Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                           Motorola
Internet-Draft                                                C. Perkins
Intended status: Standards Track                                   Nokia
Expires: November 3, 2007                                    May 2, January 6, 2008                                    July 5, 2007

                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-09
                        draft-ietf-manet-dymo-10

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The Dynamic MANET On-demand (DYMO) routing protocol is intended for
   use by mobile nodes modes in wireless, multihop networks.  It offers
   adaptation to changing network topology and determines unicast routes
   between nodes DYMO routers within the network in an on-demand fashion.

Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Data Structures  . . . . . . . . . . . . . . . . . . . . . . .  6  7
     4.1.  Route Table Entry  . . . . . . . . . . . . . . . . . . . .  6  7
     4.2.  DYMO Messages  . . . . . . . . . . . . . . . . . . . . . .  7  8
       4.2.1.  Generalized MANET Packet and Message Structure . . . .  8
       4.2.2.  Routing Messages (RM) - RREQ & RREP  . . . . . . . . .  8  9
       4.2.3.  Route Error (RERR) . . . . . . . . . . . . . . . . . . 11
   5.  Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 12 13
     5.1.  DYMO Sequence Numbers  . . . . . . . . . . . . . . . . . . 12 13
       5.1.1.  Maintaining A Node's Own Sequence Number . . . . . . . 12 13
       5.1.2.  Numerical Operations on OwnSeqNum  . . . . . . . . . . 13 14
       5.1.3.  OwnSeqNum Rollover . . . . . . . . . . . . . . . . . . 13 14
       5.1.4.  Actions After OwnSeqNum Loss . . . . . . . . . . . . . 13 14
     5.2.  DYMO Routing Table Operations  . . . . . . . . . . . . . . 13 14
       5.2.1.  Judging Routing Information's Usefulness . . . . . . . 13 14
       5.2.2.  Creating or Updating a Route Table Entry with New
               Routing Information  . . . . . . . . . . . . . . . . . 15 16
       5.2.3.  Route Table Entry Timeouts . . . . . . . . . . . . . . 16
     5.3.  Routing Messages . . . . . . . . . . . . . . . . . . . . . 17 18
       5.3.1.  RREQ Creation  . . . . . . . . . . . . . . . . . . . . 17 18
       5.3.2.  RREP Creation  . . . . . . . . . . . . . . . . . . . . 18 19
       5.3.3.  Intermediate Node DYMO Router RREP Creation . . . . . . . . . . . 18 19
       5.3.4.  RM Processing  . . . . . . . . . . . . . . . . . . . . 19 20
       5.3.5.  Adding Additional Routing Information to a RM  . . . . 20 22
     5.4.  Route Discovery  . . . . . . . . . . . . . . . . . . . . . 21 23
     5.5.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . 22 23
       5.5.1.  Active Link Monitoring . . . . . . . . . . . . . . . . 22 24
       5.5.2.  Updating Route Lifetimes During Packet Forwarding  . . 22 24
       5.5.3.  Route Error Generation . . . . . . . . . . . . . . . . 23 24
       5.5.4.  RERR Processing  . . . . . . . . . . . . . . . . . . . 23 25
     5.6.  Unknown Message & TLV Types  . . . . . . . . . . . . . . . 24 26
     5.7.  Advertising Network Addresses  . . . . . . . . . . . . . . 24 26
     5.8.  Simple Internet Attachment and Gatewaying  . . . . . . . . 24 26
     5.9.  Multiple Interfaces  . . . . . . . . . . . . . . . . . . . 26 28
     5.10. Packet/Message Generation Limits . . . . . . . . . . . . . 26 28
   6.  Configuration Parameters and Other Administrative Options  . . 26 28
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27 29
     7.1.  DYMO Message Type Specification  . . . . . . . . . . . . . 28 30
     7.2.  Packet and Message TLV Type Specification  . . . . . . . . . . . . . . 28 30
     7.3.  Address Block TLV Specification  . . . . . . . . . . . . . 29 31
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 29 31
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 30 31
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 32
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 30 32
     10.2. Informative References . . . . . . . . . . . . . . . . . . 30 32
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 33
   Intellectual Property and Copyright Statements . . . . . . . . . . 32 34

1.  Overview

   The Dynamic MANET On-demand (DYMO) routing protocol enables reactive,
   multihop unicast routing between participating nodes that wish to
   communicate. DYMO routers.  The
   basic operations of the DYMO protocol are route discovery and route
   management.  During route discovery, the
   originating node originator's DYMO router
   initiates dissemination of a Route Request (RREQ) throughout the
   network to find a route to the target node. target's DYMO router.  During this
   hop-by-hop dissemination process, each intermediate node DYMO router
   records a route to the originating node. originator.  When the target node target's DYMO router
   receives the RREQ, it responds with a Route Reply (RREP) sent hop-by-hop hop-by-
   hop toward the originating node. originator.  Each node intermediate DYMO router that
   receives the RREP records a route to the target node, target, and then the RREP is
   unicast hop-by-hop toward the originating node. originator.  When the originating node originator's DYMO
   router receives the RREP, routes have then been established between
   the originating node DYMO router and the target node DYMO router in both
   directions.

