets awaiting a route for forwarding by RREQ_Gen, if sufficient memory is available. Buffering of IP packets might have both positive and negative effects. Real- time traffic, voice, and scheduled delivery may suffer if packets are buffered and subjected to delays, but TCP connection establishment will benefit if packets are queued while route discovery is performed [Koodli01]. Recommendations for appropriate buffer methods are out of scope for this specification. Determining which packets to discard first when the buffer is full is a matter of policy at each AODVv2 router. Note that using different or no buffer methods does not affect interoperability. RREQ_Gen awaits reception of a Route Reply message (RREP) containing a route toward TargAddr. If a valid route to TargAddr is not learned within RREQ_WAIT_TIME, RREQ_Gen will retry the route discovery. To reduce congestion in a network, repeated attempts at route discovery for a particular target address utilize a binary exponential backoff: for each additional attempt, the time to wait for receipt of the RREP is multiplied by 2. If the requested route is not learned within the wait period, another RREQ is sent, up to a total of DISCOVERY_ATTEMPTS_MAX. This is the same technique used in AODV [RFC3561]. Through the use of bidirectional link monitoring and blacklists (see Section 6.2) uni-directional links on initial selected route will be ignored on subsequent route discovery attempts. Route discovery is considered to have failed after DISCOVERY_ATTEMPTS_MAX and the corresponding wait time for an RREP response to the final RREQ. After the attempted route discovery has failed, RREQ_Gen waits at least RREQ_HOLDDOWN_TIME before attempting Perkins, et al. Expires October 6, 2016 [Page 25] Internet-Draft AODVv2 April 2016 another route discovery to the same destination, in order to avoid repeatedly generating control traffic that is unlikely to discover a route. Any IP packets buffered for TargAddr are also dropped and a Destination Unreachable ICMP message (Type 3) with a code of 1 (Host Unreachable Error) is delivered to the source of the packet, so that the application knows about the failure. If RREQ_Gen does receive a route message containing a route to TargAddr within the timeout, it processes the message according to Section 7. When a valid LocalRoute entry is created in the Local Route Set, the route is also installed in the Routing Information Base, and the router will begin sending the buffered IP packets. Any retry timers for the corresponding RREQ are then cancelled. During route discovery, all routers on the path learn a route to both OrigAddr and TargAddr, so that routes are constructed in both directions. The route is optimized for the forward route. 6.7. Processing Received Route Information All AODVv2 route messages contain a route. A Route Request (RREQ) contains a route toward OrigAddr (and other addresses as indicated by OrigPrefixLen), and a Route Reply (RREP) contains a route toward TargAddr (and other addresses as indicated by TargPrefixLen). All AODVv2 routers that receive a route message are able to store the route contained within it in their Local Route Set. Incoming information is first checked to verify that it is both safe to use and offers an improvement to existing information, as explained in Section 6.7.1. If these checks pass, the Local Route Set MUST be updated according to Section 6.7.2. In the processes below, RteMsg is used to denote the route message, AdvRte is used to denote the route contained within it, and LocalRoute denotes an existing entry in the Local Route Set which matches AdvRte on address, prefix length, and metric type. AdvRte has the following properties: o AdvRte.Address := network address given by combining RteMsg.OrigAddr and RteMsg.OrigPrefixLen (in RREQ) or RteMsg.TargAddr and RteMsg.TargPrefixLen (in RREP) o AdvRte.PrefixLength := RteMsg.OrigPrefixLen (in RREQ) or RteMsg.TargPrefixLen (in RREP). If no prefix length was included in RteMsg, prefix length is the address length, in bits, of RteMsg.OrigAddr (in RREQ) or RteMsg.TargAddr (in RREP) Perkins, et al. Expires October 6, 2016 [Page 26] Internet-Draft AODVv2 April 2016 o AdvRte.SeqNum := RteMsg.OrigSeqNum (in RREQ) or RteMsg.TargSeqNum (in RREP) o AdvRte.NextHop := RteMsg.IPSourceAddress (an address of the sending interface of the router from which the RteMsg was received) o AdvRte.MetricType := RteMsg.MetricType o AdvRte.Metric := RteMsg.Metric o AdvRte.Cost := Cost(R) using the cost function associated with the route's metric type, i.e. Cost(R) = AdvRte.Metric + Cost(L), as described in Section 5, where L is the link from the advertising router o AdvRte.ValidityTime := RteMsg.ValidityTime, if included 6.7.1. Evaluating Route Information An incoming advertised route (AdvRte) is compared to existing LocalRoutes to determine whether the advertised route is to be used to update the AODVv2 Local Route Set. The incoming route information MUST be processed as follows: 1. Search for LocalRoutes in the Local Route Set matching AdvRte's address, prefix length and metric type * If no matching LocalRoute exists, AdvRte MUST be used to update the Local Route Set and no further checks are required. * If matching LocalRoutes are found, continue to Step 2. 2. Compare sequence numbers using the technique described in Section 4.4 * If AdvRte is more recent than all matching LocalRoutes, AdvRte MUST be used to update the Local Route Set and no further checks are required. * If AdvRte is stale, AdvRte MUST NOT be used to update the Local Route Set. Ignore AdvRte for further processing. * If the sequence numbers are equal, continue to Step 3. 3. Check that AdvRte is safe against routing loops compared to all matching LocalRoutes (see Section 5) Perkins, et al. Expires October 6, 2016 [Page 27] Internet-Draft AODVv2 April 2016 * If LoopFree(AdvRte, LocalRoute) returns FALSE, ignore AdvRte for further processing. AdvRte MUST NOT be used to update the Local Route Set because using the incoming information might cause a routing loop. * If LoopFree(AdvRte, LocalRoute) returns TRUE, continue to Step 4. 4. Compare route costs * If AdvRte is better than all matching LocalRoutes, it SHOULD be used to update the Local Route Set because it offers improvement. If it is not used to update the Local Route Set, the existing non-optimal LocalRoute will continue to be used, causing data traffic to use a non-optimal route. * If AdvRte is equal in cost and LocalRoute is valid, AdvRte SHOULD NOT be used to update the Local Route Set because it will offer no improvement. * If AdvRte is worse and LocalRoute is valid, ignore AdvRte for further processing. AdvRte MUST NOT be used to update the Local Route Set because it does not offer any improvement. * If AdvRte is not better (i.e., it is worse or equal) but LocalRoute is Invalid, AdvRte SHOULD be used to update the Local Route Set because it can safely repair the existing Invalid LocalRoute. If the advertised route is to be used to update the Local Route Set, the procedure in Section 6.7.2 MUST be followed. If not, non-optimal routes will remain in the Local Route Set. For information on how to apply these changes to the Routing Information Base, see Section 4.5. 6.7.2. Applying Route Updates After determining that AdvRte is to be used to update the Local Route Set (as described in Section 6.7.1), the following procedure applies. If AdvRte is learned from an RREQ message, the link to the next hop neighbor may not be confirmed as bidirectional (see Section 4.3). The route will offer improvement to the Local Route Set if the neighbor can be confirmed. If there is no existing matching route, AdvRte allows a corresponding RREP to be sent. If a matching entry already exists, AdvRte offers potential improvement. Perkins, et al. Expires October 6, 2016 [Page 28] Internet-Draft AODVv2 April 2016 The route update is applied as follows: 1. If no existing entry in the Local Route Set matches AdvRte's address, prefix length and metric type, continue to Step 4 and create a new entry in the Local Route Set. 2. If two matching LocalRoutes exist in the Local Route Set, one is a valid route, and one is an Unconfirmed route, AdvRte may offer further improvement to the Unconfirmed route, or may offer an update to the valid route. * If AdvRte.NextHop's Neighbor.State is Unknown, the advertised route may offer improvement to the existing valid route, if the link to the next hop can be confirmed as bidirectional. Continue processing from Step 5 to update the existing Unconfirmed LocalRoute. * If AdvRte.NextHop's Neighbor.State is Confirmed, the advertised route offers an update or improvement to the existing valid route. Continue processing from Step 5 to update the existing valid LocalRoute. 3. If only one matching LocalRoute exists in the Local Route Set: * If AdvRte.NextHop's Neighbor.State is Confirmed, continue processing from Step 5 to update the existing LocalRoute. * If AdvRte.NextHop's Neighbor.State is Unknown, AdvRte may offer improvement the existing LocalRoute, if the link to AdvRte.NextHop can be confirmed as bidirectional. * If LocalRoute.State is Unconfirmed, AdvRte is an improvement to an existing Unconfirmed route. Continue processing from Step 5 to update the existing LocalRoute. * If LocalRoute.State is Invalid, AdvRte can replace the existing LocalRoute. Continue processing from Step 5 to update the existing LocalRoute. * If LocalRoute.State is Active or Idle, AdvRte SHOULD be stored as an additional entry in the Local Route Set, with LocalRoute.State set to Unconfirmed. Continue processing from Step 4 to create a new LocalRoute. 4. Create an entry in the Local Route Set and initialize as follows: * LocalRoute.Address := AdvRte.Address Perkins, et al. Expires October 6, 2016 [Page 29] Internet-Draft AODVv2 April 2016 * LocalRoute.PrefixLength := AdvRte.PrefixLength * LocalRoute.MetricType := AdvRte.MetricType 5. Update the LocalRoute as follows: * LocalRoute.SeqNum := AdvRte.SeqNum * LocalRoute.NextHop := AdvRte.NextHop * LocalRoute.NextHopInterface := interface on which RteMsg was received * LocalRoute.Metric := AdvRte.Cost * LocalRoute.LastUsed := CurrentTime * LocalRoute.LastSeqNumUpdate := CurrentTime * LocalRoute.ExpirationTime := CurrentTime + AdvRte.ValidityTime if a validity time exists, otherwise INFINITY_TIME 6. If a new LocalRoute was created, or if the existing LocalRoute.State is Invalid or Unconfirmed, update LocalRoute as follows: * LocalRoute.State := Unconfirmed (if the next hop's Neighbor.State is Unknown) * LocalRoute.State := Idle (if the next hop's Neighbor.State is Confirmed) 7. If an existing LocalRoute.State changed from Invalid or Unconfirmed to become Idle, any matching Unconfirmed LocalRoute with worse metric value SHOULD be expunged. 8. If an existing LocalRoute was updated with a better metric value, any matching Unconfirmed LocalRoute with worse metric value SHOULD be expunged. 9. If this update results in LocalRoute.State of Active or Idle, which matches a route request which is still in progress, the associated route request retry timers SHOULD be cancelled. If this update to the Local Route Set results in two LocalRoutes to the same address, the best LocalRoute will be Unconfirmed. In order to improve the route used for forwarding, the router SHOULD try to determine if the link to the next hop of that LocalRoute is Perkins, et al. Expires October 6, 2016 [Page 30] Internet-Draft AODVv2 April 2016 bidirectional, by using that LocalRoute to forward future RREPs and request acknowledgements (see Section 7.2.1). 6.8. Suppressing Redundant Messages Using the Multicast Route Message Table When route messages are flooded in a MANET, an AODVv2 router may receive multiple similar messages. Regenerating every one of these gives little additional benefit, and generates unnecessary signaling traffic and might generate unnecessary interference. Each AODVv2 router stores information about recently received route messages in the AODVv2 Multicast Route Message Table (Section 4.6). Its Entries consist of: o RteMsg.MessageType o RteMsg.OrigAddr o RteMsg.OrigPrefixLen o RteMsg.TargAddr o RteMsg.TargPrefixLen o RteMsg.OrigSeqNum o RteMsg.TargSeqNum o RteMsg.MetricType o RteMsg.Metric o RteMsg.Timestamp o RteMsg.RemoveTime Entries in the Multicast Route Message Table SHOULD be maintained for at least RteMsg_ENTRY_TIME after the last Timestamp update in order to account for long-lived RREQs traversing the network. An entry MUST be deleted when the sequence number is no longer valid, i.e., after MAX_SEQNUM_LIFETIME. Memory-constrained devices MAY remove the entry before this time. Received route messages are tested against previously received route messages, and if determined to be redundant, regeneration or response can be avoided. Perkins, et al. Expires October 6, 2016 [Page 31] Internet-Draft AODVv2 April 2016 To determine if a received message is redundant: 1. Search for an entry in the Multicast Route Message Table with the same MessageType, OrigAddr, TargAddr, and MetricType * If there is no entry, the message is not redundant. * If there is an entry, continue to Step 2. 