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Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                           Motorola
Internet-Draft                                                C. Perkins
Intended status: Standards Track
Expires: October 12, 2008                                 April 10, 2008


                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-13

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on October 12, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   The Dynamic MANET On-demand (DYMO) routing protocol is intended for
   use by mobile nodes in wireless, multihop networks.  DYMO determines
   unicast routes among DYMO routers within the network in an on-demand
   fashion, offering improved convergence in dynamic topologies.






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Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Data Structures  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Route Table Entry  . . . . . . . . . . . . . . . . . . . .  7
     4.2.  DYMO Messages  . . . . . . . . . . . . . . . . . . . . . .  8
       4.2.1.  Generalized Packet and Message Structure . . . . . . .  8
       4.2.2.  Routing Messages (RM) - RREQ & RREP  . . . . . . . . .  9
       4.2.3.  Route Error (RERR) . . . . . . . . . . . . . . . . . . 12
   5.  Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 14
     5.1.  DYMO Sequence Numbers  . . . . . . . . . . . . . . . . . . 14
       5.1.1.  Maintaining A Node's Own Sequence Number . . . . . . . 15
       5.1.2.  Numerical Operations on OwnSeqNum  . . . . . . . . . . 15
       5.1.3.  OwnSeqNum Rollover . . . . . . . . . . . . . . . . . . 15
       5.1.4.  Actions After OwnSeqNum Loss . . . . . . . . . . . . . 15
     5.2.  DYMO Routing Table Operations  . . . . . . . . . . . . . . 15
       5.2.1.  Judging Routing Information's Usefulness . . . . . . . 16
       5.2.2.  Creating or Updating a Route Table Entry with
               Received Superior Routing Information  . . . . . . . . 17
       5.2.3.  Route Table Entry Timeouts . . . . . . . . . . . . . . 18
     5.3.  Routing Messages . . . . . . . . . . . . . . . . . . . . . 19
       5.3.1.  RREQ Creation  . . . . . . . . . . . . . . . . . . . . 19
       5.3.2.  RREP Creation  . . . . . . . . . . . . . . . . . . . . 20
       5.3.3.  Intermediate DYMO Router RREP Creation . . . . . . . . 20
       5.3.4.  RM Processing  . . . . . . . . . . . . . . . . . . . . 21
       5.3.5.  Adding Additional Routing Information to a RM  . . . . 24
     5.4.  Route Discovery  . . . . . . . . . . . . . . . . . . . . . 24
     5.5.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . 25
       5.5.1.  Active Link Monitoring . . . . . . . . . . . . . . . . 26
       5.5.2.  Updating Route Lifetimes During Packet Forwarding  . . 26
       5.5.3.  RERR Generation  . . . . . . . . . . . . . . . . . . . 26
       5.5.4.  RERR Processing  . . . . . . . . . . . . . . . . . . . 27
     5.6.  Unknown Message & TLV Types  . . . . . . . . . . . . . . . 28
     5.7.  Advertising Network Addresses  . . . . . . . . . . . . . . 28
     5.8.  Simple Internet Attachment . . . . . . . . . . . . . . . . 28
     5.9.  Multiple Interfaces  . . . . . . . . . . . . . . . . . . . 30
     5.10. DYMO Control Packet/Message Generation Limits  . . . . . . 30
   6.  Configuration Parameters and Other Administrative Options  . . 30
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 32
     7.1.  DYMO Message Type Specification  . . . . . . . . . . . . . 32
     7.2.  Packet and Message TLV Type Specification  . . . . . . . . 32
     7.3.  Address Block TLV Specification  . . . . . . . . . . . . . 33
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 33
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 34
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 34



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     10.2. Informative References . . . . . . . . . . . . . . . . . . 34
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 35
   Intellectual Property and Copyright Statements . . . . . . . . . . 36
















































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1.  Overview

   The Dynamic MANET On-demand (DYMO) routing protocol enables reactive,
   multihop unicast routing among participating DYMO routers.  The basic
   operations of the DYMO protocol are route discovery and route
   maintenance.

   During route discovery, the originator's DYMO router initiates
   dissemination of a Route Request (RREQ) throughout the network to
   find a route to the target's DYMO router.  During this hop-by-hop
   dissemination process, each intermediate DYMO router records a route
   to the originator.  When the target's DYMO router receives the RREQ,
   it responds with a Route Reply (RREP) sent hop-by-hop toward the
   originator.  Each intermediate DYMO router that receives the RREP
   creates a route to the target, and then the RREP is unicast hop-by-
   hop toward the originator.  When the originator's DYMO router
   receives the RREP, routes have then been established between the
   originating DYMO router and the target DYMO router in both
   directions.

   Route maintenance consists of two operations.  In order to preserve
   routes in use, DYMO routers extend route lifetimes upon successfully
   forwarding a packet.  In order to react to changes in the network
   topology, DYMO routers monitor links over which traffic is flowing.
   When a data packet is received for forwarding and a route for the
   destination is not known or the route is broken, then the DYMO router
   of source of the packet is notified.  A Route Error (RERR) is sent
   toward the packet source to indicate the current route to a
   particular destination is invalid or missing.  When the source's DYMO
   router receives the RERR, it deletes the route.  If the source's DYMO
   router later receives a packet for forwarding to the same
   destination, it will need to perform route discovery again for that
   destination.

   DYMO uses sequence numbers to ensure loop freedom [Perkins99].
   Sequence numbers enable DYMO routers to determine the temporal order
   of DYMO route discovery messages, thereby avoiding use of stale
   routing information.


2.  Applicability Statement

   The DYMO routing protocol is designed for stub or disconnected mobile
   ad hoc networks (MANETs).  DYMO handles a wide variety of mobility
   patterns by dynamically determining routes on-demand.  DYMO also
   handles a wide variety of traffic patterns.  In networks with a large
   number of routers, DYMO is best suited for sparse traffic scenarios
   where routers forward packets to with only a small portion of the



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   other DYMO routers, due to the reactive nature of route discovery and
   route maintenance.

   DYMO is applicable to memory constrained devices, since minimal
   routing state is maintained in each DYMO router.  Only routing
   information related to active sources and destinations is maintained,
   in contrast to other more proactive routing protocols that require
   routing information to all routers within the routing region be
   maintained.

   DYMO supports routers with multiple interfaces participating in the
   MANET.  DYMO routers can also perform routing on behalf of other
   nodes, attached via participating or non-participating interfaces.

   DYMO routers perform route discovery to find a route to a particular
   destination.  Therefore, DYMO routers MUST be configured to initiate
   route discovery on behalf of certain sources and find routes to
   certain destinations.  When DYMO is the only protocol interacting
   with the forwarding table, DYMO MAY be configured to perform route
   discovery for all unknown unicast destinations.

   DYMO MUST only utilizes bidirectional links.  In the case of possible
   unidirectional links, either blacklists (see Section 7.2) or other
   means (e.g. only accepting RM from bidirectional links as indicated
   by NHDP [I-D.ietf-manet-nhdp]) of ensuring bi-directionality should
   be used.  Otherwise, persistent packet loss may occur.

   The routing algorithm in DYMO may be operated at layers other than
   the network layer, using layer-appropriate addresses.  For operation
   at other layers only modification of the packet/message format should
   be required; DYMO's routing algorithm need not change.


3.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   Additionally, this document uses some terminology from
   [I-D.ietf-manet-packetbb].

