Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                             Boeing
Internet-Draft                                                C. Perkins
Expires: December 22, 2006 April 5, 2007                                             Nokia
                                                           June 20,
                                                         October 2, 2006

                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-05
                        draft-ietf-manet-dymo-06

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

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

Table of Contents

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

1.  Overview

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

   In order to react to changes in the network topology nodes maintain
   their routes and monitor their links. links over which traffic is moving.  When a
   data packet is received for forwarding if a route is not known or link that the
   route is no longer available broken, then the source of the packet is notified.  A Route
   Error (RERR) is sent to the packet source to indicate the current
   route is broken.  Once  When the source receives the RERR, it can knows that it
   must perform route discovery if it still has packets to deliver.

   DYMO uses sequence numbers as they have been proven to ensure loop freedom [Perkins99].
   Sequence numbers enable nodes to determine the order of DYMO route
   discovery messages, thereby avoiding use of stale routing
   information.

2.  Applicability

   The DYMO routing protocol is designed for mobile ad hoc networks in
   small, medium, and large node populations. networks.
   DYMO handles all a wide variety of mobility
   ranges. patterns by dynamically
   determining routes on-demand.  DYMO can handle various also handles a wide variety of
   traffic patterns, but patterns.  In large networks DYMO is most best suited for sparse traffic sources and destinations.  DYMO is designed for
   network
   scenarios where trust is assumed, since it depends on nodes properly
   forwarding traffic to the next hop toward the destination on behalf communicate with only a portion of other the source.
   nodes.

   DYMO is applicable to memory constrained devices, since little
   routing state needs to be maintained.  Only routing information
   related to active sources and destinations must be maintained, as opposed in
   contrast to other routing protocols where routing that require routing information
   to all destinations
   or a large population destinations must nodes within the autonomous system be maintained.

   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 than those specified in this document) will not be
   interoperable.

3.  Terminology

   The keywords "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
   [RFC2119].

   This document uses some terminology from packetbb[I-D.ietf-manet-
   packetbb].

   This document defines the following terminology:

   DYMO Sequence Number (SeqNum)
      A DYMO Sequence Number is maintained by each node.  This sequence
      number is used by other nodes to identify the freshness order of related routing
      information generated by a node and to ensure loop-free routes.

   Hop Count (HopCnt)
      The number of IP hops a message or piece of information must
      traverse to reach the node holding this information.

   Originator (Orig) has
      traversed.

   Originating Node (OrigNode)
      The originator originating node is the node that created 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 disseminate indicate that it does
      not have valid route to a particular destination, one or set of more particular destinations.

   Route Reply (RREP)
      Upon receiving a RREQ during route discovery, the target node
      generates a Route Reply (RREP).
      A RREP is used to disseminate routing information, on information about how to
      reach the target, RREQ target node, to nodes between the RREQ target node
      and the RREQ originator.

   Route Request (RREQ)
      A node (the RREQ originator) generates a RREQ to discover a valid
      route to a particular destination, called the target. RREQ target node.  A
      RREQ also disseminates provides routing information on how to reach the
      originator of the RREQ.

   Target Node (TargetNode)
      The target node is the ultimate destination of a message.  For
      RREQ the target node is the desired destination. destination, the destination
      for which a valid route does not exist.  For RREP the target node
      is the originator of the RREQ.

   Valid RREQ originator.

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

   Forwarding Route
      A valid route is a known route where the Route.ValidTimeout that is
      greater than the current time.  Valid routes may be used to forward data.

   When describing DYMO messages, information found data packets.  Forwarding routes
      are generally maintained in the:

   IP header is proceeded with 'IP.'

   UDP header is proceeded with 'UDP.'

   packetbb message header is proceeded with 'MsgHdr.'

   packetbb message TLVs is proceeded with 'MsgTLV.'

   packetbb address blocks is proceeded with 'AddBlk.'

   packetbb address block TLVs is proceeded with 'AddTLV.' a forwarding information base (FIB) or
      the kernel forwarding/routing table.

