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Versions: (draft-ietf-manet-aodvv2) 00 01 02 03 Draft is active
In: AD_Evaluation
Mobile Ad hoc Networks Working Group                          C. Perkins
Internet-Draft                                                 Futurewei
Intended status: Experimental                                 S. Ratliff
Expires: September 14, 2017                                      Idirect
                                                              J. Dowdell
                                                Airbus Defence and Space
                                                           L. Steenbrink
                                           HAW Hamburg, Dept. Informatik
                                                             V. Mercieca
                                                Airbus Defence and Space
                                                          March 13, 2017


      Ad Hoc On-demand Distance Vector Version 2 (AODVv2) Routing
                     draft-perkins-manet-aodvv2-00

Abstract

   The Ad Hoc On-demand Distance Vector Version 2 (AODVv2) routing
   protocol is intended for use by mobile routers in wireless, multihop
   networks.  AODVv2 determines unicast routes among AODVv2 routers
   within the network in an on-demand fashion.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 14, 2017.

Copyright Notice

   Copyright (c) 2017 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



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Applicability Statement . . . . . . . . . . . . . . . . . . .   9
   4.  Data Structures . . . . . . . . . . . . . . . . . . . . . . .  11
     4.1.  InterfaceSet  . . . . . . . . . . . . . . . . . . . . . .  11
     4.2.  Router Client Set . . . . . . . . . . . . . . . . . . . .  11
     4.3.  Neighbor Set  . . . . . . . . . . . . . . . . . . . . . .  12
     4.4.  Sequence Numbers  . . . . . . . . . . . . . . . . . . . .  13
     4.5.  Local Route Set . . . . . . . . . . . . . . . . . . . . .  14
     4.6.  Multicast Route Message Set . . . . . . . . . . . . . . .  16
     4.7.  Route Error (RERR) Set  . . . . . . . . . . . . . . . . .  18
   5.  Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   6.  AODVv2 Protocol Operations  . . . . . . . . . . . . . . . . .  20
     6.1.  Initialization  . . . . . . . . . . . . . . . . . . . . .  20
     6.2.  Next Hop Monitoring . . . . . . . . . . . . . . . . . . .  21
     6.3.  Neighbor Set Update . . . . . . . . . . . . . . . . . . .  22
     6.4.  Interaction with the Forwarding Plane . . . . . . . . . .  24
     6.5.  Message Transmission  . . . . . . . . . . . . . . . . . .  25
     6.6.  Route Discovery, Retries and Buffering  . . . . . . . . .  26
     6.7.  Processing Received Route Information . . . . . . . . . .  27
       6.7.1.  Evaluating Route Information  . . . . . . . . . . . .  28
       6.7.2.  Applying Route Updates  . . . . . . . . . . . . . . .  30
     6.8.  Suppressing Redundant Messages (Multicast Route Message
           Set)  . . . . . . . . . . . . . . . . . . . . . . . . . .  32
     6.9.  Suppressing Redundant Route Error Messages (Route Error
           Set)  . . . . . . . . . . . . . . . . . . . . . . . . . .  34
     6.10. Local Route Set Maintenance . . . . . . . . . . . . . . .  35
       6.10.1.  LocalRoute State Changes . . . . . . . . . . . . . .  35
       6.10.2.  Reporting Invalid Routes . . . . . . . . . . . . . .  37
   7.  AODVv2 Protocol Messages  . . . . . . . . . . . . . . . . . .  37
     7.1.  Route Request (RREQ) Message  . . . . . . . . . . . . . .  38
       7.1.1.  RREQ Generation . . . . . . . . . . . . . . . . . . .  39
       7.1.2.  RREQ Reception  . . . . . . . . . . . . . . . . . . .  40
       7.1.3.  RREQ Forwarding . . . . . . . . . . . . . . . . . . .  41
     7.2.  Route Reply (RREP) Message  . . . . . . . . . . . . . . .  42
       7.2.1.  RREP Generation . . . . . . . . . . . . . . . . . . .  43
       7.2.2.  RREP Reception  . . . . . . . . . . . . . . . . . . .  44
       7.2.3.  RREP Forwarding . . . . . . . . . . . . . . . . . . .  46
     7.3.  Route Reply Acknowledgement (RREP_Ack) Message  . . . . .  46



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       7.3.1.  RREP_Ack Request Generation . . . . . . . . . . . . .  47
       7.3.2.  RREP_Ack Reception  . . . . . . . . . . . . . . . . .  47
       7.3.3.  RREP_Ack Response Generation  . . . . . . . . . . . .  48
     7.4.  Route Error (RERR) Message  . . . . . . . . . . . . . . .  48
       7.4.1.  RERR Generation . . . . . . . . . . . . . . . . . . .  49
       7.4.2.  RERR Reception  . . . . . . . . . . . . . . . . . . .  51
       7.4.3.  RERR Regeneration . . . . . . . . . . . . . . . . . .  52
   8.  RFC 5444 Representation . . . . . . . . . . . . . . . . . . .  53
     8.1.  Route Request Message Representation  . . . . . . . . . .  54
       8.1.1.  Message Header  . . . . . . . . . . . . . . . . . . .  54
       8.1.2.  Message TLV Block . . . . . . . . . . . . . . . . . .  54
       8.1.3.  Address Block . . . . . . . . . . . . . . . . . . . .  54
       8.1.4.  Address Block TLV Block . . . . . . . . . . . . . . .  55
     8.2.  Route Reply Message Representation  . . . . . . . . . . .  55
       8.2.1.  Message Header  . . . . . . . . . . . . . . . . . . .  56
       8.2.2.  Message TLV Block . . . . . . . . . . . . . . . . . .  56
       8.2.3.  Address Block . . . . . . . . . . . . . . . . . . . .  56
       8.2.4.  Address Block TLV Block . . . . . . . . . . . . . . .  56
     8.3.  Route Reply Acknowledgement Message Representation  . . .  57
       8.3.1.  Message Header  . . . . . . . . . . . . . . . . . . .  57
       8.3.2.  Message TLV Block . . . . . . . . . . . . . . . . . .  57
       8.3.3.  Address Block . . . . . . . . . . . . . . . . . . . .  57
       8.3.4.  Address Block TLV Block . . . . . . . . . . . . . . .  57
     8.4.  Route Error Message Representation  . . . . . . . . . . .  58
       8.4.1.  Message Header  . . . . . . . . . . . . . . . . . . .  58
       8.4.2.  Message TLV Block . . . . . . . . . . . . . . . . . .  58
       8.4.3.  Address Block . . . . . . . . . . . . . . . . . . . .  58
       8.4.4.  Address Block TLV Block . . . . . . . . . . . . . . .  58
   9.  Simple External Network Attachment  . . . . . . . . . . . . .  59
   10. Configuration . . . . . . . . . . . . . . . . . . . . . . . .  61
     10.1.  Timers . . . . . . . . . . . . . . . . . . . . . . . . .  61
     10.2.  Protocol Constants . . . . . . . . . . . . . . . . . . .  63
     10.3.  Local Settings . . . . . . . . . . . . . . . . . . . . .  64
     10.4.  Network-Wide Settings  . . . . . . . . . . . . . . . . .  64
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  65
     11.1.  RFC 5444 Message Type Allocation . . . . . . . . . . . .  65
     11.2.  RFC 5444 Message TLV Types . . . . . . . . . . . . . . .  65
     11.3.  RFC 5444 Address Block TLV Type Allocation . . . . . . .  66
     11.4.  MetricType Allocation  . . . . . . . . . . . . . . . . .  66
     11.5.  ADDRESS_TYPE TLV Values  . . . . . . . . . . . . . . . .  66
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  67
     12.1.  Availability . . . . . . . . . . . . . . . . . . . . . .  67
       12.1.1.  Denial of Service  . . . . . . . . . . . . . . . . .  67
       12.1.2.  Malicious RERR messages  . . . . . . . . . . . . . .  68
       12.1.3.  False Confirmation of Link Bidirectionality  . . . .  70
       12.1.4.  Message Deletion . . . . . . . . . . . . . . . . . .  70
     12.2.  Confidentiality  . . . . . . . . . . . . . . . . . . . .  70
     12.3.  Integrity of Routes  . . . . . . . . . . . . . . . . . .  71



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       12.3.1.  Message Insertion  . . . . . . . . . . . . . . . . .  71
       12.3.2.  Message Modification - Man in the Middle . . . . . .  72
       12.3.3.  Replay Attacks . . . . . . . . . . . . . . . . . . .  72
     12.4.  Protection Mechanisms  . . . . . . . . . . . . . . . . .  72
       12.4.1.  Confidentiality and Authentication . . . . . . . . .  72
       12.4.2.  Message Integrity using ICVs . . . . . . . . . . . .  72
       12.4.3.  Replay Protection using Timestamps . . . . . . . . .  73
       12.4.4.  Application to AODVv2  . . . . . . . . . . . . . . .  73
     12.5.  Key Management . . . . . . . . . . . . . . . . . . . . .  78
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  80
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  80
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  80
     14.2.  Informative References . . . . . . . . . . . . . . . . .  81
   Appendix A.  AODVv2 Draft Updates . . . . . . . . . . . . . . . .  82
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  82

1.  Overview

   The Ad hoc On-Demand Distance Vector Version 2 (AODVv2) protocol
   enables dynamic, multihop routing between participating mobile nodes
   wishing to establish and maintain an ad hoc network.  The basic
   operations of the AODVv2 protocol are route discovery and route
   maintenance.  AODVv2 does not require nodes to maintain routes to
   destinations that are not in active communication.  AODVv2 allows
   mobile nodes to respond to link breakages and changes in network
   topology in a timely manner.  The operation of AODVv2 is loop-free,
   and by avoiding the Bellman-Ford "counting to infinity" problem
   offers quick convergence when the ad hoc network topology changes
   (typically, when a node moves in the network).  When links break,
   AODVv2 causes the affected set of nodes to be notified so that they
   are able to invalidate the routes using the lost link.

   One distinguishing feature of AODVv2 is its use of a destination
   sequence number for each route entry.  The destination sequence
   number is created by the destination to be included along with any
   route information it sends to requesting nodes.  Using destination
   sequence numbers ensures loop freedom and is simple to program.
   Given the choice between two routes to a destination, a requesting
   node is required to select the one with the greatest sequence number.

   Compared to AODV [RFC3561], AODVv2 has moved some features out of the
   scope of the document, notably intermediate route replies, expanding
   ring search, route lifetimes and precursor lists.  However, the
   document has been designed to allow their specification in a separate
   document.  Hello messages and local repair have been removed.  AODVv2
   provides a mechanism for the use of multiple metric types.  Message
   formats have been updated and made compliant with [RFC5444].  AODVv2
   control messages are defined as sets of data, which are mapped to



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   message elements using the Generalized MANET Packet/Message Format
   defined in [RFC5444] and sent using the parameters in [RFC5498].
   Verification of link bidirectionality has been substantially
   improved, and additional refinements made for route timeouts and
   state management.

   The basic protocol mechanisms are as follows.  Since AODVv2 is a
   reactive protocol, route discovery is initiated only when a route to
   the target is needed (i.e. when a router' client wants to send data).
   AODVv2 does this with the help of a Route Request (RREQ) and Route
   Reply (RREP) cycle: an RREQ is distributed across the network until
   it arrives at the target.  When forwarding an RREQ, all routers
   across the network store the neighbor they've received the RREQ from,
   memorizing a possible route back to the originator of the RREQ.  When
   the target receives the RREQ, it answers with an RREP, which then
   travels back to the originator along the path memorized by the
   intermediate routers.  A metric value is included within the messages
   to record the cost of the route.  AODVv2 uses sequence numbers to
   identify stale routing information, and compares route metric values
   to determine if advertised routes could form loops.  Route
   maintenance includes confirming bidirectionality of links to next-hop
   AODVv2 routers and issuing Route Error (RERR) messages informing
   other routers of broken links.  It also includes reacting to received
   Route Error messages, and extending and enforcing route timeouts.

   The on-demand nature of AODVv2 requires signals to be exchanged
   between AODVv2 and the forwarding plane.  These signals indicate
   when:

   o  a packet is to be forwarded, in order to initiate route discovery

   o  packet forwarding fails, in order to initiate route error
      reporting

   o  a packet is successfully forwarded, for route maintenance.

   Security for authentication of AODVv2 routers and encryption of
   control messages is accomplished using the TIMESTAMP and ICV TLVs
   defined in [RFC7182].

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].  In addition, this document uses terminology from
   [RFC5444], and defines the following terms:




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   AddressList
      A list of IP addresses as used in AODVv2 messages.

   AckReq
      Used in a Route Reply Acknowledgement message to indicate that a
      Route Reply Acknowledgement is expected in return.

   AdvRte
      A route advertised in an incoming route message.

   AODVv2 Router
      An IP addressable device in the ad hoc network that performs the
      AODVv2 protocol operations specified in this document.

   CurrentTime
      The current time as maintained by the AODVv2 router.

   ENAR (External Network Access Router)
      An AODVv2 router with an interface to an external, non-AODVv2
      network.

   InterfaceSet
      The set of all network interfaces supporting AODVv2.

   Invalid route
      A route that cannot be used for forwarding but still contains
      useful sequence number information.

   LocalRoute
      An entry in the Local Route Set as defined in Section 4.5.

   MANET
      A Mobile Ad Hoc Network as defined in [RFC2501].

   MetricType
      The metric type for a metric value included in a message.

   MetricTypeList
      A list of metric types associated with the addresses in the
      AddressList of a Route Error message.

   Neighbor
      An AODVv2 router from which an RREQ or RREP message has been
      received.  Neighbors exchange routing information and verify
      bidirectionality of the link to a neighbor before installing a
      route via that neighbor into the Local Route Set.

   OrigAddr



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      The source IP address of the IP packet triggering route discovery.

   OrigMetric
      The metric value associated with the route to OrigPrefix.

   OrigPrefix
      The prefix configured in the Router Client Set entry which
      includes OrigAddr.

   OrigPrefixLen
      The prefix length, in bits, configured in the Router Client Set
      entry which includes OrigAddr.

   OrigSeqNum
      The sequence number of the AODVv2 router which originated the
      Route Request on behalf of OrigAddr.

   PktSource
      The source address of the IP packet that triggered a Route Error
      message.

   PrefixLengthList
      A list of routing prefix lengths associated with the addresses in
      the AddressList of a message.

   Reactive
      Performed only in reaction to specific events.  In AODVv2, routes
      are requested only when data packets need to be forwarded.  In
      this document, "reactive" is synonymous with "on-demand".

   RERR (Route Error)
      The AODVv2 message type used to indicate that an AODVv2 router
      does not have a valid LocalRoute toward one or more particular
      destinations.

   RERR_Gen (RERR Generating Router)
      The AODVv2 router generating a Route Error message.

   RerrMsg (RERR Message)
      A Route Error (RERR) message.

   Routable Unicast IP Address
      A routable unicast IP address is a unicast IP address that is
      scoped sufficiently to be forwarded by a router.  Globally-scoped
      unicast IP addresses and Unique Local Addresses (ULAs) [RFC4193]
      are examples of routable unicast IP addresses.

   Router Client



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      An address or address range configured on an AODVv2 router, on
      behalf of which that router will initiate and respond to route
      discoveries.  These addresses may be used by the AODVv2 router
      itself or by its Router Clients that are reachable without
      traversing another AODVv2 router.

   RREP (Route Reply)
      The AODVv2 message type used to reply to a Route Request message.

   RREP_Gen (RREP Generating Router)
      The AODVv2 router that generates the Route Reply message, i.e.,
      the router configured with TargAddr as a Router Client.

   RREQ (Route Request)
      The AODVv2 message type used to discover a route to TargAddr and
      distribute information about a route to OrigPrefix.

   RREQ_Gen (RREQ Generating Router)
      The AODVv2 router that generates the Route Request message, i.e.,
      the router configured with OrigAddr as a Router Client.

   RteMsg (Route Message)
      A Route Request (RREQ) or Route Reply (RREP) message.

   SeqNum
      The sequence number maintained by an AODVv2 router to indicate
      freshness of route information.

   SeqNumList
      A list of sequence numbers associated with the addresses in the
      AddressList of a message.

   TargAddr
      The target address of a route request, i.e., the destination
      address of the IP packet triggering route discovery.

   TargMetric
      The metric value associated with the route to TargPrefix.

   TargPrefix
      The prefix configured in the Router Client Set entry which
      includes TargAddr.

   TargPrefixLen
      The prefix length, in bits, configured in the Router Client Set
      entry which includes TargAddr.

   TargSeqNum



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      The sequence number of the AODVv2 router which originated the
      Route Reply on behalf of TargAddr.

   Unreachable Address
      An address reported in a Route Error message, as described in
      Section 7.4.1.

   Upstream
      In the direction from destination to source (from TargAddr to
      OrigAddr).

   Valid route
      A route that can be used for forwarding, as described in
      Section 7.4.1.

   This document uses the notational conventions in Table 1 to simplify
   the text.

      +-----------------------+------------------------------------+
      | Notation              | Meaning                            |
      +-----------------------+------------------------------------+
      | Route[Address]        | A route toward Address             |
      | Route[Address].Field  | A field in a route toward Address  |
      | RteMsg.Field          | A field in either RREQ or RREP     |
      +-----------------------+------------------------------------+

                      Table 1: Notational Conventions

3.  Applicability Statement

   The AODVv2 routing protocol is a reactive routing protocol intended
   for use in mobile ad hoc wireless networks.  A reactive protocol only
   sends messages to discover a route when there is data to send on that
   route.  Therefore, a reactive routing protocol requires certain
   interactions with the forwarding plane (for example, to indicate when
   a packet is to be forwarded, in order to initiate route discovery).
   The set of signals exchanged between AODVv2 and the forwarding plane
   are discussed in Section 6.4.

   AODVv2 is designed for stub or disconnected mobile ad hoc networks,
   i.e., non-transit networks or those not connected to the internet.
   AODVv2 can, however, be configured to perform gateway functions when
   attached to external networks, as discussed in Section 9.

   AODVv2 handles a wide variety of mobility and traffic patterns by
   determining routes on-demand.  In networks with a large number of
   routers, AODVv2 is best suited for relatively sparse traffic
   scenarios where each router forwards IP packets to a small percentage



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   of other AODVv2 routers in the network.  In this case fewer routes
   are needed, and therefore less control traffic is produced.  In large
   networks with very frequent or bursty traffic, AODVv2 control
   messages may cause a broadcast storm, overwhelming the network with
   control messages and preventing routes from being established.  This
   especially applies to networks with point-to-point or point-to-
   multipoint traffic.  In this case, the transmission priorities
   described in Section 6.5 prioritize route maintenance traffic over
   route discovery traffic.

