Mobile Ad hoc Networks Working Group C. Perkins Internet-Draft Intended status: Standards Track I. Chakeres Expires: September 13, 2012 CenGen March 12, 2012 Dynamic MANET On-demand (AODVv2) Routing draft-ietf-manet-dymo-22 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 September 13, 2012. 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 September 13, 2012 [Page 1] Internet-Draft AODVv2 March 2012 described in the Simplified BSD License. Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Applicability Statement . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Route Table Entry . . . . . . . . . . . . . . . . . . . . 7 4.2. AODVv2 Messages . . . . . . . . . . . . . . . . . . . . . 8 4.2.1. Generalized Packet and Message Structure . . . . . . . 9 4.2.2. Routing Message (RteMsg) - RREQ and RREP . . . . . . . 10 4.2.3. Route Error (RERR) . . . . . . . . . . . . . . . . . . 11 5. Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 12 5.1. AODVv2 Sequence Numbers . . . . . . . . . . . . . . . . . 12 5.1.1. Maintaining A Node's Own Sequence Number . . . . . . . 12 5.1.2. Numerical Operations on OwnSeqNum . . . . . . . . . . 13 5.1.3. OwnSeqNum Rollover . . . . . . . . . . . . . . . . . . 13 5.1.4. Actions After OwnSeqNum Loss . . . . . . . . . . . . . 13 5.2. AODVv2 Routing Table Operations . . . . . . . . . . . . . 13 5.2.1. Judging Routing Information's Usefulness . . . . . . . 13 5.2.2. Creating or Updating a Route Table Entry with Received Preferable Routing Information . . . . . . . 15 5.2.3. Route Table Entry Timeouts . . . . . . . . . . . . . . 16 5.3. Routing Messages . . . . . . . . . . . . . . . . . . . . . 16 5.3.1. RREQ Creation . . . . . . . . . . . . . . . . . . . . 16 5.3.2. RREP Creation . . . . . . . . . . . . . . . . . . . . 17 5.3.3. RteMsg Handling . . . . . . . . . . . . . . . . . . . 18 5.4. Route Discovery . . . . . . . . . . . . . . . . . . . . . 21 5.5. Route Maintenance . . . . . . . . . . . . . . . . . . . . 22 5.5.1. Active Next-hop Router Adjacency Monitoring . . . . . 22 5.5.2. Updating Route Lifetimes During Packet Forwarding . . 23 5.5.3. RERR Generation . . . . . . . . . . . . . . . . . . . 23 5.5.4. RERR Handling . . . . . . . . . . . . . . . . . . . . 24 5.6. Unknown Message and TLV Types . . . . . . . . . . . . . . 25 5.7. Advertising Network Addresses . . . . . . . . . . . . . . 25 5.8. Simple Internet Attachment . . . . . . . . . . . . . . . . 25 5.9. Multiple Interfaces . . . . . . . . . . . . . . . . . . . 27 5.10. AODVv2 Control Packet/Message Generation Limits . . . . . 27 6. Administratively Configured Parameters and Timer Values . . . 27 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 7.1. AODVv2 Message Types Specification . . . . . . . . . . . . 30 7.2. Message and Address Block TLV Type Specification . . . . . 30 7.3. Address Block TLV Specification . . . . . . . . . . . . . 31 8. Security Considerations . . . . . . . . . . . . . . . . . . . 31 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Perkins & Chakeres Expires September 13, 2012 [Page 2] Internet-Draft AODVv2 March 2012 10.1. Normative References . . . . . . . . . . . . . . . . . . . 33 10.2. Informative References . . . . . . . . . . . . . . . . . . 33 Appendix A. Changes since the Previous Version . . . . . . . . . 34 Appendix B. Proposed additional changes for LOADng conformance . 34 Appendix C. Shifting Responsibility for an Address Between AODVv2 Routers . . . . . . . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35 Perkins & Chakeres Expires September 13, 2012 [Page 3] Internet-Draft AODVv2 March 2012 1. Overview The Dynamic MANET On-demand (AODVv2) routing protocol enables on- demand, multihop unicast routing among participating AODVv2 routers. The basic operations of the AODVv2 protocol are route discovery and route maintenance. Route discovery is performed when an AODVv2 router receives a packet from a node under its responsibility to a destination for which it does not have a route. Route maintenance is performed to help ensure that the route being used to forward packets from the source to the destination remains operational. During route discovery, the originator's AODVv2 router initiates dissemination of a Route Request (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 dissemination process, each intermediate AODVv2 router records a route to the originator. When the target's AODVv2 router receives the RREQ, it responds with a Route Reply (RREP) sent 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 sent toward the packet source to indicate the route to particular destination addresses is invalid or missing. When the source's AODVv2 router receives the RERR, it deletes the route. If this source's AODVv2 router later receives a packet for forwarding to the same destination, it will need to perform route discovery again for that destination. 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. 2. Applicability Statement The AODVv2 routing protocol is designed for stub or disconnected Perkins & Chakeres Expires September 13, 2012 [Page 4] Internet-Draft AODVv2 March 2012 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 routers forward packets to only a small portion of the other AODVv2 routers, 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 active sources and destinations is maintained, in contrast to most proactive routing protocols that require routing information to all routers within the routing region be maintained. AODVv2 supports routers with multiple interfaces participating in the MANET. AODVv2 routers can also perform routing on behalf of other nodes, attached via participating or non-participating interfaces. AODVv2 routers perform route discovery to find a route to a particular destination. Therefore, AODVv2 routers MUST be configured to initiate and respond to route discovery on behalf of certain nodes, identified by address. 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 any time within an AODVv2 routing region, only one AODVv2 router SHOULD be responsible for, i.e. "own", any particular address. 