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.  The number
   zero (0) is reserved and can be used to indicate that the field value
   for this routing entry is unknown or invalid.

   A routing

   Conceptually, a route table entry has the following fields:

   Route.Address
      The IP destination address of the node 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 on the path toward the
      Route.Address.

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

   Route.ValidTimeout
      The time at which a route table entry

   Route.Broken
      A flag indicating whether this Route is no longer valid.

   Route.DeleteTimeout
      If the current time broken.  This flag is after Route.DeleteTimeout set
      if the corresponding
      routing table entry MUST be deleted.

   The following 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 traversed before reaching the
      Route.Address node.

   Route.IsInternetGateway
      1-bit selector indicating  Route.HopCnt assists in determining whether the Route.Address
      received routing information is a an
      Internet gateway, see Section 5.8. superior to 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 is set may be
      considered to zero (0), unknown, or have a prefix length equal to the address length in bits, this address is a host address.  The
      definition of Route.Prefix is different for gateways; entries with
      Route.IsInternetGateway set to one (1), seeSection 5.8.

   Route.Used
      1-bit selector indicating whether this Route has been used to
      forward data toward the destination. (in
      bits).

   Not including this optional information may result in sub-optimal
   performance, cause performance degradation,
   but it is will not required for correct cause the protocol operation. to operate incorrectly otherwise.

   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 packetbb [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

   All

   DYMO messages conform to the generalized packet and message format as
   described in[I-D.ietf-manet-packetbb]. 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.

   All

   Most DYMO messages are sent with the IP destination address set to
   the link local multicast address LL_ALL_MANET_ROUTER unless otherwise
   stated.

   The IP TTL (IP Hop  Unicast DYMO messages specified in this document are sent
   with the IP destination set to the Route.NextHopAddress of the route
   to the target node.

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

   The length of an IP addresses (32-bits address (32 bits for IPv4 and 128-bits 128 bits for IPv6)
   inside a DYMO messages are dependent message depends on the IP packet header. 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 [RFC3513].

4.2.2.  Routing Message Messages (RM) - RREQ & RREP

   Routing Messages (RM) (RMs) are used to disseminate routing information.
   There are two DYMO message types that are RM, considered to be routing
   messages (RMs): RREQ and RREP.  They contain the same information, very similar information
   and function, but have slightly different processing rules.  The fundamental main
   difference between the two messages are is that RREQ messages require solicit a response; while
   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_ALL_MANET_ROUTERS.  For RREP
      the IP.DestinationAddress is set to the NextHopAddress toward the
      TargetNode.

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

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

   AddBlk.Target.Address

   AddBlk.TargetNode.Address
      The IP address of the message target. target node.  In a RREQ the target
      node is the
      unknown destination. destination for which a forwarding route does not
      exist and route discovery is being performed.  In a RREP the
      target node is the RREQ originator.
      Only one  The target node address can be marked as is
      the first address in the target.

   AddBlk.Orig.Address routing message.

   AddBlk.OrigNode.Address
      The IP address of the message originator. node originating this message.  This address
      is in an address block and not in the message header to allow for
      address compression and additional AddTLVs.

   AddTLV.Orig.SeqNum  This address is the
      second address in the message for RREQ.

   AddTLV.OrigNode.SeqNum
      The DYMO sequence number of the message originator. originating node.

   A RM may optionally include the following information:

   AddTLV.Target.SeqNum

   AddTLV.TargetNode.SeqNum
      The last known DYMO sequence number of the target.  If the
      AddTLV.Target.SeqNum is set target node.

   AddTLV.TargetNode.HopCnt
      The last known HopCnt to zero (0), then only the destination
      may respond to this RREQ. target node.

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

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

   AddTLV.Node.HopCnt
      The number of IP hops to reach the associated Node.Address.  This
      field is incremented at each intermediate hop, for each node
      except the target node's HopCnt information.