   Data packets may be buffered until a route to their destination is
   available, as described in Section 6.6.

   AODVv2 provides for message integrity and security against replay
   attacks by using integrity check values, timestamps and sequence
   numbers, as described in Section 12.  If security associations can be
   established, encryption can be used for AODVv2 messages to ensure
   that only trusted routers participate in routing operations.

   Since the route discovery process aims for a route to be established
   in both directions along the same path, uni-directional links are not
   suitable.  AODVv2 will detect and exclude those links from route
   discovery.  The route discovered is optimised for the requesting
   router, and the return path may not be the optimal route.

   AODVv2 is applicable to memory constrained devices, since only a
   little routing state is maintained in each AODVv2 router.  AODVv2
   routes that are not needed for forwarding data do not need to be
   maintained.  On routers unable to store persistent AODVv2 state,
   recovery can impose a performance penalty (e.g., in case of AODVv2
   router reboot), since if a router loses its sequence number, there is
   a delay before the router can resume full operations.  This is
   described in Section 6.1.

   AODVv2 supports routers with multiple interfaces and multiple IP
   addresses per interface.  A router may also use the same IP address
   on multiple interfaces.  AODVv2 requires only that each interface
   configured for AODVv2 has at least one unicast IP address.  Address
   assignment procedures are out of scope for AODVv2.

   AODVv2 supports Router Clients with multiple interfaces, as long as
   each interface is configured with its own unicast IP address.  Multi-
   homing of a Router Client IP address is not supported by AODVv2, and
   therefore an IP address SHOULD NOT be configured as a Router Client
   on more than one AODVv2 router at any one time.

   The routing algorithm in AODVv2 MAY be operated at layers other than
   the network layer, using layer-appropriate addresses.



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   AODVv2 is based on AODV [RFC3561].  The following important protocol
   mechanisms have changed:

   o  Bidirectionality is ensured using a new mechanism

   o  Alternate metrics may be used to determine route quality

   o  Support for multiple interfaces has been improved

   o  Support for multi-interface IP addresses has been added

   o  A new security model allowing end to end integrity checks has been
      added

   o  A new message format ([RFC5444]) is used.

4.  Data Structures

4.1.  InterfaceSet

   The InterfaceSet is a conceptual data structure which contains
   information about all interfaces configured for use by AODVv2.  Any
   interface with an IP address can be used.  Multiple interfaces on a
   single router can be used.  Multiple interfaces on the same router
   may be configured with the same IP address.

   Each element in the InterfaceSet MUST contain the following:

   Interface.Id
      An identifier that is unique in node-local scope and that allows
      the AODVv2 implementation to identify exactly one local network
      interface.

   If multiple interfaces of the AODVv2 router are configured for use by
   AODVv2, they MUST be configured in the InterfaceSet.

   Implementations for constrained devices using only one interface MAY
   choose not to use the InterfaceSet.

4.2.  Router Client Set

   An AODVv2 router provides route discovery services for its own local
   applications and for its Router Clients that are reachable without
   traversing another AODVv2 router.  The addresses used by these
   devices, and the AODVv2 router itself, are configured in the Router
   Client Set. An AODVv2 router will only originate Route Request and
   Route Reply messages on behalf of configured Router Client addresses.




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   Router Client Set entries MUST contain:

   RouterClient.IPAddress
      An IP address or the start of an address range that requires route
      discovery services from the AODVv2 router.

   RouterClient.PrefixLength
      The length, in bits, of the routing prefix associated with the
      RouterClient.IPAddress.  If the prefix length is not equal to the
      address length of RouterClient.IPAddress, the AODVv2 router MUST
      participate in route discovery on behalf of all addresses within
      that prefix.

   RouterClient.Cost
      The cost associated with reaching this address or address range.

4.3.  Neighbor Set

   A Neighbor Set MUST be maintained with information about neighboring
   AODVv2 routers.  Neighbor Set entries are stored when AODVv2 messages
   are received.  If the Neighbor is chosen as a next hop on an
   installed route, the link to the Neighbor MUST be tested for
   bidirectionality and the result stored in this set.  A route will
   only be considered valid when the link is confirmed to be
   bidirectional.

   Neighbor Set entries MUST contain:

   Neighbor.IPAddress
      An IP address of the neighboring router, learned from the source
      IP address of a received IP packet containing an AODVv2 route
      message.

   Neighbor.State
      Indicates whether the link to the neighbor is bidirectional.
      There are three possible states: Confirmed, Heard, and
      Blacklisted.  Heard is the initial state.  Confirmed indicates
      that the link to the neighbor has been confirmed as bidirectional.
      Blacklisted indicates that the link to the neighbor may have
      become uni-directional.  Section 6.2 discusses how to monitor link
      bidirectionality.

   Neighbor.Timeout
      Indicates at which time the Neighbor.State should be updated:

   o  If the value of Neighbor.State is Blacklisted, this indicates the
      time at which Neighbor.State will revert to Heard.  By default




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      this value is calculated at the time the router is blacklisted and
      is equal to CurrentTime + MAX_BLACKLIST_TIME.

   o  If Neighbor.State is Heard, and an RREP_Ack has been requested
      from the neighbor, it indicates the time at which Neighbor.State
      will be set to Blacklisted, if an RREP_Ack has not been received.

   o  If the value of Neighbor.State is Heard and no RREP_Ack has been
      requested, or if Neighbor.State is Confirmed, this time is set to
      INFINITY_TIME.

   Neighbor.Interface
      The interface on which the link to the neighbor was established.

   Neighbor.AckSeqNum
      The next sequence number to use for the TIMESTAMP value in an
      RREP_Ack request, in order to detect replay of an RREP_Ack
      response.  AckSeqNum is initialized to a random value.

   Neighbor.HeardRERRSeqNum
      The last heard sequence number used as the TIMESTAMP value in a
      RERR received from this neighbor, saved in order to detect replay
      of a RERR message.  HeardRERRSeqNum is initialized to zero.

   See Section 12.4.4.3 and Section 12.4.4.4 for more information on how
   Neighbor.AckSeqNum and Neighbor.HeardRERRSeqNum are used.

4.4.  Sequence Numbers

   Sequence Numbers enable AODVv2 routers to determine the temporal
   order of route discovery information that originates from any single
   AODVv2 router, and thus to identify stale routing information so that
   it can be discarded.  The sequence number fulfills the same roles as
   the "Destination Sequence Number" of DSDV [Perkins94], and the AODV
   Sequence Number in [RFC3561].  The sequence numbers from two
   different routers are not comparable.  Route discovery messages with
   sequence numbers belonging to two different routers cannot be
   compared to determine temporal ordering.

   Each AODVv2 router in the network MUST maintain its own sequence
   number.  All RREQ and RREP messages created by an AODVv2 router
   include the router's sequence number, reported as a 16-bit unsigned
   integer.  Each AODVv2 router MUST ensure that its sequence number is
   strictly increasing, and that it is incremented by one (1) whenever
   an RREQ or RREP is created, except when the sequence number is 65,535
   (the maximum value of a 16-bit unsigned integer), in which case it
   MUST be reset to one (1) to achieve wrap around.  The value zero (0)
   is reserved to indicate that the sequence number is unknown.



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   An AODVv2 router MUST only attach its own sequence number to
   information about a route to one of its configured Router Clients;
   all route messages forwarded by other routers retain the originator's
   sequence number.

   To determine if newly received information is stale and therefore
   redundant compared to other information originated by the same
   router, the sequence number attached to the information is compared
   to the sequence number of existing information about the same route.
   The comparison is carried out by subtracting the existing sequence
   number from the newly received sequence number, using unsigned
   arithmetic.  The result of the subtraction is to be interpreted as a
   signed 16-bit integer.

   o  If the result is negative, the newly received information is
      considered older than the existing information and is considered
      stale and redundant and MUST therefore be discarded.

   o  If the result is positive, the newly received information is
      considered newer than the existing information and is not
      considered stale or redundant and MUST therefore be processed.

   o  If the result is zero, the newly received information is not
      considered stale, and therefore MUST be processed further to
      determine if it is redundant.  For example, it is considered
      redundant if the metric attached to the newly received information
      is higher than the metric of existing information about the same
      route (see Section 6.7.1 and Section 6.8).

   This, along with the processes in Section 6.7.1, ensures loop
   freedom.

   An AODVv2 router SHOULD maintain its sequence number in persistent
   storage.  If the sequence number is lost, the router MUST follow the
   procedure in Section 6.1 to safely resume routing operations with a
   new sequence number.

4.5.  Local Route Set

   All AODVv2 routers MUST maintain a Local Route Set, containing
   information about routes learned from AODVv2 route messages.  The
   Local Route Set is stored separately from the forwarding plane's
   routing table (referred to as Routing Information Base (RIB)), which
   may be updated by other routing protocols operating on the AODVv2
   router as well.  The Routing Information Base is updated using
   information from the Local Route Set. Alternatively, if the
   information specified below can be added to RIB entries,




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   implementations MAY choose to modify the Routing Information Base
   directly instead of maintaining a dedicated Local Route Set.

   Routes learned from AODVv2 route messages are referred to in this
   document as LocalRoutes, and MUST contain the following information:

   LocalRoute.Address
      An address, which, when combined with LocalRoute.PrefixLength,
      describes the set of destination addresses this route includes.

   LocalRoute.PrefixLength
      The prefix length, in bits, associated with LocalRoute.Address.

   LocalRoute.SeqNum
      The sequence number associated with LocalRoute.Address, obtained
      from the last route message that successfully updated this entry.

   LocalRoute.NextHop
      The source IP address of the IP packet containing the AODVv2
      message advertising the route to LocalRoute.Address, i.e., an IP
      address of the AODVv2 router used for the next hop on the path
      toward LocalRoute.Address.

   LocalRoute.NextHopInterface
      The interface used to send IP packets toward LocalRoute.Address.

   LocalRoute.LastUsed
      If this route is installed in the Routing Information Base, the
      time it was last used to forward an IP packet.  If not, the time
      at which the LocalRoute was created.

   LocalRoute.LastSeqNumUpdate
      The time LocalRoute.SeqNum was last updated.

   LocalRoute.MetricType
      The type of metric associated with this route.

   LocalRoute.Metric
      The cost of the route toward LocalRoute.Address expressed in units
      consistent with LocalRoute.MetricType.

   LocalRoute.State
      The last known state (Unconfirmed, Idle, Active, or Invalid) of
      the route.

   LocalRoute.SeqNoRtr
      If nonzero, the IP address of the router that originated the
      Sequence Number for this route.



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   There are four possible states for a LocalRoute:

   Unconfirmed
      A route learned from a Route Request message, which has not yet
      been confirmed as bidirectional.  It MUST NOT be used for
      forwarding IP packets, except possibly for RREP packets that are
      used for route discovery and bidirectional link verification.
      Therefore it is not referred to as a valid route.  This state is
      only used for routes learned through RREQ messages.

   Idle
      A route that has been learned from a route message, and has also
      been confirmed, but has not been used in the last ACTIVE_INTERVAL.
      It is able to be used for forwarding IP packets, and therefore it
      is referred to as a valid route.

   Active
      A route that has been learned from a route message, and has also
      been confirmed, and has been used in the last ACTIVE_INTERVAL.  It
      is able to be used for forwarding IP packets, and therefore it is
      referred to as a valid route.

   Invalid
      A route that has expired or been lost.  It MUST NOT be used for
      forwarding IP packets, and therefore it is not referred to as a
      valid route.  Invalid routes contain sequence number information
      which allows incoming information to be assessed for freshness.

   If the Local Route Set is stored separately from the Routing
   Information Base, routes are added to the Routing Information Base
   when LocalRoute.State is valid (set to Active or Idle), and removed
   from the Routing Information Base when LocalRoute.State becomes
   Invalid.

   Changes to LocalRoute state are detailed in Section 6.10.1.

   Multiple valid routes for the same address and prefix length but for
   different metric types may exist in the Local Route Set, but only one
   route to a particular address and prefix length may exist in the
   Routing Information Base.  The decision of which of the routes should
   be installed in the Routing Information Base is outside the scope of
   AODVv2.

4.6.  Multicast Route Message Set

   Route Request (RREQ) messages are multicast by default and forwarded
   multiple times.  This set stores recently received RREQs in order




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   that received RREQs can be tested for redundancy to avoid unnecessary
   processing and forwarding.

   The Multicast Route Message Set is a conceptual set which contains
   information about previously received multicast route messages, so
   that incoming route messages can be compared with previously received
   messages to determine if the incoming information is redundant or
   stale, and the router can avoid sending redundant control traffic.

   Multicast Route Message Set entries MUST contain the following
   information:

   RteMsg.OrigPrefix
      The prefix associated with OrigAddr, the source address of the IP
      packet triggering the route request.

   RteMsg.OrigPrefixLen
      The prefix length associated with RteMsg.OrigPrefix, originally
      from the Router Client Set entry on RREQ_Gen which includes
      OrigAddr.

   RteMsg.TargPrefix
      The prefix associated with TargAddr, the destination address of
      the IP packet triggering the route request.  In an RREQ this MUST
      be set to TargAddr.

   RteMsg.OrigSeqNum
      The sequence number associated with the route to OrigPrefix, if
      RteMsg is an RREQ.

   RteMsg.TargSeqNum
      The sequence number associated with the route to TargPrefix.

   RteMsg.MetricType
      The metric type of the route requested.

   RteMsg.Metric
      The metric value received in the RteMsg.

   RteMsg.Timestamp
      The last time this Multicast Route Message Set entry was updated.

   RteMsg.RemoveTime
      The time at which this entry MUST be removed from the Multicast
      Route Message Set. This is set to CurrentTime +
      MAX_SEQNUM_LIFETIME, whenever the RteMsg.OrigSeqNum of this entry
      is updated.




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   RteMsg.Interface
      The interface on which the message was received.

   RteMsg.SeqNoRtr
      If nonzero, the IP address of the router that originated the
      Sequence Number for this route.

   The Multicast Route Message Set is maintained so that no two entries
   have the same OrigPrefix, OrigPrefixLen, TargPrefix, and MetricType.
   See Section 6.8 for details about updating this set.

4.7.  Route Error (RERR) Set

   Each RERR message sent because no route exists for packet forwarding
   SHOULD be recorded in a conceptual set called the Route Error (RERR)
   Set. Each entry contains the following information:

   RerrMsg.Timeout
      The time after which the entry SHOULD be deleted.

   RerrMsg.UnreachableAddress
      The UnreachableAddress reported in the AddressList of the RERR.

   RerrMsg.PktSource:
      The PktSource of the RERR.

   See section Section 6.9 for instructions on how to update the set.

5.  Metrics

   Metrics measure a cost or quality associated with a route or a link,
   e.g., latency, delay, financial cost, energy, etc.  Metric values are
   reported in Route Request and Route Reply messages.

   In Route Request messages, the metric describes the cost of the route
   from OrigPrefix to the router sending the Route Request.  For
   RREQ_Gen, this is the cost associated with the Router Client Set
   entry which includes OrigAddr.  For routers which forward the RREQ,
   this is the cost from OrigPrefix to the forwarding router, combining
   the metric value from the received RREQ message with knowledge of the
   link cost from the sender to the receiver, i.e., the incoming link
   cost.  This updated route cost is included when forwarding the Route
   Request message, and used to install a route to OrigPrefix.

   Similarly, in Route Reply messages, the metric reflects the cost of
   the route from TargPrefix to the router sending the Route Reply.  For
   RREP_Gen, this is the cost associated with the Router Client Set
   entry which includes TargAddr.  For routers which forward the RREP,



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   this is the cost from TargPrefix to the forwarding router, combining
   the metric value from the received RREP message with knowledge of the
   link cost from the sender to the receiver, i.e., the incoming link
   cost.  This updated route cost is included when forwarding the Route
   Reply message, and used to install a route to TargPrefix.

   Assuming link metrics are symmetric, the cost of the routes installed
   in the Local Route Set at each router will be correct.  While this
   assumption is not always correct, calculating incoming/outgoing
   metric data is outside of scope of this document.  The route
   discovered is optimised for the requesting router, and the return
   path may not be the optimal route.

   AODVv2 enables the use of multiple metric types.  Each route
   discovery attempt indicates the metric type which is requested for
   the route.  Each route discovery attempt MUST use only one metric
   type.

   For each MetricType, AODVv2 requires:

   o  A MetricType number, to indicate the metric type of a route.
      MetricType numbers allocated are detailed in Section 11.4.

   o  A maximum value, denoted MAX_METRIC[MetricType].  This MUST always
      be the maximum expressible metric value of type MetricType.  Field
      lengths associated with metric values are found in Section 11.4.
      If the cost of a route exceeds MAX_METRIC[MetricType], the route
      is ignored.

   o  A function for incoming link cost, denoted Cost(L).  Using
      incoming link costs means that the route learned has a path
      optimized for the direction from OrigAddr to TargAddr.

   o  A function for route cost, denoted Cost(R).

   o  A function to analyze routes for potential loops based on metric
      information, denoted LoopFree(R1, R2).  LoopFree verifies that a
      route R2 is not a sub-section of another route R1.  An AODVv2
      router invokes LoopFree() as part of the process in Section 6.7.1,
      when an advertised route (R1) and an existing LocalRoute (R2) have
      the same destination address, metric type, and sequence number.
      LoopFree returns FALSE to indicate that an advertised route is not
      to be used to update a stored LocalRoute, as it may cause a
      routing loop.  In the case where the existing LocalRoute is
      Invalid, it is possible that the advertised route includes the
      existing LocalRoute and came from a router which did not yet
      receive notification of the route becoming Invalid, so the




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      advertised route should not be used to update the Local Route Set,
      in case it forms a loop to a broken route.

   AODVv2 currently supports cost metrics where Cost(R) is strictly
   increasing, by defining:

   o  Cost(R) := Sum of Cost(L) of each link in the route

   o  LoopFree(R1, R2) := ( Cost(R1) <= Cost(R2) )

   Implementers MAY consider other metric types, but the definitions of
   Cost and LoopFree functions for such types are undefined, and
   interoperability issues need to be considered.

6.  AODVv2 Protocol Operations

   The AODVv2 protocol's operations include managing sequence numbers,
   monitoring next hop AODVv2 routers on discovered routes and updating
   the Neighbor Set, performing route discovery and dealing with
   requests from other routers, processing incoming route information
   and updating the Local Route Set, updating the Multicast Route
   Message Set and suppressing redundant messages, and reporting broken
   routes.  These processes are discussed in detail in the following
   sections.