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 router behavior for shifting responsibility for an address from one AODVv2 router to another is mentioned in Appendix C. AODVv2 only utilizes bidirectional links. In the case of possible unidirectional links, either blacklists (see Section 7.2) or other means (e.g. adjacency establishment with only neighboring routers that have bidirectional communication as indicated by NHDP [I-D.ietf-manet-nhdp]) of ensuring and monitoring bi-directionality is recommended. Otherwise, persistent packet loss may occur. The routing algorithm in AODVv2 may be operated at layers other than the network layer, using layer-appropriate addresses. 3. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", Perkins & Chakeres Expires September 13, 2012 [Page 5] Internet-Draft AODVv2 March 2012 "SHOULD", "SHOULD 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 several different pieces of information or protocols; for example, exchange of AODVv2 routing messages, other protocols (e.g. NDP [RFC4861] or NHDP [I-D.ietf-manet-nhdp]), or manual configuration. Similarly, loss of a routing adjacency may also be based upon several pieces of information, and monitoring of adjacencies where packets are being forwarded is required (see Section 5.5.1). Distance (Dist) A metric of the distance a message or piece of information has traversed. The minimum value of distance is the number of IP hops traversed. The maximum value is 65,535. AODVv2 Sequence Number (SeqNum) An AODVv2 Sequence Number is maintained by each AODVv2 router process. This sequence number is used by other AODVv2 routers to identify the temporal order of routing information generated and ensure loop-free routes. Multihop-capable Unicast IP Address A multihop-capable unicast IP address is a unicast IP address that when put into the IP.SourceAddress or IP.DestinationAddress field is scoped sufficiently to be forwarded by a router. Globally- scoped unicast IP addresses and Unique Local Addresses (ULAs) are examples of multihop-capable unicast IP addresses. Originating Node (OrigNode) The originating node is the source, its AODVv2 router creates a AODVv2 control message on its behalf in an effort to disseminate some routing information. The originating node is also referred to as a particular message's originator. Route Error (RERR) A RERR message is used to indicate that an AODVv2 router does not have a forwarding route to one or more particular addresses. Perkins & Chakeres Expires September 13, 2012 [Page 6] Internet-Draft AODVv2 March 2012 Route Reply (RREP) A RREP message is used to disseminate routing information about the RREP TargetNode to the RREP OrigNode and the AODVv2 routers between them. Route Request (RREQ) A RREQ message is used to discover a valid route to a particular destination address, called the RREQ TargetNode. When an AODVv2 router processes a RREQ, it learns routing information on how to reach the RREQ OrigNode. Target Node (TargetNode) The TargetNode is the ultimate destination of a message. This Node (ThisNode) ThisNode corresponds to the AODVv2 router process currently performing a calculation or attending to a message. Type-Length-Value structure (TLV) A generic way to represent information, please see [RFC5444] for additional information. Unreachable Node (UnreachableNode) An UnreachableNode is a node for which a forwarding route is unknown. 4. Data Structures 4.1. Route Table Entry The route table entry is a conceptual data structure. Implementations may use any internal representation that conforms to the semantics of a route as specified in this document. 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. Route.Prefix Indicates that the associated address is a network address, rather than a host address. The value is the length of the netmask/ prefix. Perkins & Chakeres Expires September 13, 2012 [Page 7] Internet-Draft AODVv2 March 2012 Route.SeqNum The AODVv2 SeqNum associated with this routing information. Route.NextHopAddress The 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.Forwarding A flag indicating whether this Route can be used for forwarding data packets. This flag MAY be provided for management and monitoring. 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 attending to a RERR (see Section 5.5.4). The following field is optional: Route.Dist A dimensionless metric indicating the distance traversed before reaching the Route.Address node. Not including optional information may cause performance degradation, but it will not cause the protocol to operate incorrectly. In addition to a route table data structure, each route table entry may have several timers associated with the information. These timers/timeouts are discussed in Section 5.2.3. 4.2. AODVv2 Messages 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, the UDP header, and fields from [RFC5444]. This document uses the following notation conventions. Information found in the table. Perkins & Chakeres Expires September 13, 2012 [Page 8] Internet-Draft AODVv2 March 2012 +---------------------------+-------------------+ | Information Location | Notational Prefix | +---------------------------+-------------------+ | IP header | IP. | | UDP header | UDP. | | RFC5444 message header | MsgHdr. | | RFC5444 message TLV | MsgTLV. | | RFC5444 address blocks | AddBlk. | | RFC5444 address block TLV | AddTLV. | +---------------------------+-------------------+ Table 1 4.2.1. Generalized Packet and Message Structure AODVv2 messages conform to the generalized packet and message format as described in [RFC5444]. Here is a brief description of the format. A packet is made up of messages. A message is made up of 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. For interoperability with other AODVv2 routers, all AODVv2 messages specified in this document SHOULD 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 stated. Therefore, all AODVv2 routers SHOULD subscribe to LL-MANET-Routers [RFC5498] for receiving control packets. Note that multicast packets MAY be sent via unicast. For example, this may occur for certain link-types (non broadcast mediums), improved robustness, or manually configured router adjacencies. Unicast AODVv2 messages (e.g. RREP) unless otherwise specified in this document are sent with the IP destination set to the Route.NextHopAddress of the route to the TargetNode. 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, it is discarded. This mechanism helps to ensures that packets have not passed through any intermediate routers, and it is known as GTSM [RFC5082]. The length of an address (32 bits for IPv4 and 128 bits for IPv6) inside an AODVv2 message depends on the msg-addr-length (MAL) in the Perkins & Chakeres Expires September 13, 2012 [Page 9] Internet-Draft AODVv2 March 2012 msg-header, as specified in [RFC5444]. AODVv2 control packets SHOULD be given priority queuing and channel access. 