2. Compare sequence numbers using the technique described in Section 4.4 * For RREQ messages, use OrigSeqNum of the entry for comparison. For RREP messages, use TargSeqNum of the entry for comparison. * If the entry has an older sequence number than the received message, the message is not redundant. * If the entry has a newer sequence number than the received message, the message is redundant. * If the entry has the same sequence number, continue to Step 3. 3. Compare the metric values * If the entry has a Metric value that is worse than or equal to the metric in the received message, the message is redundant. * If the entry has a Metric value that is better than the metric in the received message, the message is not redundant. If the message is redundant, update the Timestamp and RemoveTime on the entry, since matching route messages are still traversing the network and this entry should be maintained. This message MUST NOT be regenerated or responded to. If the message is not redundant, create an entry or update the existing entry. To update a Multicast Route Message Table entry, set: o RteMsg.MessageType := the message type of the received message o RteMsg.OrigAddr := OrigAddr from the message o RteMsg.OrigPrefixLen := the prefix length associated with OrigAddr o RteMsg.TargAddr := TargAddr from the message Perkins, et al. Expires October 6, 2016 [Page 32] Internet-Draft AODVv2 April 2016 o RteMsg.TargPrefixLen := the prefix length associated with TargAddr o RteMsg.OrigSeqNum := the sequence number associated with OrigAddr, if present in the received message o RteMsg.TargSeqNum := the sequence number associated with TargAddr, if present in the received message o RteMsg.Metric := the metric value associated with OrigAddr in a received RREQ or TargAddr in a received RREP o RteMsg.MetricType := the metric type associated with RteMsg.Metric o RteMsg.Timestamp := CurrentTime o RteMsg.RemoveTime := CurrentTime + MAX_SEQNUM_LIFETIME Where the message is determined not redundant before Step 3, it MUST be regenerated or responded to. When a message is determined to be not redundant in Step 3, it MAY be suppressed to avoid extra control traffic. However, since the processing of the message will result in an update to the Local Route Set, the message SHOULD be regenerated or responded to, to ensure other routers have up-to-date information and the best metrics. If the message is not regenerated, the best route may not be found. Regeneration or response is to be performed using the processes outlined in Section 7. 6.9. Suppressing Redundant Route Error Messages using the Route Error Table In order to avoid flooding the network with RERR messages when a stream of IP packets to an unreachable address arrives, an AODVv2 router SHOULD avoid creating duplicate messages by determining whether an equivalent RERR has recently been sent. This is achieved with the help of the Route Error Table (see Section 4.7). To determine if a received RERR is redundant: 1. Search for an entry in the Route Error Table where: * RerrMsg.AddressList == RERR.AddressList * RerrMsg.PktSource == RERR.PktSource If a matching entry is found, no further processing is required and the RERR SHOULD NOT be sent. Perkins, et al. Expires October 6, 2016 [Page 33] Internet-Draft AODVv2 April 2016 2. If no matching entry is found, a new entry with the following properties is created: * RerrMsg.Timeout := CurrentTime + RERR_TIMEOUT * RerrMsg.AddressList == RERR.AddressList * RerrMsg.PktSource == RERR.PktSource 6.10. Local Route Set Maintenance Route maintenance involves monitoring LocalRoutes in the Local Route Set, updating LocalRoute.State to handle route timeouts and reporting routes that become Invalid. 6.10.1. LocalRoute State Changes During normal operation, AODVv2 does not require any explicit timeouts to manage the lifetime of a route. At any time, any LocalRoute MAY be examined and updated according to the rules below. If timers are not used to prompt updates of LocalRoute.State, the LocalRoute.State MUST be checked before IP packet forwarding and before any operation based on LocalRoute.State. Route timeout behaviour is as follows: o An Unconfirmed route MUST be expunged at MAX_SEQNUM_LIFETIME after LocalRoute.LastSeqNumUpdate. o An Idle route MUST become Active when used to forward an IP packet. If the route is not used to forward an IP packet within MAX_IDLETIME, LocalRoute.State MUST become Invalid. o An Active route which is a timed route (i.e., with LocalRoute.ExpirationTime not equal to INFINITY_TIME) remains Active until LocalRoute.ExpirationTime, after which it MUST become Invalid. If it it not a timed route, it MUST become Idle if the route is not used to forward an IP packet within ACTIVE_INTERVAL. o An Invalid route SHOULD remain in the Local Route Set, since LocalRoute.SeqNum is used to classify future information about LocalRoute.Address as stale or fresh. o In all cases, if the time since LocalRoute.LastSeqNumUpdate exceeds MAX_SEQNUM_LIFETIME, LocalRoute.SeqNum must be set to zero. This is required to ensure that any AODVv2 routers following the initialization procedure can safely begin routing functions using a new sequence number. A LocalRoute with Perkins, et al. Expires October 6, 2016 [Page 34] Internet-Draft AODVv2 April 2016 LocalRoute.State set to Active or Idle can remain in the Local Route Set after removing the sequence number, for exmple if the route is reliably carrying traffic. If LocalRoute.State is Invalid, or later becomes Invalid, the LocalRoute MUST be expunged from the Local Route Set. LocalRoutes can become Invalid before a timeout occurs: o If an external mechanism reports a link as broken, all LocalRoutes using that link for LocalRoute.NextHop MUST immediately have LocalRoute.State set to Invalid. o LocalRoute.State MUST immediately be set to Invalid if a Route Error (RERR) message is received where: * The sender is LocalRoute.NextHop or PktSource is a Router Client address * There is an Address in AddressList which matches LocalRoute.Address, and: + The prefix length associated with this Address, if any, matches LocalRoute.PrefixLength + The sequence number associated with this Address, if any, is newer or equal to LocalRoute.SeqNum (see Section 4.4) + The metric type associated with this Address matches LocalRoute.MetricType LocalRoutes are also updated when Neighbor.State is updated: o While the value of Neighbor.State is set to Unknown, any routes in the Local Route Set using that neighbor as a next hop MUST have LocalRoute.State set to Unconfirmed. o When the value of Neighbor.State is set to Confirmed, the Unconfirmed routes in the Local Route Set using that neighbor as a next hop MUST have LocalRoute.State set to Idle. Any other matching LocalRoutes with metric values worse than LocalRoute.Metric MUST be expunged from the Local Route Set. o When the value of Neighbor.State is set to Blacklisted, any valid routes in the Local Route Set using that neighbor for their next hop MUST have LocalRoute.State set to Invalid. Perkins, et al. Expires October 6, 2016 [Page 35] Internet-Draft AODVv2 April 2016 o When a Neighbor Table entry is removed, all routes in the Local Route Set using that neighbor as next hop MUST have LocalRoute.State set to Invalid. Memory constrained devices MAY choose to expunge routes from the AODVv2 Local Route Set before LocalRoute.ExpirationTime, but MUST adhere to the following rules: o An Active route MUST NOT be expunged, as it is in use. If deleted, IP traffic forwarded to this router will prompt generation of a Route Error message, and it will be necessary for a Route Request to be generated by the originator's router to re- establish the route. o An Idle route SHOULD NOT be expunged, as it is still valid for forwarding IP traffic. If deleted, this could result in dropped IP packets and a Route Request could be generated to re-establish the route. o Any Invalid route MAY be expunged. Least recently used Invalid routes SHOULD be expunged first, since the sequence number information is less likely to be useful. o An Unconfirmed route MUST NOT be expunged if it was installed within the last RREQ_WAIT_TIME, because it may correspond to a route discovery in progress. A Route Reply message might be received which needs to use the LocalRoute.NextHop information. Otherwise, it MAY be expunged. 6.10.2. Reporting Invalid Routes When LocalRoute.State changes from Active to Invalid as a result of a broken link or a received Route Error (RERR) message, other AODVv2 routers MUST be informed by sending an RERR message containing details of the invalidated route. An RERR message MUST also be sent when an AODVv2 router receives an IP packet to forward on behalf of another router but does not have a valid route in its Routing Information Base for the destination of the packet. An RERR message MUST also be sent when an AODVv2 router receives an RREP message to regenerate, but the LocalRoute to the OrigAddr in the RREP has been lost or is marked as Invalid. The packet or message triggering the RERR MUST be discarded. Generation of an RERR message is described in Section 7.4.1. Perkins, et al. Expires October 6, 2016 [Page 36] Internet-Draft AODVv2 April 2016 7. AODVv2 Protocol Messages AODVv2 defines four message types: Route Request (RREQ), Route Reply (RREP), Route Reply Acknowledgement (RREP_Ack), and Route Error (RERR). Each AODVv2 message is defined as a set of data. Rules for the generation, reception and regeneration of each message type are described in the following sections. Section 8 discusses how the data is mapped to [RFC5444] Message TLVs, Address Blocks, and Address TLVs. 7.1. Route Request (RREQ) Message Route Request messages are used in route discovery operations to request a route to a specified target address. RREQ messages have the following contents: +-----------------------------------------------------------------+ | AddressList | +-----------------------------------------------------------------+ | PrefixLengthList (optional) | +-----------------------------------------------------------------+ | OrigSeqNum, (optional) TargSeqNum | +-----------------------------------------------------------------+ | MetricType | +-----------------------------------------------------------------+ | OrigMetric | +-----------------------------------------------------------------+ | ValidityTime (optional) | +-----------------------------------------------------------------+ Figure 1: RREQ message contents AddressList Contains OrigAddr and TargAddr, the source and destination addresses of the IP packet for which a route is requested. OrigAddr and TargAddr MUST be routable unicast addresses. PrefixLengthList Contains OrigPrefixLen, i.e., the length, in bits, of the prefix associated with the Router Client entry which includes OrigAddr. If omitted, the prefix length is equal to OrigAddr's address length in bits. OrigSeqNum The sequence number associated with OrigAddr. Perkins, et al. Expires October 6, 2016 [Page 37] Internet-Draft AODVv2 April 2016 TargSeqNum A sequence number associated with an existing Invalid route to TargAddr. This MAY be included if available, and is useful for the optional Intermediate RREP feature (see Section 10.3). MetricType The metric type associated with OrigMetric. OrigMetric The metric value associated with the LocalRoute to OrigAddr (and to any other addresses included in the given prefix length), as seen from the sender of the message. ValidityTime The length of time that the message sender is willing to offer a route toward OrigAddr (and any other addresses included in the given prefix length). Omitted if no time limit is imposed. 