   AddTLV.Node.Prefix
      The Node.Address is a network address ([I-D.ietf-manet-packetbb]).

   AddTLV.Node.IsGateway
      This AddTLV indicates that the Internet is reachable via this
      node.  That is, all nodes outside this Node's with a particular prefix are reachable
      via the advertising Node.

   AddTLV.Node.IsTarget
      If the target is not the first address in the address blocks, this
      AddTLV is used to indicate the target.

   AddTLV.Node.IsOriginator
      In the event that the originator is not the second address in the
      address blocks, this AddTLV is used to indicate the originator.

   AddTLV.AdditionalNode.IsOffPath
      This AddTLV is used to indicate that a node is not on the path
      between the originator and the target.

   AddTLV.Node.Ignore
      If the information associated with this Node.Address should not be
      used create or update a route, this flag is set.

   Not including this optional information may result in sub-optimal
   performance, but it is not required for correct protocol operation.
      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_ALL_MANET_ROUTERS            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...

   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Destination Port=TBD      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RREQ-type   |  Resv   |0|0|1|         msg-size=24         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=24| |0|HeadLength=3 |             Head              :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :  Head     (cont)    |  Target.Tail  |   Orig.Tail   |  TLV-blk-size :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       : size=7 (cont) |
       +-+-+-+-+-+-+-+-+
   ...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address TLVs Block TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |DYMOSeqNum-type| Resv  |1|0|0|0| Index Start=1 | Index Stop=1
       |       tlv-block-size=6        |DYMOSeqNum-type|Resv |0|1|0|0|0|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | tlv-length=16 Index-start=1 | tlv-length=2  |          Orig.SeqNum          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1

4.2.3.  Route Error (RERR)

   A RERR are message is used to disseminate the information that a valid route is
   not available for
   a particular destination, one or set of destinations. more particular IP addresses.

   RERR creation and processing are described in Section 5.5.3 and
   Section 5.5.4. 5.5.

   A RERR requires the following information:

   IP.DestinationAddress
      The IP address of the packet destination. is set to LL_ALL_MANET_ROUTERS.

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

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

   AddBlk.Unreachable.Address

   AddBlk.UnreachableNode.Address
      The IP address of an Unreachable Node. UnreachableNode.  Multiple Unreachable
      Addresses unreachable
      addresses may be included.  If included in a SeqNum for this address is not
      included, it is assumed to be unknown. RERR.

   A Route Error may optionally include the following information:

   AddTLV.Unreachable.SeqNum

   AddTLV.UnreachableNode.SeqNum
      The last known DYMO sequence number of the Unreachable Node.

   AddTLV.Node.Ignore unreachable node.  If the information associated with Node.Address should a
      SeqNum for an address is not included, it is assumed to be used
      unknown.  This case occurs when a node receives a message to invalidate routes, this flag is set.
      forward 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_ALL_MANET_ROUTERS            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...

   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Destination Port=TBD      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RERR-type   |  Resv   |0|0|1|         msg-size=16           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | msg-hoplimit  |  msg-hopcnt   |      msg-tlv-block-size=0     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...
   Address Block
   Message Body
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      msg-tlv-block-size=0     |Number Addrs=1 |0|HeadLength=0 |1|HeadLength=4 |       Unreachable.Addr        :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :    Unreachable.Addr (cont)
       |        TLV-blk-size=0                       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,
   information and ensure loop freedom.

5.1.1.  Maintaining A Node's Own Sequence Number

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

5.1.2.  Incrementing a Sequence Number OwnSeqNum

   When a node increments its OwnSeqNum (as described in Section 5.3) it
   MUST do so by treating the sequence number value as if it was an unsigned
   number.  A node starts with its OwnSeqNum equal to one (1).  The
   sequence number zero (0) is reserved and is
   used in several DYMO data structures to represent an unknown sequence
   number. reserved.