4.2.2. Routing Message (RteMsg) - RREQ and RREP Routing Messages (RteMsgs) are used to disseminate routing information. There are two AODVv2 message types that are considered to be routing messages (RteMsgs): RREQ and RREP. They contain very similar information and function, but have slightly different handling rules. The main difference between the two messages is that RREQ messages generally solicit a RREP, whereas a RREP is the response to RREQ. RteMsg creation and handling are described in Section 5.3. A RteMsg requires the following information: IP.SourceAddress 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.DestinationAddress The IP address of the packet destination. For multicast RREQ the IP.DestinationAddress is set to LL-MANET-Routers [RFC5498]. For unicast RREP the IP.DestinationAddress is set to the NextHopAddress toward the RREP TargetNode. IP.ProtocolNumber and UDP.DestinationPort The IP Protocol Number 138 (manet) has been reserved for MANET protocols [RFC5498]. In addition to using this IP protocol number, AODVv2 may use the UDP port 269 (manet) [RFC5498] in conjunction with the IP Protocol Number 17 (UDP). MsgHdr.HopLimit The remaining number of hops this message is allowed to traverse. AddBlk.TargetNode.Address The IP address of the message TargetNode. In a RREQ the TargetNode is the destination address for which route discovery is being performed. In a RREP the TargetNode is the RREQ OrigNode address. The TargetNode address is the first address in a routing message. Perkins & Chakeres Expires September 13, 2012 [Page 10] Internet-Draft AODVv2 March 2012 AddBlk.OrigNode.Address The IP address of the originator and its associated prefix length. In a RREQ the OrigNode is the source's address and prefix. In a RREP the OrigNode is the RREQ TargetNode's address and prefix for which a RREP is being generated. This address is the second address in the message for RREQ. OrigNode.AddTLV.SeqNum The AODVv2 sequence number of the originator's AODVv2 router. A RteMsg may optionally include the following information: TargetNode.AddTLV.SeqNum The last known AODVv2 sequence number of the TargetNode. TargetNode.AddTLV.Dist The last known Distance to the TargetNode. AddBlk.AdditionalNode.Address 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. AdditionalNode.AddTLV.SeqNum The AODVv2 sequence number associated with this routing information. OrigNode.AddTLV.Dist A metric of the distance to reach the associated OrigNode.Address. This field is incremented by at least one at each intermediate AODVv2 router. AdditionalNode.AddTLV.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. 4.2.3. Route Error (RERR) A RERR message is used to disseminate the information that a route is not available for one or more particular addresses. RERR creation and handling are described in Section 5.5. A RERR requires the following information: Perkins & Chakeres Expires September 13, 2012 [Page 11] Internet-Draft AODVv2 March 2012 IP.SourceAddress The IP address of the AODVv2 router that sent this packet. This field is generally filled automatically by the operating system and should not require special handling. IP.DestinationAddress For multicast RERR messages, The IP address is set to LL-MANET- Routers [RFC5498]. For unicast RERR messages, the IP address is set to the NextHopAddress. IP.ProtocolNumber and UDP.DestinationPort The IP Protocol Number 138 (manet) has been reserved for MANET protocols [RFC5498]. In addition to using this IP protocol number, AODVv2 may use the UDP port 269 (manet) [RFC5498] in conjunction with the IP Protocol Number 17 (UDP). MsgHdr.HopLimit The remaining number of hops this message is allowed to traverse. AddBlk.UnreachableNode.Address The address of an UnreachableNode and its associated prefix length. Multiple unreachable addresses may be included in a RERR. A Route Error may optionally include the following information: UnreachableNode.AddTLV.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 case occurs when a node receives a message to forward to a destination for which it does not have any information in its routing table. 5. Detailed Operation 5.1. AODVv2 Sequence Numbers AODVv2 sequence numbers allow AODVv2 routers to judge the freshness of routing information and ensure loop freedom. 5.1.1. Maintaining A Node's Own Sequence Number AODVv2 requires that each AODVv2 router in the network maintain its own AODVv2 sequence number (OwnSeqNum) on behalf of the addresses for which it is responsible. OwnSeqNum a 16-bit unsigned integer. The circumstances for ThisNode to increment its OwnSeqNum are described in Section 5.3. Perkins & Chakeres Expires September 13, 2012 [Page 12] Internet-Draft AODVv2 March 2012 5.1.2. Numerical Operations on OwnSeqNum When ThisNode increments its OwnSeqNum it MUST do so by treating the sequence number value as an unsigned number. 5.1.3. OwnSeqNum Rollover Incrementing an OwnSeqNum whose value is the largest largest possible number representable as a 16-bit unsigned integer (i.e., 65,535), SHOULD be set to one (1). In other words, the sequence number after 65,535 is 1. 5.1.4. Actions After OwnSeqNum Loss An AODVv2 router SHOULD maintain its sequence number in persistent storage. If an AODVv2 router's OwnSeqNum is lost, it MUST take certain actions to avoid creating routing loops. To prevent this possibility after OwnSeqNum loss an AODVv2 router MUST wait for at least ROUTE_DELETE_TIMEOUT before fully participating in the AODVv2 routing protocol. If an AODVv2 control message is received during this waiting period, the AODVv2 router SHOULD handle it normally but MUST NOT transmit or retransmit any AODVv2 messages. If a data packet is received for forwarding to another destination during this waiting period, the AODVv2 router MUST generate a RERR message indicating that this route is not available and reset its waiting timeout. At the end of the waiting period the AODVv2 router sets its OwnSeqNum to one (1) and begins participating. The longest a node need wait is ROUTE_SEQNUM_AGE_MAX_TIMEOUT. At the end of the maximum waiting period a node SHOULD set its OwnSeqNum to one (1) and begins participating. 