6.1.  Initialization

   During initialization where an AODVv2 router does not have
   information about its previous sequence number, or if its sequence
   number is lost at any point, the router resets its sequence number to
   one (1).  However, other AODVv2 routers may still hold sequence
   number information that this router previously issued.  Since
   sequence number information is removed if there has been no update to
   the sequence number in MAX_SEQNUM_LIFETIME, the initializing router
   MUST wait for MAX_SEQNUM_LIFETIME before it creates any messages
   containing its new sequence number.  It can then be sure that the
   information it sends will not be considered stale.

   During this wait period, the router is permitted to do the following:

   o  Process information in a received RREQ or RREP message to learn a
      route to the originator or target of that route discovery

   o  Forward a received RREQ or RREP

   o  Send an RREP_Ack

   o  Maintain valid routes in the Local Route Set



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   o  Create, process and forward RERR messages

6.2.  Next Hop Monitoring

   To ensure AODVv2 routers Routers do not establish routes over uni-
   directional links, AODVv2 routers MUST verify that the link to the
   next hop router is bidirectional before marking a route as valid in
   the Local Route Set.

   AODVv2 provides a mechanism for testing bidirectional connectivity
   during route discovery, and blacklisting routers where bidirectional
   connectivity is not available.  If a route discovery is retried by
   RREQ_Gen, the blacklisted routers can be excluded from the process,
   and a different route can be discovered.  Further, a route is not to
   be used for forwarding until the bidirectionality of the link to the
   next hop is confirmed.  AODVv2 routers do not need to monitor
   bidirectionality for links to neighboring routers which are not used
   as next hops on routes in the Local Route Set.

   o  Bidirectional connectivity to upstream routers is tested by
      requesting acknowledgement of RREP messages by also sending an
      RREP_Ack, including an AckReq element to indicate that an
      acknowledgement is requested.  This MUST be answered by sending an
      RREP_Ack in response.  Receipt of an RREP_Ack within
      RREP_Ack_SENT_TIMEOUT proves that bidirectional connectivity
      exists.  Otherwise, a link is determined to be unidirectional.
      All AODVv2 routers MUST support this process, which is explained
      in Section 7.2 and Section 7.3.

   o  For the downstream router, receipt of an RREP message containing
      the route to TargAddr is confirmation of bidirectionality , since
      an RREP message is a reply to a RREQ message which previously
      crossed the link in the opposite direction.

   To assist with next hop monitoring, a Neighbor Set (Section 4.3) is
   maintained.  When an RREQ or RREP is received, search for an entry in
   the Neighbor Set where all of the following conditions are met:

   o  Neighbor.IPAddress == IP address from which the RREQ or RREP was
      received

   o  Neighbor.Interface == Interface on which the RREQ or RREP was
      received.

   If such an entry does not exist, a new entry is created as described
   in Section 6.3.  While the value of Neighbor.State is Heard,
   acknowledgement of RREP messages sent to that neighbor MUST be
   requested.  If an acknowledgement is not received within the timeout



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   period, the neighbor MUST have Neighbor.State set to Blacklisted.  If
   an acknowledgement is received within the timeout period,
   Neighbor.State is set to Confirmed.  While the value of
   Neighbor.State is Confirmed, the request for an acknowledgement of
   any other RREP message is unnecessary.

   When routers perform other operations such as those from the list
   below, these MAY be used as additional indications of connectivity:

   o  NHDP HELLO Messages [RFC6130]

   o  Route timeout

   o  Lower layer triggers, e.g. message reception or link status
      notifications

   o  TCP timeouts

   o  Promiscuous listening

   o  Other monitoring mechanisms or heuristics

   If such an external process signals that the link to a neighbor is
   bidirectional, the AODVv2 router MAY update the matching Neighbor Set
   entry by changing the value of Neighbor.State to Confirmed, e.g.
   receipt of a Neighborhood Discovery Protocol HELLO message with the
   receiving router listed as a neighbor.  If an external process
   signals that a link is not bidirectional, the the value of
   Neighbor.State MAY be changed to Blacklisted, e.g. notification of a
   TCP timeout.

6.3.  Neighbor Set Update

   On receipt of an RREQ or RREP message, the Neighbor Set MUST be
   checked for an entry with Neighbor.IPAddress which matches the source
   IP address of a packet containing the AODVv2 message.  If no matching
   entry is found, a new entry is created.

   A new Neighbor Set entry is created as follows:

   o  Neighbor.IPAddress := Source IP address of the received route
      message

   o  Neighbor.State := Heard

   o  Neighbor.Timeout := INFINITY_TIME





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   o  Neighbor.Interface := Interface on which the RREQ or RREP was
      received.  MUST equal Interface.Id of one of the entries in the
      InterfaceSet (see Section 4.1).

   When an RREP_Ack is sent to a neighbor, the Neighbor Set entry is
   updated as follows:

   o  Neighbor.Timeout := CurrentTime + RREP_Ack_SENT_TIMEOUT

   When a received message is one of the following:

   o  an RREP which answers an RREQ sent within RREQ_WAIT_TIME over the
      same interface as Neighbor.Interface

   o  an RREP_Ack response received from a Neighbor with Neighbor.State
      set to Heard, where Neighbor.Timeout > CurrentTime

   then the link to the neighbor is bidirectional and the Neighbor Set
   entry is updated as follows:

   o  Neighbor.State := Confirmed

   o  Neighbor.Timeout := INFINITY_TIME

   When the Neighbor.Timeout is reached and Neighbor.State is Heard,
   then an RREP_Ack response has not been received from the neighbor
   within RREP_Ack_SENT_TIMEOUT of sending the RREP_Ack request.  The
   link is considered to be uni-directional and the Neighbor Set entry
   is updated as follows:

   o  Neighbor.State := Blacklisted

   o  Neighbor.Timeout := CurrentTime + MAX_BLACKLIST_TIME

   When the Neighbor.Timeout is reached and Neighbor.State is
   Blacklisted, the Neighbor Set entry is updated as follows:

   o  Neighbor.State := Heard

   If an external mechanism reports a link as broken, the Neighbor Set
   entry SHOULD be removed.

   Route requests from neighbors with Neighbor.State set to Blacklisted
   are ignored to avoid persistent IP packet loss or protocol failures.
   Neighbor.Timeout allows the neighbor to again be allowed to
   participate in route discoveries after MAX_BLACKLIST_TIME, in case
   the link between the routers has become bidirectional.




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6.4.  Interaction with the Forwarding Plane

   The signals descried in the following are conceptual signals, and can
   be implemented in various ways.  Conformant implementations of AODVv2
   are not mandated to implement the forwarding plane separately from
   the control plane or data plane; these signals and interactions are
   identified simply as assistance for implementers who may find them
   useful.

   AODVv2 requires signals from the forwarding plane:

   o  A packet cannot be forwarded because a route is unavailable:
      AODVv2 needs to know the source and destination IP addresses of
      the packet.  If the source of the packet is configured as a Router
      Client, the router SHOULD initiate route discovery to the
      destination.  If it is not a Router Client, the router SHOULD
      create a Route Error message.

   o  A packet is to be forwarded: AODVv2 needs to check the state of
      the route to ensure it is still valid.

   o  Packet forwarding succeeds: AODVv2 needs to update the record of
      when a route was last used to forward a packet.

   o  Packet forwarding failure occurs: AODVv2 needs to create a Route
      Error message.

   AODVv2 needs to send signals to the forwarding plane:

   o  A route discovery is in progress: buffering might be configured
      for packets requiring a route, while route discovery is attempted.

   o  A route discovery failed: any buffered packets requiring that
      route should be discarded, and the source of the packet should be
      notified that the destination is unreachable (using an ICMP
      Destination Unreachable message).  Route discovery fails if an
      RREQ cannot be generated because the control message generation
      limit has been reached, or if an RREP is not received within
      RREQ_WAIT_TIME (see Section 6.6).

   o  A route discovery is not permitted: any buffered packets requiring
      that route should be discarded.  A route discovery will not be
      attempted if the source address of the packet needing a route is
      not configured as a Router Client.

   o  A route discovery succeeded: install a corresponding route into
      the Routing Information Base and begin transmitting any buffered
      packets.



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   o  A route has been made invalid: remove the corresponding route from
      the Routing Information Base.

   o  A route has been updated: update the corresponding route in the
      Routing Information Base.

   o  CEP: If routes with more than one metric type are available to a
      destination, a way to identify the route that is allowable for
      each metric type

6.5.  Message Transmission

   AODVv2 sends [RFC5444] formatted messages using the parameters for
   port number and IP protocol specified in [RFC5498].  Mapping of
   AODVv2 data to [RFC5444] messages is detailed in Section 8.  AODVv2
   multicast messages are sent to the link-local multicast address LL-
   MANET-Routers [RFC5498].  All AODVv2 routers MUST subscribe to LL-
   MANET-Routers on all AODVv2 interfaces [RFC5498] to receive AODVv2
   messages.  Note that multicast messages MAY be sent via unicast.  For
   example, this may occur for certain link-types (non-broadcast media),
   for manually configured router adjacencies, or in order to improve
   robustness.

   When multiple interfaces are available, an AODVv2 router transmitting
   a multicast message to LL-MANET-Routers MUST send the message on all
   interfaces that have been configured for AODVv2 operation, as given
   in the InterfaceSet (Section 4.1).

   To avoid congestion, each AODVv2 router's rate of message generation
   SHOULD be limited (CONTROL_TRAFFIC_LIMIT) and administratively
   configurable.  Messages SHOULD NOT be sent more frequently than one
   message per (1 / CONTROL_TRAFFIC_LIMIT)th of a second.  If this
   threshold is reached, messages MUST be sent based on their priority:

   o  Highest priority SHOULD be given to RREP_Ack messages.  This
      allows links between routers to be confirmed as bidirectional and
      avoids undesired blacklisting of next hop routers.

   o  Second priority SHOULD be given to RERR messages for undeliverable
      IP packets.  This avoids repeated forwarding of packets over
      broken routes that are still in use by other routers.

   o  Third priority SHOULD be given to RREP messages in order that
      RREQs do not time out.

   o  Fourth priority SHOULD be given to RREQ messages.





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   o  Fifth priority SHOULD be given to RERR messages for newly
      invalidated routes.

   o  Lowest priority SHOULD be given to RERR messages generated in
      response to RREP messages which cannot be forwarded.  In this case
      the route request will be retried at a later point.

   To implement the congestion control, a queue length is set.  If the
   queue is full, in order to queue a new message, a message of lower
   priority must be removed from the queue.  If this is not possible,
   the new message MUST be discarded.  The queue should be sorted in
   order of message priority

6.6.  Route Discovery, Retries and Buffering

   AODVv2's RREQ and RREP messages are used for route discovery.  RREQ
   messages are multicast to solicit an RREP, whereas RREP are unicast.
   The constants used in this section are defined in Section 10.

   When an AODVv2 router needs to forward an IP packet (with source
   address OrigAddr and destination address TargAddr) from one of its
   Router Clients, it needs a route to TargAddr in its Routing
   Information Base.  If no route exists, the AODVv2 router generates
   (RREQ_Gen) and multicasts a Route Request message (RREQ), on all
   configured interfaces, containing information about the source and
   destination.  The procedure for this is described in Section 7.1.1.
   Each generated RREQ results in an increment to the router's sequence
   number.  The AODVv2 router generating an RREQ is referred to as
   RREQ_Gen.

   Buffering might be configured for IP packets awaiting a route for
   forwarding by RREQ_Gen, if sufficient memory is available.  Buffering
   of IP packets might have both positive and negative effects.  Real-
   time traffic, voice, and scheduled delivery may suffer if packets are
   buffered and subjected to delays, but TCP connection establishment
   will benefit if packets are queued while route discovery is performed
   [Koodli01].  Recommendations for appropriate buffer methods are out
   of scope for this specification.  Determining which packets to
   discard first when the buffer is full is a matter of policy at each
   AODVv2 router.  Note that using different or no buffer methods does
   not affect interoperability.

   RREQ_Gen awaits reception of a Route Reply message (RREP) containing
   a route toward TargAddr.  This can be achieved by monitoring the
   entry in the Multicast Route Message Table that corresponds to the
   generated RREQ.  When CurrentTime exceeds RteMsg.Timestamp +
   RREQ_WAIT_TIME and no RREP has been received, RREQ_Gen will retry the
   route discovery.



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   To reduce congestion in a network, repeated attempts at route
   discovery for a particular target address utilize a binary
   exponential backoff: for each additional attempt, the time to wait
   for receipt of the RREP is multiplied by 2.  If the requested route
   is not learned within the wait period, another RREQ is sent, up to a
   total of DISCOVERY_ATTEMPTS_MAX.  This is the same technique used in
   AODV [RFC3561].

   Through the use of bidirectional link monitoring and blacklists (see
   Section 6.2) uni-directional links on initial selected route will be
   ignored on subsequent route discovery attempts.

   Route discovery is considered to have failed after
   DISCOVERY_ATTEMPTS_MAX and the corresponding wait time for an RREP
   response to the final RREQ.  After the attempted route discovery has
   failed, RREQ_Gen waits at least RREQ_HOLDDOWN_TIME before attempting
   another route discovery to the same destination, in order to avoid
   repeatedly generating control traffic that is unlikely to discover a
   route.  Any IP packets buffered for TargAddr are also dropped and a
   Destination Unreachable ICMP message (Type 3) with a code of 1 (Host
   Unreachable Error) is delivered to the source of the packet, so that
   the application knows about the failure.

   If RREQ_Gen does receive a route message containing a route to
   TargAddr within the timeout, it processes the message according to
   Section 7.  When a valid LocalRoute entry is created in the Local
   Route Set, the route is also installed in the Routing Information
   Base, and the router will begin sending the buffered IP packets.  Any
   retry timers for the corresponding RREQ are then cancelled.

   During route discovery, all routers on the path learn a route to both
   OrigPrefix and TargPrefix, so that routes are constructed in both
   directions.  The route is optimized for the forward route.

6.7.  Processing Received Route Information

   All AODVv2 route messages contain a route.  A Route Request (RREQ)
   contains a route to OrigPrefix, and a Route Reply (RREP) contains a
   route to TargPrefix.  All AODVv2 routers that receive a route message
   are able to store the route contained within it in their Local Route
   Set. Incoming information is first checked to verify that it is both
   safe to use and offers an improvement to existing information, as
   explained in Section 6.7.1.  If these checks pass, the Local Route
   Set MUST be updated according to Section 6.7.2.

   In the processes below, RteMsg is used to denote the route message,
   AdvRte is used to denote the route contained within it, and




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   LocalRoute denotes an existing entry in the Local Route Set which
   matches AdvRte on address, prefix length, metric type, and SeqNoRtr.

   AdvRte has the following properties:

   o  AdvRte.Address := RteMsg.OrigPrefix (in RREQ) or RteMsg.TargPrefix
      (in RREP)

   o  AdvRte.PrefixLength := RteMsg.OrigPrefixLen (in RREQ) or
      RteMsg.TargPrefixLen (in RREP).  If no prefix length was included
      in RteMsg, prefix length is the address length, in bits, of
      RteMsg.OrigPrefix (in RREQ) or RteMsg.TargPrefix (in RREP)

   o  AdvRte.SeqNum := RteMsg.OrigSeqNum (in RREQ) or RteMsg.TargSeqNum
      (in RREP)

   o  AdvRte.NextHop := RteMsg.IPSourceAddress (an address of the
      sending interface of the router from which the RteMsg was
      received)

   o  AdvRte.MetricType := RteMsg.MetricType

   o  AdvRte.Metric := RteMsg.Metric

   o  AdvRte.Cost := Cost(R) using the cost function associated with the
      route's metric type, i.e. Cost(R) = AdvRte.Metric + Cost(L), as
      described in Section 5, where L is the link from the advertising
      router

   o  AdvRte.SeqNoRtr := the IP address in the Address List of type
      SeqNoRtr if one exists, otherwise 0

6.7.1.  Evaluating Route Information

   An incoming advertised route (AdvRte) is compared to existing
   LocalRoutes to determine whether the advertised route is to be used
   to update the AODVv2 Local Route Set. The incoming route information
   MUST be processed as follows:

   1.  Search for LocalRoutes in the Local Route Set matching AdvRte's
       address, prefix length, metric type, and SeqNoRtr (the AODVv2
       router address corresponding to the sequence number).

       *  If no matching LocalRoute exists, AdvRte MUST be used to
          update the Local Route Set and no further checks are required.

       *  If matching LocalRoutes are found, continue to Step 2.




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   2.  Compare sequence numbers using the technique described in
       Section 4.4

       *  If AdvRte is more recent than all matching LocalRoutes, AdvRte
          MUST be used to update the Local Route Set and no further
          checks are required.

       *  If AdvRte is stale, AdvRte MUST NOT be used to update the
          Local Route Set. Ignore AdvRte for further processing.

       *  If the sequence numbers are equal, continue to Step 3.

   3.  Check that AdvRte is safe against routing loops compared to all
       matching LocalRoutes (see Section 5)

       *  If LoopFree(AdvRte, LocalRoute) returns FALSE, ignore AdvRte
          for further processing.  AdvRte MUST NOT be used to update the
          Local Route Set because using the incoming information might
          cause a routing loop.

       *  If LoopFree(AdvRte, LocalRoute) returns TRUE, continue to Step
          4.

   4.  Compare route costs

       *  If AdvRte is better than all matching LocalRoutes, it MUST be
          used to update the Local Route Set because it offers
          improvement.

       *  If AdvRte is equal in cost and LocalRoute is valid, AdvRte
          SHOULD NOT be used to update the Local Route Set because it
          will offer no improvement.

       *  If AdvRte is worse and LocalRoute is valid, ignore AdvRte for
          further processing.  AdvRte MUST NOT be used to update the
          Local Route Set because it does not offer any improvement.

       *  If AdvRte is not better (i.e., it is worse or equal) but
          LocalRoute is Invalid, AdvRte SHOULD be used to update the
          Local Route Set because it can safely repair the existing
          Invalid LocalRoute.

   If the advertised route is to be used to update the Local Route Set,
   the procedure in Section 6.7.2 MUST be followed.  If not, non-optimal
   routes will remain in the Local Route Set.

   For information on how to apply these changes to the Routing
   Information Base, see Section 4.5.



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6.7.2.  Applying Route Updates

   After determining that AdvRte is to be used to update the Local Route
   Set (as described in Section 6.7.1), the following procedure applies.

   If AdvRte is learned from an RREQ message, the link to the next hop
   neighbor may not be confirmed as bidirectional (see Section 4.3).  If
   there is no existing matching route in the Local Route Set, AdvRte
   MUST be installed to allow a corresponding RREP to be sent.  If a
   matching entry already exists, AdvRte offers potential improvement,
   if the link to the neighbor can be confirmed as bidirectional.

   The route update is applied as follows:

   1.  If no existing entry in the Local Route Set matches AdvRte's
       address, prefix length, metric type and SeqNoRtr, continue to
       Step 4 and create a new entry in the Local Route Set.

