Mobile Ad hoc Networks Working Group C. Perkins Internet-Draft Futurewei Intended status: Standards Track I. Chakeres Expires: May 10, 2013 CenGen November 6, 2012 Dynamic MANET On-demand (AODVv2) Routing draft-ietf-manet-dymo-24 Abstract The Dynamic MANET On-demand (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, offering on-demand convergence in dynamic topologies. 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 May 10, 2013. Copyright Notice Copyright (c) 2012 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 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 Perkins & Chakeres Expires May 10, 2013 [Page 1] Internet-Draft AODVv2 November 2012 described in the Simplified BSD License. Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 7 4. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Route Table Entry . . . . . . . . . . . . . . . . . . . . 8 4.2. AODVv2 Message Structure and Information Elements . . . . 10 4.3. RteMsg-specific Protocol Elements . . . . . . . . . . . . 13 4.4. Route Error (RERR)-specific Protocol Elements . . . . . . 14 5. AODVv2 Sequence Numbers . . . . . . . . . . . . . . . . . . . 14 6. AODVv2 Operations on Route Table Entries . . . . . . . . . . . 15 6.1. Evaluating Incoming Routing Information . . . . . . . . . 15 6.2. Creating or Updating Route Table Entries . . . . . . . . . 17 6.3. Route Table Entry Timeouts . . . . . . . . . . . . . . . . 17 7. Routing Messages . . . . . . . . . . . . . . . . . . . . . . . 18 7.1. Route Discovery Retries and Buffering . . . . . . . . . . 18 7.2. RREQ Generation . . . . . . . . . . . . . . . . . . . . . 19 7.3. RREP Generation . . . . . . . . . . . . . . . . . . . . . 20 7.4. Handling a Received RteMsg . . . . . . . . . . . . . . . . 20 8. Route Maintenance . . . . . . . . . . . . . . . . . . . . . . 22 8.1. Active Next-hop Router Adjacency Monitoring . . . . . . . 22 8.2. Handling Route Lifetimes During Packet Forwarding . . . . 23 8.3. RERR Generation . . . . . . . . . . . . . . . . . . . . . 23 8.4. Receiving and Handling RERR Messages . . . . . . . . . . . 24 9. Unknown Message and TLV Types . . . . . . . . . . . . . . . . 25 10. Advertising Network Addresses . . . . . . . . . . . . . . . . 25 11. Simple Internet Attachment . . . . . . . . . . . . . . . . . . 25 12. Multiple Interfaces . . . . . . . . . . . . . . . . . . . . . 27 13. AODVv2 Control Packet/Message Generation Limits . . . . . . . 27 14. Optional Features . . . . . . . . . . . . . . . . . . . . . . 27 14.1. Expanding Rings Multicast . . . . . . . . . . . . . . . . 28 14.2. Intermediate RREP . . . . . . . . . . . . . . . . . . . . 28 14.3. Precursor Notification . . . . . . . . . . . . . . . . . . 28 14.3.1. Overview . . . . . . . . . . . . . . . . . . . . . . 28 14.3.2. Precursor Notification Details . . . . . . . . . . . 28 14.3.3. Reporting Multiple Unreachable Nodes . . . . . . . . 30 14.4. Broadcast response to RREQ . . . . . . . . . . . . . . . . 30 14.5. Message Aggregation . . . . . . . . . . . . . . . . . . . 30 14.6. Adding Additional Routing Information to a RteMsg . . . . 30 15. Administratively Configured Parameters and Timer Values . . . 33 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35 16.1. AODVv2 Message Types Specification . . . . . . . . . . . . 35 16.2. Message and Address Block TLV Type Specification . . . . . 35 16.3. Address Block TLV Specification . . . . . . . . . . . . . 36 Perkins & Chakeres Expires May 10, 2013 [Page 2] Internet-Draft AODVv2 November 2012 17. Security Considerations . . . . . . . . . . . . . . . . . . . 37 18. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 38 19. References . . . . . . . . . . . . . . . . . . . . . . . . . . 39 19.1. Normative References . . . . . . . . . . . . . . . . . . . 39 19.2. Informative References . . . . . . . . . . . . . . . . . . 39 Appendix A. Example RFC 5444-compliant packet formats . . . . . . 40 A.1. RREQ Message Format . . . . . . . . . . . . . . . . . . . 41 A.2. RREP Message Format . . . . . . . . . . . . . . . . . . . 42 A.3. RERR Message Format . . . . . . . . . . . . . . . . . . . 42 Appendix B. Changes since the Previous Version . . . . . . . . . 43 Appendix C. Previous Changes since Version ...-21 . . . . . . . . 43 Appendix D. Shifting Network Prefix Advertisement Between AODVv2 Routers . . . . . . . . . . . . . . . . . . . 45 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45 Perkins & Chakeres Expires May 10, 2013 [Page 3] Internet-Draft AODVv2 November 2012 1. Overview The Dynamic MANET On-demand (AODVv2) routing protocol [formerly named DYMO] enables on-demand, multihop unicast routing among AODVv2 routers in mobile ad hod networks [MANETs][RFC2501]. The basic operations of the AODVv2 protocol are route discovery and route maintenance. Route discovery is performed when an AODVv2 router must transmit a packet towards a destination for which it does not have a route. Route maintenance is performed to avoid prematurely expunging routes from the route table, and to avoid dropping packets when a route being used to forward packets from the source to a destination breaks. During route discovery, an AODVv2 router initiates flooding of a Route Request message (RREQ) throughout the network to find a route to a particular destination, via the AODVv2 router responsible for this destination. During this hop-by-hop flooding process, each intermediate AODVv2 router receiving the RREQ message records a route to the originator. When the target's AODVv2 router receives the RREQ, it records a route to the originator and responds with a Route Reply (RREP) unicast hop-by-hop toward the originating AODVv2 router. Each intermediate AODVv2 router that receives the RREP creates a route to the target, and then the RREP is unicast hop-by-hop toward the originator. When the originator's AODVv2 router receives the RREP, routes have then been established between the originating AODVv2 router and the target AODVv2 router in both directions. Route maintenance consists of two operations. In order to preserve routes in use, AODVv2 routers extend route lifetimes upon successfully forwarding a packet. In order to react to changes in the network topology, AODVv2 routers monitor traffic being forwarded. When a data packet is received for forwarding and a route for the destination is not known or the route is broken, then the AODVv2 router of the source of the packet is notified. A Route Error (RERR) is transmitted to indicate the route to one or more affected destination addresses is Broken or missing. When the source's AODVv2 router receives the RERR, it marks the route as broken. Before that AODVv2 router can forward a packet to the same destination, it has to perform route discovery again for that destination. Similarly to AODV, AODVv2 uses sequence numbers to ensure loop freedom [Perkins99]. Sequence numbers enable AODVv2 routers to determine the temporal order of AODVv2 route discovery messages, thereby avoiding use of stale routing information. AODVv2 uses RFC 5444 message and TLV formats. Perkins & Chakeres Expires May 10, 2013 [Page 4] Internet-Draft AODVv2 November 2012 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]. Additionally, this document uses some terminology from [RFC5444]. This document defines the following terminology: Adjacency A relationship between selected bi-directional neighboring routers for the purpose of exchanging routing information. Not every pair of neighboring routers will necessarily form an adjacency. Neighboring routers may form an adjacency based on various information or other protocols; for example, exchange of AODVv2 routing messages, other protocols (e.g. NDP [RFC4861] or NHDP [RFC6130]), or manual configuration. Loss of a routing adjacency may also be based upon similar information; monitoring of adjacencies where packets are being forwarded is required (see Section 8.1). Distance (Dist) An unsigned integer which measures the distance a message or information element has traversed. The minimum value of distance is the number of IP hops traversed, 0 for local information. The maximum value is 254. The value 255 is reserved to indicate that the distance is unknown. AODVv2 Sequence Number (SeqNum) An AODVv2 Sequence Number is an unsigned integer maintained by each AODVv2 router. This sequence number guarantees the temporal order of routing information to maintain loop-free routes. The value zero (0) is reserved to indicate that the SeqNum for a destination address is unknown. AODVv2 Router An IP addressable device in the ad-hoc network that performs the AODVv2 protocol operations specified in this document. Router Client An AODVv2 router may be configured with a list of other IP addresses and networks which correspond to other non-router nodes which require the services of the AODVv2 router for route discovery and maintenance. An AODVv2 is always its own client, so that the list of client IP addresses is never empty. Perkins & Chakeres Expires May 10, 2013 [Page 5] Internet-Draft AODVv2 November 2012 node An IP addressable device in the ad-hoc network. A node may be an AODVv2 router, or it may be a device in the network that does not perform any AODVv2 protocol operations. All nodes in this document are either AODVv2 Routers or else router clients. reactive A protocol operation is said to be "reactive" if it is performed only in reaction to specific events. As used in this document, "reactive" is essentially synonymous with "on-demand". Flooding In this document, flooding a message refers to the process of delivering the message to every AODVv2 router in the network. This may be done according to methods specified in [RFC6621]. Routable Unicast IP Address A routable unicast IP address is a unicast IP address that when put into the IP.DestinationAddress field is scoped sufficiently to be forwarded by a router. Globally-scoped unicast IP addresses and Unique Local Addresses (ULAs) [RFC6549] are examples of routable unicast IP addresses. valid route A valid route is a Route that does not have the Route.Broken flag set. Originating Node (OrigNode) The originating node is the data source node; if it is not itself an AODVv2 router, its AODVv2 router has the responsibility to create a AODVv2 RREQ message on its behalf when necessary to flood a route discovery message. The originating node is also referred to as a particular packet's originator. Target Node (TargNode) The TargetNode denotes the ultimate destination of a message. Handling Node (HandNode) HandNode denotes the AODVv2 router handling an AODVv2 message. Route Error (RERR) A RERR message is used to indicate that an AODVv2 router no longer has a route to one or more particular destinations. Route Reply (RREP) A RREP message is used to supply routing information about the RREQ TargetNode to the RREQ OrigNode and the AODVv2 routers between them. Perkins & Chakeres Expires May 10, 2013 [Page 6] Internet-Draft AODVv2 November 2012 Route Request (RREQ) An AODVv2 router uses a RREQ message to discover a valid route to a particular destination address, called the RREQ TargetNode. An AODVv2 router processing a RREQ receives routing information for the RREQ OrigNode. Type-Length-Value structure (TLV) A generic way to represent information as specified in [RFC5444]. Unreachable Node (UnreachableNode) An UnreachableNode is a node for which a forwarding route is unknown. valid route A route that can be used for forwarding; in other words a route that is not Broken or Expired. 