5.2. AODVv2 Routing Table Operations 5.2.1. Judging Routing Information's Usefulness Given a route table entry (Route.SeqNum, Route.Dist, and Route.Broken) and new incoming routing information for a particular node in a RteMsg (Node.SeqNum, Node.Dist, and RteMsg message type - RREQ/RREP), the quality of the new routing information is evaluated to determine its usefulness. Incoming routing information is classified as follows: Perkins & Chakeres Expires September 13, 2012 [Page 13] Internet-Draft AODVv2 March 2012 1. Stale If Node.SeqNum - Route.SeqNum < 0 (using signed 16-bit arithmetic) the incoming information is stale. Using stale routing information is not allowed, since doing so might result in routing loops. (Node.SeqNum - Route.SeqNum < 0) using signed 16-bit arithmetic 2. Loop-possible If Node.SeqNum == Route.SeqNum the incoming information may cause loops if used; in this case additional information MUST be examined. If Route.Dist or Node.Dist is unknown or zero (0), then the routing information is loop-possible. If Node.Dist > Route.Dist + 1, then the routing information is loop-possible. Using loop-possible routing information is not allowed, otherwise routing loops may be formed. (Node.SeqNum == Route.SeqNum) AND ((Node.Dist is unknown) OR (Route.Dist is unknown) OR (Node.Dist > Route.Dist + 1)) 3. Disfavored or equivalent In case of known equal SeqNum, the information is disfavored in multiple cases: (case i) if Node.Dist == Route.Dist + 1 (it is a greater distance route) AND Route.Broken == false; (case ii) if Node.Dist == Route.Dist (equal distance route) AND Route.Broken == false AND this RteMsg is a RREQ. This condition reduces the number of RREQ flooded by stopping forwarding of RREQ with equivalent distance. ((Node.SeqNum == Route.SeqNum) AND (((Node.Dist == Route.Dist + 1) AND (Route.Broken == false)) OR ((Node.Dist == Route.Dist) AND (RteMsg is RREQ) AND (Route.Broken == false)))) 4. Preferable Incoming routing information that does not match any of the above criteria is loop-free and better than the information existing in the routing table. Information is always preferable if Node.SeqNum - Route.SeqNum > 0 (using signed 16-bit arithmetic). In the case of equal sequence numbers, the information is preferable in multiple cases: (case i) if Node.Dist < Route.Dist; (case ii) if Node.Dist == Route.Dist + 1 AND Route.Broken == true (a broken route is being repaired); (case iii) if Node.Dist == Route.Dist AND it is a RREP (RREP with equal distance are forwarded) OR Route.Broken == true (a broken route is being Perkins & Chakeres Expires September 13, 2012 [Page 14] Internet-Draft AODVv2 March 2012 repaired). For completeness, we provide the following (optimized) pseudo-code. (Node.SeqNum - Route.SeqNum > 0) OR using signed 16-bit arithmetic ((Node.SeqNum == Route.SeqNum) AND ((Node.Dist < Route.Dist) OR ((Node.Dist == Route.Dist + 1) AND (Route.Broken == true)) OR ((Node.Dist == Route.Dist) AND ((RteMsg is RREP) OR (Route.Broken == true))))) 5.2.2. Creating or Updating a Route Table Entry with Received Preferable Routing Information The route table entry is populated with the following information: 1. the Route.Address is set to Node.Address, 2. the Route.Prefix is set to the Node.Prefix. 3. the Route.SeqNum is set to the Node.SeqNum, 4. the Route.NextHopAddress is set to the node that transmitted this AODVv2 RteMsg packet (i.e., the IP.SourceAddress), 5. the Route.NextHopInterface is set to the interface that this AODVv2 packet was received on, 6. the Route.Broken flag is set to false, 7. if known, the Route.Dist is set to the Node.Dist, Fields without known values are not populated with any value. The timer for the minimum delete timeout (ROUTE_AGE_MIN) is set to ROUTE_AGE_MIN_TIMEOUT. The timer for the maximum delete timeout (ROUTE_SEQNUM_AGE_MAX) is set to Node.AddTLV.VALIDITY_TIME [RFC5497] if included; otherwise, ROUTE_SEQNUM_AGE_MAX is set to ROUTE_SEQNUM_AGE_MAX_TIMEOUT. The usage of these timers and others are described in Section 5.2.3. At this point, a forwarding route has been created and the Route.Forwarding flag set. Afterward, the route can be used to send any queued data packets and forward any incoming data packets for Route.Address. This route also fulfills any outstanding route discovery attempts for Node.Address. Perkins & Chakeres Expires September 13, 2012 [Page 15] Internet-Draft AODVv2 March 2012 5.2.3. Route Table Entry Timeouts 5.2.3.1. Minimum Delete Timeout (ROUTE_AGE_MIN) When an AODVv2 router transmits a RteMsg, other AODVv2 routers expect the transmitting AODVv2 router to have a forwarding route to the RteMsg originator. After updating a route table entry, it SHOULD be maintained for at least ROUTE_AGE_MIN. Failure to maintain the information might result in lost messages/packets, or in the worst case scenario several duplicate messages. After the ROUTE_AGE_MIN timeout a route can safely be deleted. 5.2.3.2. Maximum Sequence Number Delete Timeout (ROUTE_SEQNUM_AGE_MAX) Sequence number information is time sensitive, and MUST be deleted after a time in order to ensure loop-free routing. After the ROUTE_SEQNUM_AGE_MAX timeout a route's sequence number information MUST be discarded. 5.2.3.3. Recently Used Timeout (ROUTE_USED) When a route is used to forward data packets, this timer is set to expire after ROUTE_USED_TIMEOUT. This operation is also discussed in Section 5.5.2. If a route has not been used recently, then a timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT. 5.2.3.4. Delete Information Timeout (ROUTE_DELETE) As time progresses the likelihood that old routing information is useful decreases, especially if the network nodes are mobile. Therefore, old information SHOULD be deleted. After the ROUTE_DELETE timeout if a forwarding route exists it SHOULD be removed, and the routing table entry SHOULD also be deleted. 