7.1.1. RREQ Generation An RREQ is generated when an IP packet needs to be forwarded for a Router Client, and no valid route currently exists for the packet's destination in the Routing Information Base. Before creating an RREQ, the router SHOULD check the Multicast Route Message Table to see if an RREQ has recently been sent for the requested destination. If so, and the wait time for a reply has not yet been reached, the router SHOULD continue to await a response without generating a new RREQ. If the timeout has been reached, a new RREQ MAY be generated. If buffering is configured, incoming IP packets awaiting this route SHOULD be buffered until the route discovery is completed. If the limit for the rate of AODVv2 control message generation has been reached, no message SHOULD be generated. If approaching the limit, the message should be sent if the priorities in Section 6.5 allow it. To generate the RREQ, the router (referred to as RREQ_Gen) follows this procedure: 1. Set AddressList := {OrigAddr, TargAddr} 2. For the PrefixLengthList: * If OrigAddr is part of an address range configured as a Router Client, set PrefixLengthList := {RouterClient.PrefixLength, null}. This allows receiving routers to learn a route to all Perkins, et al. Expires October 6, 2016 [Page 38] Internet-Draft AODVv2 April 2016 the addresses included by the prefix length, not only to OrigAddr. * Otherwise, omit PrefixLengthList. 3. For OrigSeqNum: * Increment the router SeqNum as specified in Section 4.4. * Set OrigSeqNum := SeqNum. 4. For TargSeqNum: * If an Invalid route exists in the Local Route Set matching TargAddr using longest prefix matching and has a valid sequence number, set TargSeqNum := LocalRoute.SeqNum. * If no Invalid route exists in the Local Route Set matching TargAddr, or the route doesn't have a sequence number, omit TargSeqNum. 5. Include MetricType and set the type accordingly 6. Set OrigMetric := RouterClient.Cost for the Router Client entry which includes OrigAddr 7. Include ValidityTime if advertising that the route to OrigAddr (and any other addresses included in the given prefix length) via this router is offered for a limited time, and set ValidityTime accordingly This AODVv2 message is used to create a corresponding [RFC5444] message (see Section 8) which is multicast, by default, to LL-MANET- Routers on all interfaces configured for AODVv2 operation. 7.1.2. RREQ Reception Upon receiving a Route Request, an AODVv2 router performs the following steps: 1. Update the Neighbor Table according to Section 6.3 * If the sender has Neighbor.State set to Blacklisted after the update, ignore this RREQ for further processing. 2. Verify that the message contains the required data: OrigAddr, TargAddr, OrigSeqNum, and OrigMetric, and that OrigAddr and TargAddr are valid addresses (routable and unicast) Perkins, et al. Expires October 6, 2016 [Page 39] Internet-Draft AODVv2 April 2016 * If not, ignore this RREQ for further processing. 3. Check that the MetricType is supported and configured for use * If not, ignore this RREQ for further processing. 4. Verify that the cost of the advertised route will not exceed the maximum allowed metric value for the metric type (Metric <= MAX_METRIC[MetricType] - Cost(L)) * If it will, ignore this RREQ for further processing. 5. Process the route to OrigAddr (and any other addresses included in the given prefix length) as specified in Section 6.7 6. Check if the information in the message is redundant by comparing to entries in the Multicast Route Message table, following the procedure in Section 6.8 * If redundant, ignore this RREQ for further processing. * If not redundant, continue processing. 7. Check if the TargAddr belongs to one of the Router Clients * If so, generate an RREP as specified in Section 7.2.1. * If not, continue to RREQ regeneration. 7.1.3. RREQ Regeneration By regenerating an RREQ, a router advertises that it will forward IP packets to the OrigAddr contained in the RREQ (and to other addresses included in the given prefix length) according to the information enclosed. The router MAY choose not to regenerate the RREQ, for example if the router is heavily loaded or low on energy and therefore unwilling to advertise routing capability for more traffic. This could, however, decrease connectivity in the network or result in non-optimal paths. The RREQ SHOULD NOT be regenerated if the limit for the rate of AODVv2 control message generation has been reached. If approaching the limit, the message should be sent if the priorities in Section 6.5 allow it. The procedure for RREQ regeneration is as follows: Perkins, et al. Expires October 6, 2016 [Page 40] Internet-Draft AODVv2 April 2016 1. Set AddressList, PrefixLengthList, sequence numbers and MetricType to the values in the received RREQ 2. Set OrigMetric := LocalRoute[OrigAddr].Metric 3. If the received RREQ contains a ValidityTime, or if the regenerating router wishes to limit the time that it offers a route to OrigAddr (and any other addresses included in the given prefix length), the regenerated RREQ MUST include ValidityTime * The ValidityTime is either the time limit the previous AODVv2 router specified, or the time limit this router wishes to impose, whichever is lower. This AODVv2 message is used to create a corresponding [RFC5444] message (see Section 8) which is multicast, by default, to LL-MANET- Routers on all interfaces configured for AODVv2 operation. However, the regenerated RREQ can be unicast to the next hop address of the LocalRoute toward TargAddr, if known. 7.2. Route Reply (RREP) Message When a Route Request message is received, requesting a route to a target address (TargAddr) which is configured as part of a Router Client entry, a Route Reply message is sent in response. The RREP offers a route to TargAddr (and any other addresses included in the prefix length). RREP messages have the following contents: +-----------------------------------------------------------------+ | AckReq (optional) | +-----------------------------------------------------------------+ | AddressList | +-----------------------------------------------------------------+ | PrefixLengthList (optional) | +-----------------------------------------------------------------+ | TargSeqNum | +-----------------------------------------------------------------+ | MetricType | +-----------------------------------------------------------------+ | TargMetric | +-----------------------------------------------------------------+ | ValidityTime (optional) | +-----------------------------------------------------------------+ Figure 2: RREP message contents Perkins, et al. Expires October 6, 2016 [Page 41] Internet-Draft AODVv2 April 2016 AckReq The address of the intended next hop of the RREP. This is included when the link to the next hop toward OrigAddr is not known to be bidirectional. It indicates that an acknowledgement of the RREP is requested by the sender from the intended next hop (see Section 6.2). AddressList Contains OrigAddr and TargAddr, the source and destination addresses of the IP packet for which a route is requested. OrigAddr and TargAddr MUST be routable unicast addresses. PrefixLengthList Contains TargPrefixLen, i.e., the length, in bits, of the prefix associated with the Router Client entry which includes TargAddr. If omitted, the prefix length is equal to TargAddr's address length, in bits. TargSeqNum The sequence number associated with TargAddr. MetricType The metric type associated with TargMetric. TargMetric The metric value associated with the LocalRoute to TargAddr (and any other addresses included in the given prefix length), as seen from the sender of the message. ValidityTime The length of time that the message sender is willing to offer a route toward TargAddr (and any other addresses included in the given prefix length). Omitted if no time limit is imposed. 7.2.1. RREP Generation A Route Reply message is generated when a Route Request for a Router Client of the AODVv2 router arrives. This is the case when RteMsg.TargAddr matches an address which is configured as a Router Client of the AODVv2 router. Before creating an RREP, the router SHOULD check if the corresponding RREQ is redundant, i.e., a Route Reply has already been generated in response to the RREQ, or if the limit for the rate of AODVv2 control message generation has been reached. If so, the RREP SHOULD NOT be created. If approaching the limit, the message should be sent if the priorities in Section 6.5 allow it. Perkins, et al. Expires October 6, 2016 [Page 42] Internet-Draft AODVv2 April 2016 The RREP will follow the path of the route to OrigAddr. If the best route to OrigAddr in the Local Route Set is Unconfirmed, the link to the next hop neighbor is not yet confirmed as bidirectional (as described in Section 6.2). In this case the RREP MUST include AckReq set to the intended next hop address. The AckReq indicates that an acknowledgement to the RREP is requested from the intended next hop router in the form of a Route Reply Acknowledgement (RREP_Ack). If the best route to OrigAddr in the Local Route Set is valid, the link to the next hop neighbor is already confirmed as bidirectional, and the AckReq can be omitted. Implementations MAY allow a number of retries of the RREP if a requested acknowledgement is not received within RREP_Ack_SENT_TIMEOUT, doubling the timeout with each retry, up to a maximum of RREP_RETRIES, using the same exponential backoff described in Section 6.6 for RREQ retries. The acknowledgement MUST be considered to have failed after the wait time for an RREP_Ack response to the final RREP. To generate the RREP, the router (also referred to as RREP_Gen) follows this procedure: 1. If the link to the next hop router toward OrigAddr is not known to be bidirectional, include the AckReq with the address of the intended next hop router (see Section 8.2.3) 2. Set Address List := {OrigAddr, TargAddr} 3. For the PrefixLengthList: * If TargAddr is part of an address range configured as a Router Client, set PrefixLengthList := {null, RouterClient.PrefixLength}. This allows receiving routers to learn a route to all the addresses included by the prefix length, not only to TargAddr. * Otherwise, omit PrefixLengthList. 4. For the TargSeqNum: * Increment the router SeqNum as specified in Section 4.4. * Set TargSeqNum := SeqNum. 5. Include MetricType and set the type to match the MetricType in the received RREQ message Perkins, et al. Expires October 6, 2016 [Page 43] Internet-Draft AODVv2 April 2016 6. Set TargMetric := RouterClient.Cost for the Router Client entry which includes TargAddr 7. Include ValidityTime if advertising that the route to TargAddr (and any other addresses included in the given prefix length) via this router is offered for a limited time, and set ValidityTime accordingly This AODVv2 message is used to create a corresponding [RFC5444] message (see Section 8). If the Neighbor Table contains an entry for the neighbor stored as LocalRoute[OrigAddr].NextHop, with Neighbor.State set to Confirmed, the RREP is sent by unicast to LocalRoute[OrigAddr].NextHop. Otherwise, the RREP is sent multicast to LL-MANET-Routers. The RREP MUST be sent over the same interface on which the RREQ that triggered it was received. 7.2.2. RREP Reception Upon receiving a Route Reply, an AODVv2 router performs the following steps: 1. Verify that the message contains the required data: OrigAddr, TargAddr, TargSeqNum, and TargMetric, and that OrigAddr and TargAddr are valid addresses (routable and unicast) * If not, ignore this RREP for further processing. 2. Check that the MetricType is supported and configured for use * If not, ignore this RREP for further processing. 3. If this RREP does not correspond to a RREQ generated or regenerated in the last RREQ_WAIT_TIME, ignore for further processing. 4. Update the Neighbor Table according to Section 6.3 5. Verify that the cost of the advertised route does not exceed the maximum allowed metric value for the metric type (Metric <= MAX_METRIC[MetricType] - Cost(L)) * If it does, ignore this RREP for further processing. 6. If the AckReq is present, check the intended recipient of the received RREP: * If there is an entry in the Router Client Table where RouterClient.IPAddress matches the address associated with Perkins, et al. Expires October 6, 2016 [Page 44] Internet-Draft AODVv2 April 2016 the AckReq (see Section 8.2.3), the receiving router is the intended recipient. Send an acknowledgement as specified in Section 7.3 and continue processing. * Otherwise, ignore this RREP for further processing. 7. Process the route to TargAddr (and any other addresses included in the given prefix length) as specified in Section 6.7 8. Check if the message is redundant by comparing to entries in the Multicast Route Message table (Section 6.8) * If redundant, ignore this RREP for further processing. * If not redundant, save the information in the Multicast Route Message table to identify future redundant RREP messages and continue processing. 