3. Applicability Statement The AODVv2 routing protocol is designed for stub (i.e., non-transit) or disconnected (i.e., from the Internet) mobile ad hoc networks (MANETs). AODVv2 handles a wide variety of mobility patterns by dynamically determining routes on-demand. AODVv2 also handles a wide variety of traffic patterns. In networks with a large number of routers, AODVv2 is best suited for sparse traffic scenarios where any particular router forwards packets to only a small percentage of the AODVv2 routers in the network, due to the on-demand nature of route discovery and route maintenance. AODVv2 is applicable to memory constrained devices, since little routing state is maintained in each AODVv2 router. Only routing information related to routes between active sources and destinations is maintained, in contrast to proactive routing protocols that require routing information to all routers within the routing region be maintained. AODVv2 supports routers with multiple interfaces. In addition to routing for their local processes, AODVv2 routers can also route on behalf of other non-routing nodes (i.e., "hosts"), reachable via those interfaces. Any such node which is not itself an AODVv2 router SHOULD NOT be served by more than one AODVv2 router. Although AODVv2 is closely related to AODV [RFC3561], and has some of the features of DSR [RFC4728], AODVv2 is not interoperable with either of those other two protocols. AODVv2 routers perform route discovery to find a route to a particular destination. Therefore, AODVv2 routers MUST must be Perkins & Chakeres Expires May 10, 2013 [Page 7] Internet-Draft AODVv2 November 2012 configured to respond to RREQs for a certain set of addresses. When AODVv2 is the only protocol interacting with the forwarding table, AODVv2 MAY be configured to perform route discovery for all unknown unicast destinations. At all times within an AODVv2 routing region, only one AODVv2 router SHOULD be serve any routing client. The coordination among multiple AODVv2 routers to distribute routing information correctly for a shared address (i.e. an address that is advertised and can be reached via multiple AODVv2 routers) is not described in this document. The AODVv2 router operation of shifting responsibility for a routing client from one AODVv2 router to another is mentioned in Appendix D Each AODVv2 router, if serving router clients other than itself, is configured with information about the IP addresses of its clients. There is no requirement that an AODVv2 router have information about the router clients of other AODVv2 routers. Address assignment procedures are entirely out of scope for AODVv2. AODVv2 only utilizes bidirectional links. In the case of possible unidirectional links, either blacklists (see Section 16.2) or other means (e.g. adjacency establishment with only neighboring routers that have bidirectional communication as indicated by NHDP [RFC6130]) of ensuring and monitoring bi-directionality is recommended. Otherwise, persistent packet loss could occur. The routing algorithm in AODVv2 may be operated at layers other than the network layer, using layer-appropriate addresses. The routing algorithm makes of some persistent state; if there is no persistent storage available for this state, recovery can exact a performance penalty in case of AODVv2 router reboots. 4. Data Structures 4.1. Route Table Entry The route table entry is a conceptual data structure. Implementations may use any internal representation so long as it provides access to the same information as specified below. Conceptually, a route table entry has the following fields: Route.Address The (host or network) destination address of the node(s) associated with the routing table entry. Perkins & Chakeres Expires May 10, 2013 [Page 8] Internet-Draft AODVv2 November 2012 Route.Prefix The value is the length of the netmask/prefix. If the value of the Route.Prefix is different than the length of addresses in the address family used by the AODVv2 routers, the associated address is a routing prefix, rather than a host address. Route.SeqNum The AODVv2 SeqNum associated with a route table entry. Route.NextHopAddress An IP address of the adjacent AODVv2 router on the path toward the Route.Address. Route.NextHopInterface The interface used to send packets toward the Route.Address. Route.LastUsed The time that this route was last used. Route.validity_expiration The time at which this route must expire. Route.Broken A flag indicating whether this Route is broken. This flag is set to true if the next-hop becomes unreachable or in response to processing to a RERR (see Section 8.4). Route.Dist A dimensionless metric indicating the distance to be traversed before reaching the Route.Address node. The following field is optional: Not including optional information may cause performance degradation, but it will not prohibit the protocol from discovering valid routes. A route table entry (i.e., a route) may be in one of the following states: Active An Active route is in current use for forwarding packets Idle An Idle route can be used for forwarding packets, even though it is not in current use Perkins & Chakeres Expires May 10, 2013 [Page 9] Internet-Draft AODVv2 November 2012 Expired After a route has been idle for too long, it expires, and may no longer be used for forwarding packets Broken A route marked as Broken cannot be used for forwarding packets but still has valid destination sequence number information. Timed The expiration of a Timed route is controlled by the Route.validity_expiration time of the route table entry, not MAX_IDLETIME. Until that time, a Timed route can be used for forwarding packets. Afterwards, the route must be Expired (or expunged). The route's state determines the operations that can be performed on the route table entry. During use, an Active route is maintained continuously by AODVv2 and is considered to remain active as long as it is used at least once every ACTIVE_INTERVAL. When a route is no longer Active, it becomes an Idle route. After a route remains Idle for MAX_IDLETIME, it becomes an Expired route; after that, the route is not used for forwarding, but the sequence number information is maintained until the destination sequence number has had no updates for MAX_SEQNUM_LIFETIME. After MAX_SEQNUM_LIFETIME, old sequence number information is considered no longer valuable and the route is expunged. MAX_SEQNUM_LIFETIME is the time after a reboot during which an AODVv2 router MUST NOT transmit any routing messages. Thus, if all other AODVv2 routers expunge routes to the rebooted router after that time interval, the rebooted AODVv2 router's sequence number will not be considered stale by any other AODVv2 router in the MANET. When the link to a route's next hop is broken, the route is in the Broken state, and it may no longer be used. 4.2. AODVv2 Message Structure and Information Elements IP Protocol Number 138 (manet) has been reserved for MANET protocols [RFC5498]. In addition to using this IP protocol number, AODVv2 may use UDP at destination port 269 (manet) [RFC5498]. AODVv2 messages are transmitted in packets that conform to the packet and message format as described in [RFC5444]. Here is a brief description of the format. Perkins & Chakeres Expires May 10, 2013 [Page 10] Internet-Draft AODVv2 November 2012 A packet formatted according to RFC5444 contains zero or more messages. A message contains a message header, message TLV block, and zero or more address blocks. Each of the address blocks may also have an associated address TLV block. If a packet contains only a single AODVv2 message and no packet TLVs, it need not include a packet-header [RFC5444]. All AODVv2 messages SHOULD be sent using the IP protocol number (138) reserved for manet protocols [RFC5498]; or the UDP destination port (269) reserved for manet protocols [RFC5498] and IP protocol number for UDP. Most AODVv2 messages are sent with the IP destination address set to the link-local multicast address LL-MANET-Routers [RFC5498] unless otherwise specified. Therefore, all AODVv2 routers SHOULD subscribe to LL-MANET-Routers [RFC5498] to receiving AODVv2 messages. Note that multicast packets 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 describing AODVv2 protocol messages, it is necessary to refer to fields in several distinct parts of the overall packet. These locations include the IP header, and fields from [RFC5444]. This document uses the notational conventions found in table 1. Perkins & Chakeres Expires May 10, 2013 [Page 11] Internet-Draft AODVv2 November 2012 +---------------------------+-------------------------------------+ | Notation | Information Location | +---------------------------+-------------------------------------+ | MsgHdr | RFC5444 message header | | MsgTLV | RFC5444 message TLV | | AddBlk | RFC5444 address blocks | | AddTLV | RFC5444 address block TLV | | HopCount | MsgHdr.msg-hop-count | | HopLimit | MsgHdr.msg-hop-limit | | MAL | MsgHdr.msg-addr-length | | RREQ_Gen | AODVv2 router originating an RREQ | | RREQ_Targ | Node address targeted by a RREQ | | RREP_Gen | AODVv2 router responding to an RREQ | | RREP_Targ | Node address targeted by a RREP | | Handling Router | HandRtr | | Target Router | TargRtr | | Target Node | TargNode | | Unreachable Node | UnreachableNode | | Upstream Router | UpstRtr | | RteMsg | either RREQ or RREP | | RteMsg_Orig | Originatorof a RteMsg | | RteMsgDest | RREQ_Targ or RREP_Targ | | RteMsgGen | RREQ_Gen or RREP_Gen | | Field in incoming RREQs | IncomingRREQ.{field} | | Field in outgoing RREQs | OutgoingRREQ.{field} | | Field in incoming RREPs | IncomingRREP.{field} | | Field in outgoing RREPs | OutgoingRREP.