5.1.3.  Sequence Number  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 MUST be 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 Sequence Number OwnSeqNum Loss

   A node can 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_PERIOD 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 period.  RERR generation is described in Section 5.5.3. 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 New Routing Information's Usefulness

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

   1. Stale
      If Node.SeqNum - Route.SeqNum < 0 (using signed 16-bit arithmetic)
      the 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-prone Loop-possible
      If Node.SeqNum == Route.SeqNum the information maybe loop-prone, may cause loops if
      used; in this case additional information must be examined.  If
      Route.HopCnt is
      unknown or set to zero (0), then the routing information is loop-
      prone.  Likewise, if Node.HopCnt is unknown or set to zero (0), then the
      routing information is loop-prone. loop-possible.  If Node.HopCnt >
      Route.HopCnt + 1, then the routing information is loop-prone. loop-possible.
      Using loop-prone loop-possible routing information is not allowed, since doing
      so might result in otherwise
      routing loops. loops may be formed.

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

   3. Inferior
      If Node.SeqNum == Route.SeqNum the information may be inferior, inferior;
      additional information must be examined.  If Node.HopCnt >= to
      Route.HopCnt, the current route is valid
      (by examining Route.ValidTimeout not Broken, and the current time), message is
      a RREQ, then the new information is inferior if inferior.  If Node.HopCnt > Route.HopCnt.  If
      Route.HopCnt + 1, the current route is valid, not Broken and the message
      is RREP, then the new information is also inferior inferior.  Inferior routes
      will not cause routing loops if
      Node.HopCnt introduced, but should not be used
      since better information is already available.

      (Node.SeqNum == Route.SeqNum) AND
      (Route.Broken == false) AND
      ((Node.HopCnt > Route.HopCnt) AND (RM is RREQ))
       OR ((Node.HopCnt > Route.HopCnt + 1) AND this RM (RM is a RREQ. RREP)))

   4. Fresh Superior
      Routing information that does not match any of the above criteria
      is loop-free and better than the information existing in the
      routing table.  Only this  This type of information is used to update the
      routing table.  For completeness, the following other cases are
      possible:

      (Node.SeqNum - Route.SeqNum > 0) OR
      ((Node.SeqNum == Route.Seqnum)
       AND ((Node.HopCnt == Route.HopCnt + 1)
            OR (Node.HopCnt == Route.HopCnt))
       AND (((Route.Broken == true) AND (RM is RREQ))
            OR ((Route.Broken == false) AND (RM is RREP)))) OR
      ((Node.HopCnt < Route.HopCnt + 1) AND (Route.Broken == false))

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

   If fresh routing information is received, the routing

   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 (IP.SourceAddress), (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.ValidTimeout Route.HopCnt is set to the current time +
       ROUTE_VALID_TIMEOUT, Node.HopCnt,

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

   7. 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 Route.Prefix 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 Node.Prefix,

   8.  the Route.IsInternetGateway maximum
   delete timeout (ROUTE_AGE_MAX).  ROUTE_AGE_MAX is set to
   Node.AddTLV.MaxAge if address included; otherwise, ROUTE_AGE_MAX is an Internet
       Gateway.

   Unknown values are set to zero (0).

   If a valid route exists to Node.Address at
   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 to fulfill forwarding
   any incoming data packets for Route.Address.  This route also
   fulfills any outstanding RREQ. route discovery attempts for Node.Address.

5.2.3.  Route Table Entry Timeouts

   Before using

5.2.3.1.  Minimum Delete Timeout (ROUTE_AGE_MIN)

   When a routing node transmits a RM, other nodes expect the transmitting node
   to have a forwarding route to the RM originator.  After updating a
   route table entry its timeouts must entry, it should be examined.

   If maintained for at least
   ROUTE_AGE_MIN.  Failure to maintain the current time 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 Route.DeleteTimeout a time in order to avoid conflicts due to reboots and
   rollovers.  When a node has lost its sequence number (e.g, due to
   daemon reboot or node replacement) the corresponding node must wait until routing table entry MUST
   information associated with its IP address and sequence number are no
   longer maintained by other nodes in the network to ensure loop-free
   routing.