   In order to preserve routes in use, DYMO routers extend route
   lifetimes upon successfully forwarding a packet.  In order to react
   to react to changes in the network topology nodes maintain
   their routes and topology, DYMO routers monitor
   links over which traffic is moving.  When a data packet is received
   for forwarding if 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 to toward the packet source to
   indicate the current route to a particular destination is broken.
   When the source source's DYMO router receives the RERR, it knows that deletes the
   route.  If the DYMO router later receives a packet for forwarding to
   the same destination, it must perform route discovery if it still has packets to deliver to that
   destination. again.

   DYMO uses sequence numbers to ensure loop freedom [Perkins99].
   Sequence numbers enable nodes DYMO routers to determine the 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.  DYMO handles a wide variety of mobility patterns by
   dynamically determining routes on-demand.  DYMO also handles a wide
   variety of traffic patterns.  In large networks DYMO is best suited
   for traffic scenarios where nodes communicate with only a portion of
   other the nodes.

   DYMO is applicable to memory constrained devices, since little
   routing state needs to must be maintained in each node. DYMO router.  Only routing
   information related to active sources and destinations must be
   maintained, in contrast to other routing protocols that require
   routing information to all nodes routers within the autonomous system routing region be
   maintained.

   The routing algorithm

   DYMO supports routers which have multiple interfaces participating in
   the MANET.  DYMO may also supports nodes which have non-MANET interfaces
   to which hosts can attach.

   DYMO routers perform route discovery to find a route to a particular
   destination.  Therefore, DYMO routers must be operated at layers other than configured to initiate
   route discovery for certain destinations.  When DYMO is the network only
   protocol interacting with the forwarding table, DYMO should be
   configured to perform route discovery for all unknown unicast
   destinations.

   DYMO should 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.  Only
   modification of the packet format is required.  The routing algorithm
   need not change.  Note that, using the DYMO algorithm with message
   formats (other other than those specified in this document) document will not be
   interoperable.

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 RFC 2119 [RFC2119].

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

   This document defines the following terminology:

   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.

   DYMO Sequence Number (SeqNum)
      A DYMO Sequence Number is maintained by each node. DYMO router.  This
      sequence number is used by other nodes DYMO routers to identify the
      order of routing information generated by a node and to 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.

   Hop Count (HopCnt)
      The number of IP hops a message or piece of information has
      traversed.

   Originating Node (OrigNode)
      The originating node is the node DYMO router that created creates a DYMO
      Message in an effort to disseminate some information.  The
      originating node is also referred to as a particular message's
      originator.

   Route Error (RERR)
      A node generates and disseminates a RERR to message is used indicate that it 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 nodes DYMO routers
      between them.

   Route Request (RREQ)
      A node (the RREQ OrigNode) generates a RREQ message is issued to discover a valid route to a particular
      destination address, called the RREQ TargetNode.  When a node 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 node 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].
      [I-D.ietf-manet-packetbb] for additional information.

   Unreachable Node (UnreachableNode)
      An UnreachableNode is a node for which ThisNode does not have a forwarding route. 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 destination address of the node node(s) associated with the
      routing table entry.

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

   Route.NextHopAddress
      The IP address of the next node 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 fields are optional:

   Route.HopCnt
      The number of intermediate node hops

   Route.Dist
      A metric indicating the distance traversed before reaching the
      Route.Address node.  Route.HopCnt assists in determining whether
      received routing information is better than existing known
      information.

   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.  If an address block does not have an associated
      PREFIX_LENGTH TLV [I-D.ietf-manet-packetbb], the prefix may be
      considered to have a prefix length equal to the address length (in
      bits).

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

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

4.2.  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 MANET 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 TBD. 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 unless otherwise
   stated.  Therefore, all DYMO routers SHOULD subscribe to LL MANET
   ROUTERS for receiving control packets.