   2.  If two matching LocalRoutes exist in the Local Route Set, one is
       a valid route, and one is an Unconfirmed route, AdvRte may offer
       further improvement to the Unconfirmed route, or may offer an
       update to the valid route.

       *  If AdvRte.NextHop's Neighbor.State is Heard, the advertised
          route may offer improvement to the existing valid route, if
          the link to the next hop can be confirmed as bidirectional.
          Continue processing from Step 5 to update the existing
          Unconfirmed LocalRoute.

       *  If AdvRte.NextHop's Neighbor.State is Confirmed, the
          advertised route offers an update or improvement to the
          existing valid route.  Continue processing from Step 5 to
          update the existing valid LocalRoute.

   3.  If only one matching LocalRoute exists in the Local Route Set:

       *  If AdvRte.NextHop's Neighbor.State is Confirmed, continue
          processing from Step 5 to update the existing LocalRoute.

       *  If AdvRte.NextHop's Neighbor.State is Heard, AdvRte may offer
          improvement the existing LocalRoute, if the link to
          AdvRte.NextHop can be confirmed as bidirectional.

       *  If LocalRoute.State is Unconfirmed, AdvRte is an improvement
          to an existing Unconfirmed route.  Continue processing from
          Step 5 to update the existing LocalRoute.





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       *  If LocalRoute.State is Invalid, AdvRte can replace the
          existing LocalRoute.  Continue processing from Step 5 to
          update the existing LocalRoute.

       *  If LocalRoute.State is Active or Idle, AdvRte SHOULD be stored
          as an additional entry in the Local Route Set, with
          LocalRoute.State set to Unconfirmed.  Continue processing from
          Step 4 to create a new LocalRoute.

   4.  Create an entry in the Local Route Set and initialize as follows:

       *  LocalRoute.Address := AdvRte.Address

       *  LocalRoute.PrefixLength := AdvRte.PrefixLength

       *  LocalRoute.MetricType := AdvRte.MetricType

   5.  Update the LocalRoute as follows:

       *  LocalRoute.SeqNum := AdvRte.SeqNum

       *  LocalRoute.NextHop := AdvRte.NextHop

       *  LocalRoute.NextHopInterface := interface on which RteMsg was
          received

       *  LocalRoute.Metric := AdvRte.Cost

       *  LocalRoute.LastUsed := CurrentTime

       *  LocalRoute.LastSeqNumUpdate := CurrentTime

   6.  If a new LocalRoute was created, or if the existing
       LocalRoute.State is Invalid or Unconfirmed, update LocalRoute as
       follows:

       *  LocalRoute.State := Unconfirmed (if the next hop's
          Neighbor.State is Heard)

       *  LocalRoute.State := Idle (if the next hop's Neighbor.State is
          Confirmed)

   7.  If an existing LocalRoute.State changed from Invalid or
       Unconfirmed to become Idle, any matching Unconfirmed LocalRoute
       with worse metric value SHOULD be expunged.






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   8.  If an existing LocalRoute was updated with a better metric value,
       any matching Unconfirmed LocalRoute with worse metric value
       SHOULD be expunged.

   9.  If this update results in LocalRoute.State of Active or Idle,
       which matches a route request which is still in progress, the
       associated route request retry timers MUST be cancelled.

   If this update to the Local Route Set results in two LocalRoutes to
   the same address, the best LocalRoute will be Unconfirmed.  In order
   to improve the route used for forwarding, the router SHOULD try to
   determine if the link to the next hop of that LocalRoute is
   bidirectional, by using that LocalRoute to forward future RREPs and
   request acknowledgements (see Section 7.2.1 and Section 7.3.

6.8.  Suppressing Redundant Messages (Multicast Route Message Set)

   When route messages are flooded in a MANET, an AODVv2 router may
   receive several instances of the same message.  Forwarding every one
   of these gives little additional benefit, and generates unnecessary
   signaling traffic and might generate unnecessary interference.

   Each AODVv2 router stores information about recently received route
   messages in the AODVv2 Multicast Route Message Set (Section 4.6).

   Entries in the Multicast Route Message Set SHOULD be maintained for
   at least RteMsg_ENTRY_TIME after the last Timestamp update in order
   to account for long-lived RREQs traversing the network.  An entry
   MUST be deleted when the sequence number is no longer valid, i.e.,
   after MAX_SEQNUM_LIFETIME.  Memory-constrained devices MAY remove the
   entry before this time.

   Received route messages are tested against previously received route
   messages, and if determined to be redundant, forwarding or response
   can be avoided.

   To determine if a received message is redundant:

   1.  Search for an entry in the Multicast Route Message Set with the
       same OrigPrefix, OrigPrefixLen, TargPrefix, Interface and
       MetricType

       *  If there is no entry, the message is not redundant.

       *  If there is an entry, continue to Step 2.

   2.  Compare sequence numbers using the technique described in
       Section 4.4



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       *  Use OrigSeqNum of the entry for comparison.  If the incoming
          message contains SeqNoRtr that is not comparable to the stored
          sequence number, continue to Step 3.

       *  If the entry has an older sequence number than the received
          message, the message is not redundant.

       *  If the entry has a newer sequence number than the received
          message, the message is redundant.

       *  If the entry has the same sequence number, continue to Step 3.

   3.  Compare the metric values

       *  If the entry has a Metric value that is worse than or equal to
          the metric in the received message, the message is redundant.

       *  If the entry has a Metric value that is better than the metric
          in the received message, the message is not redundant.

   If the message is redundant, update the entry as follows:

   o  RteMsg.Timestamp := CurrentTime

   o  RteMasg.RemoveTime := CurrentTime + MAX_SEQNUM_LIFETIME

   since matching route messages are still traversing the network and
   this entry should be maintained.  This message MUST NOT be forwarded
   or responded to.

   If the message is not redundant, create an entry or update the
   existing entry.

   To update a Multicast Route Message Set entry, set:

   o  RteMsg.OrigPrefix := OrigPrefix from the message

   o  RteMsg.OrigPrefixLen := the prefix length associated with
      OrigPrefix

   o  RteMsg.TargPrefix := TargPrefix from the message

   o  RteMsg.OrigSeqNum := the sequence number associated with
      OrigPrefix, if RteMsg is an RREQ

   o  RteMsg.TargSeqNum := the sequence number associated with
      TargPrefix, if RteMsg is an RREP




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   o  RteMsg.Metric := the metric value associated with OrigPrefix in a
      received RREQ

   o  RteMsg.MetricType := the metric type associated with RteMsg.Metric

   o  RteMsg.Timestamp := CurrentTime

   o  RteMsg.RemoveTime := CurrentTime + MAX_SEQNUM_LIFETIME

   Where the message is determined not redundant before Step 3, it MUST
   be forwarded or responded to.  When a message is determined to be not
   redundant in Step 3, it MAY be suppressed to avoid extra control
   traffic.  However, since the processing of the message will result in
   an update to the Local Route Set, the message SHOULD be forwarded or
   responded to, to ensure other routers have up-to-date information and
   the best metrics.  If the message is not forwarded, the best route
   may not be found.  Forwarding or response is to be performed using
   the processes outlined in Section 7.

6.9.  Suppressing Redundant Route Error Messages (Route Error Set)

   In order to avoid flooding the network with RERR messages when a
   stream of IP packets to an unreachable address arrives, an AODVv2
   router SHOULD avoid creating duplicate messages by determining
   whether an equivalent RERR has recently been sent.  This is achieved
   with the help of the Route Error Set (see Section 4.7).

   To determine if a RERR should be created:

   1.  Search for an entry in the Route Error Set where:

       *  RerrMsg.UnreachableAddress == UnreachableAddress to be
          reported

       *  RerrMsg.PktSource == PktSource to be included in the RERR

       If a matching entry is found, no further processing is required
       and the RERR SHOULD NOT be sent.

   2.  If no matching entry is found, a new entry with the following
       properties is created, and the RERR is created and sent as
       described in Section 7.4.1:

       *  RerrMsg.Timeout := CurrentTime + RERR_TIMEOUT

       *  RerrMsg.UnreachableAddress == UnreachableAddress to be
          reported




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       *  RerrMsg.PktSource == PktSource to be included in the RERR

6.10.  Local Route Set Maintenance

   Route maintenance involves monitoring LocalRoutes in the Local Route
   Set, updating LocalRoute.State to handle route timeouts or (in the
   case of possibly unidirectional links) infer confirmation of a route
   to OrigAddr, and reporting routes that become Invalid.

6.10.1.  LocalRoute State Changes

   During normal operation, AODVv2 does not require any explicit
   timeouts to manage the lifetime of a route.  At any time, any
   LocalRoute MAY be examined and updated according to the rules below.
   In case a Routing Information Base is used for forwarding, the
   corresponding RIB entry MUST be updated as soon as the state of a
   LocalRoute.State changes.  Otherwise, if timers are not used to
   prompt updates of LocalRoute.State, the LocalRoute.State MUST be
   checked before IP packet forwarding and before any operation based on
   LocalRoute.State.

   Route timeout behaviour is as follows:

   o  An Unconfirmed route MUST be expunged at MAX_SEQNUM_LIFETIME after
      LocalRoute.LastSeqNumUpdate.

   o  An Idle route MUST become Active when used to forward an IP
      packet.  If the route is not used to forward an IP packet within
      MAX_IDLETIME, LocalRoute.State MUST become Invalid.

   o  An Invalid route SHOULD remain in the Local Route Set, since
      LocalRoute.SeqNum is used to classify future information about
      LocalRoute.Address as stale or fresh.

   o  In all cases, if the time since LocalRoute.LastSeqNumUpdate
      exceeds MAX_SEQNUM_LIFETIME, LocalRoute.SeqNum must be set to 0.
      This is required to ensure that any AODVv2 routers following the
      initialization procedure can safely begin routing functions using
      a new sequence number.  A LocalRoute with LocalRoute.State set to
      Active or Idle can remain in the Local Route Set after the
      sequence number has been set to 0, for example if the route is
      reliably carrying traffic.  If LocalRoute.State is Invalid, or
      later becomes Invalid, the LocalRoute MUST be expunged from the
      Local Route Set.

   LocalRoutes can become Invalid before a timeout occurs:





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   o  If an external mechanism reports a link as broken, all LocalRoutes
      using that link for LocalRoute.NextHop MUST immediately have
      LocalRoute.State set to Invalid.

   o  LocalRoute.State MUST immediately be set to Invalid if a Route
      Error (RERR) message is received where:

      *  The sender is LocalRoute.NextHop or PktSource is a Router
         Client address

      *  There is an Address in AddressList which matches
         LocalRoute.Address, and:

         +  The prefix length associated with this Address, if any,
            matches LocalRoute.PrefixLength

         +  The sequence number associated with this Address, if any, is
            newer or equal to LocalRoute.SeqNum (see Section 4.4)

         +  The metric type associated with this Address matches
            LocalRoute.MetricType

   A LocalRoute can be Confirmed by inferring connectivity to OrigAddr.

   o  When an AODVv2 router sends an RREP to OrigAddr for destination
      TargAddr, and subsequently the AODVv2 router receives a packet
      from OrigAddr with destination TargAddr, the AODVv2 router infers
      that the route to OrigAddr has been confirmed.  The corresponding
      state for LocalRoute.OrigAddr is changed to Active.

   LocalRoutes are updated when Neighbor.State is updated:

   o  While the value of Neighbor.State is set to Heard, any routes in
      the Local Route Set using that neighbor as a next hop MUST have
      LocalRoute.State set to Unconfirmed.

   o  When the value of Neighbor.State is set to Blacklisted, any valid
      routes in the Local Route Set using that neighbor for their next
      hop MUST have LocalRoute.State set to Invalid.

   o  When a Neighbor Set entry is removed, all routes in the Local
      Route Set using that neighbor as next hop MUST have
      LocalRoute.State set to Invalid.

   Memory constrained devices MAY choose to expunge routes from the
   AODVv2 Local Route Set at other times, but MUST adhere to the
   following rules:




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   o  An Active route MUST NOT be expunged, as it is in use.  If
      deleted, IP traffic forwarded to this router will prompt
      generation of a Route Error message, and it will be necessary for
      a Route Request to be generated by the originator's router to re-
      establish the route.

   o  An Idle route SHOULD NOT be expunged, as it is still valid for
      forwarding IP traffic.  If deleted, this could result in dropped
      IP packets and a Route Request could be generated to re-establish
      the route.

   o  Any Invalid route MAY be expunged.  Least recently used Invalid
      routes SHOULD be expunged first, since the sequence number
      information is less likely to be useful.

   o  An Unconfirmed route MUST NOT be expunged if it was installed
      within the last RREQ_WAIT_TIME, because it may correspond to a
      route discovery in progress.  A Route Reply message might be
      received which needs to use the LocalRoute.NextHop information.
      Otherwise, it MAY be expunged.

6.10.2.  Reporting Invalid Routes

   When LocalRoute.State changes from Active to Invalid as a result of a
   broken link or a received Route Error (RERR) message, other AODVv2
   routers MUST be informed by sending an RERR message containing
   details of the invalidated route.

   An RERR message MUST also be sent when an AODVv2 router receives an
   RREP message to forward, but the LocalRoute to the OrigPrefix in the
   RREP has been lost or is marked as Invalid.

   An RERR message MUST also be sent when an AODVv2 router receives an
   RREP message to forward, but the LocalRoute to the OrigAddr in the
   RREP has been lost or is marked as Invalid.

   The packet or message triggering the RERR MUST be discarded.

   Generation of an RERR message is described in Section 7.4.1.

7.  AODVv2 Protocol Messages

   AODVv2 defines four message types: Route Request (RREQ), Route Reply
   (RREP), Route Reply Acknowledgement (RREP_Ack), and Route Error
   (RERR).

   Each AODVv2 message is defined as a set of data.  Rules for the
   generation, reception and forwarding of each message type are



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   described in the following sections.  Section 8 discusses how the
   data is mapped to [RFC5444] Message TLVs, Address Blocks, and Address
   TLVs.

7.1.  Route Request (RREQ) Message

   Route Request messages are used in route discovery operations to
   request a route to a specified target address.  RREQ messages have
   the following contents:

    +-----------------------------------------------------------------+
    |                          msg_hop_limit                          |
    +-----------------------------------------------------------------+
    |                           AddressList                           |
    +-----------------------------------------------------------------+
    |                   PrefixLengthList (optional)                   |
    +-----------------------------------------------------------------+
    |                OrigSeqNum, (optional) TargSeqNum                |
    +-----------------------------------------------------------------+
    |                           MetricType                            |
    +-----------------------------------------------------------------+
    |                           OrigMetric                            |
    +-----------------------------------------------------------------+

                      Figure 1: RREQ message contents

   msg_hop_limit
      The remaining number of hops allowed for dissemination of the RREQ
      message.

   AddressList
      Contains: * OrigPrefix, from the Router Client Set entry which
      includes OrigAddr, the source address of the IP packet for which a
      route is requested, * TargPrefix, set to TargAddr, the destination
      address of the IP packet for which a route is requested, and *
      Optionally, if RouterClient.SeqNoRtr is true, the IP address of
      OrigRtr -- i.e., the router that originated the Sequence Number
      for this RREQ.

   PrefixLengthList
      Contains OrigPrefixLen, i.e., the length, in bits, of the prefix
      associated with the Router Client Set entry which includes
      OrigAddr.  If omitted, the prefix length is equal to OrigAddr's
      address length in bits.

   OrigSeqNum
      The sequence number associated with OrigPrefix.




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   TargSeqNum
      A sequence number associated with an existing Invalid route to
      TargAddr.  This MAY be included if available.

   MetricType
      The metric type associated with OrigMetric.

   OrigMetric
      The metric value associated with the route to OrigPrefix, as seen
      from the sender of the message.

7.1.1.  RREQ Generation

   An RREQ is generated when an IP packet needs to be forwarded for a
   Router Client, and no valid route currently exists for the packet's
   destination in the Routing Information Base.

   Before creating an RREQ, the router SHOULD check the Multicast Route
   Message Set to see if an RREQ has recently been sent for the
   requested destination.  If so, and the wait time for a reply has not
   yet been reached, the router SHOULD continue to await a response
   without generating a new RREQ.  If the timeout has been reached, a
   new RREQ MAY be generated.  If buffering is configured, incoming IP
   packets awaiting this route SHOULD be buffered until the route
   discovery is completed.

   If the limit for the rate of AODVv2 control message generation has
   been reached, no message SHOULD be generated.

   To generate the RREQ, the router (referred to as RREQ_Gen) follows
   this procedure:

   1.  Set msg_hop_limit := MAX_HOPCOUNT

   2.  Set AddressList := {OrigPrefix, TargPrefix}

   3.  For the PrefixLengthList:

       *  If OrigAddr is part of an address range configured as a Router
          Client, set PrefixLengthList := {RouterClient.PrefixLength,
          null}.

       *  Otherwise, omit PrefixLengthList.

       *  If RouterClient.SeqNoRtr is nonzero, then add the router's own
          IP address to AddressList, with AddressType SeqNoRtr.

   4.  For OrigSeqNum:



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       *  Increment the router Sequence Number as specified in
          Section 4.4.

       *  Set OrigSeqNum := router Sequence Number.

   5.  For TargSeqNum:

       *  If an Invalid route exists in the Local Route Set matching
          TargAddr using longest prefix matching and has a valid
          sequence number, set TargSeqNum := LocalRoute.SeqNum.

       *  If no Invalid route exists in the Local Route Set matching
          TargAddr, or the route doesn't have a sequence number, omit
          TargSeqNum.

   6.  Include MetricType and set the type accordingly

   7.  Find the Router Client Set entry where RouterClient.IPAddress ==
       OrigPrefix:

       *  Set OrigMetric := RouterClient.Cost

   This AODVv2 message is used to create a corresponding [RFC5444]
   message (see Section 8) which is handed to the RFC5444 multiplexer
   for further processing.  By default, the multiplexer is instructed to
   multicast the message to LL-MANET-Routers on all interfaces
   configured for AODVv2 operation.  The RREP MUST be sent over
   LocalRoute[OrigPrefix].NextHopInterface.

7.1.2.  RREQ Reception

   Upon receiving a Route Request, an AODVv2 router performs the
   following steps:

   1.  Check and update the Neighbor Set according to Section 6.3

       *  If the sender has Neighbor.State set to Blacklisted, ignore
          this RREQ for further processing.

   2.  Verify that the message contains the required data:
       msg_hop_limit, OrigPrefix, TargPrefix, OrigSeqNum, and
       OrigMetric, and that OrigPrefix and TargPrefix are valid
       addresses

       *  If not, ignore this RREQ for further processing.