{field} | | Field in incoming RteMsgs | IncomingRteMsg.{field} | | Field in outgoing RteMsgs | OutgoingRteMsg.{field} | | Field in incoming RERRs | IncomingRERR.{field} | | Field in outgoing RERRs | OutgoingRERR.{field} | +---------------------------+-------------------------------------+ Table 1 The IPv4 TTL (IPv6 Hop Limit) field for all packets containing AODVv2 messages is set to 255. If a packet is received with a value other than 255, any AODVv2 message contained in the packet MUST be ignored by AODVv2. This mechanism, known as "The Generalized TTL Security Mechanism" (GTSM) [RFC5082] helps to ensure that packets have not traversed any intermediate routers. The length of an address (32 bits for IPv4 and 128 bits for IPv6) inside an AODVv2 message is indicated by the msg-addr-length (MAL) in the msg-header, as specified in [RFC5444]. IP packets containing AODVv2 protocol messages SHOULD be given priority queuing and channel access. Perkins & Chakeres Expires May 10, 2013 [Page 12] Internet-Draft AODVv2 November 2012 AODVv2 protocol messages require the following information: IP Source Address The IP address of the node currently sending this packet. This field is generally filled automatically by the operating system and should not require special handling. IP Destination Address The IP address of the packet destination. For multicast messages the IP DestinationAddress is set to LL-MANET-Routers [RFC5498]. For unicast messages the IP DestinationAddress is set according to the particular handling requirement of the message. HopCount The remaining number of hops this message is allowed to traverse. If an AODVv2 message within a RFC 5444 packet has traversed MAX_HOPCOUNT, that message MUST be ignored. 4.3. RteMsg-specific Protocol Elements AODVv2 message types RREQ and RREP are known as Routing Messages (RteMsgs) and used to discover routing information. RREQ and RREP have similar information and function, but have slightly different handling rules. The main difference between the two messages is that RREQ messages are generally broadcast to solicit a RREP, and conversely a RREP is the unicast response to RREQ. RteMsg creation and handling are described in Section 7. In this section, abstract terms RteMsgGen and RteMsgDest are used to reduce the amount of duplication in the specification. So, for instance, unicast RteMsgs MUST be sent with the IP destination address set to the Route.NextHopAddress of the route to the RteMsgDest. When the RteMsg is a RREP, the RteMsgDest is the RREQ_Gen -- i.e., the router that transmitted the RREQ requesting the information in the RREP. A RteMsg REQUIRES the following information in addition to the fields indicated in Section 4.2: RteMsgDest The IP address of the RteMsgDest RteMsgPref The prefix length associated with RteMsgGen Perkins & Chakeres Expires May 10, 2013 [Page 13] Internet-Draft AODVv2 November 2012 RteMsgGen The IP address of the AODVv2 router originating the RteMsg RteMsgGen.SeqNum The AODVv2 sequence number maintained by RteMsgGen A RteMsg may optionally include the following information: RteMsgDest.SeqNum The last AODVv2 sequence number known for RteMsgDest 4.4. Route Error (RERR)-specific Protocol Elements A RERR message is used to notify upstream routers that a route is not available for one or more destination addresses. RERR message creation and handling are described in Section 8. A RERR requires the following information: UnreachableNode.Address The address of an UnreachableNode. The addresses of multiple Unreachable Nodes may be included in a RERR. A Route Error may optionally include the following information: UnreachableNode.SeqNum The last known AODVv2 sequence number of the unreachable node. If a SeqNum for an address is zero (0) or not included, it is assumed to be unknown; this can occur when an AODVv2 router does not have a valid route for a packet it has received. UnreachableNode.Prefix The prefix length associated with an UnreachableNode. 5. AODVv2 Sequence Numbers AODVv2 sequence numbers allow AODVv2 routers to judge the freshness of routing information. Proper maintenance of sequence numbers ensures that the destination sequence number value stored by intermediate AODVv2 routers is monotonically increasing along any path from any source to the destination. As a consequence, loop freedom is ensured. Each AODVv2 router in the network MUST maintain its own sequence number (OwnSeqNum, a 16-bit unsigned integer). An AODVv2 router increments its OwnSeqNum as follows. Most of the time, OwnSeqNum is Perkins & Chakeres Expires May 10, 2013 [Page 14] Internet-Draft AODVv2 November 2012 incremented by simply adding one (1). But to increment OwnSeqNum when it has the value of the largest largest possible number representable as a 16-bit unsigned integer (i.e., 65,535), it MUST be set to one (1). In other words, the sequence number after 65,535 is 1. An AODVv2 router SHOULD maintain OwnSeqNum in persistent storage. If an AODVv2 router's OwnSeqNum is lost, it MUST take the following actions to avoid the danger of routing loops. First, the AODVv2 router MUST invalidate all route table entries, by setting Route.Broken for each entry. Furthermore the AODVv2 router MUST wait for at least MAX_SEQNUM_LIFETIME before transmitting or retransmitting any AODVv2 RREQ or RREP messages. If an AODVv2 protocol message is received during this waiting period, the AODVv2 router SHOULD perform normal route table entry updates. If a data packet is received for forwarding to another destination during this waiting period, the AODVv2 router MUST transmit a RERR message indicating that this route is not available. At the end of the waiting period the AODVv2 router sets its OwnSeqNum to one (1) and begins performing AODVv2 protocol functions again. 6. AODVv2 Operations on Route Table Entries 6.1. Evaluating Incoming Routing Information Whenever an AODVv2 router (HandRtr) handles an incoming RteMsg (i.e., RREQ or RREP), for every relevant address (InMsg.Addr) in the RteMsg, HandRtr searches its route table to see if there is a route table entry matching InMsg.Addr. If not, HandRtr creates a route table entry for InMsg.Addr as described in Section 6.2. Alternatively, if the Route.Broken flag is set for the InMsg.Addr, then HandRtr updates the route table entry for InMsg.Addr as described in Section 6.2. Otherwise, HandRtr compares the incoming routing information in RteMsg against the already stored routing information in the route table entry (Route) for InMsg.Addr, as described below. Suppose a route table entry (Route) contains Route.SeqNum, Route.Dist, and Route.Broken. Suppose the incoming routing information for Route.Addr is InMsg.SeqNum, InMsg.Dist, and InMsg.type (RREQ or RREP). The incoming routing information is compared as follows: 1. Stale If InMsg.SeqNum < Route.SeqNum (using signed 16-bit arithmetic) the incoming information is stale. Using stale routing information is not allowed, since that might result in routing loops. HandRtr MUST disregard the the routing information for Perkins & Chakeres Expires May 10, 2013 [Page 15] Internet-Draft AODVv2 November 2012 InMsg.Addr. Routing information which is not Stale may be considered Fresh. (InMsg.SeqNum > Route.SeqNum) 2. Not safe against loops If InMsg.SeqNum == Route.SeqNum, the comparison next considers the distance information to Route.Addr. If InMsg.Dist > Route.Dist + 1, then the incoming information is not guaranteed to prevent routing loops. Using such incoming routing information is not allowed. The following pseudocode illustrates the logical condition under which the incoming information is not guaranteed to protect against loops. (InMsg.Dist > Route.Dist + 1) 3. Offers no Improvement In case of known equal SeqNum for a route table entry, the incoming information does not offer any improvement over the existing route table information in two cases: i. the route is not any less expensive: the route is valid, but InMsg.Dist >= Route.Dist ii. there is danger of a routing loop: the route is broken, but InMsg.Dist > Route.Dist Updating route table entries using such incoming routing information is not allowed. /* (InMsg.SeqNum == Route.SeqNum) */ [(InMsg.Dist >= Route.Dist) AND (Route.Broken == FALSE)] OR [(InMsg.Dist > Route.Dist) AND (Route.Broken == TRUE)] 4. Offers improvement Incoming routing information that does not match any of the above criteria is loop-free and offers improvement compared to existing routing table information. The following pseudo-code illustrates whether incoming routing information should be used to update an existing route table entry as described in Section 6.2. (/* signed 16-bit arithmetic */ InMsg.SeqNum > Route.SeqNum) OR ((InMsg.SeqNum == Route.SeqNum) AND [(InMsg.Dist < Route.Dist) OR ((Route.Broken == true) AND (InMsg.Dist <= Route.Dist + 1)) OR ((RteMsg is RREP) AND (InMsg.Dist == Route.Dist)] Perkins & Chakeres Expires May 10, 2013 [Page 16] Internet-Draft AODVv2 November 2012 6.2. Creating or Updating Route Table Entries Each route table entry is populated with the following information: o Route.Address := RteMsg.Address o Route.Prefix := RteMsg.Prefix o Route.SeqNum := RteMsg.SeqNum o Route.NextHopAddress := IP.SourceAddress (i.e., an address of the node that last transmitted the RteMsg packet) o Route.NextHopInterface is set to the interface on which RteMsg was received o Route.Broken flag := FALSE o Route.Dist := RteMsg.Dist o Route.LastUsed := Current_Time o Route.ValidityTime := RteMsg.VALIDITY_TIME if included, otherwise Route.ValidityTime := 0 With these assignments to the route table entry, a route has been made available, and the route can be used to send any buffered data packets and subsequently to forward any incoming data packets for Route.Addr. This route also fulfills any outstanding route discovery (RREQ) attempts for Route.Addr. 6.3. Route Table Entry Timeouts During normal operation, AODVv2 does not require any explicit timeouts to manage the lifetime of a route. Instead, the route table entry MUST be examined be before it is used for forwarding a packet, as discussed in Section 8.2. Any necessary expiry or deletion can occur at that time. However, it is permissible to implement timers and timeouts to achieve the same effect. At any time, the route table can be examined and route table entries can be reclaimed according to their current state at the time of examination, as follows. o An Active route MUST NOT be expunged. o An Idle route SHOULD NOT be expunged. Perkins & Chakeres Expires May 10, 2013 [Page 17] Internet-Draft AODVv2 November 2012 o An Expired route MAY be expunged (least recently used first). o A route MUST be expunged if (Current_Time - Route.LastUsed) >= MAX_SEQNUM_LIFETIME. 