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

   The IP IPv4 TTL (IP (IPv6 Hop Limit) field for DYMO messages is set to one
   (1) for all messages specified in this document.

   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 messages and addresses contained in the payload
   use IPv6 addresses.  In the case of mixed IPv6 and IPv4 addresses,
   IPv4 addresses are carried in IPv6 as specified in [RFC4291].

4.2.2.  Routing Messages (RM) - RREQ & RREP

   Routing Messages (RMs) are used to disseminate routing information.
   There are two
   please see [I-D.ietf-manet-packetbb].

   If a packet contains only a single DYMO message types that are considered to be routing
   messages (RMs): RREQ and RREP.  They contain very similar information
   and function, 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 introducing jitter [I-D.ietf-manet-jitter].

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.DestinationAddress
      The IP address of the packet destination.  For RREQ the
      IP.DestinationAddress is set to LL MANET ROUTERS.  For RREP the
      IP.DestinationAddress is set to the NextHopAddress toward the RREP
      TargetNode.

   UDP.DestinationPort
      The UDP destination port is set to TBD. MANET [I-D.ietf-manet-iana].

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

   MsgHdr.HopCnt
      The number of hops this message has traversed.

   AddBlk.TargetNode.Address
      The IP address of the message TargetNode.  In a RREQ the
      TargetNode is the destination for which a forwarding route does
      not exist and route discovery is being performed.  In a RREP the
      target node
      TargetNode is the RREQ OrigNode. OrigNode DYMO router.  The TargetNode
      address is the first address in the a routing message.

   AddBlk.OrigNode.Address
      The IP address of the OrigNode.  This address originator.  In a RREQ the OrigNode is in an address
      block and not in the message header to allow
      source's DYMO router for address
      compression and additional AddTLVs. which a route discovery is being
      performed.  In a RREP the OrigNode is the RREQ TargetNode's DYMO
      router 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 OrigNode. 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.HopCnt

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

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

   AdditionalNode.AddTLV.SeqNum
      The DYMO sequence number of an additional intermediate node's associated with this routing information.

   Node.AddTLV.HopCnt
      The number

   Node.AddTLV.Dist
      A metric of IP hops the distance to reach the associated Node.Address.
      This field is incremented by at least one at each intermediate hop, for each node
      DYMO router, except the TargetNode.AddTLV.Dist.  The TargetNode's HopCnt information.
      distance information is not modified.

   Node.AddTLV.Prefix
      The Node.Address is a network address with a particular prefix
      length.

   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.DestinationAddress = LL MANET ROUTERS              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...

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

   A RERR requires the following information:

   IP.DestinationAddress
      The IP address is set to LL MANET ROUTERS.

   UDP.DestinationPort
      The UDP destination port is set to TBD. 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.  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.

   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.DestinationAddress = LL MANET ROUTERS              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...

   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Destination Port=TBD Port = MANET    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RERR-type   |  Resv   |0|0|1|         msg-size=16   |Resv |0|1|1|0|1|         msg-size=15           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | msg-hoplimit  |  msg-hopcnt   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       +-+-+-+-+-+-+-+-+
   ...
   Message Body
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      msg-tlv-block-size=0     |Number Addrs=1 |1|HeadLength=4 |  Resv   |0|1|1|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Unreachable.Address                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        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.

5.1.1.  Maintaining A Node's Own Sequence Number

   DYMO requires that each node 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.

   Note: The sequence number zero (0) is reserved.

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., 65535), 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 node should maintain its sequence number in persistent storage,
   between reboots.

   If a node's OwnSeqNum is lost, it must take certain actions to avoid
   creating routing loops.  To prevent this possibility after OwnSeqNum
   loss a node 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 node 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 node MUST generate a RERR
   message indicating that this route is not available and reset its
   waiting timeout.  At the end of the waiting period a node sets its
   OwnSeqNum to one (1).

   The longest a node must 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

5.2.1.  Judging Routing Information's Usefulness

   Given a route table entry (Route.SeqNum, Route.HopCnt, Route.Dist, and
   Route.Broken) and new incoming routing information for a particular
   node in a RM (Node.SeqNum, Node.HopCnt, 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)

   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.HopCnt Route.Dist or Node.HopCnt Node.Dist is unknown or zero (0), then
      the routing information is loop-possible.  If Node.HopCnt Node.Dist >
      Route.HopCnt
      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.HopCnt
      ((Node.Dist is unknown) OR
       (Route.HopCnt
       (Route.Dist is unknown) OR
       (Node.HopCnt
       (Node.Dist > Route.HopCnt Route.Dist + 1))

   3. Inferior
      Information is always inferior if Node.SeqNum - Route.SeqNum < 0
      (using 16-bit signed arithmetic).
      In case of known equal SeqNum, the information is inferior, if Node.HopCnt
      Node.Dist > Route.HopCnt Route.Dist (it is a
      longer greater distance route).  In case
      of equal SeqNum, the information is inferior, if Node.HopCnt Node.Dist == Route.HopCnt
      Route.Dist (equal distance route) AND Route.Broken == false AND
      this RM is a RREQ.  This condition stops forwarding of RREQ with
      equivalent distance.