5.3. Routing Messages 5.3.1. RREQ Creation Before an AODVv2 router creates a RREQ it SHOULD increment its OwnSeqNum by one (1) according to the rules specified in Section 5.1. Incrementing OwnSeqNum will ensure that all nodes with existing routing information will consider this new information preferable to existing routing table information. If the sequence number is not Perkins & Chakeres Expires September 13, 2012 [Page 16] Internet-Draft AODVv2 March 2012 incremented, certain AODVv2 routers might not consider this information preferable, if they have existing better routing information. First, ThisNode adds the AddBlk.TargetNode.Address to the RREQ; the unicast IP Destination Address for which a forwarding route does not exist. If a previous value of the TargetNode.SeqNum is known (from a routing table entry using longest-prefix matching), it SHOULD be placed in TargetNode.AddTLV.SeqNum in all but the last RREQ attempt. If a TargetNode.SeqNum is not included, it is assumed to be unknown by handling nodes. This operation ensures that no intermediate AODVv2 routers reply, and ensures that the TargetNode's AODVv2 router increments its sequence number. Next, the node adds AddBlk.OrigNode.Address, its prefix, and the OrigNode.AddTLV.SeqNum (OwnSeqNum) to the RteMsg. The OrigNode.Address is the address of the source for which this AODVv2 router is initiating this route discovery. The OrigNode.Address 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. If OrigNode.Dist is included it is set to a number greater than zero (0). The MsgHdr.HopLimit SHOULD be set to MSG_HOPLIMIT. For RREQ, the MsgHdr.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. The IP.DestinationAddress for multicast RREQ is set to LL-MANET- Routers. For links that do not support multicast or situations in which unicast messaging is preferred, the IP.DestinationAddress for unicast RREQ is set to the NextHopAddress. 5.3.2. RREP Creation First, the AddBlk.TargetNode.Address is added to the RREP. The TargetNode is the ultimate destination of this RREP; the RREQ OrigNode.Address. Next, AddBlk.OrigNode.Address and prefix are added to the RREP. The Perkins & Chakeres Expires September 13, 2012 [Page 17] Internet-Draft AODVv2 March 2012 AddBlk.OrigNode.Address is the RREQ TargetNode.Address. The AddBlk.OrigNode.Address MUST be a unicast IP address. ThisNode SHOULD advertise the largest known prefix containing AddBlk.OrigNode.Address. When the RteMsg TargetNode's AODVv2 router creates a RREP, if the TargetNode.SeqNum was not included in the RREQ, ThisNode MUST increment its OwnSeqNum by one (1) according to the rules specified in Section 5.1. If TargetNode.SeqNum was included in the RteMsg and TargetNode.SeqNum - OwnSeqNum < 0 (using signed 16-bit arithmetic), OwnSeqNum SHOULD be incremented by one (1) according to the rules specified in Section 5.1. If TargetNode.SeqNum is included in the RteMsg and TargetNode.SeqNum == OwnSeqNum (using signed 16-bit arithmetic) and OrigNode.Dist will not be included in the RREP being generated, OwnSeqNum SHOULD be incremented by one (1) according to the rules specified in Section 5.1. If OwnSeqNum is not incremented the routing information might be considered stale. In this case, the RREP might not reach the RREP Target. After any of the sequence number operations above, the RREP OrigNode.AddTLV.SeqNum (OwnSeqNum) MUST also be added to the RREP. 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 65,535. The Distance value will influence judgment of the routing information (Section 5.2.1) against known information at other AODVv2 routers that handle this RteMsg. The MsgHdr.HopLimit is set to MSG_HOPLIMIT. The IP.DestinationAddress for RREP is set to the IP address of the Route.NextHopAddress for the route to the RREP TargetNode. 5.3.3. RteMsg Handling First, ThisNode examines the RteMsg to ensure that it contains the required information: MsgHdr.HopLimit, AddBlk.TargetNode.Address, AddBlk.OrigNode.Address, and OrigNode.AddTLV.SeqNum. If the required information do not exist, the message is discarded and further processing stopped. Perkins & Chakeres Expires September 13, 2012 [Page 18] Internet-Draft AODVv2 March 2012 Next, ThisNode MAY selectively attend to messages based upon information in the message. ThisNode SHOULD only handle messages from adjacent AODVv2 routers. If ThisNode chooses not to handle this message, the message is discarded and further processing stopped. ThisNode checks if the AddBlk.OrigNode.Address is a valid multihop- capable (e.g. site or global scope) unicast address. If the address is not a valid unicast address, the message is discarded and further processing stopped. ThisNode also checks whether AddBlk.OrigNode.Address is an address handled by this AODVv2 router. If this node is the originating AODVv2 router, the RteMsg is dropped. ThisNode checks if the AddBlk.TargetNode.Address is a valid multihop- capable unicast address. If the address is not a valid unicast address, the message is discarded and further processing stopped. Next, ThisNode checks whether its routing table has an entry to the AddBlk.OrigNode.Address using longest-prefix matching [RFC1812]. If a route with a valid Route.SeqNum does not exist, then the new routing information is considered preferable and a new route table entry is created and updated as described in Section 5.2.2. If a route table entry does exists and it has a known Route.SeqNum, the incoming routing information is compared with the route table entry following the procedure described in Section 5.2.1. If the incoming routing information is considered preferable, the route table entry is updated as described in Section 5.2.2. For each address (except the TargetNode) in the RteMsg that includes AddTLV.Dist information, the AddTLV.Dist information MAY be incremented. If the resulting Distance value for the OrigNode is greater than 65,535, the message is discarded. If the resulting Distance value for another node is greater than 65,535, the associated address and its information are removed from the RteMsg. The updated Distance value will influence judgment of the routing information (Section 5.2.1). 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, ThisNode first checks the that the address is a multihop-capable unicast address. If the address is not a unicast address, the address and all related Perkins & Chakeres Expires September 13, 2012 [Page 19] Internet-Draft AODVv2 March 2012 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 is created and updated as described in Section 5.2.2. 