7. Routing Messages When an AODVv2 router (RREQ_Gen) needs to forward a data packet from a node (OrigNode) in its set of router clients, and it does not have a forwarding route to the packet's IP destination address (TargNode), the AODVv2 router (RREQ_Gen) generates a RREQ (as described in Section 7.2) to discover a route to the particular destination (TargNode). Subsequently RREQ_Gen awaits reception of an RREP message (generated by RREP_Gen) addressed to OrigNode. The RREQ message contains routing information to enable other nodes to route packets back to OrigNode, and the RREP message contains routing information to enable other nodes to route packets to TargNode. 7.1. Route Discovery Retries and Buffering After issuing a RREQ, the AODVv2 router (RREQ_Gen) waits for a RREP supplying the routing information for a route to TargetNode. If a route is not created within RREQ_WAIT_TIME, RREQ_Gen may retry the Route Discovery by generating another RREQ. Route Discovery SHOULD be considered to have failed after DISCOVERY_ATTEMPTS_MAX and the corresponding wait time for a RREP response to the final RREQ. To reduce congestion in a network, repeated attempts at route discovery for a particular TargetNode SHOULD utilize an binary exponential backoff. Data packets awaiting a route SHOULD be buffered by RREQ_Gen. This buffer SHOULD have a fixed limited size (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES). Determining which packets to discard first is a matter of policy at each AODVv2 router; in the absence of policy constraints, by default older data packets SHOULD be discarded first. Buffering of data packets can have both positive and negative effects (albeit usually positive), and therefore settings for buffering (i.e., BUFFER_DURING_DISCOVERY) SHOULD be administratively configurable. Nodes without sufficient memory available for buffering may be configured with BUFFER_DURING_DISCOVERY = FALSE; this will affect the latency required for launching TCP applications to new destinations. If a route discovery attempt has failed (i.e., DISCOVERY_ATTEMPTS_MAX attempts have been made without receiving a RREP) to find a route to the TargetNode, any data packets buffered for the corresponding Perkins & Chakeres Expires May 10, 2013 [Page 18] Internet-Draft AODVv2 November 2012 TargetNode MUST BE dropped and a Destination Unreachable ICMP message (Type 3) SHOULD be delivered to the source of the data packet. The code for the ICMP message is 1 (Host unreachable error). If RREQ_Gen is not the source (OrigNode), then the ICMP is sent over the interface from which the source sent the packet to the AODVv2 router. 7.2. RREQ Generation An AODVv2 router (RREQ_Gen) creates a RREQ in order to discover a route to a Target Node (TargNode), in order to route packets from OrigNode (that is, either on its own behalf, or on behalf of one of its clients). OrigNode.Addr is the address of the source for which this AODVv2 router is initiating this route discovery. The OrigNode.Addr MUST be a unicast address. This information will be used by nodes to create a route toward the OrigNode, enabling delivery of a RREP, and eventually used for proper forwarding of data packets. RREQ_Gen creates the RREQ according to the following steps. 1. RREQ_Gen MUST increment its OwnSeqNum by one (1) according to the rules specified in Section 5. This ensures that all nodes with existing routing information will use RREQ_Gen's new information to update existing routing table information. 2. RREQ_Gen adds the TargNode.Addr to the RREQ. 3. If a previous value of the TargNode's SeqNum is known (from a routing table entry using longest-prefix matching), RREQ_Gen SHOULD include TargNode.SeqNum in all but the last RREQ attempt. If TargNode.SeqNum is not included, it is assumed to be unknown by AODVv2 routers handling the RREQ. This operation ensures that no intermediate AODVv2 routers reply, and ensures that the TargNode's AODVv2 router (i.e., TargRtr) increments its sequence number. 4. RREQ_Gen adds OrigNode.Addr, its prefix, and the RREQ_Gen.SeqNum (OwnSeqNum) to the RteMsg. 5. If OrigNode.Dist is included it is set to a number, greater than zero (0), representing the distance between OrigNode and RREQ_Gen. 6. HopCount SHOULD be set to 0. Perkins & Chakeres Expires May 10, 2013 [Page 19] Internet-Draft AODVv2 November 2012 7.3. RREP Generation RREP_Gen creates the RREP according to the following steps. 1. If RREQ.TargNode is not a unicast IP address the RREP MUST NOT be generated, and processing for the RREQ is complete. Otherwise RREP.OrigNode := RREQ.TargNode and its associated prefix are added to the RREP. RREP_Gen SHOULD advertise the largest known prefix containing RREQ.TargNode. 2. RREP.TargetNode := RREQ.OrigNode is added to the RREP. RREP.TargetNode is the ultimate destination of this RREP. 3. RREP_Gen MUST increment its OwnSeqNum by one (1) according to the rules specified in Section 5; OwnSeqNum MUST be added to the RREP. 4. Other AddTLVs in the RREP for the OrigNode and TargetNode SHOULD be included and set accordingly. If OrigNode.Dist is included it is set to a number greater than zero (0) and less than or equal to 254. 5. HopCount SHOULD be set to 0. 6. The IP.DestinationAddress for RREP is set to the IP address of the Route.NextHopAddress for the route to the RREP TargetNode. 7.4. Handling a Received RteMsg When an AODVv2 router (HandNode) receives a RteMsg (i.e., RREQ or RREP), it handles the RteMsg according to the following steps. 1. First, HandNode examines the RteMsg to ensure that it contains the required information: HopCount, TargNode.Addr, OrigNode.Addr, and RteMsg_Gen.SeqNum. If the required information does not exist, the message is ignored and further processing stopped. 2. HandNode MUST handle AODVv2 messages only from adjacent routers. 3. HandNode checks if the OrigNode.Addr is a valid routable unicast address. If not, the message is ignored and further processing stopped. 4. HandNode also checks whether OrigNode.Addr is an address handled by this AODVv2 router. If this node is the originating AODVv2 router (RteMsg_Gen), the RteMsg is ignored. Perkins & Chakeres Expires May 10, 2013 [Page 20] Internet-Draft AODVv2 November 2012 5. If TargetNode.Address is not a valid unicast address, the message is ignored. 6. HandNode checks whether it has a route to the RteMsg_Gen.Addr using longest-prefix matching [RFC1812]. If a route with a valid Route.SeqNum does not exist, then the new routing information is used to create a new route table entry is created and updated as described in Section 6.2. If a route table entry does exist the incoming routing information is compared with the route table entry following the procedure described in Section 6.1. If the incoming routing information offers improvement, the route table entry is updated as described in Section 6.2. 7. At this point, if the routing information for the RteMsg_Gen offers no improvement, then this RteMsg SHOULD be ignored; no further processing of this message SHOULD be performed. 8. When RteMsg is a RREQ, if TargNode is a router client of HandNode, then a RREP is generated by the HandNode (i.e., RREP_Gen) and unicast to the RREQ OrigNode (the new RREP's TargNode). The procedure for generating a RREP is described in Section 7.3. Afterwards, RREP_Gen processing for the RREQ is complete. 9. For each address (except the TargetNode) in the RteMsg that includes AddTLV.Dist information, the AddTLV.Dist information is incremented by at least one (1). 10. If the resulting Distance value for the OrigNode is greater than 254, the message is discarded. If the resulting Distance value for another node is greater than 254, the associated address and its information are removed from the RteMsg. If the HopCount is equal to MAX_HOPCOUNT, then the message is ignored. Otherwise, the HopCount is incremented by one (1). 11. If HandNode is not the TargetNode, AND this RteMsg is a RREQ, then the current RteMsg (as altered by the procedure defined above) SHOULD be sent to the IP multicast address LL-MANET- Routers [RFC5498]. If the RREQ is unicast, the IP.DestinationAddress is set to the NextHopAddress. 12. If HandNode is not the TargetNode, AND this RteMsg is a RREP, then the current RteMsg is sent to the Route.NextHopAddress for the RREP's TargetNode.Address. If no forwarding route exists to TargetNode.Address, then a RERR SHOULD be issued to the OrigNode of the RREP. Perkins & Chakeres Expires May 10, 2013 [Page 21] Internet-Draft AODVv2 November 2012 By sending the updated RteMsg, HandNode advertises that it will route for addresses contained in the outgoing RteMsg based on the information enclosed. HandNode MAY choose not to send the RteMsg, though not resending this RteMsg could decrease connectivity in the network or result in a non-shortest distance path. The circumstances under which HandNode might choose to not re-issue a RteMsg are not specified in this document. Some examples might include the following: o HandNode is already heavily loaded and does not want to advertise routing for the contained addresses o HandNode recently issued identical routing information (e.g. in a RteMsg advertising the same distance) o HandNode is low on energy and has to reduce energy expended for sending protocol messages or packet forwarding 8. Route Maintenance Alternatively, a RERR SHOULD be issued immediately after detecting a broken link (see Section 8.1) of an Active route, to quickly notify AODVv2 routers that that route is no longer available. If a newly unavailable route has not been used recently (within ACTIVE_INTERVAL), the RERR SHOULD NOT be generated. 