      (Node.SeqNum - Route.SeqNum < 0) OR

      ((Node.SeqNum == Route.SeqNum) AND
       ((Node.HopCnt
       ((Node.Dist > Route.HopCnt) Route.Dist) OR
        ((Node.HopCnt
        ((Node.Dist == Route.HopCnt) Route.Dist) AND
         (RM is RREQ) AND (Route.Broken == false))))

   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 16-bit signed arithmetic).  In the case
      of equal sequence numbers, the information is superior, if
      Node.HopCnt
      Node.Dist < Route.HopCnt. Route.Dist.  In the case of equal sequence numbers,
      the information is superior, if Node.HopCnt Node.Dist ==
      Route.HopCnt Route.Dist AND it is
      a RREP (RREP with equal HopCnt 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
      ((Node.SeqNum == Route.SeqNum) AND
       ((Node.HopCnt
       ((Node.Dist < Route.HopCnt) Route.Dist) OR
        ((Node.HopCnt
        ((Node.Dist == Route.HopCnt) Route.Dist) AND
         ((RM is RREP) OR (Route.Broken == true)))))

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

   The route table entry is populated with the following information:

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

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

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

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

   5.  if known, the Route.HopCnt Route.Dist is set to the Node.HopCnt, Node.Dist,

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

   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 to indicate a recently learned route
   (ROUTE_NEW) is set to ROUTE_NEW_TIMEOUT.  A timer for the maximum
   delete timeout (ROUTE_AGE_MAX).  ROUTE_AGE_MAX is set to
   Node.AddTLV.MaxAge if included; otherwise, ROUTE_AGE_MAX is set to
   ROUTE_AGE_MAX_TIMEOUT.  The usage of these timers and others are
   described in Section 5.2.3.

   At this point, a forwarding route should be installed.  Afterward,
   the route can be used to send any queued data packets and forwarding 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 node DYMO router transmits a RM, other nodes DYMO routers expect the
   transmitting node 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 avoid conflicts due to reboots and
   rollovers.  When a node DYMO router has lost its sequence number (e.g, due
   to daemon reboot or node replacement) the node DYMO router must wait until
   routing information associated with its that IP address and sequence
   number are no longer maintained by other nodes DYMO routers in the network
   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.  New Information Timeout (ROUTE_NEW)

   As time progresses the likelihood that a route remains intact
   decreases, if the network nodes are mobile.  Maintaining and using
   old routing information can lead to many DYMO messages and excess
   route discovery delay.

   After the ROUTE_NEW timeout if the route has not been used, a timer
   for deleting the route (ROUTE_DELETE) is set to ROUTE_DELETE_TIMEOUT.

5.2.3.4.  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.

5.2.3.5.  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.

5.3.  Routing Messages

5.3.1.  RREQ Creation

   When a node 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 to consider this new information fresh.  If the
   sequence number is not incremented, certain nodes DYMO routers might not
   consider this information useful if they have superior information
   already.

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

   If a previous value of the TargetNode.SeqNum is known (from a routing
   table entry), 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 nodes DYMO
   routers reply, and ensures that the
   TargetNode TargetNode's DYMO router
   increments its sequence number.

   Similarly, if a previous value of the TargetNode.HopCnt TargetNode.Dist is known, it
   SHOULD be placed in TargetNode.AddTLV.HopCnt. TargetNode.AddTLV.Dist.  Otherwise, the
   TargetNode.AddTLV.HopCnt
   TargetNode.AddTLV.Dist is not included and assumed unknown by
   processing nodes.

   Next, the node adds AddBlk.OrigNode.Address to the RM and the
   OrigNode.AddTLV.SeqNum (OwnSeqNum) in an address block TLV.

   The OrigNode.Address is the address of the DYMO router that is
   initiating this node's address, and it route discovery.  The OrigNode.Address must be a
   routable IP address.  If this DYMO router is performing route
   discovery on behalf of an attached node (the source of the data
   packet forcing this route discovery), it MUST advertise it's address
   and prefix that contain the source address.  This information will be
   used by nodes to create a route toward the OrigNode and OrigNode, enable delivery
   of a RREP. RREP, and eventually for data packets.