9. Check if the OrigAddr belongs to one of the Router Clients * If so, no further processing is necessary. * If not, continue to Step 10. 10. Check if a valid (Active or Idle) or Unconfirmed LocalRoute exists to OrigAddr * If so, continue to RREP regeneration. * If not, a Route Error message SHOULD be transmitted to TargAddr according to Section 7.4.1 and the RREP SHOULD be discarded and not regenerated. 7.2.3. RREP Regeneration A received Route Reply message is regenerated toward OrigAddr. By regenerating a RREP, a router advertises that it will forward IP packets to TargAddr. The RREP SHOULD NOT be regenerated if CONTROL_TRAFFIC_LIMIT has been reached. If approaching the limit, the message should be sent if the priorities in Section 6.5 allow it. Otherwise, the router MUST regenerate the RREP. The procedure for RREP regeneration is as follows: Perkins, et al. Expires October 6, 2016 [Page 45] Internet-Draft AODVv2 April 2016 1. If the link to the next hop router toward OrigAddr is not known to be bidirectional, include the AckReq with the address of the intended next hop router 2. Set AddressList, PrefixLengthList, TargSeqNum and MetricType to the values in the received RREP 3. Set TargMetric := LocalRoute[TargAddr].Metric 4. If the received RREP contains a ValidityTime, or if the regenerating router wishes to limit the time that it will offer a route to TargAddr (and any other addresses included in the given prefix length), the regenerated RREP MUST include ValidityTime * The ValidityTime is either the time limit the previous AODVv2 router specified, or the time limit this router wishes to impose, whichever is lower. This AODVv2 message is used to create a corresponding [RFC5444] message (see Section 8). If the Neighbor Table contains an entry for the neighbor stored as LocalRoute[OrigAddr].NextHop, with Neighbor.State set to Confirmed, the RREP is sent by unicast to LocalRoute[OrigAddr].NextHop. Otherwise, the RREP is sent multicast to LL-MANET-Routers. The RREP MUST be sent over LocalRoute[OrigAddr].NextHopInterface. 7.3. Route Reply Acknowledgement (RREP_Ack) Message The Route Reply Acknowledgement is a response to a Route Reply message. When the RREP_Ack message is received by the sender of the RREP, it confirms that the link between the two routers is bidirectional (see Section 6.2). The RREP_Ack has no further data. 7.3.1. RREP_Ack Generation An RREP_Ack MUST be generated if a received Route Reply includes an AckReq with an address matching one of the receiving router's IP addresses. The RREP_Ack SHOULD NOT be generated if the limit for the rate of AODVv2 control message generation has been reached. There is no further data in an RREP_Ack. The [RFC5444] representation is discussed in Section 8. The RREP_Ack is unicast, by default, to the source IP address of the RREP message that requested it. It MUST be sent over the same interface on which the RREP that triggered it was received. Perkins, et al. Expires October 6, 2016 [Page 46] Internet-Draft AODVv2 April 2016 7.3.2. RREP_Ack Reception Upon receiving an RREP_Ack, an AODVv2 router performs the following steps: 1. Check if the RREP_Ack was expected: * Check if the Multicast Route Message Table contains an entry where: + RteMsg.MessageType == RREP + RteMsg.AckReqAddr matches the source IP address of the RREP_Ack + RteMsg.Timestamp > CurrentTime - RREP_Ack_SENT_TIMEOUT * If it does, the router cancels any associated timeouts and processing continues to Step 2. * Otherwise no actions are required and processing ends. 2. Update the Neighbor Table according to Section 6.3 7.4. Route Error (RERR) Message A Route Error message is generated by an AODVv2 router to notify other AODVv2 routers of routes that are no longer available. An RERR message has the following contents: +-----------------------------------------------------------------+ | PktSource (optional) | +-----------------------------------------------------------------+ | AddressList | +-----------------------------------------------------------------+ | PrefixLengthList (optional) | +-----------------------------------------------------------------+ | SeqNumList (optional) | +-----------------------------------------------------------------+ | MetricTypeList | +-----------------------------------------------------------------+ Figure 3: RERR message contents PktSource The source address of the IP packet triggering the RERR. If the RERR is triggered by a broken link, PktSource is not required. Perkins, et al. Expires October 6, 2016 [Page 47] Internet-Draft AODVv2 April 2016 AddressList The addresses of the routes not available through RERR_Gen. PrefixLengthList The prefix lengths, in bits, associated with the routes not available through RERR_Gen. These values indicate whether routes represent a single device or an address range. SeqNumList The sequence numbers of the routes not available through RERR_Gen (where known). MetricTypeList The metric types associated with the routes not available through RERR_Gen. 7.4.1. RERR Generation A Route Error message is generated when an AODVv2 router (also referred to as RERR_Gen) needs to report that a destination is not reachable. There are three events that cause this response: o When an IP packet that has been forwarded from another router, but cannot be forwarded further because there is no valid route in the Routing Information Base for its destination, the source of the packet needs to be informed that the route to the destination of the packet does not exist. The RERR generated MUST include PktSource set to the source address of the IP packet, and MUST contain only one unreachable address in the AddressList, i.e., the destination address of the IP packet. RERR_Gen MUST discard the IP packet that triggered generation of the RERR. The prefix length, sequence number and metric type SHOULD be included if known from an existing Invalid LocalRoute to the unreachable address. o When an RREP message cannot be regenerated because the LocalRoute to OrigAddr has been lost or is Invalid, RREP_Gen needs to be informed that the route to OrigAddr does not exist. The RERR generated MUST include PktSource set to the TargAddr of the RREP, and MUST contain only one unreachable address in the AddressList, the OrigAddr from the RREP. RERR_Gen MUST discard the RREP message that triggered generation of the RERR. The prefix length, sequence number and metric type SHOULD be included if known from an Invalid LocalRoute to the unreachable address. o When a link breaks, multiple LocalRoutes may become Invalid, and the RERR generated MAY contain multiple unreachable addresses. The RERR MUST include MetricTypeList. PktSource is omitted. All Perkins, et al. Expires October 6, 2016 [Page 48] Internet-Draft AODVv2 April 2016 previously Active LocalRoutes that used the broken link MUST be reported. The AddressList, PrefixLengthList, SeqNumList, and MetricTypeList will contain entries for each LocalRoute which has become Invalid. An RERR message is only sent if an Active LocalRoute becomes Invalid, though an AODVv2 router can also include Idle LocalRoutes that become Invalid if the configuration parameter ENABLE_IDLE_IN_RERR is set (see Section 11.3). The RERR SHOULD NOT be generated if CONTROL_TRAFFIC_LIMIT has been reached. If approaching the limit, the message should be sent if the priorities in Section 6.5 allow it. The RERR also SHOULD NOT be generated if it is a duplicate, as determined by Section 6.9. Incidentally, if an AODVv2 router receives an ICMP error packet to or from the address of one of its Router Clients, it forwards the ICMP packet in the same way as any other IP packet, and will not generate any RERR message based on the contents of the ICMP packet. To generate the RERR, the router follows this procedure: 1. If necessary, include PktSource and set the value as given above 2. For each LocalRoute that needs to be reported: * Insert LocalRoute.Address into the AddressList. * Insert LocalRoute.PrefixLength into PrefixLengthList, if known and not equal to the address length. * Insert LocalRoute.SeqNum into SeqNumList, if known. * Insert LocalRoute.MetricType into MetricTypeList. The AODVv2 message is used to create a corresponding [RFC5444] message (see Section 8). If the RERR is sent in response to an undeliverable IP packet or RREP message, i.e., if PktSource is included, the RERR SHOULD be sent unicast to the next hop on the route to PktSource. It MUST be sent over the same interface on which the undeliverable IP packet was received. If there is no route to PktSource, the RERR MUST be multicast to LL-MANET-Routers. If the RERR is sent in response to a broken link, i.e., PktSource is not included, the RERR is, by default, multicast to LL-MANET-Routers. Section 10.2 describes processing steps when the optional precursor lists feature is enabled. Perkins, et al. Expires October 6, 2016 [Page 49] Internet-Draft AODVv2 April 2016 7.4.2. RERR Reception Upon receiving a Route Error, an AODVv2 router performs the following steps: 1. Verify that the message contains the required data: at least one unreachable address * If not, ignore this RERR for further processing. 2. For each address in the AddressList, check that: * The address is valid (routable and unicast) * The MetricType is supported and configured for use * There is a LocalRoute with the same MetricType matching the address using longest prefix matching * Either the LocalRoute's next hop is the sender of the RERR and the next hop interface is the interface on which the RERR was received, or PktSource is present in the RERR and is a Router Client address * The unreachable address' sequence number is either unknown, or is greater than the LocalRoute's sequence number If any of the above are false the address does not match a LocalRoute and MUST NOT be processed or regenerated in a RERR. If all of the above are true, the LocalRoute which matches the address is no longer valid. If the LocalRoute was previously Active, it MUST be reported in a regenerated RERR. If the LocalRoute was previously Idle, it MAY be reported in a regenerated RERR, if ENABLE_IDLE_IN_RERR is configured. The Local Route Set MUST be updated according to these rules: * If the LocalRoute's prefix length is the same as the unreachable address' prefix length, set LocalRoute.State to Invalid. * If the LocalRoute's prefix length is longer than the unreachable address' prefix length, the LocalRoute MUST be expunged from the Local Route Set, since it is a sub-route of the route which is reported to be Invalid. * If the prefix length is different, create a new LocalRoute with the unreachable address, and its prefix length and Perkins, et al. Expires October 6, 2016 [Page 50] Internet-Draft AODVv2 April 2016 sequence number, and set LocalRoute.State to Invalid. These Invalid routes are retained to avoid processing stale messages. * Update the sequence number on the existing LocalRoute, if the reported sequence number is determined to be newer using the comparison technique described in Section 4.4. 3. If there are previously Active LocalRoutes that MUST be reported, as identified in step 2.: * Regenerate the RERR as detailed in Section 7.4.3. 