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 5.2.1. If the incoming routing information is considered preferable, the route table entry is updated as described in Section 5.2.2. If the routing information for an AdditionalNode.Address is not considered preferable, then it is removed from the RteMsg. Removing this information ensures that the information is not propagated. At this point, if the routing information for the OrigNode was not preferable then this RteMsg SHOULD be discarded and no further processing of this message SHOULD be performed. If the ThisNode is the AODVv2 router responsible for the TargetNode and this RteMsg is a RREQ, then ThisNode responds with a RREP to the RREQ OrigNode (the new RREP's TargetNode). The procedure for issuing a new RREP is described in Section 5.3.2. At this point, ThisNode need not perform any more operations for the RteMsg being processed. As an alternative to issuing a RREP, ThisNode MAY choose to distribute routing information about ThisNode (the RREQ TargetNode) more widely. That is, ThisNode MAY optionally perform a route discovery; by issuing a RREQ with ThisNode listed as the TargetNode, using the procedure in Section 5.3.1. At this point, ThisNode need not perform any more operations for the RteMsg being processed. If the resulting Distance value for the OrigNode is greater than 65,535, the message is discarded. If the resulting Distance value for another node is greater than 65,535, the associated address and its information are removed from the RteMsg. Next, the MsgHdr.HopLimit is decremented by one (1). If this RteMsg's MsgHdr.HopLimit is greater than or equal to one (1), ThisNode is not the TargetNode, AND this RteMsg is a RREQ, then the current RteMsg (altered by the procedure defined above) SHOULD be sent to the IP.DestinationAddress LL-MANET-Routers [RFC5498]. If the RREQ is unicast, the IP.DestinationAddress is set to the NextHopAddress. If this RteMsg's MsgHdr.HopLimit is greater than or equal to one (1), ThisNode is not the TargetNode, AND this RteMsg is a RREP, then the current RteMsg is sent to the Route.NextHopAddress for the RREP's Perkins & Chakeres Expires September 13, 2012 [Page 20] Internet-Draft AODVv2 March 2012 TargetNode.Address. If no forwarding route exists to TargetNode.Address, then a RERR SHOULD be issued to the OrigNode of the RREP. By sending the updated RteMsg, ThisNode advertises that it will route for addresses contained in the outgoing RteMsg based on the information enclosed. ThisNode 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. Some examples of why ThisNode might choose to not re-issue a RteMsg are: if ThisNode does not want to advertise routing for the contained addresses because it is already heavily loaded; if ThisNode has already issued nearly identical routing information (e.g. ThisNode had recently issued a RteMsg with nearly the same distance); or if ThisNode is low on energy and does not want to expend energy for control message sending or packet forwarding. The exact circumstances producing such behavior are not specified in this document. 5.4. Route Discovery When a source's AODVv2 router needs to forward a data packet on behalf of an attached node and it does not have a forwarding route to the data packet's unicast IP destination address, ThisNode sends a RREQ (described in Section 5.3.1) to discover a route to the particular destination (TargetNode). After issuing a RREQ, the OrigNode AODVv2 router waits for a route to be created to the TargetNode. If a route is not created within RREQ_WAIT_TIME, ThisNode may again try to discover a route by issuing another RREQ using the procedure defined in Section 5.3.1 again. Route discovery SHOULD be considered failed after DISCOVERY_ATTEMPTS_MAX and the final RREQ's corresponding RREQ_WAIT_TIME. To reduce congestion in a network, repeated attempts at route discovery for a particular TargetNode SHOULD utilize an exponential backoff. For example, the first time an AODVv2 router issues a RREQ, it waits RREQ_WAIT_TIME for a route to the TargetNode. If a route is not found within that time, the AODVv2 router MAY send another RREQ. If a route is not found within two (2) times the current waiting time, another RREQ MAY be sent. No more than DISCOVERY_ATTEMPTS_MAX route discovery attempts SHOULD be made before considering route discovery for this destination to have failed. For each additional attempt, the waiting time for the previous RREQ is multiplied by two (2) so Perkins & Chakeres Expires September 13, 2012 [Page 21] Internet-Draft AODVv2 March 2012 that the waiting time conforms to a binary exponential backoff. Data packets awaiting a route SHOULD be buffered by the source's AODVv2 router. This buffer SHOULD have a fixed limited size (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES) and older data packets SHOULD be discarded first. Buffering of data packets can have both positive and negative effects, and therefore buffer settings (BUFFER_DURING_DISCOVERY) SHOULD be administratively configurable or intelligently controlled. If a route discovery attempt has failed (i.e. an attempt or multiple attempts have been made without receiving a RREP) to find a route to the TargetNode, any data packets buffered for the corresponding TargetNode are dropped and a Destination Unreachable ICMP message SHOULD be delivered to the source. 5.5. Route Maintenance A RERR SHOULD be issued if a data packet is to be forwarded and it cannot be delivered to the next-hop because no forwarding route for the IP.DestinationAddress exists; RERR generation is described in Section 5.5.3. Upon this condition, an ICMP Destination Unreachable message SHOULD NOT be generated unless this router is responsible for the IP.DestinationAddress and that IP.DestinationAddress is known to be unreachable. In addition to inability to forward a data packet, a RERR SHOULD be issued immediately after detecting a broken link (see Section 5.5.1) of a forwarding route to quickly notify AODVv2 routers that certain routes are no longer available. If a newly unavailable route has not been used recently (indicated by ROUTE_USED), the RERR SHOULD NOT be generated. 