   If OrigNode.HopCnt OrigNode.Dist is included it is set to zero (0).

   The MsgHdr.HopCnt is set to zero (0).  The MsgHdr.HopLimit should be set to MAX_HOPLIMIT, but may be set
   smaller.

   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 network and possibly reduce route
   discovery overhead.

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

5.3.2.  RREP Creation

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

   If ThisNode.SeqNum TargetNode.SeqNum is included in the RM and ThisNode.SeqNum TargetNode.SeqNum from
   the RM is less than OwnSeqNum, 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 would not reach the RREP
   Target.

   ThisNode first adds

   First, the RREP 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 is added to the RREP.

   ThisNode then adds  The
   AddBlk.OrigNode.Address must be a routable IP address.  If the RREQ
   TargetNode is this DYMO router, its address added to the RREP AddBlk.OrigNode.Address
   (ThisNode.Address) as the
   OrigNode.Address.  If the RREQ TargetNode is attached to this DYMO
   router, it MUST advertise its address and prefix that contain the
   RREQ TargetNode.Address.  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.HopCnt OrigNode.Dist is included it is set
   to zero (0).

   The MsgHdr.HopCnt is set to zero (0).  The MsgHdr.HopLimit is set to MAX_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 Node DYMO Router RREP Creation

   Sometimes a node DYMO router other than the TargetNode TargetNode's DYMO router (call
   it an "intermediate
   node") DYMO router") has routing information that can
   satisfy an incoming RREQ.  When an intermediate node DYMO router
   originates a RREP in response to a RREQ, RREQ on behalf of the TargetNode,
   it sends the RREP to the RREQ OrigNode with additional routing
   information (Address, SeqNum, etc.) about the RREQ TargetNode.

   Appending additional routing information is described in
   Section 5.3.5.

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

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

5.3.4.  RM Processing

   Before processing a RM, a node the DYMO router checks the IP.Destination to
   ensure that it is a link-local packet. was sent to LL MANET ROUTERS.

   When a RM is received the MsgHdr.HopLimit is decremented by one (1)
   and MsgHdr.HopCnt is incremented by one (1).

   For each address (except the TargetNode) in the RM that includes
   AddTLV.HopCnt
   AddTLV.Dist information, the AddTLV.HopCnt AddTLV.Dist information is incremented
   by one (1).

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

   Next, this node 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 and the address is a unicast address, 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 new node's incoming routing information is
   compared with the route table entry following the procedure described
   in Section 5.2.1.  If the new node's incoming routing information is considered
   superior, the route table 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) in the near future.

   For each of the additional addresses considered, if the address is a
   unicast address and the routing table does not have a matching route
   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 new
   node's
   incoming routing information is compared with the route table entry
   following the procedure described in Section 5.2.1.  If the new node's 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 a
   unicast address and 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 is performed.

   If the ThisNode is the DYMO router for the TargetNode and this RM is
   a RREQ, then ThisNode responds with a RREQ flood (a RREQ addressed to
   oneself) or 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.
   Note: it is important that when creating the RREP, the RREP
   OrigNode.Address be the same as the RREQ TargetNode.Address, if
   ThisNode has is responsible for several addresses.  At this point,
   ThisNode need not perform any more operations for this 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 (Route.TargetNode.SeqNum)
   greater than or equal to the RREQ TargetNode.AddTLV.SeqNum; then this
   node MAY respond with an intermediate node DYMO router RREP.  The
   procedure for performing intermediate node DYMO router RREP is described
   in Section 5.3.3.  At this point, ThisNode need not perform any more
   operations for this 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 a cost value.  Advice regarding the cost value is not included in
   this specification, it is left up to the implementation.

   The updated distance value will be an measure in determining whether
   the routing information is inferior or superior to known information
   at other DYMO routers that process this RM.

   If the resulting distance value for the OrigNode is greater than 254,
   the message is discarded.  If the resulting distance value for
   another node is greater than 254, the associated address and its
   information are removed from the RM.

   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) is SHOULD be sent to
   the LL MANET ROUTERS IP.DestinationAddress.

   By sending the 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 send the RM are: if
   ThisNode does not want to advertise routing for the contained IP
   addresses because it is already congested; 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.

   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.

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 nodes DYMO routers use
   this information to update their routing tables.