   After the ROUTE_AGE_MAX timeout a route must be deleted.

   If  All
   information about the current time route is later than 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 entry's
   Route.ValidTimeout, 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 stale and cannot be used set to ROUTE_DELETE_TIMEOUT.

5.2.3.4.  Recently Used Timeout (ROUTE_USED)

   When a route
   packets.  The information in invalid entries is still used for
   filling fields to forward data packets, this timer is set to
   expire after ROUTE_USED_TIMEOUT.  This operation is also discussed in outgoing RM with last known values.
   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 Message Messages

5.3.1.  RREQ Creation

   When a node creates a RREQ it SHOULD increment its OwnSeqNum by one
   (1) according to the rules specified in (Section 5.1.2).

   Fist, 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 might not consider this
   information useful if they have better information already.

   First, the node adds the AddBlk.Target.Address AddBlk.TargetNode.Address to the RM.

   If a previous value of the Target.SeqNum TargetNode.SeqNum is known (from an existing a routing
   table entry), it SHOULD should be placed in AddTLV.Target.SeqNum. AddTLV.TargetNode.SeqNum.  If a Target.SeqNum
   TargetNode.SeqNum is not included, it is assumed to be unknown by
   processing nodes and only the target is allowed to respond.  A
   Target.SeqNum of zero (0) MAY be set to indicate that any node with
   valid routing information about this destination can respond to this
   RREQ if the node is so enabled, though the process for doing so is
   not described in this document. nodes.

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

   These AddTLVs associated with the target SHOULD node should be set to maximum
   improve protocol efficiency, but they may be omitted to reduce message size. omitted.

   Next, the node adds AddBlk.Orig.Address AddBlk.OrigNode.Address to the RM and the
   AddTLV.Orig.SeqNum
   AddTLV.OrigNode.SeqNum (OwnSeqNum) in an address block TLV.  The
   Orig.Address
   OrigNode.Address is this node's primary addresses/identifier.  The
   Orig.Address addresses/identifier, and it
   must be a routable IP address.  This information will be used by
   nodes to create a route toward the OrigNode and enable delivery of a
   RREP.

   Other AddTLVs for the originator SHOULD OrigNode should be set to maximum improve protocol
   efficiency, but they may be omitted omitted.  If OrigNode.HopCnt is included
   it is set to reduce message size. zero (0).

   The MsgHdr.HopCnt is set to zero (0).  The MsgHdr.HopLimit SHOULD should be
   set to NET_DIAMETER, but MAY may be set smaller.  For RREQ, the
   MsgHdr.HopLimit MAY 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 the
   LL_ALL_MANET_ROUTERS.

5.3.2.  RREP Creation

   When a node creates a RREP in response to a RREQ, it MUST increment increments its
   OwnSeqNum under by one (1) according to the following conditions:

   o  Target.SeqNum is not included rules specified in the message, OR

   o  Target.SeqNum is zero (0), OR

   o  Target.SeqNum - OwnSeqNum > 0 (using 16-bit signed arithmetic), OR

   o  Target.SeqNum == OwnSeqNum AND Target.HopCnt is unknown, OR

   o  Target.SeqNum ==
   Section 5.1.2.  If OwnSeqNum AND Orig.HopCnt is unknown, OR

   o  Target.SeqNum == OwnSeqNum AND Target.HopCnt (the last know hop
      count value) < Orig.HopCnt (the not incremented the routing
   information might be considered stale.  In this case, the RREP would
   not reach the originating node.

   Note: We are currently discussing and investigating mechanisms to
   avoid incrementing the sequence number of hops traversed by before issuing a route reply.
   An update to this
      RREQ behavior will likely happen in the next revision.
   Avoiding incrementation of the sequence number when issuing a RREP is
   an important mechanism to reach reduce the target).

   First, unnecessary devaluing of good
   routing information, and the ability to issue intermediate node
   replies.  Further when intermediate node replies are coupled with
   expanding ring search, route discovery cost can be further reduced.