   3.  Check that the MetricType is supported and configured for use




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       *  If not, ignore this RREQ for further processing.

   4.  Verify that the cost of the advertised route will not exceed the
       maximum allowed metric value for the metric type (Metric <=
       MAX_METRIC[MetricType] - Cost(L))

       *  If it will, ignore this RREQ for further processing.

   5.  Process the route to OrigPrefix as specified in Section 6.7

   6.  Check if the information in the message is redundant by comparing
       to entries in the Multicast Route Message Set, following the
       procedure in Section 6.8

       *  If redundant, ignore this RREQ for further processing.

       *  If not redundant, create a new entry in the Multicast Route
          Message Set and continue processing.

   7.  Check if the TargPrefix matches an entry in the Router Client Set

       *  If so, generate an RREP as specified in Section 7.2.1.

       *  If not, continue to RREQ forwarding.

7.1.3.  RREQ Forwarding

   By forwarding an RREQ, a router advertises that it will forward IP
   packets to the OrigPrefix contained in the RREQ according to the
   information enclosed.  The router MAY choose not to forward the RREQ,
   for example if the router is heavily loaded or low on energy and
   therefore unwilling to advertise routing capability for more traffic.
   This could, however, decrease connectivity in the network or result
   in non-optimal paths.

   The RREQ SHOULD NOT be forwarded if the limit for the rate of AODVv2
   control message generation has been reached.

   The procedure for RREQ forwarding is as follows:

   1.  Set msg_hop_limit := received msg_hop_limit - 1

   2.  If msg_hop_limit is now zero, discontinue the forwarding process

   3.  Set OrigMetric := LocalRoute[OrigPrefix].Metric

   This modified message is handed to the [RFC5444] multiplexer for
   further processing.  By default, the multiplexer is instructed to



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   multicast the message to LL-MANET-Routers on all interfaces
   configured for AODVv2 operation.

7.2.  Route Reply (RREP) Message

   When a Route Request message is received, requesting a route to a
   target address (TargAddr) which is configured as part of a Router
   Client Set entry, a Route Reply message is sent in response.  The
   RREP offers a route to TargPrefix.

   RREP messages have the following contents:

    +-----------------------------------------------------------------+
    |                          msg_hop_limit                          |
    +-----------------------------------------------------------------+
    |                           AddressList                           |
    +-----------------------------------------------------------------+
    |                   PrefixLengthList (optional)                   |
    +-----------------------------------------------------------------+
    |                           TargSeqNum                            |
    +-----------------------------------------------------------------+
    |                           MetricType                            |
    +-----------------------------------------------------------------+
    |                           TargMetric                            |
    +-----------------------------------------------------------------+

                      Figure 2: RREP message contents

   msg_hop_limit
      The remaining number of hops allowed for dissemination of the RREP
      message.

   AddressList
      Contains: * OrigPrefix, from the Router Client entry which
      includes OrigAddr, the source address of the IP packet for which a
      route is requested * TargPrefix, set to TargAddr, the destination
      address of the IP packet for which a route is requested. *
      Optionally, if RouterClient.SeqNoRtr is true, the IP address of
      TargRtr -- i.e., the router that originated the Sequence Number
      for this RREP.

   PrefixLengthList
      Contains TargPrefixLen, i.e., the length, in bits, of the prefix
      associated with the Router Client Set entry which includes
      TargAddr.  If omitted, the prefix length is equal to TargAddr's
      address length, in bits.

   TargSeqNum



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      The sequence number associated with TargPrefix.

   MetricType
      The metric type associated with TargMetric.

   TargMetric
      The metric value associated with the route to TargPrefix, as seen
      from the sender of the message.

7.2.1.  RREP Generation

   A Route Reply message is generated when a Route Request for a Router
   Client of the AODVv2 router arrives.  This is the case when
   RteMsg.TargPrefix matches an entry in the Router Client Set of the
   AODVv2 router.

   Before creating an RREP, the router SHOULD check if
   CONTROL_TRAFFIC_LIMIT has been reached.  If so, the RREP SHOULD NOT
   be created.

   The RREP will follow the path of the route to OrigPrefix.  If the
   best route to OrigPrefix in the Local Route Set is Unconfirmed, the
   link to the next hop neighbor is not yet confirmed as bidirectional
   (as described in Section 6.2).  In this case an RREP_Ack MUST also be
   sent as described in Section 7.3, in order to request an
   acknowledgement message from the next hop router to prove that the
   link is bidirectional.  If the best route to OrigPrefix in the Local
   Route Set is valid, the link to the next hop neighbor is already
   confirmed as bidirectional, and no acknowledgement is required.

   Implementations MAY allow a number of retries of the RREP if a
   requested acknowledgement is not received within
   RREP_Ack_SENT_TIMEOUT, doubling the timeout with each retry, up to a
   maximum of RREP_RETRIES, using the same exponential backoff described
   in Section 6.6 for RREQ retries.  The acknowledgement MUST be
   considered to have failed after the wait time for an RREP_Ack
   response to the final RREP.

   To generate the RREP, the router (also referred to as RREP_Gen)
   follows this procedure:

   1.  Set msg_hop_limit := MAX_HOPCOUNT - msg_hop_limit from the
       received RREQ message

   2.  Set Address List := {OrigPrefix, TargPrefix}

       *  If RouterClient.SeqNoRtr is nonzero, then add the router's own
          IP address to AddressList, with AddressType SeqNoRtr.



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   3.  For the PrefixLengthList:

       *  If TargAddr is part of an address range configured as a Router
          Client, set PrefixLengthList := {null,
          RouterClient.PrefixLength}.

       *  Otherwise, omit PrefixLengthList.

   4.  For the TargSeqNum:

       *  Increment the router Sequence Number as specified in
          Section 4.4.

       *  Set TargSeqNum := router Sequence Number.

   5.  Include MetricType and set the type to match the MetricType in
       the received RREQ message.

   6.  Set TargMetric := RouterClient.Cost for the Router Client Set
       entry which includes TargAddr.

   This AODVv2 message is used to create a corresponding [RFC5444]
   message (see Section 8) which is handed to the RFC5444 multiplexer
   for further processing.  The multiplexer is instructed to unicast the
   RREP to LocalRoute[OrigPrefix].NextHop.  The RREP MUST be sent over
   LocalRoute[OrigPrefix].NextHopInterface.

7.2.2.  RREP Reception

   Upon receiving a Route Reply, an AODVv2 router performs the following
   steps:

   1.  Verify that the message contains the required data:
       msg_hop_limit, OrigPrefix, TargPrefix, TargSeqNum, and
       TargMetric, and that OrigPrefix and TargPrefix are valid
       addresses

       *  If not, ignore this RREP for further processing.

   2.  Check that the MetricType is supported and configured for use

       *  If not, ignore this RREP for further processing.

   3.  If this RREP does not correspond to an RREQ generated or
       forwarded in the last RREQ_WAIT_TIME, ignore for further
       processing.





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   4.  If the Multicast Route Message Set does not contain an entry
       where:

   o  RteMsg.OrigPrefix == RREP.OrigPrefix

   o  RteMsg.OrigPrefixLen == RREP.OrigPrefixLen

   o  RteMsg.TargAddr exists within RREP.TargPrefix

   o  RteMsg.OrigSeqNum <= RREP.OrigSeqNum

   o  RteMsg.SeqNoRtr <= RREP.SeqNoRtr

   o  RteMsg.MetricType == RREP.MetricType

   o  RteMsg.Timestamp > CurrentTime - RREQ_WAIT_TIME

   o  RteMsg.Interface == The interface on which the RREP was received

   then, ignore this RREP for further processing, since it does not
   correspond to a previously sent RREQ.

   1.  Update the Neighbor Set according to Section 6.3

   2.  Verify that the cost of the advertised route does not exceed the
       maximum allowed metric value for the metric type (Metric <=
       MAX_METRIC[MetricType] - Cost(L))

       *  If it does, ignore this RREP for further processing.

   3.  Process the route to TargPrefix as specified in Section 6.7

   4.  Check if the message is redundant by comparing to entries in the
       Multicast Route Message Set (Section 6.8)

       *  If redundant, ignore this RREP for further processing.

       *  If not redundant, save the information in the Multicast Route
          Message Set to identify future redundant RREP messages and
          continue processing.

   5.  Check if the OrigPrefix matches an entry in the Router Client Set

       *  If so, no further processing is necessary.

       *  If not, continue to Step 10.  CEP: There is no step 10.





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   6.  Check if a valid (Active or Idle) or Unconfirmed LocalRoute
       exists to OrigPrefix

       *  If so, continue to RREP forwarding.

       *  If not, a Route Error message SHOULD be transmitted toward
          TargPrefix according to Section 7.4.1 and the RREP SHOULD be
          discarded and not forwarded.

7.2.3.  RREP Forwarding

   A received Route Reply message is forwarded toward OrigPrefix.  By
   forwarding an RREP, a router advertises that it will forward IP
   packets to TargPrefix.

   The RREP SHOULD NOT be forwarded if CONTROL_TRAFFIC_LIMIT has been
   reached.  Otherwise, the router MUST forward the RREP.

   The procedure for RREP forwarding is as follows:

   1.  Set msg_hop_limit := received msg_hop_limit - 1

   2.  If msg_hop_limit is now zero, do not continue the forwarding
       process

   3.  Set TargMetric := LocalRoute[TargPrefix].Metric

   This modified message is handed to the [RFC5444] multiplexer for
   further processing.  The multiplexer is instructed to unicast the
   RREP to LocalRoute[OrigPrefix].NextHop.  The RREP MUST be sent over
   LocalRoute[OrigPrefix].NextHopInterface.

7.3.  Route Reply Acknowledgement (RREP_Ack) Message

   The Route Reply Acknowledgement is used as both a request and a
   response message to test bidirectionality of a link over which a
   Route Reply has also been sent.  The router which forwards the RREP
   MUST send a Route Reply Acknowledgement message to the intended next
   hop, if the link to the next hop neighbor is not yet confirmed as
   bidirectional.

   The receiving router MUST then reply with a Route Reply
   Acknowledgement response message.

   When the Route Reply Acknowledgement response message is received by
   the sender of the RREP, it confirms that the link between the two
   routers is bidirectional (see Section 6.2).




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   If the Route Reply Acknowledgement is not received within
   RREP_Ack_SENT_TIMEOUT, the link is determined to be unidirectional.

    +-----------------------------------------------------------------+
    |                        AckReq (optional)                        |
    +-----------------------------------------------------------------+

                    Figure 3: RREP_Ack message contents

7.3.1.  RREP_Ack Request Generation

   An RREP_Ack MUST be generated if a Route Reply is sent over a link
   which is not known to be bidirectional.  It includes an AckReq
   element to indicate that it is a request for acknowledgement.

   The RREP_Ack SHOULD NOT be generated if the limit for the rate of
   AODVv2 control message generation has been reached.

   The [RFC5444] representation of the RREP_Ack is discussed in
   Section 8.

   The RREP_Ack request MUST be sent unicast to the
   LocalRoute[OrigPrefix].NextHop via
   LocalRoute[OrigPrefix].NextHopInterface.  The multiplexer MAY be
   instructed to send the RREP_Ack in the same [RFC5444] packet as the
   RREP.

   The Neighbor Set entry for LocalRoute[OrigPrefix].NextHop MUST also
   be updated to indicate that an RREP_Ack is required (see
   Section 6.3).

7.3.2.  RREP_Ack Reception

   Upon receiving an RREP_Ack, an AODVv2 router performs the following
   steps:

   1.  Check if an AckReq element is included:

       *  If so, create an RREP_Ack Response as described in
          Section 7.3.3.  No further processing is required.

       *  If not, continue to step 2.

   2.  Check if the RREP_Ack was expected:

       *  Check if the Neighbor Set contains an entry where:





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          +  Neighbor.IPAddress == IP.SourceAddress of the RREP_Ack
             message

          +  Neighbor.State == Heard

          +  Neighbor.Timeout < CurrentTime

          +  Neighbor.Interface matches the interface on which the
             RREP_Ack was received

       *  If it does, the router sets Neighbor.Timeout to INFINITY_TIME,
          and processing continues to Step 3.

       *  Otherwise no actions are required and processing ends.

   3.  Update the Neighbor Set according to Section 6.3, including
       updating routes using this Neighbor as LocalRoute.NextHop.

7.3.3.  RREP_Ack Response Generation

   An RREP_Ack response MUST be generated if a received RREP_Ack
   includes an AckReq.

   The RREP_Ack response SHOULD NOT be generated if the limit for the
   rate of AODVv2 control message generation has been reached.

   There is no further data in an RREP_Ack response.  The [RFC5444]
   representation is discussed in Section 8.  In this case, the
   multiplexer is instructed to unicast the RREP_Ack to the source IP
   address of the RREP_Ack message that requested it, over the same
   interface on which the RREP_Ack was received.

7.4.  Route Error (RERR) Message

   A Route Error message is generated by an AODVv2 router to notify
   other AODVv2 routers of routes that are no longer available.  An RERR
   message has the following contents:














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    +-----------------------------------------------------------------+
    |                       PktSource (optional)                      |
    +-----------------------------------------------------------------+
    |                           AddressList                           |
    +-----------------------------------------------------------------+
    |                   PrefixLengthList (optional)                   |
    +-----------------------------------------------------------------+
    |                       SeqNumList (optional)                     |
    +-----------------------------------------------------------------+
    |                          MetricTypeList                         |
    +-----------------------------------------------------------------+

                      Figure 4: RERR message contents

   PktSource
      The source address of the IP packet triggering the RERR.  If the
      RERR is triggered by a broken link, PktSource is not required.

   AddressList
      The addresses of the routes not available through RERR_Gen.

   PrefixLengthList
      The prefix lengths, in bits, associated with the routes not
      available through RERR_Gen.  These values indicate whether routes
      represent a single device or an address range.

   SeqNumList
      The sequence numbers of the routes not available through RERR_Gen
      (where known).

   MetricTypeList
      The metric types associated with the routes not available through
      RERR_Gen.

7.4.1.  RERR Generation

   A Route Error message is generated when an AODVv2 router (also
   referred to as RERR_Gen) needs to report that a destination is not
   reachable.  There are three events that cause this response:

   o  When an IP packet that has been forwarded from another router, but
      cannot be forwarded further because there is no valid route in the
      Routing Information Base for its destination, the source of the
      packet needs to be informed that the route to the destination of
      the packet does not exist.  The RERR generated MUST include
      PktSource set to the source address of the IP packet, and MUST
      contain only one unreachable address in the AddressList, i.e., the
      destination address of the IP packet.  RERR_Gen MUST discard the



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      IP packet that triggered generation of the RERR.  The prefix
      length, sequence number and metric type SHOULD be included if
      known from an existing Invalid LocalRoute to the unreachable
      address.

   o  When an RREP message cannot be forwarded because the LocalRoute to
      OrigPrefix has been lost or is Invalid, RREP_Gen needs to be
      informed that the route to OrigPrefix does not exist.  The RERR
      generated MUST include PktSource set to the TargPrefix of the
      RREP, and MUST contain only one unreachable address in the
      AddressList, the OrigPrefix from the RREP.  RERR_Gen MUST discard
      the RREP message that triggered generation of the RERR.  The
      prefix length, sequence number and metric type SHOULD be included
      if known from an Invalid LocalRoute to the unreachable address.

   o  When a link breaks, multiple LocalRoutes may become Invalid, and
      the RERR generated MAY contain multiple unreachable addresses.
      The RERR MUST include MetricTypeList.  PktSource is omitted.  All
      previously Active LocalRoutes that used the broken link MUST be
      reported.  The AddressList, SeqNumList, and MetricTypeList will
      contain entries for each LocalRoute which has become Invalid.
      PrefixLengthList will be included if needed to report invalid
      routes to a non-default prefix.  An RERR message is only sent if
      an Active LocalRoute becomes Invalid, though an AODVv2 router can
      also include Idle LocalRoutes that become Invalid if the
      configuration parameter ENABLE_IDLE_IN_RERR is set (see
      Section 10.3).

   The RERR SHOULD NOT be generated if CONTROL_TRAFFIC_LIMIT has been
   reached.  The RERR also SHOULD NOT be generated if it is a duplicate,
   as determined by Section 6.9.

   Incidentally, if an AODVv2 router receives an ICMP error packet to or
   from the address of one of its Router Clients, it forwards the ICMP
   packet in the same way as any other IP packet, and will not generate
   any RERR message based on the contents of the ICMP packet.

   To generate the RERR, the router follows this procedure:

   1.  If necessary, include PktSource and set the value as given above

   2.  For each LocalRoute that needs to be reported:

       *  Insert LocalRoute.Address into the AddressList.

       *  Insert LocalRoute.PrefixLength into PrefixLengthList, if known
          and not equal to the address length.




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       *  Insert LocalRoute.SeqNum into SeqNumList, if known.

       *  Insert LocalRoute.MetricType into MetricTypeList.

   The AODVv2 message is used to create a corresponding [RFC5444]
   message (see Section 8).

   If the RERR is sent in response to an undeliverable IP packet or RREP
   message, i.e., if PktSource is included, the RERR SHOULD be sent
   unicast to the next hop on the route to PktSource.  It MUST be sent
   over the same interface on which the undeliverable IP packet was
   received.  If there is no route to PktSource, the RERR SHOULD be
   multicast to LL-MANET-Routers.  If the RERR is sent in response to a
   broken link, i.e., PktSource is not included, the RERR is, by
   default, multicast to LL-MANET-Routers.

7.4.2.  RERR Reception

   Upon receiving a Route Error, an AODVv2 router performs the following
   steps:

   1.  Verify that the message contains the required data: at least one
       unreachable address

       *  If not, ignore this RERR for further processing.

   2.  For each address in the AddressList, check that:

       *  The address is valid (routable and unicast).

       *  The MetricType is supported and configured for use.

       *  There is a LocalRoute with the same MetricType matching the
          address using longest prefix matching.

       *  Either the LocalRoute's next hop is the sender of the RERR and
          the next hop interface is the interface on which the RERR was
          received, or PktSource is present in the RERR and is a Router
          Client address.

       *  The unreachable address' sequence number is either unknown, or
          is greater than the LocalRoute's sequence number.

       If any of the above are false the address does not match a
       LocalRoute and MUST NOT be processed or regenerated in a RERR.

       If all of the above are true, the LocalRoute which matches the
       address is no longer valid.  If the LocalRoute was previously



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       Active, it MUST be reported in a regenerated RERR.  If the
       LocalRoute was previously Idle, it MAY be reported in a
       regenerated RERR, if ENABLE_IDLE_IN_RERR is configured.  The
       Local Route Set MUST be updated according to these rules:

       *  If the LocalRoute's prefix length is the same as the
          unreachable address' prefix length, set LocalRoute.State to
          Invalid.