7.4.3. RERR Regeneration The Route Error message SHOULD NOT be regenerated if CONTROL_TRAFFIC_LIMIT has been reached. If approaching the limit, the message should be sent if the priorities in Section 6.5 allow it. The procedure for RERR regeneration is as follows: 1. If PktSource was included in the original RERR, and PktSource is not a Router Client, copy it into the regenerated RERR 2. For each LocalRoute that needs to be reported as identified in Section 7.4.1: * Insert LocalRoute.Address into the AddressList. * Insert LocalRoute.PrefixLength into PrefixLengthList, if known and not equal to the address length. * Insert LocalRoute.SeqNum into SeqNumList, if known. * Insert LocalRoute.MetricType into MetricTypeList. The AODVv2 message is used to create a corresponding [RFC5444] message (see Section 8). If the RERR contains PktSource, the regenerated RERR SHOULD be sent unicast to the next hop on the LocalRoute to PktSource. It MUST be sent over the same interface on which the undeliverable IP packet was received. If there is no route to PktSource, or PktSource is a Router Client, it MUST be multicast to LL-MANET-Routers. If the RERR is sent in response to a broken link, the RERR is, by default, multicast to LL-MANET-Routers. Perkins, et al. Expires October 6, 2016 [Page 51] Internet-Draft AODVv2 April 2016 8. RFC 5444 Representation AODVv2 specifies that all control messages between routers MUST use the Generalized Mobile Ad Hoc Network Packet/Message Format [RFC5444], and therefore AODVv2's route messages comprise data which is mapped to message elements in [RFC5444]. [RFC5444] provides a multiplexed transport for multiple protocols. An [RFC5444] multiplexer MAY choose to optimize the content of certain message elements to reduce control message overhead. A brief summary of the [RFC5444] format: 1. A packet contains zero or more messages 2. A message contains a Message Header, one Message TLV Block, zero or more Address Blocks, and one Address Block TLV Block per Address Block 3. The Message TLV Block MAY contain zero or more Message TLVs 4. An Address Block TLV Block MAY include zero or more Address Block TLVs 5. Each TLV value in an Address Block TLV Block can be associated with all of the addresses, or with a contiguous set of addresses, or with a single address in the Address Block AODVv2 does not require access to the [RFC5444] packet header. In the message header, AODVv2 uses and . The field indicates the length of any addresses in the message, using := (address length in octets - 1), i.e. 3 for IPv4 and 15 for IPv6. The addresses in an Address Block MAY appear in any order, and values in a TLV in the Address Block TLV Block must be associated with the correct address in the Address Block by the [RFC5444] implementation. To indicate which value is associated with each address, the AODVv2 message representation uses lists where the order of the addresses in the AODVv2 AddressList matches the order of values in other data lists, e.g., the order of SeqNums in the SeqNumList in an RERR. [RFC5444] maps this information to Address Block TLVs associated with the relevant addresses in the Address Block. Each address included in the Address Block is identified as OrigAddr, TargAddr, PktSource, or Unreachable Address by including an ADDRESS_TYPE TLV in the Address Block TLV Block. Perkins, et al. Expires October 6, 2016 [Page 52] Internet-Draft AODVv2 April 2016 The following sections show how AODVv2 data is represented in [RFC5444] messages. AODVv2 makes use of the VALIDITY_TIME Address Block TLV from [RFC5497], and defines (in Section 12) a number of new TLVs. To calculate the time-value for the VALIDITY_TIME Address Block TLV, the value of C is defined in Section 11.2. Where the extension type of a TLV is set to zero, this is the default [RFC5444] value and the extension type will not be included in the message. 8.1. Route Request Message Representation 8.1.1. Message Header +-------+---------------+--------+ | Data | Header Field | Value | +-------+---------------+--------+ | None | | RREQ | +-------+---------------+--------+ 8.1.2. Message TLV Block An RREQ contains no Message TLVs. 8.1.3. Address Block An RREQ contains two addresses, OrigAddr and TargAddr, and each address has an associated prefix length. If the prefix length has not been included in the AODVv2 message, it is equal to the address length in bits. +-------------------------+------------------------------+ | Data | Address Block | +-------------------------+------------------------------+ | OrigAddr/OrigPrefixLen |
+ | | TargAddr/TargPrefixLen |
+ | +-------------------------+------------------------------+ 8.1.4. Address Block TLV Block Address Block TLVs are always associated with one or more addresses in the Address Block. The following sections show the TLVs that apply to each address. Perkins, et al. Expires October 6, 2016 [Page 53] Internet-Draft AODVv2 April 2016 8.1.4.1. Address Block TLVs for OrigAddr +--------------+---------------+------------+-----------------------+ | Data | TLV Type | Extension | Value | | | | Type | | +--------------+---------------+------------+-----------------------+ | None | ADDRESS_TYPE | 0 | ADDRTYPE_ORIGADDR | | OrigSeqNum | SEQ_NUM | 0 | Sequence number of | | | | | RREQ_Gen, the router | | | | | which initiated route | | | | | discovery. | | OrigMetric | PATH_METRIC | MetricType | Metric value for the | | /MetricType | | | route to OrigAddr, | | | | | using MetricType. | | ValidityTime | VALIDITY_TIME | 0 | ValidityTime for | | | | | route to OrigAddr, | | | | | represented as | | | | | detailed in | | | | | [RFC5497]. | +--------------+---------------+------------+-----------------------+ 8.1.4.2. Address Block TLVs for TargAddr +------------+--------------+-------------+-------------------------+ | Data | TLV Type | Extension | Value | | | | Type | | +------------+--------------+-------------+-------------------------+ | None | ADDRESS_TYPE | 0 | ADDRTYPE_TARGADDR | | TargSeqNum | SEQ_NUM | 0 | The last known | | | | | TargSeqNum for | | | | | TargAddr. | +------------+--------------+-------------+-------------------------+ 8.2. Route Reply Message Representation 8.2.1. Message Header +-------+---------------+--------+ | Data | Header Field | Value | +-------+---------------+--------+ | None | | RREP | +-------+---------------+--------+ 8.2.2. Message TLV Block An RREP contains no Message TLVs. Perkins, et al. Expires October 6, 2016 [Page 54] Internet-Draft AODVv2 April 2016 8.2.3. Address Block An RREP contains a minimum of two addresses, OrigAddr and TargAddr, and each address has an associated prefix length. If the prefix length has not been included in the AODVv2 message, it is equal to the address length in bits. It MAY also contain the address of the intended next hop, in order to request acknowledgement to confirm bidirectionality of the link, as described in Section 6.2. The prefix length associated with this address is equal to the address length in bits. +-------------------------+------------------------------+ | Data | Address Block | +-------------------------+------------------------------+ | OrigAddr/OrigPrefixLen |
+ | | TargAddr/TargPrefixLen |
+ | | AckReq |
+ | +-------------------------+------------------------------+ 8.2.4. Address Block TLV Block Address Block TLVs are always associated with one or more addresses in the Address Block. The following sections show the TLVs that apply to each address. 8.2.4.1. Address Block TLVs for OrigAddr +-------+---------------+-----------------+--------------------+ | Data | TLV Type | Extension Type | Value | +-------+---------------+-----------------+--------------------+ | None | ADDRESS_TYPE | 0 | ADDRTYPE_ORIGADDR | +-------+---------------+-----------------+--------------------+ 8.2.4.2. Address Block TLVs for TargAddr Perkins, et al. Expires October 6, 2016 [Page 55] Internet-Draft AODVv2 April 2016 +--------------+---------------+------------+-----------------------+ | Data | TLV Type | Extension | Value | | | | Type | | +--------------+---------------+------------+-----------------------+ | None | ADDRESS_TYPE | 0 | ADDRTYPE_TARGADDR | | TargSeqNum | SEQ_NUM | 0 | Sequence number of | | | | | RREP_Gen, the router | | | | | which created the | | | | | RREP. | | TargMetric | PATH_METRIC | MetricType | Metric value for the | | /MetricType | | | route to TargAddr, | | | | | using MetricType. | | ValidityTime | VALIDITY_TIME | 0 | ValidityTime for | | | | | route to TargAddr, | | | | | represented as | | | | | detailed in | | | | | [RFC5497]. | +--------------+---------------+------------+-----------------------+ 8.2.4.3. Address Block TLVs for AckReq Intended Recipient Address +-------+---------------+-----------------+------------------+ | Data | TLV Type | Extension Type | Value | +-------+---------------+-----------------+------------------+ | None | ADDRESS_TYPE | 0 | ADDRTYPE_INTEND | +-------+---------------+-----------------+------------------+ 8.3. Route Reply Acknowledgement Message Representation 8.3.1. Message Header +-------+---------------+-----------+ | Data | Header Field | Value | +-------+---------------+-----------+ | None | | RREP_Ack | +-------+---------------+-----------+ 8.3.2. Message TLV Block An RREP_Ack contains no Message TLVs. 8.3.3. Address Block An RREP_Ack contains no Address Block. Perkins, et al. Expires October 6, 2016 [Page 56] Internet-Draft AODVv2 April 2016 8.3.4. Address Block TLV Block An RREP_Ack contains no Address Block TLV Block. 8.4. Route Error Message Representation Route Error Messages MAY be split into multiple [RFC5444] messages when the desired contents would exceed the MTU. However, all of the resulting messages MUST have the same message header as described below. If PktSource is included in the AODVv2 message, it MUST be included in all of the resulting [RFC5444] messages. 8.4.1. Message Header +-------+---------------+--------+ | Data | Header Field | Value | +-------+---------------+--------+ | None | | RERR | +-------+---------------+--------+ 8.4.2. Message TLV Block An RERR contains no Message TLVs. 8.4.3. Address Block The Address Block in an RERR MAY contain PktSource, the source address of the IP packet triggering RERR generation, as detailed in Section 7.4. The prefix length associated with PktSource is equal to the address length in bits. Address Block always contains one address per route that is no longer valid, and each address has an associated prefix length. If a prefix length has not been included for this address, it is equal to the address length in bits. +------------------------------+------------------------------------+ | Data | Address Block | +------------------------------+------------------------------------+ | PktSource |
+ for | | | PktSource | | AddressList/PrefixLengthList |
+ for | | | each unreachable address in | | | AddressList | +------------------------------+------------------------------------+ Perkins, et al. Expires October 6, 2016 [Page 57] Internet-Draft AODVv2 April 2016 8.4.4. Address Block TLV Block Address Block TLVs are always associated with one or more addresses in the Address Block. The following sections show the TLVs that apply to each type of address in the RERR. 8.4.4.1. Address Block TLVs for PktSource +------------+---------------+----------------+---------------------+ | Data | TLV Type | Extension Type | Value | +------------+---------------+----------------+---------------------+ | PktSource | ADDRESS_TYPE | 0 | ADDRTYPE_PKTSOURCE | +------------+---------------+----------------+---------------------+ 8.4.4.2. Address Block TLVs for Unreachable Addresses +----------------+--------------+------------+----------------------+ | Data | TLV Type | Extension | Value | | | | Type | | +----------------+--------------+------------+----------------------+ | None | ADDRESS_TYPE | 0 | ADDRTYPE_UNREACHABLE | | SeqNumList | SEQ_NUM | 0 | Sequence number | | | | | associated with | | | | | invalid route to the | | | | | unreachable address. | | MetricTypeList | PATH_METRIC | MetricType | None. Extension Type | | | | | set to MetricType of | | | | | the route to the | | | | | unreachable address. | +----------------+--------------+------------+----------------------+ 9. Simple External Network Attachment Figure 4 shows a stub (i.e., non-transit) network of AODVv2 routers which is attached to an external network via a single External Network Access Router (ENAR). The interface to the external network MUST NOT be configured in the InterfaceSet. As in any externally-attached network, AODVv2 routers and Router Clients that wish to be reachable from the external network MUST have IP addresses within the ENAR's routable and topologically correct prefix (e.g., 191.0.2.0/24 in Figure 4). This AODVv2 network and networks attached to routers within it will be advertised to the external network using procedures which are out of scope for this specification. Perkins, et al. Expires October 6, 2016 [Page 58] Internet-Draft AODVv2 April 2016 /-------------------------\ / +----------------+ \ / | AODVv2 Router | \ | | 191.0.2.2/32 | | | +----------------+ | Routable | +-----+--------+ Prefix | | ENAR | /191.0.2.0/24 | | AODVv2 Router| / | | 191.0.2.1 |/ /---------------\ | | serving net +------+ External \ | | 191.0.2.0/24 | \ Network / | +-----+--------+ \---------------/ | +----------------+ | | | AODVv2 Router | | | | 191.0.2.3/32 | | \ +----------------+ / \ / \-------------------------/ Figure 4: Simple External Network Attachment Example When an AODVv2 router within the AODVv2 MANET wants to discover a route toward an address on the external network, it uses the normal AODVv2 route discovery for that IP Destination Address. The ENAR MUST respond to RREQ on behalf of all external network destinations, e.g., destinations not on the configured 191.0.2.0/24 network. RREQs for addresses inside the AODVv2 network, e.g. destinations on the configured 191.0.2.0/24 network, are handled using the standard processes described in Section 7. Note that AODvv2 does not support RREQs for prefixes that do not equal address length. When an IP packet from an address on the external network destined for an address in the AODVv2 MANET reaches the ENAR, if the ENAR does not have a route toward that destination in its Routing Information Base, it will perform normal AODVv2 route discovery for that destination. Configuring the ENAR as a default router is outside the scope of this specification. 