   Nodes

   DYMO routers can append routing information to a RM.  Appending additional
   routing information can help alleviate future RREQ.  This option
   should be administratively configurable.

   Prior to appending its own 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 fresh, 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.

   If an address controlled by this DYMO router is included ThisNode.HopCnt,
   ThisNode.Dist, it is set to zero (0).  Additional information about
   the address(es) can also be appended, such as a PREFIX_LENGTH AddTLV.

5.4.  Route Discovery

   When a node originates a source's DYMO router needs to forward a data packet and it
   does not have a forwarding route to the IP.DestinationAddress, it
   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.

   To reduce congestion in a network, repeated attempts at route
   discovery for a particular TargetNode should utilize an exponential
   backoff.

   For example, the first time a node 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 node 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 at by the source. 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 may have positive or negative impact, and
   therefore must be administratively configurable.

   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
   application.
   source.

5.5.  Route Maintenance

   A RERR MUST 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.Destination exists; RERR generation is described in
   Section 5.5.3.  In

   Upon this case, condition, an ICMP Destination Unreachable message SHOULD
   NOT be generated, generated unless this router is responsible for the
   IP.Destination and the that IP.Destination is not reachable. 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 nodes 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.

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 detecting a link break (or an unreachable next hop) ThisNode
   must remove the affected forwarding routes (those with an unreachable
   next hop).  ThisNode also flags these routes 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,
   a node 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, a node 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.  Route Error Generation

   A RERR informs the IP.SourceAddress or RREP.OrigNode.Address DYMO routers that the
   route does not exist, and a route to certain destinations is
   not available through this node.

   When creating a new RERR, the address of first UnreachableNode
   (IP.DestinationAddress from the a data packet or RREP.TargetNode.Address)
   is inserted into an Address Block AddBlk.UnreachableNode.Address.  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 MAX_HOPLIMIT.  The
   MsgHdr.HopCnt is set to one (1).

   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.  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.

   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. valid and flags
   those routes as broken.

   The RERR is sent to the IP.DestinationAddress LL MANET ROUTERS.
   Sending the RERR to the LL MANET ROUTERS address notifies nearby
   nodes that might depend on the now broken link.

   The packet or message that forced generation of this RERR is
   discarded.

5.5.4.  RERR Processing

   Before processing a RERR, a node the DYMO router checks the IP.Destination
   to ensure that it is a link-local packet. addressed to LL MANET ROUTERS.

   When a node DYMO router processes a RERR, it processes each
   UnreachableNode's information.  The processing node DYMO router removes
   the forwarding route and sets the broken flag 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).

   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.

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

   If this RERR's 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.

5.6.  Unknown Message & TLV Types

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

   If a message contains TLVs of an unknown type, a node ignores these
   during processing.  The processing node can remove these TLVs from
   any resulting transmitted messages.  The behavior for unknown TLV
   types should be administratively configurable.

5.7.  Advertising Network Addresses

   Any node can advertise DYMO router advertises a network address by using a PREFIX_LENGTH
   TLV [I-D.ietf-manet-packetbb].  Any nodes (other than the advertising
   node)
   DYMO router) within the advertised prefix SHOULD NOT participate in
   the DYMO protocol directly and these nodes MUST be reachable by
   forwarding packets to the node DYMO router advertising connectivity.
   Nodes other than the advertising node DYMO router that do participate in
   DYMO must forward the DYMO control packets to the advertising node. DYMO
   router.  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 node DYMO
   router with address A.B.C.1.

5.8.  Simple Internet Attachment and Gatewaying

   Simple Internet attachment consists of a stub network of MANET nodes router
   connected to the Internet via a single Internet gateway node.  The
   gateway is responsible for responding to RREQs for TargetNodes
   outside its configured DYMO prefix, as well as delivering packets to
   destinations outside the MANET.

         /--------------------------\
        /          Internet          \
        \                            /
         \------------+-------------/
       Gateway's      |
       Advertised     | A.B.C.X A.B.C.X/24
       Prefix         |
                +-----+-----+
                |   DYMO    |
         /------|  Internet |------\ |--------\
        /       |  Gateway  |         \
       /        |  A.B.C.1  |          \
       |        +-----------+          |
       |         DYMO Region           |
       |                               |
       | +------------+ +--------------+              |
       | |  DYMO Node Router |              |
       | |    A.B.C.2   |              |
       | +------------+ +--------------+              |
       |              +------------+              +--------------+ |
       |              |  DYMO Node Router | |
       |              |    A.B.C.3   | |
       \              +------------+              +--------------+ /
        \                             /
         \-------------------------/
         \---------------------------/

               Figure 7: Simple Internet Attachament Example

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

   When nodes DYMO router within the MANET want to send messages to nodes in
   the Internet, they simply issue RREQ for those
   IP.DestinationAddresses.  The gateway is responsible for responding
   to RREQ on behalf of the Internet destinations and maintaining their
   associated sequence
   numbers. number.