8.1. Active Next-hop Router Adjacency Monitoring Nodes SHOULD monitor connectivity to adjacent next-hop AODVv2 routers on forwarding routes. This monitoring can be accomplished by one or several mechanisms, including: o Neighborhood discovery [RFC6130] o Route timeout o Lower layer trigger that a neighboring router is no longer reachable o Other monitoring mechanisms or heuristics Upon determining that a next-hop AODVv2 router has become unreachable, the router MUST invalidate all affected routes (those using the unreachable next-hop) and set the Route.Broken flag. Perkins & Chakeres Expires May 10, 2013 [Page 22] Internet-Draft AODVv2 November 2012 8.2. Handling Route Lifetimes During Packet Forwarding Before using a route to forward a packet, an AODVv2 router MUST check the status of the route. If the route is marked has been marked as Broken, it cannot be used for forwarding. If Current_Time - Route.LastUsed > (ACTIVE_INTERVAL+MAX_IDLETIME), the route cannot be used, and a RERR SHOULD be generated. If Current_Time - Route.LastUsed > (MAX_SEQNUM_LIFETIME), the route table entry MUST be expunged. Otherwise, Route.LastUsed := Current_Time, and the packet is forwarded to the route's next hop. 8.3. RERR Generation An AODVv2 router generates a RERR message when it needs to notify one or more upstream routers that packets can no longer be delivered to certain destinations. There are two cases when this can happen. The two cases differ in the way that the neighboring destination address for the RERR (i.e., RERR_dest) is chosen, and in the way that the set of UnreachableNodes is identified. Case 1: Undeliverable Packet The first case happens when the router receives a packet but does not have a route for the destination of the packet. In this case, there is exactly one UnreachableNode to be included in the RERR's AddressBlock. In this case, RERR_dest SHOULD be the multicast address LL-MANET-Routers, but RERR_Gen MAY instead set RERR_dest to be the source IP address of the packet which was undeliverable; such unicast packets MUST be forwarded along the link to the the AODVv2 neighbor transmitting the undeliverable packet. Case 2: Broken Link The second case happens when the link breaks to an active downstream neighbor (i.e., the next hop of an active route). In this case, RERR_dest MUST be the multicast address LL-MANET- Routers. The set of UnreachableNodes is found by determining which Active routes use the broken link. Idle routes that use the broken link SHOULD also be included, up to MAX_UnreachableNode entries in the RERR address block. In contrast to the previous case, in this case the set of UnreachableNodes may be empty. If the set of UnreachableNodes is empty, no RERR is generated. Otherwise, RERR_Gen creates a new RERR, and the address of each UnreachableNode (IP.DestinationAddress from a data packet or RREP.TargetNode.Address) is inserted into an AddrBlock. If a prefix is known for the UnreachableNode.Address, it SHOULD be included. Perkins & Chakeres Expires May 10, 2013 [Page 23] Internet-Draft AODVv2 November 2012 Otherwise, the UnreachableNode.Address is assumed to be a host address with a full length prefix. If a value for the UnreachableNode's SeqNum (UnreachableNode.SeqNum) is known, it SHOULD be placed in the RERR. The MsgHdr.HopCount SHOULD be set to MAX_HOPCOUNT. If UnreachableNode's SeqNum information is not included in the RERR, all nodes handling the RERR will assume their routing information associated with the UnreachableNode is no longer valid and flag those routes as broken. If an RERR is generated because of an undeliverable packet, RERR_Gen MUST discard the packet or message that triggered generation of the RERR. 8.4. Receiving and Handling RERR Messages When an AODVv2 router (RERR_Hand) receives a RERR message, it uses the information provided to invalidate affected routes. If the information in the RERR may be useful to upstream neighbors using those routes, RERR_Hand subsequently sends another RERR to those neighbors. This operation may be viewed as relaying the RERR information, but each RERR message is only transmitted over a single hop. First, HandNode examines the incoming RERR to ensure that it contains HopCount and at least one UnreachableNode.Address. If the required information does not exist, the incoming RERR message is discarded and further processing stopped. For each UnreachableNode.Address, HandNode searches its route table for a route using longest prefix matching. If a route is found, HandNode performs the following steps: 1. The UnreachableNode.Address is a routable unicast address. 2. The Route.NextHopAddress is the same as the RERR IP.SourceAddress. 3. The Route.NextHopInterface is the same as the interface on which the RERR was received. 4. The UnreachableNode.SeqNum is unknown, OR Route.SeqNum <= UnreachableNode.SeqNum (using signed 16-bit arithmetic). 5. If the route satisfies all of the above conditions, HandNode sets the Route.Broken flag for that route. Furthermore, if HopCount is less than MAX_HOPCOUNT, then HandNode adds the UnreachableNode address information to an AddrBlk for for delivery in an outgoing Perkins & Chakeres Expires May 10, 2013 [Page 24] Internet-Draft AODVv2 November 2012 RERR message to one or more of HandNode's upstream neighbors. If there are no UnreachableNode addresses to be transmitted in an RERR to the upstream routers, HandNode MUST discard the RERR. If UnreachableNode.SeqNum exists in the RERR and is not zero (0), then Route.SeqNum SHOULD be set to UnreachableNode.SeqNum. Setting Route.SeqNum can reduce future RERR handling and forwarding. Otherwise, the HopCount is incremented by one (1). The outgoing RERR SHOULD be sent to the same IP destination address as was used in the received (incoming) RERR message -- in other words, either LL-MANET- Routers [RFC5498] multicast address, or the address of a source of a data packet that triggered the RERR message generation. 9. Unknown Message and TLV Types If a message with an unknown type is received, the message is ignored. For handling of messages that contain unknown TLV types, ignore the information for processing, preserve it unmodified for forwarding. 10. Advertising Network Addresses AODVv2 routers MAY specify a prefix length for each advertised address. Any nodes (other than the advertising AODVv2 router) within the advertised prefix MUST NOT participate in the AODVv2 protocol directly. For example, advertising 192.0.2.1 with a prefix length of 24 indicates that all nodes with the matching 192.0.2.X are reachable through this AODVv2 router. An AODVv2 router MUST NOT advertise network addresses unless it can guarantee its ability for forwarding packets to any host address within the address range of the corresponding network. 11. Simple Internet Attachment Simple Internet attachment consists of a stub (i.e., non-transit) network of AODVv2 routers connected to the Internet via a single Internet AODVv2 router (IAR). As in any Internet-attached network, AODVv2 routers, and hosts behind these routers, wishing to be reachable from hosts on the Internet MUST have IP addresses within the IAR's routable and topologically correct prefix (e.g. 192.0.2.0/24). Perkins & Chakeres Expires May 10, 2013 [Page 25] Internet-Draft AODVv2 November 2012 The IAR is responsible for generating RREQ to find nodes within the AODVv2 Region on behalf of nodes on the Internet, as well as responding to route requests from the AODVv2 region on behalf of the nodes on the Internet. /--------------------------\ / Internet \ \ / \------------+-------------/ | Routable & | Topologically | Correct | Prefix | +-----+--------+ | Internet | /------| AODVv2 |-------\ / | Router | \ / |192.0.2.1/32 | \ | |Responsible | | | | for | | | |AODVv2 Region | | | |192.0.2.0/24 | | | +--------------+ | | +----------------+ | | | AODVv2 Router | | | | 192.0.2.2/32 | | | +----------------+ | | +----------------+ | | | AODVv2 Router | | | | 192.0.2.3/32 | | \ +----------------+ / \ / \-----------------------------/ Figure 1: Simple Internet Attachment Example When an AODVv2 router within the AODVv2 Region wants to discover a route to a node on the Internet, it uses the normal AODVv2 route discovery for that IP Destination Address. The IAR MUST respond to RREQ on behalf of the Internet destination. When a packet from a node on the Internet destined for a node in the AODVv2 region reaches the IAR, if the IAR does not have a route to that destination it will perform normal AODVv2 route discovery for that destination. Perkins & Chakeres Expires May 10, 2013 [Page 26] Internet-Draft AODVv2 November 2012 12. Multiple Interfaces AODVv2 may be used with multiple interfaces; therefore, the particular interface over which packets arrive MUST be known whenever a packet is received. Whenever a new route is created, the interface through which the Route.Address can be reached is also recorded in the route table entry. When multiple interfaces are available, a node transmitting a multicast packet with IP.DestinationAddress set to LL-MANET-Routers SHOULD send the packet on all interfaces that have been configured for AODVv2 operation. Similarly, AODVv2 routers SHOULD subscribe to LL-MANET-Routers on all their AODVv2 interfaces. 13. AODVv2 Control Packet/Message Generation Limits To ensure predictable messaging overhead, AODVv2 router's rate of packet/message generation SHOULD be limited. The rate and algorithm for limiting messages (CONTROL_TRAFFIC_LIMITS) is left to the implementor and should be administratively configurable. AODVv2 messages SHOULD be discarded in the following order of preference: RREQ, RREP, and finally RERR. 14. Optional Features Several optional features of AODVv2, and associated with AODV, are not required by minimal implementations. These features are expected to be useful in networks with greater mobility, or larger node populations, or requiring shorter latency for application launches. The optional features are as follows: o Expanding Rings Multicast o Intermediate RREPs (iRREPs): Without iRREP, only the destination can respond to a RREQ. o Precursor lists. o Reporting Multiple Unreachable Nodes. An RERR message can carry more than one Unreachable Destination node for cases when a single link breakage causes multiple destinations to become unreachable from an intermediate router. Perkins & Chakeres Expires May 10, 2013 [Page 27] Internet-Draft AODVv2 November 2012 14.1. Expanding Rings Multicast For multicast RREQ, the HopLimit MAY be set in accordance with an expanding ring search as described in [RFC3561] to limit the RREQ propagation to a subset of the local network and possibly reduce route discovery overhead. 14.2. Intermediate RREP This specification has been published as a separate Internet Draft . 14.3. Precursor Notification The Dynamic MANET On-demand (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, offering on-demand convergence in dynamic topologies. This document specifies a simple modification to AODVv2 (and possibly other reactive routing protocols) enabling faster notifications to known sources of traffic upon determination that a route for such traffic's destination has become Broken. 