10. Optional Features A number of optional features for AODVv2, associated initially with AODV, may be useful in networks with greater mobility or larger populations, or networks requiring reduced latency for application launches. These features are not required by minimal implementations. Perkins, et al. Expires October 6, 2016 [Page 59] Internet-Draft AODVv2 April 2016 10.1. Expanding Rings Multicast For multicast RREQ, the [RFC5444] message may initially be limited to a low number of hops to limit the RREQ propagation to a subset of the local network and possibly reduce route discovery overhead. If the route is not discovered, the number of hops allowed for distribution of the RREQ is increased, in accordance with an expanding ring search, as described in [RFC3561]. 10.2. Precursor Lists This section specifies an interoperable enhancement to AODVv2 enabling more economical Route Error notifications. There can be several sources of traffic for a certain destination. Each source of traffic and each upstream router between the forwarding AODVv2 router and the traffic source is known as a "precursor" for the destination. For each destination, an AODVv2 router MAY choose to keep track of precursors that have provided traffic for that destination. Route Error messages about that destination can be sent unicast to these precursors instead of multicast to all AODVv2 routers. Since an RERR will be regenerated if it comes from a next hop on a valid LocalRoute, the RERR SHOULD ideally be sent backwards along the route that the source of the traffic uses, to ensure it is regenerated at each hop and reaches the traffic source. If the reverse path is unknown, the RERR SHOULD be sent toward the source along some other route. Therefore, the options for saving precursor information are as follows: o Save the next hop on an existing route to the IP packet's source address as the precursor. In this case, it is not guaranteed that an RERR that is sent will follow the reverse of the source's route. In rare situations, this may prevent the route from being invalidated at the source of the data traffic. o Save the IP packet's source address as the precursor. In this case, the RERR can be sent along any existing route to the source of the data traffic, and SHOULD include PktSource to ensure that the route will be invalidated at the source of the traffic, in case the RERR does not follow the reverse of the source's route. o By inspecting the MAC address of each forwarded IP packet, determine which router forwarded the packet, and save the router address as a precursor. This ensures that when an RERR is sent to the precursor router, the route will be invalidated at that Perkins, et al. Expires October 6, 2016 [Page 60] Internet-Draft AODVv2 April 2016 router, and the RERR will be regenerated toward the source of the IP packet. During normal operation, each AODVv2 router maintaining precursor lists for a LocalRoute must update the precursor list whenever it uses this route to forward traffic to the destination. Precursors are classified as Active if traffic has recently been forwarded by the precursor. The precursor is marked with a timestamp to indicate the time it last forwarded traffic on this route. When an AODVv2 router detects that one or more LocalRoutes are broken, it MAY notify each Active precursor using a unicast Route Error message instead of creating multicast traffic. Unicast is applicable when there are few Active precursors compared to the number of neighboring AODVv2 routers. However, the default multicast behavior is still preferable when there are many precursors, since fewer message transmissions are required. When an AODVv2 router supporting precursor lists receives an RERR message, it MAY identify the list of its own affected Active precursors for the routes in the RERR, and choose to send a unicast RERR to those, rather than send a multicast RERR. When a LocalRoute is expunged, any precursor list associated with it MUST also be expunged. 10.3. Intermediate RREP Without iRREP, only the AODVv2 router responsible for the target address can respond to an RREQ. Using iRREP, route discoveries can be faster and create less control traffic. This specification has been published as a separate Internet Draft [I-D.perkins-irrep]. 10.4. Message Aggregation Delay The aggregation of multiple messages into a packet is specified in [RFC5444]. Implementations MAY choose to briefly delay transmission of messages for the purpose of aggregation (into a single packet) or to improve performance by using jitter [RFC5148]. 11. Configuration AODVv2 uses various parameters which can be grouped into the following categories: o Timers Perkins, et al. Expires October 6, 2016 [Page 61] Internet-Draft AODVv2 April 2016 o Protocol constants o Administrative parameters and controls This section show the parameters along with their definitions and default values (if any). Note that several fields have limited size (bits or bytes). These sizes and their encoding may place specific limitations on the values that can be set. 11.1. Timers AODVv2 requires certain timing information to be associated with Local Route Set entries and message replies. The default values are as follows: +------------------------+----------------+ | Name | Default Value | +------------------------+----------------+ | ACTIVE_INTERVAL | 5 second | | MAX_IDLETIME | 200 seconds | | MAX_BLACKLIST_TIME | 200 seconds | | MAX_SEQNUM_LIFETIME | 300 seconds | | RERR_TIMEOUT | 3 seconds | | RteMsg_ENTRY_TIME | 12 seconds | | RREQ_WAIT_TIME | 2 seconds | | RREP_Ack_SENT_TIMEOUT | 1 second | | RREQ_HOLDDOWN_TIME | 10 seconds | +------------------------+----------------+ Table 2: Timing Parameter Values The above timing parameter values have worked well for small and medium well-connected networks with moderate topology changes. The timing parameters SHOULD be administratively configurable. Ideally, for networks with frequent topology changes the AODVv2 parameters SHOULD be adjusted using experimentally determined values or dynamic adaptation. For example, in networks with infrequent topology changes MAX_IDLETIME MAY be set to a much larger value. If MAX_SEQNUM_LIFETIME was configured differently across the network, and any of the routers lost their sequence number or rebooted, this could result in their next route messages being classified as stale at any AODVv2 router using a greater value for MAX_SEQNUM_LIFETIME. This would delay route discovery from and to the re-initializing router. Perkins, et al. Expires October 6, 2016 [Page 62] Internet-Draft AODVv2 April 2016 11.2. Protocol Constants AODVv2 protocol constants typically do not require changes. The following table lists these constants, along with their values and a reference to the section describing their use. +------------------------+---------+--------------------------------+ | Name | Default | Description | +------------------------+---------+--------------------------------+ | DISCOVERY_ATTEMPTS_MAX | 3 | Section 6.6 | | RREP_RETRIES | 2 | Section 7.2.1 | | MAX_METRIC[MetricType] | [TBD] | Section 5 | | MAX_METRIC[HopCount] | 255 | Section 5 and Section 7 | | INFINITY_TIME | [TBD] | Maximum expressible clock time | | | | (Section 6.7.2) | | C | 1/1024 | Constant used in validity time | | | | calculation [RFC5497] | +------------------------+---------+--------------------------------+ Table 3: AODVv2 Constants MAX_METRIC[MetricType] MUST always be the maximum expressible metric value of type MetricType. Field lengths associated with metric values are found in Section 11.6. These protocol constants MUST have the same values for all AODVv2 routers in the ad hoc network. If the values were configured differently, the following consequences may be observed: o DISCOVERY_ATTEMPTS_MAX: Routers with higher values are likely to be more successful at finding routes, at the cost of additional control traffic. o RREP_RETRIES: Routers with lower values are more likely to blacklist neighbors when there is a o MAX_METRIC[MetricType]: No interoperability problems due to variations on different routers, but routers with lower values may exhibit overly restrictive behavior during route comparisons. temporary fluctuation in link quality. o INFINITY_TIME: No interoperability problems due to variations on different routers, but if a lower value is used, route state management may exhibit overly restrictive behavior. o C: Routers with lower values will invalidate timed routes before routers with higher values, which will cause Route Error messages Perkins, et al. Expires October 6, 2016 [Page 63] Internet-Draft AODVv2 April 2016 to be generated and the route will effectively take on the shorter validity time. 11.3. Local Settings The following table lists AODVv2 parameters which SHOULD be administratively configured for each router: +------------------------+------------------------+--------------+ | Name | Default Value | Description | +------------------------+------------------------+--------------+ | InterfaceSet | | Section 4.1 | | BUFFER_SIZE_PACKETS | 2 | Section 6.6 | | BUFFER_SIZE_BYTES | MAX_PACKET_SIZE [TBD] | Section 6.6 | | CONTROL_TRAFFIC_LIMIT | [TBD - 50 pkts/sec?] | Section 7 | +------------------------+------------------------+--------------+ Table 4: Configuration for Local Settings 11.4. Network-Wide Settings The following administrative controls MAY be used to change the operation of the network. The same settings SHOULD be used across the network. Inconsistent settings at different routers in the network will not result in protocol errors, but poor performance may result. +----------------------+-----------+----------------+ | Name | Default | Description | +----------------------+-----------+----------------+ | ENABLE_IDLE_IN_RERR | Disabled | Section 7.4.1 | +----------------------+-----------+----------------+ Table 5: Configuration for Network-Wide Settings 11.5. Optional Feature Settings These options are not required for correct routing behavior, although they may reduce AODVv2 protocol overhead in certain situations. The default behavior is to leave these options disabled. Perkins, et al. Expires October 6, 2016 [Page 64] Internet-Draft AODVv2 April 2016 +---------------------------+----------+----------------------------+ | Name | Default | Description | +---------------------------+----------+----------------------------+ | PRECURSOR_LISTS | Disabled | Local setting (Section | | | | 10.2) | | MSG_AGGREGATION | Disabled | Local setting (Section | | | | 10.4) | | ENABLE_IRREP | Disabled | Network-wide setting | | | | (Section 10.3) | | EXPANDING_RINGS_MULTICAST | Disabled | Network-wide setting | | | | (Section 10.1) | +---------------------------+----------+----------------------------+ Table 6: Configuration for Optional Features 11.6. MetricType Allocation The metric types used by AODVv2 are identified according to the assignments in [RFC6551]. All implementations MUST use these values. +---------------------+----------+--------------------+ | Name of MetricType | Type | Metric Value Size | +---------------------+----------+--------------------+ | Unassigned | 0 | Undefined | | Hop Count | 3 [TBD] | 1 octet | | Unallocated | 9 - 254 | TBD | | Reserved | 255 | Undefined | +---------------------+----------+--------------------+ Table 7: AODVv2 Metric Types 12. IANA Considerations This section specifies several [RFC5444] message types and address tlv-types required for AODVv2. 