   For an Internet gateway and other nodes DYMO routers that maintain the
   sequence number on behalf of other nodes, these routers must be
   administratively configurable to know the IP addresses for which they
   must generate DYMO messages and maintain OwnSeqNum.

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.  Packet/Message Generation Limits

   To avoid congestion, a node'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.
   Messages should be discarded in the following order of preferences
   RREQ, RREP, and finally RERR.

6.  Configuration Parameters and Other Administrative Options

                        Suggested Parameter Values

         +------------------------------+------------------------+
         |             Name             |          Value         |
         +------------------------------+------------------------+
         |         MAX_HOPLIMIT         |         10 hops        |
         |      NET_TRAVERSAL_TIME      |    1000 milliseconds   |
         |         ROUTE_TIMEOUT        |        5 seconds       |
         |     ROUTE_AGE_MIN_TIMEOUT    |   NET_TRAVERSAL_TIME   |
         |     ROUTE_AGE_MAX_TIMEOUT    |       60 seconds       |
         |       ROUTE_NEW_TIMEOUT      |      ROUTE_TIMEOUT     |
         |      ROUTE_USED_TIMEOUT      |      ROUTE_TIMEOUT     |
         |     ROUTE_DELETE_TIMEOUT     |    2 * ROUTE_TIMEOUT   |
         |     ROUTE_RREQ_WAIT_TIME     | 2 * NET_TRAVERSAL_TIME |
         |          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 infrequent 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.  The following table enumerates several of the options and
   suggested values.

                        Suggested Options Settings

   +-------------------------------------+----------------------------+
   |                 Name                |            Value           |
   +-------------------------------------+----------------------------+
   |        RESPONSIBLE_ADDRESSES        |       Self or Prefix       |
   |           DYMO_INTERFACES           |       User Specified       |
   |         INCLUDE_INFORMATION         |  Yes-SeqNum,HopCnt,Prefix   Yes-SeqNum,Dist,Prefix   |
   |            APPEND_ADDRESS           |      Yes - RREQ & RREP     |
   | APPEND_OWN_ADDRESS_INCREMENT_SEQNUM |        Yes for RREQ        |
   |      GENERATE_RERR_IMMEDIATELY      |             No             |
   |    RERR_INCLUDE_ALL_UNREACHABLES    |             Yes            |
   |        UNKNOWN_TYPE_HANDLING        |           Ignore           |
   |         BUFFER_SIZE_PACKETS         |         50 packets         |
   |          BUFFER_SIZE_BYTES          | 1500 * BUFFER_SIZE_PACKETS |
   +-------------------------------------+----------------------------+

                                  Table 3

7.  IANA Considerations

   DYMO requires a UDP port number to carry protocol packets - TBD. MANET
   [I-D.ietf-manet-iana].  DYMO also requires the link-local multicast
   address LL MANET ROUTERS;
   IPv4 TBD, IPv6 TBD [I-D.chakeres-manet-iana]. ROUTERS [I-D.ietf-manet-iana].

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

   Future types will be allocated using standard actions as described in
   [RFC2434].

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 |        | 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 may assume that  |
   |                   |      |        | the link is unidirectional    |
   |                   |      |        | and may blacklist the link to |
   |                   |      |        | this node.                    |
   +-------------------+------+--------+-------------------------------+

                                  Table 5

7.3.  Address Block TLV Specification

                          Address Block TLV Types

   +----------------+------+---------+---------------------------------+

   +----------------+-------+--------+---------------------------------+
   |      Name      |  Type | Length | Value                           |
   +----------------+------+---------+---------------------------------+
   +----------------+-------+--------+---------------------------------+
   |   DYMOSeqNum   |  10 - |   16 bits   | The DYMO sequence num           |
   |                |  TBD  |  bits  | associated with this address.   |
   |                |       |        | The sequence number may be the  |
   |                |       |        | last known sequence number.     |
   |    HopCount    Distance    |  11 - | 8 bits | The number A metric of hops traversed by the distance        |
   |                |  TBD  |        | traversed by the information associated with    |
   |                |       |        | associated with this address.   |
   |     MaxAge     |  12 - |   Any        | The maximum number amount of time that |
   |                |  TBD  |  length        | milliseconds that the information can be maintained   |
   |                |       |        | associated routing information before being deleted.  This TLV |
   |                |       |        | can be kept before being conforms to                     |
   |                |       |        | deleted. [I-D.ietf-manet-timetlv]        |
   +----------------+------+---------+---------------------------------+
   |                |       |        | VALIDITY_TIME TLV, except that  |
   |                |       |        | the TLV is attached to          |
   |                |       |        | addresses.                      |
   +----------------+-------+--------+---------------------------------+