       *  If the LocalRoute's prefix length is longer than the
          unreachable address' prefix length, the LocalRoute MUST be
          expunged from the Local Route Set, since it is a sub-route of
          the route which is reported to be Invalid.

       *  If the prefix length is different, create a new LocalRoute
          with the unreachable address, and its prefix length and
          sequence number, and set LocalRoute.State to Invalid.  These
          Invalid routes are retained to avoid processing stale
          messages.

       *  Update the sequence number on the existing LocalRoute, if the
          reported sequence number is determined to be newer using the
          comparison technique described in Section 4.4.

   3.  If there are previously Active LocalRoutes that MUST be reported,
       as identified in step 2.:

       *  Regenerate the RERR as detailed in Section 7.4.3.

7.4.3.  RERR Regeneration

   The Route Error message SHOULD NOT be regenerated if
   CONTROL_TRAFFIC_LIMIT has been reached.

   The procedure for RERR regeneration is as follows:

   1.  If PktSource was included in the original RERR, and PktSource is
       not a Router Client, copy it into the regenerated RERR

   2.  For each LocalRoute that needs to be reported as identified in
       Section 7.4.1:

       *  Insert LocalRoute.Address into the AddressList.

       *  Insert LocalRoute.PrefixLength into PrefixLengthList, if known
          and not equal to the address length.

       *  Insert LocalRoute.SeqNum into SeqNumList, if known.



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       *  Insert LocalRoute.MetricType into MetricTypeList.

   The AODVv2 message is used to create a corresponding [RFC5444]
   message (see Section 8).  If the RERR contains PktSource, the
   regenerated RERR SHOULD be sent unicast to the next hop on the
   LocalRoute to PktSource.  It MUST be sent over the same interface on
   which the undeliverable IP packet was received.  If there is no route
   to PktSource, or PktSource is a Router Client, it SHOULD be multicast
   to LL-MANET-Routers.  If the RERR is sent in response to a broken
   link, the RERR is, by default, multicast to LL-MANET-Routers.

8.  RFC 5444 Representation

   AODVv2 specifies that all control messages between routers MUST use
   the Generalized Mobile Ad Hoc Network Packet/Message Format
   [RFC5444], and therefore AODVv2's route messages comprise data which
   is mapped to message elements in [RFC5444].

   [RFC5444] provides a multiplexed transport for multiple protocols.
   An [RFC5444] implementation MAY choose to optimize the content of
   certain elements during message creation to reduce control message
   overhead.

   A brief summary of the [RFC5444] format:

   1.  A packet contains zero or more messages

   2.  A message contains a Message Header, one Message TLV Block, zero
       or more Address Blocks, and one Address Block TLV Block per
       Address Block

   3.  The Message TLV Block MAY contain zero or more Message TLVs

   4.  An Address Block TLV Block MAY include zero or more Address Block
       TLVs

   5.  Each TLV value in an Address Block TLV Block can be associated
       with all of the addresses, or with a contiguous set of addresses,
       or with a single address in the Address Block

   AODVv2 does not require access to the [RFC5444] packet header.

   In the message header, AODVv2 uses <msg-type>, <msg-hop-limit> and
   <msg-addr-length>.  The <msg-addr-length> field indicates the length
   of any addresses in the message, using <msg-addr-length> := (address
   length in octets - 1), i.e. 3 for IPv4 and 15 for IPv6.





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   The addresses in an Address Block MAY appear in any order, and values
   in a TLV in the Address Block TLV Block must be associated with the
   correct address in the Address Block by the [RFC5444] implementation.
   To indicate which value is associated with each address, the AODVv2
   message representation uses lists where the order of the addresses in
   the AODVv2 AddressList matches the order of values in other data
   lists, e.g., the order of SeqNums in the SeqNumList in an RERR.
   [RFC5444] maps this information to Address Block TLVs associated with
   the relevant addresses in the Address Block.

   Each address included in the Address Block is identified as
   OrigPrefix, TargPrefix, PktSource, or Unreachable Address by
   including an ADDRESS_TYPE TLV in the Address Block TLV Block.

   The following sections show how AODVv2 data is represented in
   [RFC5444] messages.  In Section 11.3, AODVv2 defines several new
   TLVs.

   Where the extension type of a TLV is set to zero, this is the default
   [RFC5444] value and the extension type will not be included in the
   message.

8.1.  Route Request Message Representation

8.1.1.  Message Header

   +---------------+-----------------+---------------------------------+
   | Data          | Header Field    | Value                           |
   +---------------+-----------------+---------------------------------+
   | None          | <msg-type>      | RREQ                            |
   | msg_hop_limit | <msg-hop-limit> | MAX_HOPCOUNT, reduced by number |
   |               |                 | of hops traversed so far by the |
   |               |                 | message.                        |
   +---------------+-----------------+---------------------------------+

8.1.2.  Message TLV Block

   AODVv2 does not define any Message TLVs for an RREQ message.

8.1.3.  Address Block

   An RREQ contains OrigPrefix and TargPrefix, and each of these
   addresses has an associated prefix length.  If the prefix length has
   not been included in the AODVv2 message, it is equal to the address
   length in bits.






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       +----------------------------+------------------------------+
       | Data                       | Address Block                |
       +----------------------------+------------------------------+
       | OrigPrefix/OrigPrefixLen   | <address> + <prefix-length>  |
       | TargPrefix/TargPrefixLen   | <address> + <prefix-length>  |
       | SeqNoRtr/PrefixLen <addre  | ss> + <prefix-length>        |
       +----------------------------+------------------------------+

8.1.4.  Address Block TLV Block

   Address Block TLVs are always associated with one or more addresses
   in the Address Block.  The following sections show the TLVs that
   apply to each address.

8.1.4.1.  Address Block TLVs for OrigPrefix

   +-------------+--------------+------------+-------------------------+
   | Data        | TLV Type     | Extension  | Value                   |
   |             |              | Type       |                         |
   +-------------+--------------+------------+-------------------------+
   | None        | ADDRESS_TYPE | 0          | ORIGPREFIX              |
   | OrigSeqNum  | SEQ_NUM      | 0          | Sequence number of      |
   |             |              |            | RREQ_Gen, the router    |
   |             |              |            | which initiated route   |
   |             |              |            | discovery.              |
   | OrigMetric  | PATH_METRIC  | MetricType | Metric value for the    |
   | /MetricType |              |            | route to OrigPrefix,    |
   |             |              |            | using MetricType.       |
   +-------------+--------------+------------+-------------------------+

8.1.4.2.  Address Block TLVs for TargPrefix

   +------------+--------------+-------------+-------------------------+
   | Data       | TLV Type     | Extension   | Value                   |
   |            |              | Type        |                         |
   +------------+--------------+-------------+-------------------------+
   | None       | ADDRESS_TYPE | 0           | TARGPREFIX              |
   | TargSeqNum | SEQ_NUM      | 0           | The last known          |
   |            |              |             | TargSeqNum for          |
   |            |              |             | TargPrefix.             |
   +------------+--------------+-------------+-------------------------+

8.2.  Route Reply Message Representation








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8.2.1.  Message Header

   +---------------+-----------------+---------------------------------+
   | Data          | Header Field    | Value                           |
   +---------------+-----------------+---------------------------------+
   | None          | <msg-type>      | RREP                            |
   | msg_hop_limit | <msg-hop-limit> | MAX_HOPCOUNT - msg_hop_limit    |
   |               |                 | from the corresponding RREQ,    |
   |               |                 | reduced by number of hops       |
   |               |                 | traversed so far by the         |
   |               |                 | message.                        |
   +---------------+-----------------+---------------------------------+

8.2.2.  Message TLV Block

   AODVv2 does not define any Message TLVs for an RREP message.

8.2.3.  Address Block

   An RREP contains OrigPrefix and TargPrefix, and each of these
   addresses has an associated prefix length.  If the prefix length has
   not been included in the AODVv2 message, it is equal to the address
   length in bits.

       +----------------------------+------------------------------+
       | Data                       | Address Block                |
       +----------------------------+------------------------------+
       | OrigPrefix/OrigPrefixLen   | <address> + <prefix-length>  |
       | TargPrefix/TargPrefixLen   | <address> + <prefix-length>  |
       | SeqNoRtr/PrefixLen <addre  | ss> + <prefix-length>        |
       +----------------------------+------------------------------+

8.2.4.  Address Block TLV Block

   Address Block TLVs are always associated with one or more addresses
   in the Address Block.  The following sections show the TLVs that
   apply to each address.

8.2.4.1.  Address Block TLVs for OrigPrefix

         +-------+---------------+-----------------+-------------+
         | Data  | TLV Type      | Extension Type  | Value       |
         +-------+---------------+-----------------+-------------+
         | None  | ADDRESS_TYPE  | 0               | ORIGPREFIX  |
         +-------+---------------+-----------------+-------------+






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8.2.4.2.  Address Block TLVs for TargPrefix

   +--------------+--------------+------------+------------------------+
   | Data         | TLV Type     | Extension  | Value                  |
   |              |              | Type       |                        |
   +--------------+--------------+------------+------------------------+
   | None         | ADDRESS_TYPE | 0          | TARGPREFIX             |
   | TargSeqNum   | SEQ_NUM      | 0          | Sequence number of     |
   |              |              |            | RREP_Gen, the router   |
   |              |              |            | which created the      |
   |              |              |            | RREP.                  |
   | TargMetric   | PATH_METRIC  | MetricType | Metric value for the   |
   | /MetricType  |              |            | route to TargPrefix,   |
   |              |              |            | using MetricType.      |
   +--------------+--------------+------------+------------------------+

8.3.  Route Reply Acknowledgement Message Representation

8.3.1.  Message Header

                   +-------+---------------+-----------+
                   | Data  | Header Field  | Value     |
                   +-------+---------------+-----------+
                   | None  | <msg-type>    | RREP_Ack  |
                   +-------+---------------+-----------+

8.3.2.  Message TLV Block

   AODVv2 defines an AckReq Message TLV, included when an
   acknowledgement of this message is required, in order to monitor
   adjacency, as described in Section 6.2.

            +---------+-----------+-----------------+--------+
            | Data    | TLV Type  | Extension Type  | Value  |
            +---------+-----------+-----------------+--------+
            | AckReq  | ACK_REQ   | 0               | None   |
            +---------+-----------+-----------------+--------+

8.3.3.  Address Block

   AODVv2 does not define an Address Block for an RREP_Ack message.

8.3.4.  Address Block TLV Block

   AODVv2 does not define any Address Block TLVs for an RREP_Ack
   message.





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8.4.  Route Error Message Representation

   Route Error Messages MAY be split into multiple [RFC5444] messages
   when the desired contents would exceed the MTU.  However, all of the
   resulting messages MUST have the same message header as described
   below.  If PktSource is included in the AODVv2 message, it MUST be
   included in all of the resulting [RFC5444] messages.

8.4.1.  Message Header

                    +-------+---------------+--------+
                    | Data  | Header Field  | Value  |
                    +-------+---------------+--------+
                    | None  | <msg-type>    | RERR   |
                    +-------+---------------+--------+

8.4.2.  Message TLV Block

   AODVv2 does not define any Message TLVs for an RERR message.

8.4.3.  Address Block

   The Address Block in an RERR MAY contain PktSource, the source
   address of the IP packet triggering RERR generation, as detailed in
   Section 7.4.  The prefix length associated with PktSource is equal to
   the address length in bits.

   Address Block always contains one address per route that is no longer
   valid, and each address has an associated prefix length.  If a prefix
   length has not been included for this address, it is equal to the
   address length in bits.

   +------------------------------+------------------------------------+
   | Data                         | Address Block                      |
   +------------------------------+------------------------------------+
   | PktSource                    | <address> + <prefix-length> for    |
   |                              | PktSource                          |
   | AddressList/PrefixLengthList | <address> + <prefix-length> for    |
   |                              | each unreachable address in        |
   |                              | AddressList                        |
   +------------------------------+------------------------------------+

8.4.4.  Address Block TLV Block

   Address Block TLVs are always associated with one or more addresses
   in the Address Block.  The following sections show the TLVs that
   apply to each type of address in the RERR.




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8.4.4.1.  Address Block TLVs for PktSource

       +------------+---------------+-----------------+------------+
       | Data       | TLV Type      | Extension Type  | Value      |
       +------------+---------------+-----------------+------------+
       | PktSource  | ADDRESS_TYPE  | 0               | PKTSOURCE  |
       +------------+---------------+-----------------+------------+

8.4.4.2.  Address Block TLVs for Unreachable Addresses

   +----------------+--------------+------------+----------------------+
   | Data           | TLV Type     | Extension  | Value                |
   |                |              | Type       |                      |
   +----------------+--------------+------------+----------------------+
   | None           | ADDRESS_TYPE | 0          | UNREACHABLE          |
   | SeqNumList     | SEQ_NUM      | 0          | Sequence number      |
   |                |              |            | associated with      |
   |                |              |            | invalid route to the |
   |                |              |            | unreachable address. |
   | MetricTypeList | PATH_METRIC  | MetricType | None. Extension Type |
   |                |              |            | set to MetricType of |
   |                |              |            | the route to the     |
   |                |              |            | unreachable address. |
   +----------------+--------------+------------+----------------------+

9.  Simple External Network Attachment

   Figure 5 shows a stub (i.e., non-transit) network of AODVv2 routers
   which is attached to an external network via a single External
   Network Access Router (ENAR).  The interface to the external network
   MUST NOT be configured in the InterfaceSet.

   As in any externally-attached network, AODVv2 routers and Router
   Clients that wish to be reachable from the external network MUST have
   IP addresses within the ENAR's routable and topologically correct
   prefix (e.g., 191.0.2.0/24 in Figure 5).  This AODVv2 network and
   networks attached to routers within it will be advertised to the
   external network using procedures which are out of scope for this
   specification.












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       /-------------------------\
      / +----------------+        \
     /  |  AODVv2 Router |         \
     |  |  191.0.2.2/32  |         |
     |  +----------------+         |            Routable
     |                       +-----+--------+   Prefix
     |                       |     ENAR     |  /191.0.2.0/24
     |                       | AODVv2 Router| /
     |                       |  191.0.2.1   |/      /---------------\
     |                       | serving net  +------+    External     \
     |                       | 191.0.2.0/24 |      \     Network     /
     |                       +-----+--------+       \---------------/
     |         +----------------+  |
     |         |  AODVv2 Router |  |
     |         |  191.0.2.3/32  |  |
     \         +----------------+  /
      \                           /
       \-------------------------/

           Figure 5: Simple External Network Attachment Example

   When an AODVv2 router within the AODVv2 MANET wants to discover a
   route toward an address on the external network, it uses the normal
   AODVv2 route discovery for that IP Destination Address.

   The ENAR MUST respond to RREQ on behalf of all external network
   destinations, that is, destinations which are not on the configured
   191.0.2.0 /24 network.  The ENAR MUST NOT respond with a TargPrefix
   and TargPrefixLen which includes any of the networks configured as
   part of the AODVv2 network.  Sending a Route Request for a gateway is
   not currently supported.  If more than one gateway is configured to
   serve the same external network, each such gateway MUST configure
   that external network as a Router Client with its IP address as the
   value of SeqNoRtr for the RouterClient.

   RREQs for addresses inside the AODVv2 network, e.g. destinations on
   the configured 191.0.2.0/24 network, are handled using the standard
   processes described in Section 7.  Note that AODVv2 does not
   currently support route discovery for prefixes that do not equal
   address length, but RREPs do advertise the prefix on which TargAddr
   resides.

   When an IP packet from an address on the external network destined
   for an address in the AODVv2 MANET reaches the ENAR, if the ENAR does
   not have a route toward that destination in its Routing Information
   Base, it will perform normal AODVv2 route discovery for that
   destination.




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   Configuring the ENAR as a default router is outside the scope of this
   specification.

10.  Configuration

   AODVv2 uses various parameters which can be grouped into the
   following categories:

   o  Timers

   o  Protocol constants

   o  Administrative parameters and controls

   This section show the parameters along with their definitions and
   default values (if any).

   Note that several fields have limited size (bits or bytes).  These
   sizes and their encoding may place specific limitations on the values
   that can be set.

10.1.  Timers

   AODVv2 requires certain timing information to be associated with
   Local Route Set entries and message replies.  The default values are
   as follows:

                +------------------------+----------------+
                | Name                   | Default Value  |
                +------------------------+----------------+
                | ACTIVE_INTERVAL        | 5 second       |
                | MAX_IDLETIME           | 200 seconds    |
                | MAX_BLACKLIST_TIME     | 200 seconds    |
                | MAX_SEQNUM_LIFETIME    | 300 seconds    |
                | RERR_TIMEOUT           | 3 seconds      |
                | RteMsg_ENTRY_TIME      | 12 seconds     |
                | RREQ_WAIT_TIME         | 2 seconds      |
                | RREP_Ack_SENT_TIMEOUT  | 1 second       |
                | RREQ_HOLDDOWN_TIME     | 10 seconds     |
                +------------------------+----------------+

                     Table 2: Timing Parameter Values

   The above timing parameter values have worked well for small and
   medium well-connected networks with moderate topology changes.  The
   timing parameters SHOULD be administratively configurable.  Ideally,
   for networks with frequent topology changes the AODVv2 parameters
   SHOULD be adjusted using experimentally determined values or dynamic



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   adaptation.  For example, in networks with infrequent topology
   changes MAX_IDLETIME MAY be set to a much larger value.  If the
   values were configured differently, the following consequences may be
   observed:

   o  If MAX_SEQNUM_LIFETIME was configured differently across the
      network, and any of the routers lost their sequence number or
      rebooted, this could result in their next route messages being
      classified as stale at any AODVv2 router using a greater value for
      MAX_SEQNUM_LIFETIME.  This would delay route discovery from and to
      the re-initializing router.

   o  Routers with lower values for ACTIVE_INTERVAL + MAX_IDLETIME will
      invalidate routes more quickly and free resources used to maintain
      them.  This can affect bursty traffic flows which have quiet
      periods longer than ACTIVE_INTERVAL + MAX_IDLETIME.  A route which
      has timed out due to perceived inactivity is not reported.  When
      the bursty traffic resumes, it would cause a RERR to be generated,
      and the traffic itself would be dropped.  This route would be
      removed from all upstream routers, even if those upstream routers
      had larger ACTIVE_INTERVAL or MAX_IDLETIME values.  A new route
      discovery would be required to re-establish the route, causing
      extra routing protocol traffic and disturbance to the bursty
      traffic.

   o  Routers with lower values for MAX_BLACKLIST_TIME would allow
      neighboring routers to participate in route discovery sooner than
      routers with higher values.  This could result in failed route
      discoveries if un-blacklisted links are still uni-directional.
      Since RREQs are retried, this would not affect success of route
      discovery unless this value was so small as to un-blacklist the
      router before the RREQ is retried.  This value need not be
      consistent across the network since it is used for maintaining a
      1-hop blacklist.  However it MUST be greater than RREQ_WAIT_TIME.

   o  Routers with lower values for RERR_TIMEOUT may create more RERR
      messages than routers with higher values.  This value should be
      large enough that a RERR will reach all routers using the route
      reported within it before the timer expires, so that no further
      data traffic will arrive, and no duplicated RERR messages will be
      generated.

   o  Routers with lower values for RteMsg_ENTRY_TIME may not consider
      received redundant multicast route messages as redundant, and may
      forward these messages unnecessarily.

   o  Routers with lower values for RREQ_WAIT_TIME may send more
      frequent RREQ messages and wrongly determine that a route does not



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      exist, if the delay in receiving an RREP is greater than this
      interval.

   o  Routers with lower values for RREP_Ack_SENT_TIMEOUT may wrongly
      determine links to neighbors to be unidirectional if an RREP_Ack
      is delayed longer than this timeout.

   o  Routers with lower values for RREQ_HOLDDOWN_TIME will retry failed
      route discoveries sooner than routers with higher values.  This
      may be an advantage if the network topology is frequently
      changing, or may unnecessarily cause more routing protocol
      traffic.