14.3.1. Overview If an AODVv2 router, while attempting to forward a packet to a particular destination, determines that the next hop (one of its neighbors) is no longer reachable, AODVv2 specifies that the router notify the source of that packet that the route to the destination has become Broken. In the existing specification, the notification to the source is a unicast RERR message. However, in many cases there will be several sources of of traffic for that particular destination. In fact, the broken link for the next hop in question may be a path component of numerous other routes for other destinations, and in that case the node detecting the broken link must mark as Broken multiple routes, one for each of the newly unreachable destinations. Each route that uses the newly broken link is no longer valid. For each such route, every node along the way from the source using that route, to the node detecting the broken link, is known as a "precursor" for the broken next hop. All the precursors for a particular next hop should be notified about the change in status of their route to a destination downstream from the broken next hop. 14.3.2. Precursor Notification Details During normal operation, each node wishing to enable the improved notification for precursors of any links to its next hop neighbors Perkins & Chakeres Expires May 10, 2013 [Page 28] Internet-Draft AODVv2 November 2012 has to keep track of the precursors. This is done by maintaining a precursor table and updating the table whenever the node initiates or relays a RREP message back to a node originating a RREQ message. When the node transmits the RREP message, it is implicitly agreeing to forward traffic from the RREQ originator towards the RREP originator (i.e., along the next hop link to the neighbor from which the RREP was received). The "other" next hop, which is the neighbor along the way towards the originator of the RREQ message, is then the next precursor for the route towards the destination requested by the RREQ. Each such precursor should then be recorded as a precursor for a route along the next hop. The same next hop may be in service for routes to multiple destinations, but for precursor list management it is only important to keep track of precursors for a particular next hop; the exact destination does not matter, only the particular next hop towards the destination(s). When a node observes that one of its neighbors is no longer reachable, the node first checks to see whether the link to that neighbor is a next hop for any more distant destination in its route table. If not, then the node simply updates any relevant neighorhood information and takes no further action. Otherwise, for all destinations no longer reachable because of the changed status of the next hop, the node first checks to see whether the link to that neighbor is a next hop for any more distant destination in its route table. If not, then the node simply updates any relevant neighorhood information and takes no further action. For each precursor of the next hop, the node MAY notify the precursor in one of three ways: o unicast RERR o broadcast RERR o multicast RERR to multicast group PRECURSOR_RERR_RECEIVERS, by default LL-MANET-Routers [RFC5498]. Each precursor then MAY execute the same procedure until all affected traffic sources have received the RERR route maintenance information. When a precursor receives a unicast RERR, the precursor MUST further unicast the RERR message towards the affected traffic source. If a precursor receives a broadcast or multicast RERR, the precursor MAY further retransmit the RERR using the same destination address is used in the received RERR. Perkins & Chakeres Expires May 10, 2013 [Page 29] Internet-Draft AODVv2 November 2012 14.3.3. Reporting Multiple Unreachable Nodes By default, only broken links cause an RERR message to report multiple unreachable destinations. If only a single upstream is to be notified, it should be discussed how to identify which of the possibly several upstream routers should receive the RERR. It should also be discussed whether or not an RERR message should report broken routes under other circumstances. 14.4. Broadcast response to RREQ As an alternative to issuing a RREP, the RREQ Target Router (RREQ_TargRtr) MAY choose to distribute routing information about the route to the RREQ TargetNode (TargRtr's client) more widely. That is, RREQ_TargRtr MAY optionally perform the steps of a route discovery by issuing a RREQ with RREQ_TargetNode listed as the TargetNode, using the procedure in Section 7.2. Afterwards, RREQ_TargRtr processing for the incoming RREQ is complete. Broadcast response to incoming RREQ was originally specified to handle unidirectional links, but it is expensive. 14.5. Message Aggregation The aggregation of multiple messages into a packet is specified in RFC 5444 [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]. 14.6. Adding Additional Routing Information to a RteMsg DSR [RFC4728] includes source routes as part of the data of its RREPs and RREQs. Doign so allows additional topology information to be flooded along with the RteMsg, and potentially allows updating for stale routing information at MANET routers along new paths between source and destination. To maintain this functionality, AODVv2 has defined a somewhat more general method that enables inclusion of source routes in RteMsgs. Appending routing information can alleviate route discovery attempts to the nodes whose information is included, if other AODVv2 routers use this information to update their routing tables. Note that, since the initial merger of DSR with AODV to create this protocol, further experimentation has shown that including the additional routing information is not always helpful. Sometimes it Perkins & Chakeres Expires May 10, 2013 [Page 30] Internet-Draft AODVv2 November 2012 seems to help, and other times it seems to reduce overall performance. An AODVv2 router (RteMsg_Hande) MAY optionally append AdditionalNode routing information to a RteMsg. This is controllable by an option (APPEND_INFORMATION) which SHOULD be administratively configurable or controlled according to the traffic characteristics of the network. Prior to appending an address controlled by this AODVv2 router to a RteMsg, RteMsg_Hand MAY increment its OwnSeqNum as defined in Section 5. If OwnSeqNum is not incremented the appended routing information might not be usable, when received by nodes with existing routing information. Incrementation of the sequence number when appending information to a RteMsg in transit (APPEND_INFORMATION_SEQNUM) SHOULD be administratively configurable. Note that, during handling of this RteMsg, OwnSeqNum may have already been incremented; and in this case OwnSeqNum need not be incremented again. If the address information of a client served by this AODVv2 router includes Route.Dist, it is set to a number greater than zero (0) which measures the hops between the AODVv2 router and the router client. For added addresses (and their prefixes) not controlled by this AODVv2 router, Route.Dist can be included if known. Otherwise, Route.Dist is set to MAX_HOPCOUNT The VALIDITY_TIME of routing information for appended address(es) MUST be included, to inform routers about when to expire this information. A typical value for VALIDITY_TIME is (ACTIVE_INTERVAL+ MAX_IDLETIME) - (Current_Time - Route.LastUsed) but other values (less than MAX_SEQNUM_TIME) MAY be chosen. The VALIDITY_TIME TLV is defined in Section 16.3. Additional information (e.g. SeqNum and Dist) about any appended address(es) MUST be included. Routing information about the TargetNode MUST NOT be added. Also, duplicate address entries SHOULD NOT be added. Instead, only the best routing information (Section 6.1) for a particular address SHOULD be included. The following notation is used to specify the methods for inclusion of routing information for addtional nodes. Perkins & Chakeres Expires May 10, 2013 [Page 31] Internet-Draft AODVv2 November 2012 AddlNode The IP address of an additional node that can be reached via the AODVv2 router adding this information. Each AdditionalNode.Address MUST include its prefix. Each AdditionalNode.Address MUST also have an associated Node.SeqNum in the address TLV block. AddlNode.SeqNum The AODVv2 sequence number associated with this routing information. AddlNode.Dist A metric of the distance to reach the associated AdditionalNode.Address. This field is incremented by at least one at each intermediate AODVv2 router. An intermediate node (i.e., RteMsg_Hand) obeys the following procedures when processing AdditionalNode.Address information and other associated TLVs that are included with a RteMsg. For each AdditionalNode (except the TargetNode) in the RteMsg that includes AddTLV.Dist information, the AddTLV.Dist information MUST be incremented. If the resulting Distance value for the OrigNode is greater than 254, the message is discarded. If the resulting Distance value for another node is greater than 254, the associated address and its information are removed from the RteMsg. After handling the OrigNode's routing information, then each address that is not the TargetNode MAY be considered for creating and updating routes. Creating and updating routes to other nodes can eliminate RREQ for those IP destinations, in the event that data needs to be forwarded to the IP destination(s) now or in the near future. For each of the additional addresses considered, RteMsg_Hand first checks that the address is a routable unicast address. If the address is not a unicast address, then the address and all related information MUST be removed. If the routing table does not have a matching route with a known Route.SeqNum for this additional address using longest-prefix matching, then a route MAY be created and updated as described in Section 6.2. If a route table entry exists with a known Route.SeqNum, the incoming routing information is compared with the route table entry following the procedure described in Section 6.1. If the incoming routing information is used, the route table entry SHOULD be updated as described in Section 6.2. If the routing information for an AdditionalNode.Address is not used, Perkins & Chakeres Expires May 10, 2013 [Page 32] Internet-Draft AODVv2 November 2012 then it is removed from the RteMsg. 