                                  Table 6

8.  Security Considerations

   Currently, DYMO does not specify any special security measures.
   Routing protocols, however, are prime targets for impersonation
   attacks.

   In networks situations where the node membership is not known, it confidentiality o DYMO messages is
   difficult to determine the occurrence of impersonation attacks, and
   security prevention important,
   traditional cryptographic techniques are difficult at best.  However, when
   the network membership is known and there is a danger of such
   attacks, can be applied.

   Securing routing information integrity will likely require DYMO
   routers to authenticate DYMO messages must be protected by upon reception.  Also, since
   routing information is distributed hop-by-hop, DYMO routers will also
   likely need to authenticate the use of authentication
   techniques, such as those involving generation source of unforgeable and
   cryptographically strong message digests or digital signatures.
   While DYMO does not place restrictions on the authentication
   mechanism used for this purpose, IPsec Authentication Message (AH) is
   an appropriate choice for cases where routing information,
   the nodes share an appropriate
   security association source's DYMO router.

   Note that enables the use of AH.

   In particular, RM messages SHOULD be authenticated to avoid creation
   of spurious routes to a destination.  Otherwise, an attacker could
   masquerade as is important that destination and maliciously deny service to the
   destination and/or maliciously inspect any confidentiality and consume traffic intended
   for delivery to the destination.  RERR messages SHOULD be
   authenticated in order integrity
   algorithms used permit multiple receivers to prevent malicious nodes from disrupting
   active routes between communicating nodes.

   If the mobile nodes in the ad hoc network have pre-established
   security associations, the purposes for which the security
   associations are created should include that of authorizing process the
   processing of message,
   since all DYMO control packets.  Given this understanding, the
   mobile nodes should be able to use the same authentication mechanisms
   based on their IP addresses as they would have used otherwise. messaging is multicast.

9.  Acknowledgments

   DYMO is a descendant of the design of previous MANET reactive
   protocols, especially AODV [RFC3561] and DSR [Johnson96]. [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 and Krop, Henner Jakob and Alexandru Petrescu for
   reviewing of DYMO, as well as several specification suggestions.

10.  References

10.1.  Normative References

   [I-D.ietf-manet-iana]
              Chakeres, I., "Internet Assigned Numbers Authority (IANA)
              Allocations for the Mobile Ad hoc  Networks (MANET)
              Working Group", draft-ietf-manet-iana-05 (work in
              progress), June 2007.

   [I-D.ietf-manet-packetbb]
              Clausen, T., "Generalized MANET Packet/Message Format",
              draft-ietf-manet-packetbb-03
              draft-ietf-manet-packetbb-07 (work in progress),
              January
              July 2007.

   [I-D.ietf-manet-timetlv]
              Clausen, T. and C. Dearlove, "Representing multi-value
              time in MANETs", draft-ietf-manet-timetlv-01 (work in
              progress), July 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.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

10.2.  Informative References

   [I-D.chakeres-manet-iana]
              Chakeres, I., "MANET IANA Needs",
              draft-chakeres-manet-iana-02

   [I-D.ietf-manet-jitter]
              Clausen, T., "Jitter considerations in MANETs",
              draft-ietf-manet-jitter-01 (work in progress),
              October 2006. July 2007.

   [I-D.ietf-manet-nhdp]
              Clausen, T., "MANET Neighborhood Discovery Protocol
              (NHDP)", draft-ietf-manet-nhdp-01 draft-ietf-manet-nhdp-04 (work in progress),
              February
              July 2007.

   [Johnson96]
              Johnson, D. and D. Maltz, "Dynamic Source Routing (DSR) in
              Ad hoc Networks", In Mobile Computing, Chapter 5, pp. 153-
              181, 1996.

   [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 Systems Research Center
   975 Page Mill Road, Suite 200
   Palo Alto, CA  94304-1003
   USA

   Phone: +1-650-496-4402
   Fax:   +1-650-739-0779
   Email: charles.perkins@nokia.com

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