12.1. RFC 5444 Message Types This specification defines four Message Types, to be allocated from the 0-223 range of the "Message Types" namespace defined in [RFC5444], as specified in Table 8. Perkins, et al. Expires October 6, 2016 [Page 65] Internet-Draft AODVv2 April 2016 +-----------------------------------------+-----------+ | Name of Message | Type | +-----------------------------------------+-----------+ | Route Request (RREQ) | 10 (TBD) | | Route Reply (RREP) | 11 (TBD) | | Route Error (RERR) | 12 (TBD) | | Route Reply Acknowledgement (RREP_Ack) | 13 (TBD) | +-----------------------------------------+-----------+ Table 8: AODVv2 Message Types 12.2. RFC 5444 Address Block TLV Types This specification defines three Address Block TLV Types, to be allocated from the "Address Block TLV Types" namespace defined in [RFC5444], as specified in Table 9. +------------------------+----------+---------------+---------------+ | Name of TLV | Type | Length | Reference | | | | (octets) | | +------------------------+----------+---------------+---------------+ | PATH_METRIC | 11 (TBD) | depends on | Section 7 | | | | MetricType | | | SEQ_NUM | 12 (TBD) | 2 | Section 7 | | ADDRESS_TYPE | 13 (TBD) | 1 | Section 8 | +------------------------+----------+---------------+---------------+ Table 9: AODVv2 Address Block TLV Types 12.3. ADDRESS_TYPE TLV Values These values are used in the [RFC5444] Address Type TLV discussed in Section 8. All implementations MUST use these values. +---------------+--------+ | Address Type | Value | +---------------+--------+ | ORIGADDR | 0 | | TARGADDR | 1 | | UNREACHABLE | 2 | | PKTSOURCE | 3 | | INTEND | 4 | | UNSPECIFIED | 255 | +---------------+--------+ Table 10: AODVv2 Address Types Perkins, et al. Expires October 6, 2016 [Page 66] Internet-Draft AODVv2 April 2016 13. Security Considerations This section describes various security considerations and potential avenues to secure AODVv2 routing. The main objective of the AODVv2 protocol is for each router to communicate reachability information about addresses for which it is responsible, and for routes it has learned from other AODVv2 routers. Networks using AODVv2 to maintain connectivity and establish routes on demand may be vulnerable to certain well-known types of threats, which will be detailed in the following. Some of the threats described can be mitigated or eliminated. Tools to do so will be described also. Since route messages are regenerated at each router, AODVv2 assumes a security model of transitive trust. The sender of a message MUST be trusted in order for receiving one-hop neighbours to store the routing information it provides and regenerate the message to their own one-hop neighbours. Routes are installed based on information received from trusted neighbours. Therefore a chain of trust back to the originator of a message is assumed by any router using the routing information received. Since messages are regenerated rather than forwarded, the message concepts known as RREQ, RREP and RERR do not travel as a single unchanged entity between source and destination, and therefore message integrity cannot be assured end-to-end between OrigAddr and TargAddr. The on-demand nature of AODVv2 route discovery automatically reduces the vulnerability to route disruption. Since control traffic for updating route tables is diminished, there is less opportunity for attack and failure. 13.1. Availability Threats to AODVv2 which reduce availability are considered below. 13.1.1. Denial of Service Flooding attacks using RREQ amount to a (BLIND) denial of service for route discovery: By issuing RREQ messages for targets that don't exist, an attacker can flood the network, blocking resources and drowning out legitimate traffic. The effect of this attack is dampened by the fact that duplicate RREQ messages are dropped (preventing the network from DDoSing itself). Processing Perkins, et al. Expires October 6, 2016 [Page 67] Internet-Draft AODVv2 April 2016 requirements for AODVv2 messages are typically quite small, however AODVv2 routers receiving RREQs do allocate resources in the form of Neighbor Table, Local Route Set and Multicast Route Message Table entries. The attacker can maximize their impact on table growth by changing OrigAddr for each RREQ. If a specific node is to be targeted, this attack may be carried out in a DISTRIBUTED fashion, either by compromising its direct neighbors or by specifying the target's address as TargAddr. Note that it might be more economical for the attacker to simply jam the medium; an attack which AODVv2 cannot defend itself against. Mitigation: o If AODVv2 routers always verify that the sender of the RERR message is trusted, this threat is reduced. Processing requirements would typically be dominated by calculations to verify integrity. This has the effect of reducing (but by no means eliminating) AODVv2's vulnerability to denial of service attacks. o Authentication of senders can prevent foreign nodes from DoSing an AODVv2 router. However, this does not protect the network if an attacker has access to an already authorized router. 13.1.2. Malicious RERR messages RERR messages are designed to cause removal of installed routes. A malicious node could send an RERR message with false information to attempt to get other routers to remove a route to one or more specific destinations, therefore disrupting traffic to the advertised destinations. Routes will be deleted if an RERR is received, withdrawing a route for which the sender is the receiver's next hop, and when the RERR includes the MetricType of the installed route, and includes either no sequence number for the route, or includes a greater sequence number than the sequence number stored with that route in the receiver's Local Route Set. Routes will also be deleted if a received RERR contains a PktSource address corresponding to a Router Client. The information necessary to construct a malicious RERR could be learned by eavesdropping, either by listening to AODVv2 messages or by watching data packet flows. Since the RERR is multicast, it can be received by many routers in the ad hoc network, and will be regenerated when processing results in an active route being removed. This threat could have serious Perkins, et al. Expires October 6, 2016 [Page 68] Internet-Draft AODVv2 April 2016 impact on applications communicating by way of the sender of the RERR message. o The set of routers which use the malicious router as a next hop may be targeted with a malicious RERR with no PktSource address included, if the RERR contains routes for which the malicious router is a next hop from the receiving router. However, since the sender of the RERR message is either malicious or broken, it is better that it is not used as a next hop for these routes anyway. o A single router which does not use the malicious router as part of its route may be targeted with a malicious RERR with a PktSource address included. o Replayed RERR messages could be used to disrupt active routes. Mitigation: o Protection against eavesdropping of AODVv2 messages would mitigate this attack to some extent, but eavesdropping of data packets can also be used to deduce the information about which routes could be targeted. o Protection against a malicious router becoming part of a route will mitigate the attack where a set of routers are targeted. This will not protect against the attack if a PktSource address is included. o By only regenerating RERR messages where active routes are removed, the spread of the malicious RERR is limited. o Including sequence numbers in RERR messages offers protection against attacks using replays of these RERR messages. o If AODVv2 routers always verify that the sender of the RERR message is trusted, this threat is reduced. 13.1.3. False Confirmation of Link Bidirectionality Links could be erroneously treated as bidirectional if malicious unsolicited or spoofed RREP messages were to be accepted. This would result in a route being installed which could not in fact be used to forward data to the destination, and may divert data packets away from the intended destination. Perkins, et al. Expires October 6, 2016 [Page 69] Internet-Draft AODVv2 April 2016 There is a window of RREQ_WAIT_TIME after an RREQ is sent, in which any malicious router could send an RREP in response, in order for the link to the malicious router to be deemed as bidirectional. Mitigation: o Ignoring unsolicited RREP and RREP_Ack messages partially mitigates against this threat. o If AODVv2 routers always verify that the sender of the RERR message is trusted, this threat is reduced. 13.1.4. Message Deletion A malicious router could decide not to regenerate a RREQ or RREP or RERR message. Not regenerating a RERR or RREP message would disrupt route discovery. Not regenerating a RERR message would result in the source of data packets continuing to maintain and use the route, and further RERR messages being generated by the sender of the non- regenerated RERR. A malicious router could intentionally disrupt traffic flows by not allowing the source of data traffic to re- discover a new route when one breaks. Failing to send a RREP_Ack would also disrupt route establishment, by not allowing the reverse route to be validated. Return traffic which needs that route will prompt a new route discovery, wasting resources and incurring a slight delay but not disrupting the ability for applications to communicate. Mitigation: o None. also note that malicious router would have to wait for a route to break before it could perform this attack. 13.2. Confidentiality Passive inspection (eavesdropping) of AODVv2 control messages could enable unauthorized devices to gain information about the network topology, since exchanging such information is the main purpose of AODVv2. Eavesdropping of data traffic could allow a malicious device to obtain information about how data traffic is being routed. With knowledge of source and destination addresses, malicious messages could be constructed to disrupt normal operation. Perkins, et al. Expires October 6, 2016 [Page 70] Internet-Draft AODVv2 April 2016 13.3. Integrity Integrity of route information can be compromised in the following types of attack: 13.3.1. Message Insertion Valid route table entries can be replaced or modified by maliciously constructed AODVv2 messages, destroying existing routes and the network's integrity. Any router may pose as another router by sending RREQ, RREP, RREP_Ack and RERR messages in its name. o Sending an RREQ message with false information can disrupt traffic to OrigAddr, if the sequence number attached is not stale compared to any existing information about OrigAddr. Since RREQ is multicast and likely to be received by all routers in the ad hoc network, this threat could have serious impact on applications communicating with OrigAddr. The actual threat to disrupt routes to OrigAddr is reduced by the AODVv2 mechanism of marking RREQ- derived routes as "Unconfirmed" until the link to the next hop is confirmed. o Sending an RREP message with false information can disrupt traffic to TargAddr. Since RREP is unicast, and ignored if a corresponding RREQ was not recently sent, this threat is minimized, and is restricted to receivers along the path from OrigAddr to TargAddr. o Sending an RREP_Ack message with false information can cause the route advertised to a target address in an RREP to be erroneously accepted even though the route would contain a unidirectional link and thus not be suitable for most traffic. Since RREP_Ack is unicast, and ignored if a RREP was not sent recently to the sender of the RREP_Ack, this threat is minimized and is strictly local to the RREP transmitter expecting the acknowledgement. Unsolicited RREP_Acks are ignored. o Sending an RERR message with false information is discussed in Section 13.1.2. Mitigation: * If AODVv2 routers always verify that the sender of a message is trusted, this threat is reduced. 13.3.2. Message Modification - Man in the Middle Any AODVv2 router can regenerate messages with modified data. Mitigation: Perkins, et al. Expires October 6, 2016 [Page 71] Internet-Draft AODVv2 April 2016 o If AODVv2 routers verify the integrity of AODVv2 messages, then the threat of disruption is minimized. A man in the middle with no knowledge of the shared secret key used to calculate an integrity check value MAY modify a message but the message will be rejected when it fails an integrity check. 13.3.3. Replay Attacks Replaying of RREQ or RREP messages would be of less use to an attacker, since they would be dropped immediately due to their stale sequence number. RERR messages MAY or MAY NOT include sequence numbers and are therefore susceptible to replay attacks. RREP_Ack messages do not include sequence numbers and are therefore susceptible to replay attacks. Mitigation: o Use of timestamps or sequence numbers prevents replay attacks. 13.4. Protection Mechanisms 13.4.1. Confidentiality and Authentication Encryption MAY be used for AODVv2 messages. If the routers share a packet-level security association, the message data can be encrypted prior to message transmission. The establishment of such security associations is outside the scope of this specification. Encryption will not only protect against unauthorized devices obtaining information about network topology (eavesdropping) but will ensure that only trusted routers participate in routing operations. 