   This document defines the following terminology:








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   Distance (Dist)
      A metric of the distance a message or piece of information has
      traversed.  The minimum value of distance is the number of IP hops
      traversed.  The maximum value is 65,535.

   DYMO Sequence Number (SeqNum)
      A DYMO Sequence Number is maintained by each DYMO router.  This
      sequence number is used by other DYMO routers to identify the
      temporal order of routing information generated and ensure loop-
      free routes.

   Forwarding Route
      A route that is used to forward data packets.  Forwarding routes
      are generally maintained in a forwarding information base (FIB) or
      the kernel forwarding/routing table.

   Originating Node (OrigNode)
      The originating node is the source, its DYMO router creates a DYMO
      control message on its behalf in an effort to disseminate some
      routing information.  The originating node is also referred to as
      a particular message's originator.

   Route Error (RERR)
      A RERR message is used indicate that a DYMO router does not have
      forwarding route to one or more particular addresses.

   Route Reply (RREP)
      A RREP message is used to disseminate routing information about
      the RREP OrigNode, to the RREP TargetNode and the DYMO routers
      between them.

   Route Request (RREQ)
      A RREQ message is issued to discover a valid route to a particular
      destination address, called the RREQ TargetNode.  When a DYMO
      router processes a RREQ, it learns routing information on how to
      reach the RREQ OrigNode.

   Target Node (TargetNode)
      The TargetNode is the ultimate destination of a message.

   This Node (ThisNode)
      ThisNode corresponds to the DYMO router currently performing a
      calculation or processing a message.

   Type-Length-Value structure (TLV)
      A generic way to represent information, please see
      [I-D.ietf-manet-packetbb] for additional information.




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   Unreachable Node (UnreachableNode)
      An UnreachableNode is a node for which a forwarding route does not
      exist.


4.  Data Structures

4.1.  Route Table Entry

   The route table entry is a conceptual data structure.
   Implementations may use any internal representation that conforms to
   the semantics of a route as specified in this document.

   Conceptually, a route table entry has the following fields:

   Route.Address
      The IP (host or network) destination address of the node(s)
      associated with the routing table entry.

   Route.Prefix
      Indicates that the associated address is a network address, rather
      than a host address.  The value is the length of the netmask/
      prefix.

   Route.SeqNum
      The DYMO SeqNum associated with this routing information.

   Route.NextHopAddress
      The IP address of the next DYMO router on the path toward the
      Route.Address.

   Route.NextHopInterface
      The interface used to send packets toward the Route.Address.

   Route.Broken
      A flag indicating whether this Route is broken.  This flag is set
      if the next-hop becomes unreachable or in response to processing a
      RERR (see Section 5.5.4).

   The following field is optional:

   Route.Dist
      A metric indicating the distance traversed before reaching the
      Route.Address node.

   Not including optional information may cause performance degradation,
   but it will not cause the protocol to operate incorrectly.




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   In addition to a route table data structure, each route table entry
   may have several timers associated with the information.  These
   timers/timeouts are discussed in Section 5.2.3.

4.2.  DYMO Messages

   When describing DYMO protocol messages, it is necessary to refer to
   fields in several distinct parts of the overall packet.  These
   locations include the IP or IPv6 header, the UDP header, and fields
   from [I-D.ietf-manet-packetbb].  This document uses the following
   notation conventions.  Information found in the table.

            +----------------------------+-------------------+
            |    Information Location    | Notational Prefix |
            +----------------------------+-------------------+
            |          IP header         |        IP.        |
            |         UDP header         |        UDP.       |
            |   packetbb message header  |      MsgHdr.      |
            |    packetbb message TLV    |      MsgTLV.      |
            |   packetbb address blocks  |      AddBlk.      |
            | packetbb address block TLV |      AddTLV.      |
            +----------------------------+-------------------+

                                  Table 1

4.2.1.  Generalized Packet and Message Structure

   DYMO messages conform to the generalized packet and message format as
   described in [I-D.ietf-manet-packetbb].  Here is a brief description
   of the format.  A packet is made up of messages.  A message is made
   up of a message header, message TLV block, and zero or more address
   blocks.  Each of the address blocks may also have an associated
   address TLV block.

   All DYMO messages specified in this document are sent using UDP to
   the destination port MANET [I-D.ietf-manet-iana].

   Most DYMO messages are sent with the IP destination address set to
   the link-local multicast address LL-MANET-ROUTERS
   [I-D.ietf-manet-iana] unless otherwise stated.  Therefore, all DYMO
   routers SHOULD subscribe to LL-MANET-ROUTERS [I-D.ietf-manet-iana]
   for receiving control packets.

   Unicast DYMO messages (e.g.  RREP) specified in this document are
   sent with the IP destination set to the Route.NextHopAddress of the
   route to the TargetNode.

   The IPv4 TTL (IPv6 Hop Limit) field for all packets containing DYMO



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   messages is set to 255.  If a packet is received with a value other
   than 255, it is discarded.  This mechanism helps to ensures packets
   have not passed through any intermediate routers, and it is known as
   GTSM [RFC5082].

   The length of an IP address (32 bits for IPv4 and 128 bits for IPv6)
   inside a DYMO message depends on the IP packet header containing the
   DYMO message/packet.  For example, if the IP header uses IPv6
   addresses then all addresses contained in the payload use IPv6
   addresses of the same length.  In the case of mixed IPv6 and IPv4
   addresses, please use the methods specified in
   [I-D.ietf-manet-packetbb].

   If a packet contains only a single DYMO message and no packet TLVs,
   it need not include a packet-header [I-D.ietf-manet-packetbb].

   The aggregation of multiple messages into a packet is not specified
   in this document, but the IP.SourceAddress and IP.DestinationAddress
   of all contained messages MUST be the same.

   Implementations MAY choose to temporarily delay transmission of
   messages for the purpose of aggregation (into a single packet) or to
   improve performance by using jitter [I-D.ietf-manet-jitter].

   DYMO control packets SHOULD be given priority queue and channel
   access.

4.2.2.  Routing Messages (RM) - RREQ & RREP

   Routing Messages (RMs) are used to disseminate routing information.
   There are two DYMO message types that are considered to be routing
   messages (RMs): RREQ and RREP.  They contain very similar information
   and function, but have slightly different processing rules.  The main
   difference between the two messages is that RREQ messages generally
   solicit a RREP, whereas a RREP is the response to RREQ.

   RM creation and processing are described in Section 5.3.

   A RM requires the following information:

   IP.SourceAddress
      The IP address of the node currently sending this packet.  This
      field is generally filled automatically by the operating system
      and should not require special handling.







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   IP.DestinationAddress
      The IP address of the packet destination.  For RREQ the
      IP.DestinationAddress is set to LL-MANET ROUTERS
      [I-D.ietf-manet-iana].  For RREP the IP.DestinationAddress is set
      to the NextHopAddress toward the RREP TargetNode.

   UDP.DestinationPort
      By default, the UDP destination port is set to MANET
      [I-D.ietf-manet-iana].

   MsgHdr.HopLimit
      The remaining number of hops this message is allowed to traverse.

   AddBlk.TargetNode.Address
      The IP address of the message TargetNode.  In a RREQ the
      TargetNode is the destination address for which route discovery is
      being performed.  In a RREP the TargetNode is the RREQ OrigNode
      address.  The TargetNode address is the first address in a routing
      message.