5.5.1. Active Next-hop Router Adjacency Monitoring Nodes MUST 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 [I-D.ietf-manet-nhdp] o Route timeout o Lower layer feedback that a particular adjacent router is no longer reachable Perkins & Chakeres Expires September 13, 2012 [Page 22] Internet-Draft AODVv2 March 2012 o Other monitoring mechanisms or heuristics Upon determining that a next-hop AODVv2 router is unreachable, ThisNode MUST remove the affected forwarding routes (those with an unreachable next-hop) and unset the Route.Forwarding flag. ThisNode also flags the associated routes in AODVv2's routing table as Broken. For each broken route the timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT. 5.5.2. Updating Route Lifetimes During Packet Forwarding To avoid removing the forwarding route to reach the IP.SourceAddress, ThisNode SHOULD set the "ROUTE_USED" timeout to the value ROUTE_USED_TIMEOUT for the route to the IP.SourceAddress upon receiving a data packet. If the timer for ROUTE_DELETE is set, it is removed. To avoid removing the forwarding route to the IP.DestinationAddress that is being used, ThisNode SHOULD set the "ROUTE_USED" timeout to the value ROUTE_USED_TIMEOUT for the route to the IP.DestinationAddress upon sending a data packet. If the timer for ROUTE_DELETE is set, it is removed. 5.5.3. RERR Generation A RERR informs AODVv2 routers that a route to certain destinations is not available through ThisNode. When creating a new RERR, the address of the first UnreachableNode (IP.DestinationAddress from a data packet or RREP.TargetNode.Address) is inserted into an Address Block AddBlk.UnreachableNode.Address. If a prefix is known for the UnreachableNode.Address, it SHOULD be included. 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.AddTLV.SeqNum) is known, it SHOULD be placed in the RERR. The MsgHdr.HopLimit is set to MSG_HOPLIMIT. If SeqNum information is not known or 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. A multicast RERR is sent to the IP.DestinationAddress LL-MANET- Routers [RFC5498]. Sending the RERR to the LL-MANET-Routers address notifies all nearby AODVv2 routers that might depend on the now broken link. If the RERR is unicast, the IP.DestinationAddress is set to the NextHopAddress. Perkins & Chakeres Expires September 13, 2012 [Page 23] Internet-Draft AODVv2 March 2012 At this point, the packet or message that forced generation of this RERR SHOULD be discarded. 5.5.4. RERR Handling First, ThisNode examines the RteMsg to ensure that it contains the required information: MsgHdr.HopLimit and AddBlk.UnreachableNode.Address. If the required information do not exist, the message is discarded and further processing stopped. Next, ThisNode MAY selectively handle messages based upon information in the message. ThisNode MAY choose to only handle messages from adjacent AODVv2 routers. If ThisNode chooses not to handle this message, the message is discarded and further processing stopped. When an AODVv2 router handles a RERR, it examines each UnreachableNode's information. The attending AODVv2 router removes the forwarding route, unsets the Route.Forwarding flag, sets the Route.Broken flag, and the timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT for each UnreachableNode.Address found using longest prefix matching that meets all of the following conditions: 1. The UnreachableNode.Address is a multihop-capable 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 Route.SeqNum is zero (0), unknown, OR the UnreachableNode.SeqNum is zero (0), unknown, OR Route.SeqNum - UnreachableNode.SeqNum <= 0 (using signed 16-bit arithmetic). During handling if Route.SeqNum is zero (0) or unknown and UnreachableNode.SeqNum exists in the RERR and is not zero (0), then Route.SeqNum MAY be set to UnreachableNode.SeqNum. Setting Route.SeqNum can reduce future RERR handling and forwarding. Each UnreachableNode that did not result in a broken route is removed from the RERR, since propagation of this information will not result in any benefit. Each UnreachableNode that did result in a broken route SHOULD remain in the RERR. If any UnreachableNode was removed, all other information (AddTLVs) Perkins & Chakeres Expires September 13, 2012 [Page 24] Internet-Draft AODVv2 March 2012 associated with the removed address(es) MUST also be removed. After handling if Route.SeqNum is known and an UnreachableNode.SeqNum is not included in the RERR, then Route.SeqNum (i.e. UnreachableNode.SeqNum) MAY be added to the RERR. Including UnreachableNode.SeqNum can reduce future RERR handling and forwarding. If no UnreachableNode addresses remain in the RERR, no other handling is required and the RERR is discarded. If handling continues, the MsgHdr.HopLimit is decremented by one (1). Further, if this RERR's new MsgHdr.HopLimit is greater than one (1) and at least one unreachable node address remains in the RERR, then the updated RERR SHOULD be sent. A multicast RERR is sent to the IP.DestinationAddress LL-MANET- Routers [RFC5498]. If the RERR is unicast, the IP.DestinationAddress is set to the NextHopAddress. 5.6. Unknown Message and TLV Types If a message with an unknown type is received, the message is discarded. For handling of messages that contain unknown TLV types, the default behavior is to leave the information in control messages unmodified. Although, this behavior (UNKNOWN_TYPES) MAY be administratively controlled. 5.7. Advertising Network Addresses AODVv2 routers specify the 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. 5.8. Simple Internet Attachment Simple Internet attachment consists of a stub network of AODVv2 routers connected to the Internet via a single Internet AODVv2 router (IDR). AODVv2 routers, and hosts behind these routers, wishing to be reachable from hosts on the Internet MUST have IP addresses within the IDR's routable and topologically correct prefix (e.g. Perkins & Chakeres Expires September 13, 2012 [Page 25] Internet-Draft AODVv2 March 2012 192.0.2.0/24). The IDR 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 IDR is responsible for properly responding 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 IDR, if the IDR does not have a route to that destination it will perform normal AODVv2 route discovery for Perkins & Chakeres Expires September 13, 2012 [Page 26] Internet-Draft AODVv2 March 2012 that destination. 5.9. 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. 5.10. AODVv2 Control Packet/Message Generation Limits To ensure predictable control 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 or intelligently controlled. AODVv2 control messages SHOULD be discarded in the following order of preference: RREQ, RREP, and finally RERR. 6. 