13.4.2. Integrity and Trust using ICVs Cryptographic Integrity Check Values (ICVs) can be used to ensure integrity of received messages, protecting against man in the middle attacks. Further, by using ICVs, only those routers with knowledge of a shared secret key are allowed to participate in routing information exchanges. [RFC7182] defines ICV TLVs for use with [RFC5444]. The data contained in AODVv2 routing protocol messages MUST be verified using Integrity Check Values, to avoid the use of message data if the message has been tampered with. The method of distribution of shared secret keys is out of the scope of this protocol. Key management is not specified for the following reasons: Perkins, et al. Expires October 6, 2016 [Page 72] Internet-Draft AODVv2 April 2016 13.4.3. Replay Protection using Timestamps Replay attacks MUST be prevented by using timestamps or sequence numbers in messages. [RFC7182] defines a TIMESTAMP TLV for use with [RFC5444]. The data contained in AODVv2 routing protocol messages MUST be protected with a TIMESTAMP value to ensure the protection against replaying of the message. Sequence numbers can be used as timestamps, since they are known to be strictly increasing. 13.4.4. Application to AODVv2 Implementations of AODVv2 MUST support ICV TLVs using type-extensions 1 and 2, hash-function HASH_FUNCTION, and cryptographic function CRYPTOGRAPHIC_FUNCTION. An ICV MUST be included with every message. The ICV value MAY be truncated as specified in [RFC7182]. Implementations of AODVv2 MUST support a TIMESTAMP TLV using type- extension 0. The timestamp used is a sequence number, and therefore the length of the field matches the AODVv2 sequence number defined in Section 4.4. The TIMESTAMP TLV MUST be included in RREP_Ack and RERR messages. When more than one message is included in an RFC5444 packet, using a single ICV Packet TLV or single TIMESTAMP Packet TLV is more efficient than including ICV and TIMESTAMP Message TLVs in each message created. In this case, the RFC5444 multiplexer MUST be instructed to include the Packet TLVs in packets containing AODVv2 messages, or MUST be selected because it always performs these additions. If the multiplexer is not capable of adding the Packet TLVs, the TLVs MUST be included as Message TLVs in each AODVv2 message in the packet. After message generation but before transmission, the ICV and TIMESTAMP TLVs MUST be added according to each message type as detailed in the following sections. The following steps list the generic procedure to be performed: 1. The considerations in Section 8 of [RFC7182] are followed, removing existing ICV TLVs and adjusting the size and flags fields. 2. The ICV is calculated over the fields specified below, depending on message type. This value MAY be truncated (as specified in [RFC7182]). Perkins, et al. Expires October 6, 2016 [Page 73] Internet-Draft AODVv2 April 2016 3. If the TIMESTAMP is to be included, add the TIMESTAMP TLV, updating size fields as necessary. 4. Add the ICV TLV, updating size fields as necessary. 5. The changes made in Step 1 are reversed to re-add any existing ICV TLVs and adjusting the size and flags fields. The ICV MUST be verified at the receiver. Verification of a received ICV value is performed by repeating Step 1 and Step 2. If the ICV value calculated from the received message or packet does not match the value of in the received message or packet, the validation fails and the AODVv2 message MUST be discarded. Verification of a received TIMESTAMP value is performed differently depending on message type. 13.4.4.1. RREQ Generation and Reception Since OrigAddr is included in the RREQ, the ICV can be calculated and verified using all of the message contents. This provides message integrity and endpoint authentication, because trusted routers MUST hold the shared key in order to calculate the ICV value. The ICV TLV has type extension := 1. Since RREQ_Gen's sequence number is incremented for each new RREQ, replay protection is already afforded and no extra timestamp mechanism is required. 13.4.4.2. RREP Generation and Reception Since TargAddr is included in the RREP, the ICV can be calculated and verified using all of the message contents. This provides message integrity and endpoint authentication, because trusted routers MUST hold the shared key in order to calculate the ICV value. The ICV TLV has type extension := 1. Since RREP_Gen's sequence number is incremented for each new RREP, replay protection is afforded and no extra timestamp mechanism is required. 13.4.4.3. RREP_Ack Generation and Reception The RREP_Gen uses the source IP address of the RREP_Ack to identify the sender to look up whether the RREP_Ack is expected and update the Neighbour Table, and so the ICV MUST be calculated using the message contents and the IP source address. The ICV TLV has type extension := 2 in order to accomplish this. This provides message integrity Perkins, et al. Expires October 6, 2016 [Page 74] Internet-Draft AODVv2 April 2016 and endpoint authentication, because trusted routers MUST hold the shared key in order to calculate the ICV value. The message MUST also include a timestamp to protect against replay attacks, using TargSeqNum from the RREP as the value in the TIMESTAMP TLV. Verification of a received TIMESTAMP value is performed by comparing the sequence number in the field with the sequence number in a recently sent RREP awaiting acknowledgement from the sender of the RREP_Ack. If the sequence number is not equal, the AODVv2 message MUST be discarded. 13.4.4.4. RERR Generation and Reception The receiver of the RERR MUST use the source IP address of the RERR to identify the sender to look up routes using that sender as next hop, and so the ICV MUST be calculated using the message contents and the IP source address. The ICV TLV has type extension := 2 in order to accomplish this. This provides message integrity and endpoint authentication, because trusted routers MUST hold the shared key in order to calculate the ICV value. The message MUST also include a timestamp to protect against replay attacks, incrementing and using RERR_Gen's sequence number as the value in the TIMESTAMP TLV. Verification of a received TIMESTAMP value is performed by comparing the sequence number in the field with the last seen sequence number from the sender of the RERR. If the sequence number is not greater, the AODVv2 message MUST be discarded. 14. Acknowledgments AODVv2 is a descendant of the design of previous MANET on-demand protocols, especially AODV [RFC3561] and DSR [RFC4728]. Changes to previous MANET on-demand protocols stem from research and implementation experiences. Thanks to Elizabeth Belding and Ian Chakeres for their long time authorship of AODV. Additional thanks to Derek Atkins, Emmanuel Baccelli, Abdussalam Baryun, Ramon Caceres, Thomas Clausen, Justin Dean, Christopher Dearlove, Fatemeh Ghassemi, Ulrich Herberg, Henner Jakob, Ramtin Khosravi, Luke Klein-Berndt, Lars Kristensen, Tronje Krop, Koojana Kuladinithi, Kedar Namjoshi, Keyur Patel, Alexandru Petrescu, Henning Rogge, Fransisco Ros, Pedro Ruiz, Christoph Sommer, Romain Thouvenin, Richard Trefler, Jiazi Yi, Seung Yi, Behnaz Yousefi, and Cong Yuan, for their reviews of AODVv2 and DYMO, as well as numerous specification suggestions. Perkins, et al. Expires October 6, 2016 [Page 75] Internet-Draft AODVv2 April 2016 15. References 15.1. 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, . [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006, . [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C. Pignataro, "The Generalized TTL Security Mechanism (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007, . [RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, "Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format", RFC 5444, DOI 10.17487/RFC5444, February 2009, . [RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497, DOI 10.17487/RFC5497, March 2009, . [RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network (MANET) Protocols", RFC 5498, DOI 10.17487/RFC5498, March 2009, . [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, . [RFC7182] Herberg, U., Clausen, T., and C. Dearlove, "Integrity Check Value and Timestamp TLV Definitions for Mobile Ad Hoc Networks (MANETs)", RFC 7182, DOI 10.17487/RFC7182, April 2014, . Perkins, et al. Expires October 6, 2016 [Page 76] Internet-Draft AODVv2 April 2016 15.2. Informative References [I-D.perkins-irrep] Perkins, C., "Intermediate RREP for dynamic MANET On- demand (AODVv2) Routing", draft-perkins-irrep-03 (work in progress), May 2015. [Koodli01] Koodli, R. and C. Perkins, "Fast handovers and context transfers in mobile networks", Proceedings of the ACM SIGCOMM Computer Communication Review 2001, Volume 31 Issue 5, 37-47, October 2001. [Perkins94] Perkins, C. and P. Bhagwat, "Highly Dynamic Destination- Sequenced Distance-Vector Routing (DSDV) for Mobile Computers", Proceedings of the ACM SIGCOMM '94 Conference on Communications Architectures, Protocols and Applications, London, UK, pp. 234-244, August 1994. [Perkins99] Perkins, C. and E. Royer, "Ad hoc On-Demand Distance Vector (AODV) Routing", Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and Applications, New Orleans, LA, pp. 90-100, February 1999. [RFC2501] Corson, S. and J. Macker, "Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations", RFC 2501, DOI 10.17487/RFC2501, January 1999, . [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005, . [RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source Routing Protocol (DSR) for Mobile Ad Hoc Networks for IPv4", RFC 4728, DOI 10.17487/RFC4728, February 2007, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . Perkins, et al. Expires October 6, 2016 [Page 77] Internet-Draft AODVv2 April 2016 [RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter Considerations in Mobile Ad Hoc Networks (MANETs)", RFC 5148, DOI 10.17487/RFC5148, February 2008, . [RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP)", RFC 6130, DOI 10.17487/RFC6130, April 2011, . [Sholander02] Sholander, P., Coccoli, P., Oakes, T., and S. Swank, "A Portable Software Implementation of a Hybrid MANET Routing Protocol", 2002. Appendix A. AODVv2 Draft Updates This section lists the changes between AODVv2 revisions ...-13.txt and ...-14.txt. o Moved Address Type TLV Value definitions to IANA section. o Removed use of MAX_HOPCOUNT and [RFC5444] msg-hop-limit, msg-hop- count. o Allow only one Unconfirmed route. o Incorporated changes from Justin Dean's review, including removing, moving, extending and clarifying text. o Extended Introduction. o Clarified wording such as "recently sent", "the expected time", or "the expected RREP_Ack" or substituted it with instructions. o Extended and reorganized Security Considerations. o Updated text regarding message prioritization. o Updated text regarding buffering. o Added references to other sections where needed for clarity. o Added RteMsg.AckReqAddr to the Multicast Route Message Table to check whether an RREP_Ack was expected. o Renamed AODVv2_INTERFACES to InterfaceSet, extended its definition. Perkins, et al. Expires October 6, 2016 [Page 78] Internet-Draft AODVv2 April 2016 o Added Route Error Table to check for duplicate RERR messages. o Turned SHOULDs into MUSTs where appropriate. o Updated forwarding plane text. o RREPs MUST be regenerated if CONTROL_TRAFFIC_LIMIT is not reached o Explained why you'd want to keep routes with a lost sequence number o Included interfaces in the Neighbor Table, next hop neighbor monitoring and message transmission o Clarified that AODVv2 currently doesn't support RREQs for prefixes. Authors' Addresses Charles E. Perkins Futurewei Inc. 2330 Central Expressway Santa Clara, CA 95050 USA Phone: +1-408-330-4586 Email: charliep@computer.org Stan Ratliff Idirect 13861 Sunrise Valley Drive, Suite 300 Herndon, VA 20171 USA Email: ratliffstan@gmail.com John Dowdell Airbus Defence and Space Celtic Springs Newport, Wales NP10 8FZ United Kingdom Email: john.dowdell@airbus.com Perkins, et al. Expires October 6, 2016 [Page 79] Internet-Draft AODVv2 April 2016 Lotte Steenbrink HAW Hamburg, Dept. Informatik Berliner Tor 7 D-20099 Hamburg Germany Email: lotte.steenbrink@haw-hamburg.de Victoria Mercieca Airbus Defence and Space Celtic Springs Newport, Wales NP10 8FZ United Kingdom Email: victoria.mercieca@airbus.com Perkins, et al. Expires October 6, 2016 [Page 80]