   AddBlk.OrigNode.Address
      The IP address of the originator and its associated prefix length.
      In a RREQ the OrigNode is the source's address and prefix.  In a
      RREP the OrigNode is the RREQ TargetNode's address and prefix for
      which a RREP is being generated.  This address is the second
      address in the message for RREQ.

   OrigNode.AddTLV.SeqNum
      The DYMO sequence number of the originator's DYMO router.

   A RM may optionally include the following information:

   TargetNode.AddTLV.SeqNum
      The last known DYMO sequence number of the TargetNode.

   TargetNode.AddTLV.Dist
      The last known distance to the TargetNode.

   AddBlk.AdditionalNode.Address
      The IP address of an additional node that can be reached via the
      DYMO router adding this information.  Each AdditionalNode.Address
      MUST include its prefix.  Each AdditionalNode.Address MUST also
      have an associated Node.SeqNum in the address TLV block.

   AdditionalNode.AddTLV.SeqNum
      The DYMO sequence number associated with this routing information.





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   OrigNode.AddTLV.Dist
      A metric of the distance to reach the associated OrigNode.Address.
      This field is incremented by at least one at each intermediate
      DYMO router.

   AdditionalNode.AddTLV.Dist
      A metric of the distance to reach the associated
      AdditionalNode.Address.  This field is incremented by at least one
      at each intermediate DYMO router.










































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   Example IPv4 RREQ

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   IP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     IP.SourceAddress                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         IP.DestinationAddress = LL-MANET-ROUTERS              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    IP TTL/HopLimit = 255      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Destination Port = MANET    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RREQ-type   |R|C|N|1|1|0|1|0|         msg-size=23           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | msg-hoplimit  |
       +-+-+-+-+-+-+-+-+
   Message TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     msg-tlv-block-size=0      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Number Addrs=2 | Rsv |0|0|0|1|0|  HeadLength=3 |     Head      :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :          Head (cont)          |  Target.Tail  |   Orig.Tail   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       tlv-block-size=6        |DYMOSeqNum-type|Rsv|0|1|0|0|0|0|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Index-start=1 | tlv-length=2  |          Orig.SeqNum          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

4.2.3.  Route Error (RERR)

   A RERR message is used to disseminate the information that a route is
   not available for one or more particular IP addresses.

   RERR creation and processing are described in Section 5.5.



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   A RERR requires the following information:

   IP.SourceAddress
      The IP address of the node currently sending this packet.  This
      field is generally filled automatically by the operating system
      and should not require special handling.

   IP.DestinationAddress
      The IP address is set to LL-MANET-ROUTERS [I-D.ietf-manet-iana].

   UDP.DestinationPort
      By default, the UDP destination port is set to MANET
      [I-D.ietf-manet-iana].

   MsgHdr.HopLimit
      The remaining number of hops this message is allowed to traverse.

   AddBlk.UnreachableNode.Address
      The IP address of an UnreachableNode and its associated prefix
      length.  Multiple unreachable addresses may be included in a RERR.

   A Route Error may optionally include the following information:

   UnreachableNode.AddTLV.SeqNum
      The last known DYMO sequence number of the unreachable node.  If a
      SeqNum for an address is not included, it is assumed to be
      unknown.  This case occurs when a node receives a message to
      forward to a destination for which it does not have any
      information in its routing table.






















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   Example IPv4 RERR

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   IP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     IP.SourceAddress                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         IP.DestinationAddress = LL-MANET-ROUTERS              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    IP.TTL/HopLimit = 255      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Destination Port = MANET    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RERR-type   |R|C|N|1|1|0|1|0|         msg-size=15           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | msg-hoplimit  |
       +-+-+-+-+-+-+-+-+
   Message TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     msg-tlv-block-size=0      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block
                                       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                       |Number Addrs=1 | Rsv |0|0|0|1|1|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Unreachable.Address                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        TLV-blk-size=0         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2


5.  Detailed Operation

5.1.  DYMO Sequence Numbers

   DYMO sequence numbers allow nodes to judge the freshness of routing
   information and ensure loop freedom.





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5.1.1.  Maintaining A Node's Own Sequence Number

   DYMO requires that each DYMO router in the network to maintain its
   own DYMO sequence number (OwnSeqNum), a 16-bit unsigned integer.  The
   circumstances for ThisNode to incrementing its OwnSeqNum are
   described in Section 5.3.

5.1.2.  Numerical Operations on OwnSeqNum

   When ThisNode increments its OwnSeqNum (as described in Section 5.3)
   it MUST do so by treating the sequence number value as an unsigned
   number.

5.1.3.  OwnSeqNum Rollover

   If the sequence number has been assigned to be the largest possible
   number representable as a 16-bit unsigned integer (i.e., 65,535),
   then the sequence number is set to 256 when incremented.  Setting the
   sequence number to 256 allows other nodes to detect that the number
   has rolled over and the node has not lost its sequence number.

5.1.4.  Actions After OwnSeqNum Loss

   A DYMO router SHOULD maintain its sequence number in persistent
   storage.

   If a DYMO router's OwnSeqNum is lost, it MUST take certain actions to
   avoid creating routing loops.  To prevent this possibility after
   OwnSeqNum loss a DYMO router MUST wait for at least
   ROUTE_DELETE_TIMEOUT before fully participating in the DYMO routing
   protocol.  If a DYMO control message is received during this waiting
   period, the DYMO router SHOULD process it normally but MUST NOT
   transmit or retransmit any DYMO messages.  If a data packet is
   received for forwarding to another destination during this waiting
   period, the DYMO router MUST generate a RERR message indicating that
   this route is not available and reset its waiting timeout.  At the
   end of the waiting period the DYMO router sets its OwnSeqNum to one
   (1) and begins participating.

   The longest a node need wait is ROUTE_AGE_MAX_TIMEOUT.  At the end of
   the maximum waiting period a node sets its OwnSeqNum to one (1) and
   begins participating.

5.2.  DYMO Routing Table Operations







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5.2.1.  Judging Routing Information's Usefulness

   Given a route table entry (Route.SeqNum, Route.Dist, and
   Route.Broken) and new incoming routing information for a particular
   node in a RM (Node.SeqNum, Node.Dist, and RM message type - RREQ/
   RREP), the quality of the new routing information is evaluated to
   determine its usefulness.  Incoming routing information is classified
   as follows:

   1. Stale
      If Node.SeqNum - Route.SeqNum < 0 (using signed 16-bit arithmetic)
      the incoming information is stale.  Using stale routing
      information is not allowed, since doing so might result in routing
      loops.

      (Node.SeqNum - Route.SeqNum < 0)
          using signed 16-bit arithmetic

   2. Loop-possible
      If Node.SeqNum == Route.SeqNum the incoming information may cause
      loops if used; in this case additional information MUST be
      examined.  If Route.Dist or Node.Dist is unknown or zero (0), then
      the routing information is loop-possible.  If Node.Dist >
      Route.Dist + 1, then the routing information is loop-possible.
      Using loop-possible routing information is not allowed, otherwise
      routing loops may be formed.