   MAX_SEQNUM_LIFETIME MUST be configured to have the same values for
   all AODVv2 routers in the network.

10.2.  Protocol Constants

   AODVv2 protocol constants typically do not require changes.  The
   following table lists these constants, along with their values and a
   reference to the section describing their use.

   +------------------------+---------+--------------------------------+
   | Name                   | Default | Description                    |
   +------------------------+---------+--------------------------------+
   | DISCOVERY_ATTEMPTS_MAX | 3       | Section 6.6                    |
   | RREP_RETRIES           | 2       | Section 7.2.1                  |
   | MAX_METRIC[MetricType] | [TBD]   | Section 5                      |
   | MAX_METRIC[HopCount]   | 255     | Section 5 and Section 7        |
   | MAX_HOPCOUNT           | 20      | Limit to number of hops an     |
   |                        |         | RREQ or RREP message can       |
   |                        |         | traverse                       |
   | INFINITY_TIME          | [TBD]   | Maximum expressible clock time |
   |                        |         | (Section 6.7.2)                |
   +------------------------+---------+--------------------------------+

                         Table 3: AODVv2 Constants

   MAX_HOPCOUNT cannot be larger than 255.

   MAX_METRIC[MetricType] MUST always be the maximum expressible metric
   value of type MetricType.  Field lengths associated with metric
   values are found in Section 11.4.

   These protocol constants MUST have the same values for all AODVv2
   routers in the ad hoc network.  If the values were configured
   differently, the following consequences may be observed:




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   o  DISCOVERY_ATTEMPTS_MAX: Routers with higher values are likely to
      be more successful at finding routes, at the cost of additional
      control traffic.

   o  RREP_RETRIES: Routers with lower values are more likely to
      blacklist neighbors when there is a temporary fluctuation in link
      quality.

   o  MAX_METRIC[MetricType]: No interoperability problems due to
      variations on different routers, but routers with lower values may
      exhibit overly restrictive behavior during route comparisons.

   o  MAX_HOPCOUNT: Routers with a value too small would not be able to
      discover routes to distant addresses.

   o  INFINITY_TIME: No interoperability problems due to variations on
      different routers, but if a lower value is used, route state
      management may exhibit overly restrictive behavior.

10.3.  Local Settings

   The following table lists AODVv2 parameters which SHOULD be
   administratively configured for each router:

    +------------------------+------------------------+--------------+
    | Name                   | Default Value          | Description  |
    +------------------------+------------------------+--------------+
    | InterfaceSet           |                        | Section 4.1  |
    | Router Client Set      |                        | Section 4.2  |
    | BUFFER_SIZE_PACKETS    | 2                      | Section 6.6  |
    | BUFFER_SIZE_BYTES      | MAX_PACKET_SIZE [TBD]  | Section 6.6  |
    | CONTROL_TRAFFIC_LIMIT  | [TBD - 50 pkts/sec?]   | Section 7    |
    +------------------------+------------------------+--------------+

                 Table 4: Configuration for Local Settings

10.4.  Network-Wide Settings

   The following administrative controls MAY be used to change the
   operation of the network.  The same settings SHOULD be used across
   the network.  Inconsistent settings at different routers in the
   network will not result in protocol errors, but poor performance may
   result.








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           +----------------------+-----------+----------------+
           | Name                 | Default   | Description    |
           +----------------------+-----------+----------------+
           | ENABLE_IDLE_IN_RERR  | Disabled  | Section 7.4.1  |
           +----------------------+-----------+----------------+

             Table 5: Configuration for Network-Wide Settings

11.  IANA Considerations

   This section specifies several [RFC5444] message types and address
   tlv-types required for AODVv2.

11.1.  RFC 5444 Message Type Allocation

   This specification defines four Message Types, to be allocated from
   the 0-223 range of the "Message Types" namespace defined in
   [RFC5444].

          +-----------------------------------------+-----------+
          | Name of Message                         | Type      |
          +-----------------------------------------+-----------+
          | Route Request (RREQ)                    | 10 (TBD)  |
          | Route Reply (RREP)                      | 11 (TBD)  |
          | Route Error (RERR)                      | 12 (TBD)  |
          | Route Reply Acknowledgement (RREP_Ack)  | 13 (TBD)  |
          +-----------------------------------------+-----------+

11.2.  RFC 5444 Message TLV Types

   This specification defines one Message TLV Type, to be allocated from
   the Message-Type-specific "Message TLV Types" namespace defined in
   [RFC5444], as specified in Table 6.

   +------------------------+----------+---------------+---------------+
   | Name of TLV            | Type     | Length        | Reference     |
   |                        |          | (octets)      |               |
   +------------------------+----------+---------------+---------------+
   | ACK_REQ                | 128      | 0             | Section 6.2   |
   |                        | (TBD)    |               |               |
   +------------------------+----------+---------------+---------------+

                     Table 6: AODVv2 Message TLV Types








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11.3.  RFC 5444 Address Block TLV Type Allocation

   This specification defines three Address Block TLV Types, to be
   allocated from the Message-Type-specific "Address Block TLV Types"
   namespace defined in [RFC5444], as specified in Table 7.

   +------------------------+----------+---------------+---------------+
   | Name of TLV            | Type     | Length        | Reference     |
   |                        |          | (octets)      |               |
   +------------------------+----------+---------------+---------------+
   | PATH_METRIC            | 129      | depends on    | Section 7     |
   |                        | (TBD)    | MetricType    |               |
   | SEQ_NUM                | 130      | 2             | Section 7     |
   |                        | (TBD)    |               |               |
   | ADDRESS_TYPE           | 131      | 1             | Section 8     |
   |                        | (TBD)    |               |               |
   +------------------------+----------+---------------+---------------+

                  Table 7: AODVv2 Address Block TLV Types

11.4.  MetricType Allocation

   The metric types used by AODVv2 are identified according to Table 8.
   All implementations MUST use these values.

          +---------------------+----------+--------------------+
          | Name of MetricType  | Type     | Metric Value Size  |
          +---------------------+----------+--------------------+
          | Unassigned          | 0        | Undefined          |
          | Hop Count           | 1        | 1 octet            |
          | Unallocated         | 2 - 254  | TBD                |
          | Reserved            | 255      | Undefined          |
          +---------------------+----------+--------------------+

                       Table 8: AODVv2 Metric Types

11.5.  ADDRESS_TYPE TLV Values

   These values are used in the [RFC5444] Address Type TLV discussed in
   Section 8.  All implementations MUST use these values.











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                        +---------------+--------+
                        | Address Type  | Value  |
                        +---------------+--------+
                        | ORIGPREFIX    | 0      |
                        | TARGPREFIX    | 1      |
                        | UNREACHABLE   | 2      |
                        | PKTSOURCE     | 3      |
                        | UNSPECIFIED   | 255    |
                        +---------------+--------+

                       Table 9: AODVv2 Address Types

12.  Security Considerations

   This section describes various security considerations and potential
   avenues to secure AODVv2 routing.  The main objective of the AODVv2
   protocol is for each router to communicate reachability information
   about addresses for which it is responsible, and for routes it has
   learned from other AODVv2 routers.

   Networks using AODVv2 to maintain connectivity and establish routes
   on demand may be vulnerable to certain well-known types of threats,
   which will be detailed in this section.  Some of the threats
   described can be mitigated or eliminated.  Tools to do so will be
   described.

   With the exception of metric values, AODVv2 assures the integrity of
   all RteMsg data end-to-end though the use of ICVs (see
   Section 12.4.2.

   The on-demand nature of AODVv2 route discovery automatically reduces
   the vulnerability to route disruption.  Since control traffic for
   updating route tables is diminished, there is less opportunity for
   attack and failure.

12.1.  Availability

   Threats to AODVv2 which reduce availability are considered below.

12.1.1.  Denial of Service

   Flooding attacks using RREQ amount to a (BLIND) denial of service for
   route discovery: By issuing RREQ messages for targets that don't
   exist, an attacker can flood the network, blocking resources and
   drowning out legitimate traffic.  By triggering the generation of
   CONTROL_TRAFFIC_LIMIT amount of messages (for example by sending
   RREQs for many non-existent destinations), an attacker can prevent
   legitimate messages from being generated.  The effect of this attack



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   is dampened by the fact that duplicate RREQ messages are dropped
   (preventing the network from DDoSing itself).  Processing
   requirements for AODVv2 messages are typically quite small, however
   AODVv2 routers receiving RREQs do allocate resources in the form of
   Neighbor Set, Local Route Set and Multicast Route Message Set
   entries.  The attacker can maximize their impact on set growth by
   changing OrigPrefix or OrigPrefixLen for each RREQ.  If a specific
   node is to be targeted, this attack may be carried out in a
   DISTRIBUTED fashion, either by compromising its direct neighbors or
   by specifying the target's address with TargPrefix and TargPrefixLen.
   Note that it might be more economical for the attacker to simply jam
   the medium; an attack which AODVv2 cannot defend itself against.

   Mitigation:

   o  If AODVv2 routers always verify that the sender of the RERR
      message is trusted, this threat is reduced.  Processing
      requirements would typically be dominated by calculations to
      verify integrity.  This has the effect of reducing (but by no
      means eliminating) AODVv2's vulnerability to denial of service
      attacks.

   o  Authentication of senders can prevent unauthenticated routers from
      launching a Denial of Service attack on another AODVv2 router.
      However, this does not protect the network if an attacker has
      access to an already authenticated router.

12.1.2.  Malicious RERR messages

   RERR messages are designed to cause removal of installed routes.  A
   malicious node could send an RERR message with false information to
   attempt to get other routers to remove a route to one or more
   specific destinations, therefore disrupting traffic to the advertised
   destinations.

   Routes will be deleted if an RERR is received, withdrawing a route
   for which the sender is the receiver's next hop, under the following
   conditions:

   o  when the RERR includes the MetricType of the installed route,

   o  includes either no sequence number for the route, or includes a
      greater sequence number than the sequence number stored with that
      route in the receiver's Local Route Set.

   Routes will also be deleted if a received RERR contains a PktSource
   address corresponding to a Router Client.




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   The information necessary to construct a malicious RERR could be
   learned by eavesdropping, either by listening to AODVv2 messages or
   by watching data packet flows.

   When the RERR is multicast, it can be received by many routers in the
   ad hoc network, and will be regenerated when processing results in an
   active route being removed.  This threat could have serious impact on
   applications communicating by way of the sender of the RERR message.

   o  The set of routers which use the malicious router as a next hop
      may be targeted with a malicious RERR with no PktSource address
      included, if the RERR contains routes for which the malicious
      router is a next hop from the receiving router.  However, since
      the sender of the RERR message is either malicious or broken, it
      is better that it is not used as a next hop for these routes
      anyway.

   o  A single router which does not use the malicious router as part of
      its route may be targeted with a malicious RERR with a PktSource
      address included.

   o  Replayed RERR messages could be used to disrupt active routes.

   Mitigation:

   o  Protection against eavesdropping of AODVv2 messages would mitigate
      this attack to some extent, but eavesdropping of data packets can
      also be used to deduce the information about which routes could be
      targeted.

   o  Protection against a malicious router becoming part of a route
      will mitigate the attack where a set of routers are targeted.
      This will not protect against the attack if a PktSource address is
      included.

   o  By only regenerating RERR messages where active routes are
      removed, the spread of the malicious RERR is limited.

   o  Including sequence numbers in RERR messages offers protection
      against attacks using replays of these RERR messages.

   o  If AODVv2 routers always verify that the sender of the RERR
      message is trusted, this threat is reduced.








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12.1.3.  False Confirmation of Link Bidirectionality

   Links could be erroneously treated as bidirectional if malicious
   unsolicited or spoofed RREP messages were to be accepted.  This would
   result in a route being installed which could not in fact be used to
   forward data to the destination, and may divert data packets away
   from the intended destination.

   There is a window of RREQ_WAIT_TIME after an RREQ is sent, in which
   any malicious router could send an RREP in response, in order for the
   link to the malicious router to be deemed as bidirectional.

   Mitigation:

   o  Ignoring unsolicited RREP and RREP_Ack messages partially
      mitigates against this threat.

   o  If AODVv2 routers always verify that the sender of the RREP
      message is trusted, this threat is reduced.

12.1.4.  Message Deletion

   A malicious router could decide not to forward an RREQ or RREP or
   RERR message.  Not forwarding a RERR or RREP message would disrupt
   route discovery.  Not regenerating a RERR message would result in the
   source of data packets continuing to maintain and use the route, and
   further RERR messages being generated by the sender of the non-
   regenerated RERR.  A malicious router could intentionally disrupt
   traffic flows by not allowing the source of data traffic to re-
   discover a new route when one breaks.

   Failing to send an RREP_Ack would also disrupt route establishment,
   by not allowing the reverse route to be validated.  Return traffic
   which needs that route will prompt a new route discovery, wasting
   resources and incurring a slight delay but not disrupting the ability
   for applications to communicate.

   Mitigation:

   o  None.  Note that malicious router would have to wait for a route
      to break before it could perform this attack.

12.2.  Confidentiality

   Passive inspection (eavesdropping) of AODVv2 control messages could
   enable unauthorized devices to gain information about the network
   topology, since exchanging such information is the main purpose of
   AODVv2.



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   Eavesdropping of data traffic could allow a malicious device to
   obtain information about how data traffic is being routed.  With
   knowledge of source and destination addresses, malicious messages
   could be constructed to disrupt normal operation.

12.3.  Integrity of Routes

   Integrity of route information can be compromised in the following
   types of attack:

12.3.1.  Message Insertion

   Valid route set entries can be replaced or modified by maliciously
   constructed AODVv2 messages, destroying existing routes and the
   network's integrity.  Any router may pose as another router by
   sending RREQ, RREP, RREP_Ack and RERR messages in its name.

   o  Sending an RREQ message with false information can disrupt traffic
      to OrigPrefix, if the sequence number attached is not stale
      compared to any existing information about OrigPrefix.  Since RREQ
      is multicast and likely to be received by all routers in the ad
      hoc network, this threat could have serious impact on applications
      communicating with OrigPrefix.

   o  The actual threat to disrupt routes to OrigPrefix is reduced by
      the AODVv2 mechanism of marking RREQ-derived routes as
      "Unconfirmed" until the route to OrigAddr can be confirmed.

   o  Sending an RREP message with false information can disrupt traffic
      to TargPrefix.  Since RREP is unicast, and ignored if a
      corresponding RREQ was not recently sent, this threat is
      minimized, and is restricted to receivers along the path from
      OrigAddr to TargAddr.

   o  Sending an RREP_Ack response message with false information can
      cause the route to an originator address to be erroneously
      accepted even though the route would contain a unidirectional link
      and thus not be suitable for most traffic.  Since the RREP_Ack
      response is unicast, and ignored if a RREP_Ack was not sent
      recently to the sender of this RREP_Ack response, this threat is
      minimized and is strictly local to the RREP transmitter expecting
      the acknowledgement.  Unsolicited RREP_Acks are ignored.

   o  Sending an RERR message with false information is discussed in
      Section 12.1.2.

   Mitigation:




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   o  If AODVv2 routers always verify that the sender of a message is
      trusted, this threat is reduced.

12.3.2.  Message Modification - Man in the Middle

   Any AODVv2 router can forward messages with modified data.

   Mitigation:

   o  If AODVv2 routers verify the integrity of AODVv2 messages, then
      the threat of disruption is minimized.  A man in the middle with
      no knowledge of the key used to calculate an integrity check value
      may modify a message but the message will be rejected when it
      fails an integrity check.

12.3.3.  Replay Attacks

   Replaying of RREQ or RREP messages would be of less use to an
   attacker, since they would be dropped immediately due to their stale
   sequence number.  RERR messages may or may not include sequence
   numbers and are therefore susceptible to replay attacks.  RREP_Ack
   messages do not include sequence numbers and are therefore
   susceptible to replay attacks.

   Mitigation:

   o  Use of timestamps or sequence numbers prevents replay attacks.

12.4.  Protection Mechanisms

12.4.1.  Confidentiality and Authentication

   Encryption MAY be used for AODVv2 messages.  If the routers share a
   packet-level security association, the message data can be encrypted
   prior to message transmission.  The establishment of such security
   associations is outside the scope of this specification.  Encryption
   will not only protect against unauthorized devices obtaining
   information about network topology (eavesdropping) but will ensure
   that only trusted routers participate in routing operations.

12.4.2.  Message Integrity using ICVs

   Cryptographic Integrity Check Values (ICVs) can be used to ensure
   integrity of received messages, protecting against man in the middle
   attacks.  Further, by using ICVs, only those routers with knowledge
   of a shared secret key are allowed to participate in routing
   information exchanges.  [RFC7182] defines ICV TLVs for use with
   [RFC5444].



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   The data contained in AODVv2 routing protocol messages MUST be
   verified using Integrity Check Values, to avoid accepting tampered
   messages.

12.4.3.  Replay Protection using Timestamps

   [RFC7182] defines a TIMESTAMP TLV for use with [RFC5444] which can be
   used to prevent replay attacks when sequence numbers are not already
   included.

   The data contained in AODVv2 routing protocol messages must be
   protected with a TIMESTAMP value to ensure the protection against
   replaying of the message.  Sequence numbers can be used as
   timestamps, since they are known to be strictly increasing.

12.4.4.  Application to AODVv2

   AODVv2 implementations MUST support ICV and TIMESTAMP TLVs, unless
   the implementation is intended solely for an environment in which
   security is unnecessary.  AODVv2 deployments SHOULD be configured to
   use these TLVs to secure messages.