   The node then adds the AddBlk.Target.Address AddBlk.TargetNode.Address to the RM. RREP.  The
   Target.Address
   TargetNode.Address is copied from the incoming RREQ AddBlk.Orig.Address.
   AddBlk.OrigNode.Address.

   Next, the node adds the AddBlk.Orig.Address AddBlk.OrigNode.Address to the RM RREP and the
   AddTLV.Orig.SeqNum
   AddTLV.OrigNode.SeqNum (OwnSeqNum) in an address block TLV.  The
   Orig.Address
   OrigNode.Address is copied from the incoming RREQ AddBlk.Target.Address.
   AddBlk.TargetNode.Address.

   Other AddTLVs for the originator OrigNode and target SHOULD TargetNode should be set to maximum
   improve protocol efficiency, but they may be omitted omitted.  If
   OrigNode.HopCnt is included it is set to reduce message size. zero (0).

   The MsgHdr.HopCnt is set to zero (0).  The MsgHdr.HopLimit is set to
   NET_DIAMETER.

   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.  RM Processing

   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 information
   except the target and those addresses tagged with the AddTLV-Ignore,
   AddTLV.HopCnt information, the AddTLV-HopCnt AddTLV.HopCnt information is
   incremented by one (1).

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

   If the routing information for the originator is not fresh then this
   RM must be discarded and no further

   After processing of this message is
   performed.

   If the originator's OrigNode's routing information was considered fresh, information, then each
   address that is not the target and is not flagged with the
   Ignore address-block-tlv SHOULD TargetNode should be considered for creating
   and updating routes.  If routing table space is limited, only the routing
   information about the originator is required.  Creating and updating routes for to other locations nodes can
   eliminate RREQ for those destination, IP destinations, in the event that data
   needs to be forwarded to these destinations the IP destination(s) in the near future.

   For each of these the additional addresses considered, if 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 routing
   route table entry exists, the new node's information is compared with
   the route table entry following the procedure described in
   Section 5.2.1.  If the new node's routing information is considered fresh,
   superior, the route table entry is updated as described in
   Section 5.2.2.

   If the routing information for an Node.Address AdditionalNode.Address is not
   considered
   fresh, superior, then if MUST be it is removed from the RM.  Removing this
   information ensures that non-fresh the information is not propagated.

   If

   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 receiving node is the target TargetNode AND this RM is a RREQ, then
   this node responds with a RREP.  This node creates  The procedure for creating a new
   RREP as is described in Section 5.3.2.

   After processing a RM or creating a new RM, a node MAY can append
   additional routing information to the RM, according to the process procedure
   described in Section 5.3.4.  The additional routing information will can
   help reduce route discoveries at the expense of increased message
   size.

   If this RM's MsgHdr.HopLimit is greater than one (1), this node is
   not the target, TargetNode, AND this RM is a RREQ, then the current RM
   (altered by the process procedure defined above) SHOULD be is sent to the
   LL_ALL_MANET_ROUTERS IP.DestinationAddress.

   If this RM's MsgHdr.HopLimit is greater than one (1), this node is
   not the target, TargetNode, AND this RM is a RREP, then the new current RM SHOULD be is
   sent to the Route.NextHopAddress for the RREP's Target.Address. TargetNode.Address.

   If no forwarding route exists to Target.Address, then a RERR is
   issued to the originator of the RREP.

   If this node is the target, TargetNode of the current RM's information RM, the current RM is not
   retransmitted.

5.3.4.  Adding Additional Routing Information to a RM

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

   Nodes MAY can append routing information to a RM, and should if the node believe
   believes that this additional routing information will alleviate
   future RREQ.  This option should be administratively controlled. configured.

   Prior to appending their its own address to a RM, a node MUST should increment
   its OwnSeqNum as defined in Section 5.1.2.  Then the node appends its
   IP address (AddBlk-Address) and  If OwnSeqNum (AddTLV-SeqNum).  It MAY
   also append other 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 its address, such as prefix and/or
   that it is
   an Internet Gateway. RM in transit should be administratively configured.