      (Node.SeqNum == Route.SeqNum) AND
      ((Node.Dist is unknown) OR
       (Route.Dist is unknown) OR
       (Node.Dist > Route.Dist + 1))

   3. Inferior
      In case of known equal SeqNum, the information is inferior in
      multiple cases: (case i) if Node.Dist == Route.Dist + 1 (it is a
      greater distance route) AND Route.Broken == false; (case ii) if
      Node.Dist == Route.Dist (equal distance route) AND Route.Broken ==
      false AND this RM is a RREQ.  The inferior condition stops
      forwarding of RREQ with equivalent distance.

      ((Node.SeqNum == Route.SeqNum) AND
       (((Node.Dist == Route.Dist + 1) AND (Route.Broken == false)) OR
        ((Node.Dist == Route.Dist) AND
         (RM is RREQ) AND (Route.Broken == false))))







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   4. Superior
      Incoming routing information that does not match any of the above
      criteria is loop-free and better than the information existing in
      the routing table.  Information is always superior if Node.SeqNum
      - Route.SeqNum > 0 (using signed 16-bit arithmetic).  In the case
      of equal sequence numbers, the information is superior in multiple
      cases: (case i) if Node.Dist < Route.Dist; (case ii) if Node.Dist
      == Route.Dist + 1 AND Route.Broken == true (a broken route is
      being repaired); (case iii) if Node.Dist == Route.Dist AND it is a
      RREP (RREP with equal distance are forwarded) OR Route.Broken ==
      true (a broken route is being repaired).  For completeness, we
      provide the following (optimized) pseudo-code.

      (Node.SeqNum - Route.SeqNum > 0) OR
          using signed 16-bit arithmetic
      ((Node.SeqNum == Route.SeqNum) AND
       ((Node.Dist < Route.Dist) OR
        ((Node.Dist == Route.Dist + 1) AND (Route.Broken == true)) OR
        ((Node.Dist == Route.Dist) AND
         ((RM is RREP) OR (Route.Broken == true)))))

5.2.2.  Creating or Updating a Route Table Entry with Received Superior
        Routing Information

   The route table entry is populated with the following information:

   1.  the Route.Address is set to Node.Address,

   2.  the Route.Prefix is set to the Node.Prefix.

   3.  the Route.SeqNum is set to the Node.SeqNum,

   4.  the Route.NextHopAddress is set to the node that transmitted this
       DYMO RM packet (i.e., the IP.SourceAddress),

   5.  the Route.NextHopInterface is set to the interface that this DYMO
       packet was received on,

   6.  if known, the Route.Dist is set to the Node.Dist,

   Fields without known values are not populated with any value.

   Previous timers for this route table entry are removed.  A timer for
   the minimum delete timeout (ROUTE_AGE_MIN) is set to
   ROUTE_AGE_MIN_TIMEOUT.  A timer for the maximum delete timeout
   (ROUTE_AGE_MAX).  ROUTE_AGE_MAX is set to Node.AddTLV.VALIDITY_TIME
   [I-D.ietf-manet-timetlv] if included; otherwise, ROUTE_AGE_MAX is set
   to ROUTE_AGE_MAX_TIMEOUT.  The usage of these timers and others are



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   described in Section 5.2.3.

   At this point, a forwarding route should be created.  Afterward, the
   route can be used to send any queued data packets and forward any
   incoming data packets for Route.Address.  This route also fulfills
   any outstanding route discovery attempts for Node.Address.

5.2.3.  Route Table Entry Timeouts

5.2.3.1.  Minimum Delete Timeout (ROUTE_AGE_MIN)

   When a DYMO router transmits a RM, other DYMO routers expect the
   transmitting DYMO router to have a forwarding route to the RM
   originator.  After updating a route table entry, it should be
   maintained for at least ROUTE_AGE_MIN.  Failure to maintain the
   information might result in lost messages/packets, or in the worst
   case scenario several duplicate messages.

   After the ROUTE_AGE_MIN timeout a route can safely be deleted.

5.2.3.2.  Maximum Delete Timeout (ROUTE_AGE_MAX)

   Sequence number information is time sensitive, and MUST be deleted
   after a time in order to ensure loop-free routing.

   After the ROUTE_AGE_MAX timeout a route MUST be deleted.  All
   information about the route is deleted upon ROUTE_AGE_MAX timeout.
   If a forwarding route exists it is also removed.

5.2.3.3.  Recently Used Timeout (ROUTE_USED)

   When a route is used to forward data packets, this timer is set to
   expire after ROUTE_USED_TIMEOUT.  This operation is also discussed in
   Section 5.5.2.

   If a route has not been used recently, then a timer for ROUTE_DELETE
   is set to ROUTE_DELETE_TIMEOUT.

5.2.3.4.  Delete Information Timeout (ROUTE_DELETE)

   As time progresses the likelihood that old routing information is
   useful decreases, especially if the network nodes are mobile.
   Therefore, old information should be deleted.

   After the ROUTE_DELETE timeout, the routing table entry should be
   deleted.  If a forwarding route exists, it should also be removed.





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5.3.  Routing Messages

5.3.1.  RREQ Creation

   Before a DYMO router creates a RREQ it SHOULD increment its OwnSeqNum
   by one (1) according to the rules specified in Section 5.1.2.
   Incrementing OwnSeqNum will ensure that all nodes with existing
   routing information will consider this new information superior to
   existing routing table information.  If the sequence number is not
   incremented, certain DYMO routers might not consider this information
   superior, if they have existing better routing information already.

   First, ThisNode adds the AddBlk.TargetNode.Address to the RREQ; the
   unicast IP Destination Address for which a forwarding route does not
   exist.

   If a previous value of the TargetNode.SeqNum is known (from a routing
   table entry using longest-prefix matching), it SHOULD be placed in
   TargetNode.AddTLV.SeqNum in all but the last RREQ attempt.  If a
   TargetNode.SeqNum is not included, it is assumed to be unknown by
   processing nodes.  This operation ensures that no intermediate DYMO
   routers reply, and ensures that the TargetNode's DYMO router
   increments its sequence number.

   Next, the node adds AddBlk.OrigNode.Address, its prefix, and the
   OrigNode.AddTLV.SeqNum (OwnSeqNum) to the RM.

   The OrigNode.Address is the address of the source for which this DYMO
   router is initiating this route discovery.  The OrigNode.Address MUST
   be a unicast IP address.  This information will be used by nodes to
   create a route toward the OrigNode, enabling delivery of a RREP, and
   eventually used for proper forwarding of data packets.

   If OrigNode.Dist is included it is set to a number greater than zero
   (0).

   The MsgHdr.HopLimit SHOULD be set to MSG_HOPLIMIT.

   For RREQ, the MsgHdr.HopLimit MAY be set in accordance with an
   expanding ring search as described in [RFC3561] to limit the RREQ
   propagation to a subset of the local network and possibly reduce
   route discovery overhead.

   The IP.DestinationAddress for RREQ is set to LL-MANET-ROUTERS.







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5.3.2.  RREP Creation

   First, the AddBlk.TargetNode.Address is added to the RREP.  The
   TargetNode is the ultimate destination of this RREP; the RREQ
   OrigNode.Address.

   Next, AddBlk.OrigNode.Address and prefix are added to the RREP.  The
   AddBlk.OrigNode.Address is the RREQ TargetNode.Address.  The
   AddBlk.OrigNode.Address MUST be a unicast IP address.  ThisNode
   SHOULD advertise the largest known prefix containing
   AddBlk.OrigNode.Address.