   Implementations of AODVv2 MUST support ICV TLVs using type-extensions
   1 and 2, hash-function HASH_FUNCTION, and cryptographic function
   CRYPTOGRAPHIC_FUNCTION.  An ICV MUST be included with every message.
   The ICV value MAY be truncated as specified in [RFC7182].

   Since the msg-hop-limit and PATH_METRIC values are mutable when
   included in AODVv2 messages, these values are set to zero before
   calculating an ICV.  This means that these values are not protected
   end-to-end and are therefore susceptible to manipulation.  This form
   of attack is described in Section 12.3.2.

   Implementations of AODVv2 MUST support a TIMESTAMP TLV using type-
   extension 0.  The timestamp used is a sequence number, and therefore
   the length of the <TIMESTAMP-value> field matches the AODVv2 sequence
   number defined in Section 4.4.  The TIMESTAMP TLV MUST be included in
   RREP_Ack and RERR messages.

   When more than one message is included in an RFC5444 packet, using a
   single ICV Packet TLV or single TIMESTAMP Packet TLV is more
   efficient than including ICV and TIMESTAMP Message TLVs in each
   message created.  If the RFC5444 multiplexer is capable of adding the
   Packet TLVs, it SHOULD be instructed to include the Packet TLVs in
   packets containing AODVv2 messages.  However, if the multiplexer is
   not capable of adding the Packet TLVs, the TLVs MUST be included as
   Message TLVs in each AODVv2 message in the packet.




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   After message generation but before transmission, the ICV and
   TIMESTAMP TLVs MUST be added according to each message type as
   detailed in the following sections.  The following steps list the
   procedure to be performed:

   1.  If the TIMESTAMP is to be included, depending on AODVv2 message
       type as specified below, add the TIMESTAMP TLV.

   o  When a TIMESTAMP Packet TLV is being added, the Packet TLV Block
      size field MUST be updated.

   o  When a TIMESTAMP Message TLV is being added, the Message TLV Block
      size field MUST be updated.

   1.  The considerations in Section 8 and section 9 of [RFC7182] are
       followed, removing existing ICV TLVs and adjusting the size and
       flags fields as appropriate:

   o  When an ICV Packet TLV is being added, existing ICV Packet TLVs
      MUST be removed and the Packet TLV Block size MUST be updated.  If
      the Packet TLV Block now contains no TLVs, the phastlv bit in the
      <pkt-flags> field in the Packet Header MUST be cleared.

   o  When an ICV Message TLV is being added, existing ICV Message TLVs
      are removed and the Message TLV Block Size MUST be updated.

   1.  Mutable fields in the message must have their mutable values set
       to zero before calculating the ICV.

   o  If the msg-hop-limit field is included in the [RFC5444] message
      header, msg-hop-limit MUST be set to zero before calculating the
      ICV.

   o  If a PATH_METRIC TLV is included, any values present in the TLV
      MUST be set to zero before calculating the ICV value.

   1.  Depending on the message type, the ICV is calculated over the
       appropriate fields (as specified in sections Section 12.4.4.1,
       Section 12.4.4.2, Section 12.4.4.3 and Section 12.4.4.4) to
       include the fields <hash-function>, <cryptographic-function>,
       <key-id-length>, and, if present, <key-id> (in that order),
       followed by the entire packet or message.  This value MAY be
       truncated (as specified in [RFC7182]).

   2.  Add the ICV TLV, updating size fields as necessary.






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   3.  The changes made in Step 2 and Step 3 are reversed to re-add any
       existing ICV TLVs, re-adjust the relevant size and flags fields,
       and set the msg-hop-limit and PATH_METRIC TLV values.

   On message reception, and before message processing, verification of
   the received message MUST take place:

   1.  The considerations in Section 8 and Section 9 of [RFC7182] are
       followed, removing existing ICV TLVs and adjusting the size and
       flags fields as appropriate.

   o  When verifying the ICV value in an ICV Packet TLV, all ICV Packet
      TLVs present in the Packet TLV Block MUST be removed before
      calculating the ICV, and the Packet TLV Block size MUST be
      updated.  If there are no remaining Packet TLVs, the Packet TLV
      Block MUST be removed and the phastlv bit in the <pkt-flags> field
      MUST be cleared.

   o  When verifying the ICV value in an ICV Message TLV, all ICV
      Message TLVs present in the Message TLV Block MUST be removed
      before calculating the ICV, and the Message TLV Block size MUST be
      updated.

   1.  Mutable fields in the message MUST have their mutable values set
       to zero before calculating the ICV.

   o  If the msg-hop-limit field is included in the [RFC5444] message
      header, msg-hop-limit MUST be set to zero before calculating the
      ICV.

   o  If a PATH_METRIC TLV is included, any values present in the TLV
      MUST be set to zero before calculating the ICV value.

   1.  The ICV is calculated following the considerations in
       Section 12.2 of [RFC7182], to include the fields <hash-function>,
       <cryptographic-function>, <key-id-length>, and, if present, <key-
       id> (in that order), followed by the entire packet or message.

   o  If the received ICV value is truncated, the calculated ICV value
      MUST also be truncated (as specified in [RFC7182]), before
      comparing.

   o  If the ICV value calculated from the received message or packet
      does not match the value of <ICV-data> in the received message or
      packet, the validation fails and the AODVv2 message MUST be
      discarded and NOT processed or forwarded.





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   o  If the ICV values do match, the values set to zero before
      calculating the ICV are reset to the received values, and
      processing continues to Step 4.

   1.  Verification of a received TIMESTAMP value MUST be performed.
       The procedure depends on message type as specified in the
       following sub sections.

   o  If the TIMESTAMP value in the received message is not valid, the
      AODVv2 message MUST be discarded and NOT processed or forwarded.

   o  If the TIMESTAMP value is valid, processing continues as defined
      in Section 7.

12.4.4.1.  RREQ Generation and Reception

   Since OrigPrefix is included in the RREQ, the ICV can be calculated
   and verified using the [RFC5444] contents.The ICV TLV has type
   extension := 1.  Inclusion of an ICV TLV message integrity and
   endpoint authentication, because trusted routers MUST hold the shared
   key in order to calculate the ICV value, both to include when
   creating a message, and to validate the message by checking that the
   ICV is correct.

   Since RREQ_Gen's sequence number is incremented for each new RREQ,
   replay protection is already afforded and no extra TIMESTAMP TLV is
   required.

   After message generation and before message transmission:

   1.  Add the ICV TLV as described above.

   On message reception and before message processing:

   1.  Verify the received ICV value as described above.

   2.  Verification of the sequence number is handled according to
       Section 7.

12.4.4.2.  RREP Generation and Reception

   Since TargPrefix is included in the RREP, the ICV can be calculated
   and verified using the [RFC5444] contents.  The ICV TLV has type
   extension 1.  Inclusion of an ICV provides message integrity and
   endpoint authentication, because trusted routers MUST hold a valid
   key in order to calculate the ICV value, both to include when
   creating a message, and to validate the message by checking that the
   ICV is correct.



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   Since RREP_Gen's sequence number is incremented for each new RREP,
   replay protection is already afforded and no extra TIMESTAMP TLV is
   required.

   After message generation and before message transmission:

   1.  Add the ICV TLV as described above.

   On message reception and before message processing:

   1.  Verify the received ICV value as described above.

   2.  Verification of the sequence number is handled according to
       Section 7.

12.4.4.3.  RREP_Ack Generation and Reception

   Since no sequence number is included in the RREP_Ack, a TIMESTAMP TLV
   MUST be included to protect against replay attacks.  The value in the
   TIMESTAMP TLV is set as follows:

   o  For RREP_Ack request, use Neighbor.AckSeqNum.

   o  For RREP_Ack response, use the sequence number from the TIMESTAMP
      TLV in the received RREP_Ack request.

   Since no addresses are included in the RREP_Ack, and the receiver of
   the RREP_Ack uses the source IP address of a received RREP_Ack to
   identify the sender, the ICV MUST be calculated using the message
   contents and the IP source address.  The ICV TLV has type extension
   := 2 in order to accomplish this.  This provides message integrity
   and endpoint authentication, because trusted routers MUST hold the
   correct key in order to calculate the ICV value.

   After message generation and before message transmission:

   1.  Add the TIMESTAMP TLV and ICV TLV as described above.

   On message reception and before message processing:

   1.  Verify the received ICV value as described above.

   2.  Verify the received TIMESTAMP value by comparing the sequence
       number in the value field of the TIMESTAMP TLV as follows:

   o  For a received RREP_Ack request, there is no need to verify the
      timestamp value.  Proceed to message processing as defined in
      Section 7.



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   o  For a received RREP_Ack response, compare with the
      Neighbor.AckSeqNum of the Neighbor Set entry for sender of the
      RREP_Ack request.

   o  If the sequence number does not match, the AODVv2 message MUST be
      discarded.  Otherwise, Neighbor.AckSeqNum is incremented by 1 and
      processing continues according to Section 7.

12.4.4.4.  RERR Generation and Reception

   Since the sender's sequence number is not contained in the RERR, a
   TIMESTAMP TLV MUST be included to protect against replay attacks.
   The value in the TIMESTAMP TLV is set by incrementing and using
   RERR_Gen's sequence number.

   Since the receiver of the RERR MUST use the source IP address of the
   RERR to identify the sender, the ICV MUST be calculated using the
   message contents and the IP source address.  The ICV TLV has type
   extension := 2 in order to accomplish this.  This provides message
   integrity and endpoint authentication, because trusted routers MUST
   hold the shared key in order to calculate the ICV value.

   After message generation and before message transmission:

   1.  Add the TIMESTAMP TLV and ICV TLV as described above.

   On message reception and before message processing:

   1.  Verify the received ICV value as described above.

   2.  Verify the received TIMESTAMP value by comparing the sequence
       number in the value field of the TIMESTAMP TLV with the
       Neighbor.HeardRERRSeqNum.  If the sequence number in the message
       is lower than the stored value, the AODVv2 message MUST be
       discarded.  Otherwise, the Neighbor.HeardRERRSeqNum MUST be set
       to the received value and processing continues according to
       Section 7.

12.5.  Key Management

   The method of distribution of shared secret keys is out of the scope
   of this protocol.  Key management is not specified for the following
   reasons:

   Against [RFC4107], an analysis as to whether automated or manual key
   management should be used shows a compelling case for automated
   management.  In particular:




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   o  a potentially large number of routers may have to be managed,
      belonging to several organisations, for example in vehicular
      applications.

   o  a stream cipher is likely to be used, such as an AES variant.

   o  long term session keys might be used by more than two parties,
      including multicast operations.  AODVv2 makes extensive use of
      multicast.

   o  there may be frequent turnover of devices.

   On reviewing the case for manual key management against the same
   document, it can be seen that manual management might be advantageous
   in environments with limited bandwidth or high round trip times.
   AODVv2 lends itself to sparse ad hoc networks where transmission
   conditions may indeed be limited, depending on the bearers selected
   for use.

   However, [RFC4107] assumes that the connectivity between endpoints is
   already available.  In AODVv2, no route is available to a given
   destination until a router client requests that user traffic be
   transmitted.  It is required to secure the signalling path of the
   routing protocol that will establish the path across which key
   exchange functions might subsequently be applied, which is clearly
   the reverse of the expected functionality.  A different strategy is
   therefore required.

   There are two possible solutions.  In each case, it is assumed that a
   defence in depth security posture is being adopted by the system
   integrator, such that each function in the network as a whole is
   appropriately secured or defended as necessary, and that there is not
   complete reliance on security mechanisms built in to AODVv2.  Such
   additional mechanisms could include a suitable wireless device
   security technology, so that wireless devices are authenticated and
   secured by their peers prior to exchanging user data, which in this
   case would include AODVV2 signalling traffic as a payload, and
   mechanisms which verify the authenticity and/or integrity of
   application-layer user data transported once a route has been
   established.

   1.  In the case that no AODVv2 routers have any detailed prior
       knowledge of any other AODVv2 router, but does have knowledge of
       the credentials of other organisations in which the router has
       been previously configured to trust, it is possible for an AODVv2
       router to send an initialisation vector as part of an exchange,
       which could be verified against such credentials.  Such an
       exchange could make use of Identity-Based Signatures



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       ([I-D.ietf-manet-ibs]), based on Elliptic Curve-Based
       Certificateless Signatures for Identity-Based Encryption
       [RFC6507], which eliminate the need for a handshake process to
       establish trust.

   2.  If it is impossible to use Identity-Based Signatures, and the
       risk to the AODVv2 signalling traffic is considered to be low due
       to the use of security countermeasures elsewhere in the system, a
       simple pre-placed shared secret could be used between routers,
       which is used as-is or is used to generate some ephemeral secret
       based on another known variable, such as time of day if that is
       universally available at a level of accuracy sufficient to make
       such a system viable.

13.  Acknowledgments

   AODVv2 is a descendant of the design of previous MANET on-demand
   protocols, especially AODV [RFC3561] and DSR [RFC4728].  Changes to
   previous MANET on-demand protocols stem from research and
   implementation experiences.  Thanks to Elizabeth Belding and Ian
   Chakeres for their long time authorship of AODV.  Additional thanks
   to Derek Atkins, Emmanuel Baccelli, Abdussalam Baryun, Ramon Caceres,
   Justin Dean, Christopher Dearlove, Fatemeh Ghassemi, Ulrich Herberg,
   Henner Jakob, Ramtin Khosravi, Luke Klein-Berndt, Lars Kristensen,
   Tronje Krop, Koojana Kuladinithi, Kedar Namjoshi, Keyur Patel,
   Alexandru Petrescu, Henning Rogge, Fransisco Ros, Pedro Ruiz,
   Christoph Sommer, Romain Thouvenin, Richard Trefler, Jiazi Yi, Seung
   Yi, Behnaz Yousefi, and Cong Yuan, for their reviews of AODVv2 and
   DYMO, as well as numerous specification suggestions.

14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3561]  Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
              Demand Distance Vector (AODV) Routing", RFC 3561,
              DOI 10.17487/RFC3561, July 2003,
              <http://www.rfc-editor.org/info/rfc3561>.

   [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized Mobile Ad Hoc Network (MANET) Packet/Message
              Format", RFC 5444, DOI 10.17487/RFC5444, February 2009,
              <http://www.rfc-editor.org/info/rfc5444>.



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   [RFC5498]  Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
              (MANET) Protocols", RFC 5498, DOI 10.17487/RFC5498, March
              2009, <http://www.rfc-editor.org/info/rfc5498>.

   [RFC7182]  Herberg, U., Clausen, T., and C. Dearlove, "Integrity
              Check Value and Timestamp TLV Definitions for Mobile Ad
              Hoc Networks (MANETs)", RFC 7182, DOI 10.17487/RFC7182,
              April 2014, <http://www.rfc-editor.org/info/rfc7182>.

14.2.  Informative References

   [I-D.ietf-manet-ibs]
              Dearlove, C., "Identity-Based Signatures for MANET Routing
              Protocols", draft-ietf-manet-ibs-05 (work in progress),
              March 2016.

   [Koodli01]
              Koodli, R. and C. Perkins, "Fast handovers and context
              transfers in mobile networks", Proceedings of the ACM
              SIGCOMM Computer Communication Review 2001, Volume 31
              Issue 5, 37-47, October 2001.

   [Perkins94]
              Perkins, C. and P. Bhagwat, "Highly Dynamic Destination-
              Sequenced Distance-Vector Routing (DSDV) for Mobile
              Computers", Proceedings of the ACM SIGCOMM '94 Conference
              on Communications Architectures, Protocols and
              Applications, London, UK, pp. 234-244, August 1994.

   [RFC2501]  Corson, S. and J. Macker, "Mobile Ad hoc Networking
              (MANET): Routing Protocol Performance Issues and
              Evaluation Considerations", RFC 2501,
              DOI 10.17487/RFC2501, January 1999,
              <http://www.rfc-editor.org/info/rfc2501>.

   [RFC4107]  Bellovin, S. and R. Housley, "Guidelines for Cryptographic
              Key Management", BCP 107, RFC 4107, DOI 10.17487/RFC4107,
              June 2005, <http://www.rfc-editor.org/info/rfc4107>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
              <http://www.rfc-editor.org/info/rfc4193>.

   [RFC4728]  Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
              Routing Protocol (DSR) for Mobile Ad Hoc Networks for
              IPv4", RFC 4728, DOI 10.17487/RFC4728, February 2007,
              <http://www.rfc-editor.org/info/rfc4728>.




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   [RFC6130]  Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
              Network (MANET) Neighborhood Discovery Protocol (NHDP)",
              RFC 6130, DOI 10.17487/RFC6130, April 2011,
              <http://www.rfc-editor.org/info/rfc6130>.

   [RFC6507]  Groves, M., "Elliptic Curve-Based Certificateless
              Signatures for Identity-Based Encryption (ECCSI)",
              RFC 6507, DOI 10.17487/RFC6507, February 2012,
              <http://www.rfc-editor.org/info/rfc6507>.

Appendix A.  AODVv2 Draft Updates

   This section lists the changes between AODVv2 revisions ...-16.txt
   and ...-17.txt.

   o  Removed wording that suggested RREP_Gen could add multiple
      (unrelated) subnets.

   o  Changed wording in accordance with decision to pursue Proposed
      Standard.

   o  Resolved an error scenario that was based on confirming routes to
      OrigAddr before the route to OrigAddr was known to be operational.
      But, another AODVv2 router closer to OrigAddr might forward
      packets along a previously confirmed route with an obsolete
      Sequence Number.  These two conditions together were found to
      allow for routing loops.

   o  Enabled multihoming by creating new address type SeqNoRtr, along
      with rules prohibiting comparison of sequence numbers from
      distinct multihoming routers per advertised prefix.

Authors' Addresses

   Charles E. Perkins
   Futurewei Inc.
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Phone: +1-408-330-4586
   Email: charliep@computer.org









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   Stan Ratliff
   Idirect
   13861 Sunrise Valley Drive, Suite 300
   Herndon, VA  20171
   USA

   Email: ratliffstan@gmail.com


   John Dowdell
   Airbus Defence and Space
   Celtic Springs
   Newport, Wales  NP10 8FZ
   United Kingdom

   Email: john.dowdell@airbus.com


   Lotte Steenbrink
   HAW Hamburg, Dept. Informatik
   Berliner Tor 7
   D-20099 Hamburg
   Germany

   Email: lotte.steenbrink@haw-hamburg.de


   Victoria Mercieca
   Airbus Defence and Space
   Celtic Springs
   Newport, Wales  NP10 8FZ
   United Kingdom

   Email: victoria.mercieca@airbus.com

















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