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. | +------------------------+------------------------------------------+ Perkins & Chakeres Expires September 13, 2012 [Page 27] Internet-Draft AODVv2 March 2012 Table 2 AODVv2 contains a number of timers. The default timing parameter values follow: Default Timing Parameter Values +------------------------------+-------------------+ | Name | Value | +------------------------------+-------------------+ | ROUTE_TIMEOUT | 5 seconds | | ROUTE_AGE_MIN_TIMEOUT | 1 second | | ROUTE_SEQNUM_AGE_MAX_TIMEOUT | 60 seconds | | ROUTE_USED_TIMEOUT | ROUTE_TIMEOUT | | ROUTE_DELETE_TIMEOUT | 2 * ROUTE_TIMEOUT | | 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 example, in networks with infrequent topology changes ROUTE_USED_TIMEOUT may be set to a much larger value. Default Parameter Values +------------------------+-------+----------------------------------+ | Name | Value | Description | +------------------------+-------+----------------------------------+ | MSG_HOPLIMIT | 10 | 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 Perkins & Chakeres Expires September 13, 2012 [Page 28] Internet-Draft AODVv2 March 2012 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 routing control 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 | +-------------------------+-----------------------------------------+ | BUFFER_DURING_DISCOVERY | Whether and how much data to buffer | | | during route discovery. | | UNKNOWN_TYPES | What action to take when an unknown TLV | | | type is received. The default action | | | is to forward this information | | | unmodified. Another action would be to | | | remove this information. | | CONTROL_TRAFFIC_LIMITS | AODVv2 control messaging SHOULD be | | | limited to avoid consuming all the | | | network bandwidth. | +-------------------------+-----------------------------------------+ Table 5 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.HopLimit is a 8-bit field and therefore MSG_HOPLIMIT cannot be larger than 255. 7. IANA Considerations In its default mode of operation, AODVv2 uses the UDP port MANET [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. Perkins & Chakeres Expires September 13, 2012 [Page 29] Internet-Draft AODVv2 March 2012 7.1. 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 7.2. Message and Address Block TLV Type Specification Message TLV Types +-------------------+------+--------+-------------------------------+ | 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 message within | | | | | UNICAST_MESSAGE_SENT_TIMEOUT. | | | | | Any unicast packet will serve | | | | | this purpose, and it MAY be | | | | | an ICMP REPLY message. If a | | | | | message is not sent, then the | | | | | previous hop can assume that | | | | | the link is unidirectional | | | | | and MAY blacklist the link to | | | | | this node. | +-------------------+------+--------+-------------------------------+ Table 7 Perkins & Chakeres Expires September 13, 2012 [Page 30] Internet-Draft AODVv2 March 2012 7.3. Address Block TLV Specification Address Block TLV Types +----------------+------------+----------+--------------------------+ | Name | Type | Length | Value | +----------------+------------+----------+--------------------------+ | AODVv2 | 10 - TBD | up to 2 | The AODVv2 sequence num | | Sequence | | octets | associated with this | | Number | | | address. The sequence | | (AODVv2SeqNum) | | | number may 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 8. 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 Perkins & Chakeres Expires September 13, 2012 [Page 31] Internet-Draft AODVv2 March 2012 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, like 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. 9. 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 AODVv2. 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. Many good ideas from LOADng [I-D.clausen-lln-loadng] are shaping this evolution of the [manet] 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 LLNs. 10. References Perkins & Chakeres Expires September 13, 2012 [Page 32] Internet-Draft AODVv2 March 2012 10.1. 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. 10.2. Informative References [I-D.chakeres-manet-manetid] Chakeres, I., "MANET_ID TLV", draft-chakeres-manet-manetid-03 (work in progress), February 2008. [I-D.clausen-lln-loadng] Clausen, T., Verdiere, A., Yi, J., Niktash, A., Igarashi, Y., and U. Herberg, "The LLN On-demand Ad hoc Distance- vector Routing Protocol - Next Generation (LOADng)", draft-clausen-lln-loadng-01 (work in progress), October 2011. [I-D.ietf-manet-nhdp] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP)", draft-ietf-manet-nhdp-15 (work in progress), December 2010. [I-D.ietf-ospf-multi-instance] Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi- Instance Extensions", draft-ietf-ospf-multi-instance-09 (work in progress), January 2012. Perkins & Chakeres Expires September 13, 2012 [Page 33] Internet-Draft AODVv2 March 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. [RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On- Demand Distance Vector (AODV) Routing", RFC 3561, July 2003. [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. Appendix A. Changes since the Previous Version o Protocol renamed to be AODVv2 o Intermediate RREPs (iRREPs) are to be put into new document. Without iRREP, only the destination can respond to a RREQ. o Precursor lists not supported, based on reported performance loss. o Routing Messages MUST be originated with the MsgHdr.HopLimit set to MSG_HOPLIMIT. Previously, this was not mandated. o Adding additional unreachable destinations to RERR is not specified in this document, to match LOADng behavior. Appendix B. Proposed additional changes for LOADng conformance Perkins & Chakeres Expires September 13, 2012 [Page 34] Internet-Draft AODVv2 March 2012 o Revise message formats to be compatible with LOADng requirements, removing RFC 5444 headers for minimal packet size o Adding RREP-ACK message type instead of relying on reception of arbitrary packets as sufficient response to establish bidirectionality. Appendix C. Shifting Responsibility for an Address 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 pass responsibility of an address correct AODVv2 routing behavior must be observed. The AODVv2 router adding the new address must wait for any exiting routing information about this address 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 participating and advertising routing information on its behalf. Authors' Addresses Charles E. Perkins Central Expressway San Jose, CA 95050 USA Phone: +1-408-421-1172 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 September 13, 2012 [Page 35]