   When the TargetNode's DYMO router creates a RREP, if the
   TargetNode.SeqNum was not included in the RREQ, ThisNode MUST
   increment its OwnSeqNum by one (1) according to the rules specified
   in Section 5.1.2.

   If TargetNode.SeqNum is included in the RM and TargetNode.SeqNum -
   OwnSeqNum < 0 (using signed 16-bit arithmetic), OwnSeqNum SHOULD be
   incremented by one (1) according to the rules specified in
   Section 5.1.2.

   If TargetNode.SeqNum is included in the RM and TargetNode.SeqNum ==
   OwnSeqNum (using signed 16-bit arithmetic) and Dist will not be
   included in the RREP being generated, OwnSeqNum SHOULD be incremented
   by one (1) according to the rules specified in Section 5.1.2.

   If OwnSeqNum is not incremented the routing information might be
   considered stale.  In this case, the RREP might not reach the RREP
   Target.

   After any of the sequence number operations above, the RREP
   OrigNode.AddTLV.SeqNum (OwnSeqNum) MUST also added to the RREP.

   Other AddTLVs in the RREP for the OrigNode and TargetNode SHOULD be
   included and set accordingly.  If OrigNode.Dist is included it is set
   to a number greater than zero (0).

   The MsgHdr.HopLimit is set to MSG_HOPLIMIT.

   The IP.DestinationAddress for RREP is set to the IP address of the
   Route.NextHopAddress for the route to the RREP TargetNode.

5.3.3.  Intermediate DYMO Router RREP Creation

   Sometimes a DYMO router other than the TargetNode's DYMO router (call
   it an "intermediate DYMO router") has routing information that can
   satisfy an incoming RREQ.  An intermediate DYMO router can issue a



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   intermediate DYMO router RREP on behalf of the TargetNode's DYMO
   router.

   Before creating a intermediate DYMO router RREP, OwnSeqNum SHOULD be
   incremented by one (1) according to the rules specified in
   Section 5.1.2.

   If OwnSeqNum is not incremented the routing information about
   ThisNode might be considered stale by a processing DYMO router.  In
   this case, the RREP would not reach the RREP TargetNode.

   When an intermediate DYMO router originates a RREP in response to a
   RREQ on behalf of the TargetNode's DYMO router, it sends the RREP to
   the RREQ OrigNode with additional routing information (Address,
   Prefix, SeqNum, Dist, etc.) about the RREQ TargetNode.  Appending
   additional routing information is described in Section 5.3.5.

   The Intermediate DYMO router SHOULD also issue a RREP to the RREQ
   TargetNode, so that the RREQ TargetNode receives routing information
   on how to reach the RREQ OrigNode.

   When an intermediate DYMO router creates this RREP, it sends a RREP
   to the RREQ TargetNode with additional routing information (Address,
   Prefix, SeqNum, Dist, etc.) about the RREQ OrigNode.

5.3.4.  RM Processing

   ThisNode first checks whether AddBlk.OrigNode.Address is an address
   handled by this DYMO router.  If this node is the originating DYMO
   router, the RM is dropped.

   Before processing a RREQ, the DYMO router checks the IP.Destination
   to ensure that it was sent to LL-MANET-ROUTERS [I-D.ietf-manet-iana].
   If the RREQ was not sent to LL-MANET-ROUTERS, it SHOULD be discarded
   and further processing stopped.

   Next, ThisNode checks if the AddBlk.OrigNode.Address is a valid
   unicast IP address.  If the address is not a valid unicast IP
   address, the messages is discarded and further processing stopped.

   Next, ThisNode checks whether its routing table has an entry to the
   AddBlk.OrigNode.Address using longest-prefix matching [RFC1812].  If
   a route does not exist, then the new routing information is
   considered fresh and a new route table entry is created and updated
   as described in Section 5.2.2.  If a route table entry does exists,
   the incoming routing information is compared with the route table
   entry following the procedure described in Section 5.2.1.  If the
   incoming routing information is considered superior, the route table



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   entry is updated as described in Section 5.2.2.

   After processing the OrigNode's routing information, then each
   address that is not the TargetNode should be considered for creating
   and updating routes.  Creating and updating routes to other nodes can
   eliminate RREQ for those IP destinations, in the event that data
   needs to be forwarded to the IP destination(s) now or in the near
   future.

   For each of the additional addresses considered, ThisNode first
   checks the that the address is a unicast IP address.  If the address
   is not a unicast IP address, the address and all related information
   MUST be removed.  If the routing table does not have a matching route
   for this additional address using longest-prefix matching, then a
   route is created and updated as described in Section 5.2.2.  If a
   route table entry exists, the incoming routing information is
   compared with the route table entry following the procedure described
   in Section 5.2.1.  If the incoming routing information is considered
   superior, the route table entry is updated as described in
   Section 5.2.2.

   If the routing information for an AdditionalNode.Address is not
   considered superior, then it is removed from the RM.  Removing this
   information ensures that the information is not propagated.

   At this point, if the routing information for the OrigNode was not
   superior then this RM SHOULD be discarded and no further processing
   of this message SHOULD be performed.

   If the ThisNode is the DYMO router responsible for the TargetNode and
   this RM is a RREQ, then ThisNode responds with a RREP to the RREQ
   OrigNode (the new RREP's TargetNode).  The procedure for issuing a
   new RREP is described in Section 5.3.2.  At this point, ThisNode need
   not perform any more operations for this RM.

   Alternatively ThisNode MAY choose to distribute routing information
   about ThisNode (the RREQ TargetNode) more widely, ThisNode MAY
   optionally perform a route discovery; by issuing a RREQ with ThisNode
   listed as the TargetNode, using the procedure in Section 5.3.1.  At
   this point, ThisNode need not perform any more operations for the
   original RM.

   If ThisNode is not the TargetNode, this RM is a RREQ, the RREQ
   contains the TargetNode.AddTLV.SeqNum, and ThisNode has a forwarding
   route to the TargetNode with a SeqNum where Route.TargetNode.SeqNum -
   RREQ.TargetNode.AddTLV.SeqNum >= 0 (using signed 16-bit arithmetic);
   then this node MAY respond with an intermediate DYMO router RREP.
   The procedure for performing intermediate DYMO router RREP is



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   described in Section 5.3.3.  If an intermediate DYMO router RREP is
   sent, ThisNode need not perform any more operations for the original
   RM.

   After processing a RM or creating a new RM, a node can append
   additional routing information to the RM, according to the procedure
   described in Section 5.3.5.  The additional routing information can
   help reduce route discoveries at the expense of increased message
   size.

   For each address (except the TargetNode) in the RM that includes
   AddTLV.Dist information, the AddTLV.Dist information is incremented
   by at least one (1).  The updated distance value will influence
   judgment of the routing information (Section 5.2.1) against known
   information at other DYMO routers that process this RM.

   If the resulting distance value for the OrigNode is greater than
   65,535, the message is discarded.  If the resulting distance value
   for another node is greater than 65,535, the associated address and
   its information are removed from the RM.

   Next, the MsgHdr.HopLimit is decremented by one (1).  If this RM's
   MsgHdr.HopLimit is greater than or equal to one (1), ThisNode is not
   the TargetNode, AND this RM is a RREQ, then the current RM (altered
   by the procedure defined above) SHOULD be sent to the
   IP.DestinationAddress LL-MANET-ROUTERS [I-D.ietf-manet-iana].