15. Administratively Configured Parameters and Timer Values AODVv2 contains several parameters which MUST be administratively configured. The list of these follows: Required Administratively Configured Parameters +------------------------+------------------------------------------+ | Name | Description | +------------------------+------------------------------------------+ | RESPONSIBLE_ADDRESSES | List of addresses or routing prefixes, | | | for which this AODVv2 router is | | | responsible. If, RESPONSIBLE_ADDRESSES | | | is zero, this AODVv2 router is only | | | responsible for its own addresses. | | AODVv2_INTERFACES | List of the interfaces participating in | | | AODVv2 routing protocol. | +------------------------+------------------------------------------+ Table 2 AODVv2 contains a number of timers. The default timing parameter values follow: Default Timing Parameter Values +------------------------------+-------------+ | Name | Value | +------------------------------+-------------+ | ACTIVE_INTERVAL | 5 second | | MAX_IDLETIME | 200 seconds | | MAX_SEQNUM_LIFETIME | 300 seconds | | ROUTE_RREQ_WAIT_TIME | 2 seconds | | UNICAST_MESSAGE_SENT_TIMEOUT | 1 second | +------------------------------+-------------+ Table 3 The above timing parameter values work well for small and medium well-connected networks with moderate topology changes. The timing parameters SHOULD be administratively configurable for the network where AODVv2 is used. Ideally, for networks with frequent topology changes the AODVv2 parameters should be adjusted using either experimentally determined values or dynamic adaptation. For Perkins & Chakeres Expires May 10, 2013 [Page 33] Internet-Draft AODVv2 November 2012 example, in networks with infrequent topology changes MAX_IDLETIME may be set to a much larger value. Default Parameter Values +------------------------+-------+----------------------------------+ | Name | Value | Description | +------------------------+-------+----------------------------------+ | MAX_HOPCOUNT | 20 | This value MUST be larger than | | | hops | the AODVv2 network diameter. | | | | Otherwise, routing messages may | | | | not reach their intended | | | | destinations. | | DISCOVERY_ATTEMPTS_MAX | 3 | The number of route discovery | | | | attempts to make before | | | | indicating that a particular | | | | address is not reachable. | +------------------------+-------+----------------------------------+ Table 4 In addition to the above parameters and timing values, several administrative options exist. These options have no influence on correct routing behavior, although they may potentially reduce AODVv2 protocol messaging in certain situations. The default behavior is to NOT enable any of these options; and although many of these options can be administratively controlled, they may be better served by intelligent control. The following table enumerates several of the options. Administratively Controlled Options +--------------------------+----------------------------------------+ | Name | Description | +--------------------------+----------------------------------------+ | APPEND_INFORMATION | Whether to append routing information | | | for AdditionalNodes to a RteMsg. | | BUFFER_DURING_DISCOVERY | Whether and how much data to buffer | | | during route discovery. | | APPEND_EXTRA_UNREACHABLE | Whether to append additional | | | Unreachable information to RERR. | | CONTROL_TRAFFIC_LIMITS | AODVv2 messaging SHOULD be limited to | | | avoid consuming all the network | | | bandwidth. | +--------------------------+----------------------------------------+ Table 5 Perkins & Chakeres Expires May 10, 2013 [Page 34] Internet-Draft AODVv2 November 2012 Note: several fields have limited size (bits or bytes) these sizes and their encoding may place specific limitations on the values that can be set. For example, MsgHdr.HopCount is a 8-bit field and therefore MAX_HOPCOUNT cannot be larger than 255. 16. IANA Considerations In its default mode of operation, AODVv2 uses the UDP port 269 [RFC5498] to carry protocol packets. AODVv2 also uses the link-local multicast address LL-MANET-Routers [RFC5498]. This section specifies several message types, message tlv-types, and address tlv-types. 16.1. AODVv2 Message Types Specification AODVv2 Message Types +------------------------+----------+ | Name | Type | +------------------------+----------+ | Route Request (RREQ) | 10 - TBD | | Route Reply (RREP) | 11 - TBD | | Route Error (RERR) | 12 - TBD | +------------------------+----------+ Table 6 16.2. Message and Address Block TLV Type Specification Message TLV Types Perkins & Chakeres Expires May 10, 2013 [Page 35] Internet-Draft AODVv2 November 2012 +-------------------+------+--------+-------------------------------+ | Name | Type | Length | Value | +-------------------+------+--------+-------------------------------+ | Unicast Response | 10 - | 0 | Indicates to the processing | | Request | TBD | octets | node that the previous hop | | | | | (IP.SourceAddress) expects a | | | | | unicast reply message within | | | | | UNICAST_MESSAGE_SENT_TIMEOUT. | | | | | Any unicast packet will serve | | | | | this purpose, and it MAY be | | | | | an ICMP REPLY message. If | | | | | the reply is not received, | | | | | then the previous hop can | | | | | assume that the link is | | | | | unidirectional and MAY | | | | | blacklist the link to this | | | | | node. | +-------------------+------+--------+-------------------------------+ Table 7 16.3. Address Block TLV Specification Address Block TLV Types +---------------+------------+----------+---------------------------+ | Name | Type | Length | Value | +---------------+------------+----------+---------------------------+ | Sequence | 10 - TBD | up to 2 | The AODVv2 sequence | | Number | | octets | number associated with | | (SeqNum) | | | this address. The | | | | | sequence number MUST be | | | | | the last known sequence | | | | | number. | | Distance | 11 - TBD | up to 2 | A metric of the distance | | | | octets | traversed by the | | | | | information associated | | | | | with this address. | | VALIDITY_TIME | 1[RFC5497] | | The maximum amount of | | | | | time that information can | | | | | be maintained before | | | | | being deleted. The | | | | | VALIDITY_TIME TLV is | | | | | defined in [RFC5497]. | +---------------+------------+----------+---------------------------+ Table 8 Perkins & Chakeres Expires May 10, 2013 [Page 36] Internet-Draft AODVv2 November 2012 17. Security Considerations The objective of the AODVv2 protocol is for each router to communicate reachability information to addresses for which it is responsible. Positive routing information (i.e. a route exists) is distributed via RteMsgs and negative routing information (i.e. a route does not exist) via RERRs. AODVv2 routers that handle these messages store the contained information to properly forward data packets, and they generally provide this information to other AODVv2 routers. This section does not mandate any specific security measures. Instead, this section describes various security considerations and potential avenues to secure AODVv2 routing. The most important security mechanisms for AODVv2 routing are integrity/authentication and confidentiality. In situations where routing information or router identity are suspect, integrity and authentication techniques SHOULD be applied to AODVv2 messages. In these situations, routing information that is distributed over multiple hops SHOULD also verify the integrity and identity of information based on originator of the routing information. A digital signature could be used to identify the source of AODVv2 messages and information, along with its authenticity. A nonce or timestamp SHOULD also be used to protect against replay attacks. S/MIME and OpenPGP are two authentication/integrity protocols that could be adapted for this purpose. In situations where confidentiality of AODVv2 messages is important, cryptographic techniques can be applied. In certain situations, for example sending a RREP or RERR, an AODVv2 router could include proof that it has previously received valid routing information to reach the destination, at one point of time in the past. In situations where routers are suspected of transmitting maliciously erroneous information, the original routing information along with its security credentials SHOULD be included. Note that if multicast is used, any confidentiality and integrity algorithms used MUST permit multiple receivers to handle the message. Routing protocols, however, are prime targets for impersonation attacks. In networks where the node membership is not known, it is difficult to determine the occurrence of impersonation attacks, and security prevention techniques are difficult at best. However, when Perkins & Chakeres Expires May 10, 2013 [Page 37] Internet-Draft AODVv2 November 2012 the network membership is known and there is a danger of such attacks, AODVv2 messages must be protected by the use of authentication techniques, such as those involving generation of unforgeable and cryptographically strong message digests or digital signatures. While AODVv2 does not place restrictions on the authentication mechanism used for this purpose, IPsec Authentication Message (AH) is an appropriate choice for cases where the nodes share an appropriate security association that enables the use of AH. In particular, routing messages SHOULD be authenticated to avoid creation of spurious routes to a destination. Otherwise, an attacker could masquerade as that destination and maliciously deny service to the destination and/or maliciously inspect and consume traffic intended for delivery to the destination. RERR messages SHOULD be authenticated in order to prevent malicious nodes from disrupting active routes between communicating nodes. If the mobile nodes in the ad hoc network have pre-established security associations, the purposes for which the security associations are created should include that of authorizing the processing of AODVv2 control packets. Given this understanding, the mobile nodes should be able to use the same authentication mechanisms based on their IP addresses as they would have used otherwise. 18. 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-Royer for her long time authorship of AODV. Additional thanks to Luke Klein- Berndt, Pedro Ruiz, Fransisco Ros, Koojana Kuladinithi, Ramon Caceres, Thomas Clausen, Christopher Dearlove, Seung Yi, Romain Thouvenin, Tronje Krop, Henner Jakob, Alexandru Petrescu, Christoph Sommer, Cong Yuan, Lars Kristensen, and Derek Atkins for reviewing of AODVv2, as well as several specification suggestions. This revision of AODVv2 separates the minimal base specification from other optional features to expedite the process of ensuring compatibility with the existing LOADng specification [I-D.clausen-lln-loadng] (minimal reactive routing protocol specification). Thanks are due to T. Clausen, A. Colin de Verdiere, J. Yi, A. Niktash, Y. Igarashi, Satoh. H., and U. Herberg for their development of LOADng and sharing details for ensuring appropriateness of AODVv2 for their application. Perkins & Chakeres Expires May 10, 2013 [Page 38] Internet-Draft AODVv2 November 2012 19. References 19.1. Normative References [RFC1812] Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, June 1995. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C. Pignataro, "The Generalized TTL Security Mechanism (GTSM)", RFC 5082, October 2007. [RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, "Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format", RFC 5444, February 2009. [RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497, March 2009. [RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network (MANET) Protocols", RFC 5498, March 2009. 19.2. Informative References [I-D.clausen-lln-loadng] Clausen, T., Verdiere, A., Yi, J., Niktash, A., Igarashi, Y., Satoh, H., Herberg, U., Lavenu, C., Lys, T., Perkins, C., and J. Dean, "The Lightweight On-demand Ad hoc Distance-vector Routing Protocol - Next Generation (LOADng)", draft-clausen-lln-loadng-06 (work in progress), October 2012. [Perkins99] Perkins, C. and E. Belding-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. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2501] Corson, M. and J. Macker, "Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations", RFC 2501, January 1999. [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- Perkins & Chakeres Expires May 10, 2013 [Page 39] Internet-Draft AODVv2 November 2012 Demand Distance Vector (AODV) Routing", RFC 3561, July 2003. [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, 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, February 2007. [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. [RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter Considerations in Mobile Ad Hoc Networks (MANETs)", RFC 5148, February 2008. [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, July 2008. [RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP)", RFC 6130, April 2011. [RFC6549] Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi- Instance Extensions", RFC 6549, March 2012. [RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621, May 2012. Appendix A. Example RFC 5444-compliant packet formats The following three subsections show example RFC 5444-compliant packets for AODVv2 message types RREQ, RREP, and RERR. These proposed message formats are designed based on expected savings from IPv6 addressable MANET nodes, and a layout for the Address TLVs that may be viewed as natural, even if perhaps not the absolute most compact possible encoding. For RteMsgs RREQ and RREP, the msg-hdr fields are followed by at least one and optionally two Address Blocks. There is always an Address Block containing the RteMsg_Orig address and RteMsg_Targ address. For that Address Block, there must be a Address TLV block of type Seqnum with one or two Seqnum values; for RREQ messages, sometimes the Seqnum for RteMsg_Targ is unknown. Perkins & Chakeres Expires May 10, 2013 [Page 40] Internet-Draft AODVv2 November 2012 In addition to the Seqnum TLV, there MAY be an Address TLV block of type Cost. When there is no Cost TLV block, then RteMsg_Orig and RteMsg_Targ are both AODVv2 routers and the msg-hop-count is measures the cost of traversing the route followed by the RteMsg from RteMsg_Orig to the current intermediate AODVv2 router handling the RteMsg. When the Cost TLV block is present, alternate Cost metrics are enabled by the inclusion of the CostType Message TLV. When there is no such CostType Message TLV present, then the Cost Address TLV block simply provides a way for the RteMsg_Orig to supply an initial nonzero hopcount for the cost of the route between the RteMsg_Orig and the RteMsg_Gen, i.e., the AODVv2 router that serves RteMsg_Orig. AdditionalNode information MAY be included in a RteMsg by adding a second Address Block. Seqnum and Cost information MUST be provided for each such AdditionalNode, so that the second Address Block MUST also contain the Seqnum and Cost Address TLV blocks. To enable alternate Cost metrics for the Cost Address TLV, a second CostType msg-TLV may be added to the msg header. A.1. RREQ Message Format The figure below illustrates a packet format for an example RREQ message. Example IPv4 RREQ 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PV=0 | PF=0 | msg-type=RREQ | MF=2 | MAL=3 | msg-size=23 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | msg-size=23 | msg-hop-count | msg.tlvs-length=0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num-addr=2 |1|0|0|0|0| Rsv | head-length=3 |Head(Orig&Targ)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Head (bytes for Orig & Target)| Orig.Tail | Target.Tail | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | addr.tlvs-length=6 | type=SeqNum |0|1|0|1|0|0|Rsv| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Index-start=0 | tlv-length=2 | Orig.Node Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RREQ with Msg Seq# added, and: - two addresses in Address Block - address length = 4 [IPv4], shared initial bytes = 3 - Sequence Number available only for Orig.Node in addr.tlv - Addresses stored from Originator to Target Figure 2 Perkins & Chakeres Expires May 10, 2013 [Page 41] Internet-Draft AODVv2 November 2012 A.2. RREP Message Format The figure below illustrates a packet format for an example RREP message. Example IPv4 RREP 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PV=0 | PF=0 | msg-type=RREP | MF=2 | MAL=3 | msg-size=25 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | msg-size=25 | msg-hop-count | msg.tlvs-length=0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num-addr=2 |1|0|0|0|0| Rsv | head-length=3 |Head(Orig&Targ)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Head (bytes for Orig & Target)| Orig.Tail | Target.Tail | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | addr.tlvs-length=8 | type=SeqNum |0|1|0|1|0|0|Rsv| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Index-start=0 | tlv-length=2 | Orig.Node Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Target.Node Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RREP with Msg Seq# added, and: - two addresses in Address Block - address length = 4 [IPv4], shared initial bytes = 3 - Two Sequence Numbers available in addr.tlv - Addresses stored from Originator to Target Figure 3 A.3. RERR Message Format The figure below illustrates a packet format for an example RERR message. Perkins & Chakeres Expires May 10, 2013 [Page 42] Internet-Draft AODVv2 November 2012 Example IPv4 RERR 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PV=0 | PF=0 | msg-type=RERR | MF=2 | MAL=3 | msg-size=25 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | msg-size=25 | msg-hop-count | msg.tlvs-length=0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | num-addr=2 |1|0|0|0|0| Rsv | head-length=3 |Head(Orig&Targ)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Head (bytes for Orig & Target)| Orig.Tail | Target.Tail | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | addr.tlvs-length=8 | type=SeqNum |0|1|0|1|0|0|Rsv| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Index-start=0 | tlv-length=2 | Orig.Node Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Target.Node Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RERR with - Two Unreachable Node address in Address Block - address length = 4 [IPv4], shared initial bytes = 3 - Two Sequence Numbers available in addr.tlv - Addresses stored from Originator to Target Figure 4 Appendix B. Changes since the Previous Version o Many changes for RFC 5444 compliance o Reorganized and simplified route lifetime management o Reorganized document structure, combining closely related small sections and eliminating top-level "Detailed ..." section. o More later... Appendix C. Previous Changes since Version ...-21 o Internet-Facing AODVv2 router renamed to be IAR o "Optional Features" section created to contain features not required within base specification, including: o Perkins & Chakeres Expires May 10, 2013 [Page 43] Internet-Draft AODVv2 November 2012 * Intermediate RREPs (iRREPs): Without iRREP, only the destination can respond to a RREQ. * Precursor lists. * An RERR may reporting multiple unreachable nodes. * Message Aggregation. o Sequence number MUST (instead of SHOULD) be set to 1 after rollover. o AODVv2 routers MUST (instead of SHOULD) only handle AODVv2 messages from adjacent routers. o Clarification that Additional Routing information in RteMsgs is optional (MAY) to use. o Clarification that if Additional Routing information in RteMsgs is used, then the Route Table Entry SHOULD be updated using normal procedures as described in Section 6.2. o Clarification in Section 7.1 that nodes may be configured to buffer zero packets. o Clarification in Section 7.1 that buffered packets MUST be dropped if route discovery fails. o In Section 8.1, relax mandate for monitoring connectivity to next- hop AODVv2 neighbors (from MUST to SHOULD), in order to allow for minimal implementations o Remove Route.Forwarding flag; identical to "NOT" Route.Broken. o Routing Messages MUST are now originated with the MsgHdr.HopCount instead of MsgHdr.HopLimit. o Routing Messages MUST be originated with the MsgHdr.HopCount set to MAX_HOPCOUNT. Previously, MsgHdr.HopLimit was not mandated. o Maximum hop count set to 254, with 255 reserved for "unknown". Since the current draft only uses hop-count as distance, this is also the current maximum distance. Perkins & Chakeres Expires May 10, 2013 [Page 44] Internet-Draft AODVv2 November 2012 Appendix D. Shifting Network Prefix Advertisement Between AODVv2 Routers Only one AODVv2 router within a routing region SHOULD be responsible for a particular address at any time. If two AODVv2 routers dynamically shift the advertisement of a network prefix, correct AODVv2 routing behavior must be observed. The AODVv2 router adding the new network prefix must wait for any existing routing information about this network prefix to be purged from the network. Therefore, it must wait at least ROUTER_SEQNUM_AGE_MAX_TIMEOUT after the previous AODVv2 router for this address stopped advertising routing information on its behalf. Authors' Addresses Charles E. Perkins Futurewei Inc. 2330 Central Expressway Santa Clara, CA 95050 USA Phone: +1-408-330-5305 Email: charliep@computer.org Ian D Chakeres CenGen 9250 Bendix Road North Columbia, Maryland 21045 USA Email: ian.chakeres@gmail.com URI: http://www.ianchak.com/ Perkins & Chakeres Expires May 10, 2013 [Page 45]