   If this RM's MsgHdr.HopLimit is greater than or equal to one (1),
   ThisNode is not the TargetNode, AND this RM is a RREP, then the
   current RM is sent to the Route.NextHopAddress for the RREP's
   TargetNode.Address.  If no forwarding route exists to Target.Address,
   then a RERR is issued to the OrigNode of the RREP.

   By sending the updated RM ThisNode is advertising that it will
   provide routing for IP addresses contained in the outgoing RM based
   on the information enclosed.  ThisNode MAY choose not to send the RM,
   though not resending this RM could decrease connectivity in the
   network or result in a non-shortest distance path.

   Some examples of why ThisNode might choose to not re-issue a RM are:
   if ThisNode does not want to advertise routing for the contained IP
   addresses because it is already heavily loaded; if ThisNode has
   already issued nearly identical routing information (e.g.  ThisNode
   had recently issued a RM with nearly the same distance); or if
   ThisNode is low on energy and does not want to expend energy for
   control message sending or packet forwarding.  This type of advanced
   behavior is not defined in this specification.




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5.3.5.  Adding Additional Routing Information to a RM

   Appending routing information can alleviate route discovery attempts
   to the nodes whose information is included, if other DYMO routers use
   this information to update their routing tables.

   DYMO routers can append routing information to a RM.  This option
   should be administratively configurable or intelligently controlled.

   Prior to appending an address controlled by this DYMO router to a RM,
   ThisNode MAY increment its OwnSeqNum as defined in Section 5.1.2.  If
   OwnSeqNum is not incremented the appended routing information might
   not be considered superior, when received by nodes with existing
   routing information.  Incrementation of the sequence number when
   appending information to an RM in transit should be administratively
   configurable or intelligently controlled.

   If an address controlled by this DYMO router includes ThisNode.Dist,
   it is set to a number greater than zero (0).

   For added addresses (and their prefixes) not controlled by this DYMO
   router, Route.Dist can be included if known.  If Route.Dist is not
   known, it MUST NOT be included.

   MaxAge information about the appended address(es) MUST be included.

   Additional information (e.g.  SeqNum and Dist) about any appended
   address(es) SHOULD be included.

   Note that, the routing information about the TargetNode MUST NOT be
   added.  Also, duplicate address entries SHOULD NOT be added.
   Instead, only the best routing information (Section 5.2.1) for a
   particular address SHOULD be included.

5.4.  Route Discovery

   When a source's DYMO router needs to forward a data packet on behalf
   of an attached node and it does not have a forwarding route to the
   data packet's unicast IP destination address, ThisNode sends a RREQ
   (described in Section 5.3.1) to discover a route to the particular
   destination (TargetNode).

   After issuing a RREQ, the OrigNode DYMO router waits for a route to
   be created to the TargetNode.  If a route is not created within
   RREQ_WAIT_TIME, ThisNode may again try to discover a route by issuing
   another RREQ using the procedure defined in Section 5.3.1 again.

   To reduce congestion in a network, repeated attempts at route



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   discovery for a particular TargetNode SHOULD utilize an exponential
   backoff.

   For example, the first time a DYMO router issues a RREQ, it waits
   RREQ_WAIT_TIME for a route to the TargetNode.  If a route is not
   found within that time, the DYMO router MAY send another RREQ.  If a
   route is not found within two (2) times the current waiting time,
   another RREQ may be sent, up to a total of RREQ_TRIES.  For each
   additional attempt, the waiting time for the previous RREQ is
   multiplied by two (2) so that the waiting time conforms to a binary
   exponential backoff.

   Data packets awaiting a route SHOULD be buffered by the source's DYMO
   router.  This buffer SHOULD have a fixed limited size
   (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES) and older data packets
   SHOULD be discarded first.

   Buffering of data packets can have both positive and negative
   effects, and therefore buffer settings SHOULD be administratively
   configurable or intelligently controlled.

   If a route discovery has been attempted RREQ_TRIES times without
   receiving a route to the TargetNode, all data packets destined for
   the corresponding TargetNode are dropped from the buffer and a
   Destination Unreachable ICMP message should be delivered to the
   source.

5.5.  Route Maintenance

   A RERR SHOULD be issued if a data packet is to be forwarded and it
   cannot be delivered to the next-hop because no forwarding route for
   the IP.DestinationAddress exists; RERR generation is described in
   Section 5.5.3.

   Upon this condition, an ICMP Destination Unreachable message SHOULD
   NOT be generated unless this router is responsible for the
   IP.DestinationAddress and that IP.DestinationAddress is known to be
   unreachable.

   In addition to inability to forward a data packet, a RERR SHOULD be
   issued immediately after detecting a broken link of an forwarding
   route to quickly notify DYMO routers that a link break occurred and
   that certain routes are no longer available.  If the route with the
   broken link has not been used recently (indicated by ROUTE_USED), the
   RERR SHOULD NOT be generated.






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5.5.1.  Active Link Monitoring

   Nodes MUST monitor next-hop links on forwarding routes.  This
   monitoring can be accomplished by one or several mechanisms,
   including:

   o  Link layer feedback

   o  Neighborhood discovery [I-D.ietf-manet-nhdp]

   o  Route timeout

   o  Other monitoring mechanisms or heuristics

   Upon determining that a link is broken or the next-hop is
   unreachable, ThisNode MUST remove the affected forwarding routes
   (those with an unreachable next-hop).  ThisNode also flags the
   associated routes in DYMO's routing table as Broken.  For each broken
   route a timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT.

5.5.2.  Updating Route Lifetimes During Packet Forwarding

   To avoid removing the forwarding route to reach the IP.SourceAddress,
   ThisNode SHOULD set a timeout (ROUTE_USED) to ROUTE_USED_TIMEOUT for
   the route to the IP.SourceAddress upon receiving a data packet.  If a
   timer for ROUTE_DELETE is set, it is removed.

   To avoid removing the forwarding route to the IP.DestinationAddress
   that is being used, ThisNode SHOULD set a timeout (ROUTE_USED) to
   ROUTE_USED_TIMEOUT for the route to the IP.DestinationAddress upon
   sending a data packet.  If a timer for ROUTE_DELETE is set, it is
   removed.

5.5.3.  RERR Generation

   A RERR informs DYMO routers that a route to certain destinations is
   not available through ThisNode.

   When creating a new RERR, the address of first UnreachableNode
   (IP.DestinationAddress from a data packet or RREP.TargetNode.Address)
   is inserted into an Address Block AddBlk.UnreachableNode.Address.  If
   a prefix is known for the UnreachableNode.Address, it SHOULD be
   included.  Otherwise, the UnreachableNode.Address assumed to be a
   host address with a full length prefix.  If a value for the
   UnreachableNode's SeqNum (UnreachableNode.AddTLV.SeqNum) is known, it
   SHOULD be placed in the RERR.  The MsgHdr.HopLimit is set to
   MSG_HOPLIMIT.




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   Additional UnreachableNodes that require the same unavailable link
   (routes with the same Route.NextHopAddress and
   Route.NextHopInterface) SHOULD be added to the RERR, as additional
   AddBlk.UnreachableNode.Address entries with their associated prefix.
   The SeqNum if known SHOULD also be included.  Appending
   UnreachableNode information notifies each processing node of
   additional routes that are no longer available.  This option SHOULD
   be administratively configurable or intelligently controlled.

   If SeqNum information is not known or not included in the RERR, all
   nodes processing the RERR will assume their routing information
   associated with the UnreachableNode is no longer valid and flag those
   routes as broken.

   The RERR is sent to the IP.DestinationAddress LL-MANET-ROUTERS
   [I-D.ietf-manet-iana].  Sending the RERR to the LL-MANET-ROUTERS
   address notifies nearby nodes that might depend on the now broken
   link.

   At this point, the packet or message that forced generation of this
   RERR SHOULD be discarded.

5.5.4.  RERR Processing

   Before processing a RERR, the DYMO router checks the
   IP.DestinationAddress to ensure that it is addressed to LL-MANET-
   ROUTERS [I-D.ietf-manet-iana].

   When a DYMO router processes a RERR, it processes each
   UnreachableNode's information.  The processing DYMO router removes
   the forwarding route, sets the broken flag, and a timer for
   ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT for each
   UnreachableNode.Address found using longest prefix matching that meet
   all of the following conditions:

   1.  The UnreachableNode.Address is a unicast address.

   2.  The Route.NextHopAddress is the same as the RERR
       IP.SourceAddress.

   3.  The Route.NextHopInterface is the same as the interface on which
       the RERR was received.

   4.  The Route.SeqNum is zero (0), unknown, OR the
       UnreachableNode.SeqNum is zero (0), unknown, OR Route.SeqNum -
       UnreachableNode.SeqNum <= 0 (using signed 16-bit arithmetic).

   During processing if Route.SeqNum is zero (0) or unknown and



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   Unreachable.SeqNum exists in the RERR, then Route.SeqNum MAY be set
   to Unreachable.SeqNum.  Setting Route.SeqNum can reduce future RRER
   processing and forwarding.

   Each UnreachableNode that did not result in a broken route is removed
   from the RERR, since propagation of this information will not result
   in any benefit.  Any other information (AddTLVs) associated with the
   removed address(es) is also removed.

   After processing if Route.SeqNum is known and an Unreachable.SeqNum
   is not included in the RERR, then Route.SeqNum (i.e.
   Unreachable.SeqNum) MAY be added to the RERR.  Including
   Unreachable.SeqNum can reduce future RRER processing and forwarding.

   If no UnreachableNode addresses remain in the RERR, no other
   processing is required and the RERR is discarded.

   If processing continues, the MsgHdr.HopLimit is decremented by one
   (1).  Further, if this RERR's new MsgHdr.HopLimit is greater than one
   (1) and at least one unreachable node address remains in the RERR,
   then the updated RERR is sent to the IP.DestinationAddress LL-MANET-
   ROUTERS [I-D.ietf-manet-iana].

5.6.  Unknown Message & TLV Types

   If a message with an unknown type is received, the message is
   discarded.

   For processing of messages that contain unknown TLV types, operation
   should be administratively controlled.

5.7.  Advertising Network Addresses

   DYMO routers advertise specify the prefix length for each advertised
   address.  Any nodes (other than the advertising DYMO router) within
   the advertised prefix MUST NOT participate in the DYMO protocol
   directly.  For example, A.B.C.1 with a prefix length of 24 indicates
   all nodes with the matching A.B.C.X are reachable through the DYMO
   router with address A.B.C.1.

5.8.  Simple Internet Attachment

   Simple Internet attachment consists of a stub network of MANET
   routers connected to the Internet via a single Internet DYMO router
   (IDR).  The Internet may be connected via multiple DYMO routers, but
   such behavior is not specified in this document.

   The IDR is responsible for responding to RREQs for DYMO routers on



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   behalf of TargetNodes on the Internet, as well as delivering packets
   to destinations on the Internet.

         /--------------------------\
        /          Internet          \
        \                            /
         \------------+-------------/
                      |
       Routable &     |
       Topologically  | A.B.C.X/24
       Correct        |
       Prefix         |
                +-----+-----+
                |  Internet |
         /------|  DYMO     |--------\
        /       |  Router   |         \
       /        |  A.B.C.1  |          \
       |        +-----------+          |
       |         DYMO Region           |
       |                               |
       | +--------------+              |
       | |  DYMO Router |              |
       | |    A.B.C.2   |              |
       | +--------------+              |
       |              +--------------+ |
       |              |  DYMO Router | |
       |              |    A.B.C.3   | |
       \              +--------------+ /
        \                             /
         \---------------------------/

               Figure 7: Simple Internet Attachment Example

   DYMO routers wishing to be reachable from nodes in the Internet MUST
   have IP addresses within the IDR's routable and topologically correct
   prefix.  Given a node with a routeable address or care-of address
   handled by the IDR, the IDR is responsible for routing and forwarding
   packets received from the Internet destined for nodes inside its
   MANET.

   When DYMO router within the MANET want to send packets to a node on
   the Internet, they simply issue RREQ for those IP Destination
   Addresses; using normal DYMO route discovery.  The IDR is responsible
   for properly responding to RREQ on behalf of the Internet
   destinations, and maintaining their associated sequence number(s).

   For an IDR and other DYMO routers that maintain the sequence number
   on behalf of other nodes, these routers MUST know the IP addresses



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   for which they MUST generate DYMO messages and maintain OwnSeqNum.
   Likewise, they MUST be capable of advertising an address within the
   same prefix as these IP addresses.  Alternatively, they may behave as
   a proxy on behalf of Internet destinations.

5.9.  Multiple Interfaces

   DYMO may be used with multiple interfaces; therefore, the particular
   interface over which packets arrive MUST be known whenever a packet
   is received.  Whenever a new route is created, the interface through
   which the Route.Address can be reached is also recorded in the route
   table entry.

   When multiple interfaces are available, a node transmitting a packet
   with IP.DestinationAddress set to LL-MANET-ROUTERS SHOULD send the
   packet on all interfaces that have been configured for DYMO
   operation.

   Similarly, DYMO routers should subscribe to LL-MANET-ROUTERS on all
   their DYMO interfaces.

5.10.  DYMO Control Packet/Message Generation Limits

   To ensure predictable control overhead, DYMO router's rate of packet/
   message generation SHOULD be limited.  The rate and algorithm for
   limiting messages is left to the implementor and should be
   administratively configurable or intelligently controlled.  DYMO
   control messages SHOULD be discarded in the following order of
   preferences RREQ, RREP, and finally RERR.


6.  Configuration Parameters and Other Administrative Options



















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                        Suggested Parameter Values

           +------------------------------+-------------------+
           |             Name             |       Value       |
           +------------------------------+-------------------+
           |         MSG_HOPLIMIT         |      10 hops      |
           |         ROUTE_TIMEOUT        |     5 seconds     |
           |     ROUTE_AGE_MIN_TIMEOUT    |      1 second     |
           |     ROUTE_AGE_MAX_TIMEOUT    |     60 seconds    |
           |      ROUTE_USED_TIMEOUT      |   ROUTE_TIMEOUT   |
           |     ROUTE_DELETE_TIMEOUT     | 2 * ROUTE_TIMEOUT |
           |     ROUTE_RREQ_WAIT_TIME     |     2 seconds     |
           |          RREQ_TRIES          |      3 tries      |
           | UNICAST_MESSAGE_SENT_TIMEOUT |      1 second     |
           +------------------------------+-------------------+

                                  Table 2

   These suggested values work well for small and medium well connected
   networks with moderate topology changes.  These parameters SHOULD be
   administratively configurable for the network where DYMO is used.
   Ideally, for networks with frequent topology changes the DYMO
   parameters should be adjusted using either experimentally determined
   values or dynamic adaptation.  For example, in networks with
   infrequent topology changes ROUTE_USED_TIMEOUT may be set to a much
   larger value.

   In addition to the parameters above several administrative options
   exist.  Many of these options can be administratively controlled, but
   they may be better served by intelligent control.  The following
   table enumerates several of the options.

                            Important Settings

   +------------------------+------------------------------------------+
   |          Name          |                Description               |
   +------------------------+------------------------------------------+
   |  RESPONSIBLE_ADDRESSES |  List of addresses, and their associated |
   |                        |   prefix, for which this DYMO router is  |
   |                        |               responsible.               |
   |     DYMO_INTERFACES    |  List of the interfaces participating in |
   |                        |          DYMO routing protocol.          |
   +------------------------+------------------------------------------+

                                  Table 3






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7.  IANA Considerations

   In its default mode of operation, DYMO uses the UDP port MANET
   [I-D.ietf-manet-iana] to carry protocol packets.  DYMO also uses the
   link-local multicast address LL-MANET-ROUTERS [I-D.ietf-manet-iana].

   This section specifies several messages types, message tlv-types, and
   address tlv-types.

7.1.  DYMO Message Type Specification

                            DYMO Message Types

                   +------------------------+----------+
                   |          Name          |   Type   |
                   +------------------------+----------+
                   |  Route Request (RREQ)  | 10 - TBD |
                   |   Route Reply (RREP)   | 11 - TBD |
                   |   Route Error (RERR)   | 12 - TBD |
                   +------------------------+----------+

                                  Table 4

7.2.  Packet and Message TLV Type Specification

                             Packet TLV Types

   +-------------------+------+--------+-------------------------------+
   |        Name       | Type | Length | Value                         |
   +-------------------+------+--------+-------------------------------+
   |  Unicast Response | 10 - |    0   | Indicates to the processing   |
   |      Request      |  TBD | octets | node that the previous hop    |
   |                   |      |        | (IP.SourceAddress) expects a  |
   |                   |      |        | unicast message within        |
   |                   |      |        | UNICAST_MESSAGE_SENT_TIMEOUT. |
   |                   |      |        | Any unicast packet will serve |
   |                   |      |        | this purpose, and it MAY be   |
   |                   |      |        | an ICMP REPLY message.  If a  |
   |                   |      |        | message is not sent, then the |
   |                   |      |        | previous hop can assume that  |
   |                   |      |        | the link is unidirectional    |
   |                   |      |        | and MAY blacklist the link to |
   |                   |      |        | this node.                    |
   +-------------------+------+--------+-------------------------------+

                                  Table 5





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7.3.  Address Block TLV Specification

                          Address Block TLV Types

   +---------------+--------------+--------+---------------------------+
   |      Name     |     Type     | Length | Value                     |
   +---------------+--------------+--------+---------------------------+
   |   DYMOSeqNum  |   10 - TBD   |  up to | The DYMO sequence num     |
   |               |              |    2   | associated with this      |
   |               |              | octets | address.  The sequence    |
   |               |              |        | number may be the last    |
   |               |              |        | known sequence number.    |
   |    Distance   |   11 - TBD   |  up to | A metric of the distance  |
   |               |              |    2   | traversed by the          |
   |               |              | octets | information associated    |
   |               |              |        | with this address.        |
   | VALIDITY_TIME |      TBD     |        | The maximum amount of     |
   |  - AKA MaxAge | [I-D.ietf-ma |        | time that information can |
   |               | n et-timetlv |        | be maintained before      |
   |               | ]            |        | being deleted.  The       |
   |               |              |        | VALIDITY_TIME TLV is      |
   |               |              |        | defined in                |
   |               |              |        | [I-D.ietf-manet-timetlv]. |
   +---------------+--------------+--------+---------------------------+

                                  Table 6


8.  Security Considerations

   Currently, DYMO does not specify any special security measures.

   In situations where confidentiality of DYMO messages is important,
   traditional cryptographic techniques can be applied.

   Securing routing information integrity will likely require DYMO
   routers to authenticate DYMO messages upon reception.  Also, since
   routing information is distributed hop-by-hop, DYMO routers will also
   likely need to authenticate the source of the routing information,
   the source's DYMO router.

   Note that is important that any confidentiality and integrity
   algorithms used permit multiple receivers to process the message,
   since much of DYMO's messaging is multicast.







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9.  Acknowledgments

   DYMO is a descendant of the design of previous MANET reactive
   protocols, especially AODV [RFC3561] and DSR [RFC4728].  Changes to
   previous MANET reactive protocols stem from research and
   implementation experiences.  Thanks to Elizabeth Belding-Royer for
   her long time authorship of DYMO.  Additional thanks to Luke Klein-
   Berndt, Pedro Ruiz, Fransisco Ros, Koojana Kuladinithi, Ramon
   Caceres, Thomas Clausen, Christopher Dearlove, Seung Yi, Romain
   Thouvenin, Tronje Krop, Henner Jakob, Alexandru Petrescu, Christoph
   Sommer, Cong Yuan, and Lars Kristensen for reviewing of DYMO, as well
   as several specification suggestions.


10.  References

10.1.  Normative References

   [I-D.ietf-manet-iana]
              Chakeres, I., "IANA Allocations for MANET Protocols",
              draft-ietf-manet-iana-07 (work in progress),
              November 2007.

   [I-D.ietf-manet-packetbb]
              Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized MANET Packet/Message Format",
              draft-ietf-manet-packetbb-12 (work in progress),
              March 2008.

   [I-D.ietf-manet-timetlv]
              Clausen, T. and C. Dearlove, "Representing multi-value
              time in MANETs", draft-ietf-manet-timetlv-04 (work in
              progress), November 2007.

   [RFC1812]  Baker, F., "Requirements for IP Version 4 Routers",
              RFC 1812, June 1995.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, October 2007.

10.2.  Informative References

   [I-D.ietf-manet-jitter]
              Clausen, T., Dearlove, C., and B. Adamson, "Jitter



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              considerations in Mobile Ad Hoc Networks (MANETs)",
              draft-ietf-manet-jitter-04 (work in progress),
              December 2007.

   [I-D.ietf-manet-nhdp]
              Clausen, T., Dearlove, C., and J. Dean, "MANET
              Neighborhood Discovery Protocol (NHDP)",
              draft-ietf-manet-nhdp-06 (work in progress), March 2008.

   [Perkins99]
              Perkins, C. and E. Belding-Royer, "Ad hoc On-Demand
              Distance Vector (AODV) Routing", Proceedings of the 2nd
              IEEE Workshop on Mobile            Computing Systems and
              Applications, New Orleans, LA,            pp. 90-100,
              February 1999.

   [RFC3561]  Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
              Demand Distance Vector (AODV) Routing", RFC 3561,
              July 2003.

   [RFC4728]  Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
              Routing Protocol (DSR) for Mobile Ad Hoc Networks for
              IPv4", RFC 4728, February 2007.


Authors' Addresses

   Ian D Chakeres
   Motorola
   Bangalore
   India

   Email: ian.chakeres@gmail.com
   URI:   http://www.ianchak.com/


   Charles E. Perkins
   Palo Alto, CA
   USA

   Email: charliep@computer.org










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