   If included, included the Node.HopCnt for this node is included, it is set to one (1).

   Routing
   zero (0).  Additional information about other nodes MAY the address(es) can also be added.  If this
   information is included, it must be flagged with the
   AddTLV.AdditionalNode.IsOffPath.

   Note an address may appear only once in a message's address blocks.
   Prior to adding any address, the message is searched for existing
   entries.  If an existing entry exists, this entry will have the
   information
   appended, such as this node's routing table information (created or
   updated while processing the RM) and therefore no update is
   necessary.

   In the event a newly appended address already has an AddTLV-Ignore
   flag set, it is removed. PREFIX_LENGTH AddTLV.

5.4.  Route Discovery

   A node creates and sends a RREQ (described in Section 5.3.1) to
   discover a route to a particular destination (target).  The
   IP.DestinationAddress (TargetNode) for this RREQ is set to the
   LL_ALL_MANET_ROUTERS.  Then the RM is transmitted. which
   it does not currently have a forwarding route.

   After issuing a RREQ, the originating node OrigNode waits for a route to be created to
   the target. TargetNode.  If a route is not found created within RREQ_WAIT_TIME
   milliseconds, RREQ_WAIT_TIME,
   this node MAY 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 target SHOULD node should utilize a binary an exponential
   backoff.  The

   For example, the first time a node issues a RREQ, it waits
   RREQ_WAIT_TIME milliseconds for a route to the target. target node.  If a route is not
   found within that time, the node 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 should be buffered.  This buffer SHOULD should
   have a fixed limited size (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES)
   and discard older data packets should be discarded first.

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

5.5.  Route Maintenance

   A RERR MUST be issued if a data packet is received and it cannot be
   delivered to the next hop, hop when no forwarding route exists; RERR
   generation is described in Section 5.5.3.

   In addition to inability to deliver a data packet, A RERR MAY should be
   issued immediately after detecting a broken link of an active forwarding
   route to quickly notify nodes that a link break occurred and that
   certain routes are no longer available.  If a the route with the broken
   link has not been used, a used recently (indicated by ROUTE_USED), the RERR SHOULD NOT
   should not be generated unless
   generation is expected to reduce future traffic. generated.

5.5.1.  Active Link Monitoring

   Nodes MUST monitor links on active routes that are being used. next hop links on forwarding routes.  This
   may
   monitoring can be accomplished by one or several mechanisms.  Including: 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) the
   detecting node MUST set the
   Route.ValidTimeout to must remove the current time for all active affected forwarding routes
   utilizing the (those with
   an unreachable next hop).  The node also flags these routes as
   Broken.  For each broken link. route a timer for ROUTE_DELETE is set to
   ROUTE_DELETE_TIMEOUT.

5.5.2.  Updating Route Lifetimes during Packet Forwarding

   To avoid route timeouts for active routes, removing forwarding routes that are being used, a node
   SHOULD update the
   Route.ValidTimeout set a timeout (ROUTE_USED) to ROUTE_USED_TIMEOUT for the IP.SourceAddress route
   to be the current time +
   ROUTE_VALID_TIMEOUT IP.SourceAddress upon receiving a data packet.  This route's
   Route.Used bit  If a timer for
   ROUTE_DELETE is also set, if implemented. it is removed.

   To avoid route timeouts for active routes, removing forwarding routes that are being used, a node
   SHOULD update the
   Route.ValidTimeout set a timeout (ROUTE_USED) to ROUTE_USED_TIMEOUT for the IP.DestinationAddress route
   to be the current
   time + ROUTE_VALID_TIMEOUT IP.DestinationAddress upon successfully transmitting sending a packet to
   the next hop.  This route's Route.Used bit data packet.  If a timer
   for ROUTE_DELETE is also set. set, it is removed.

5.5.3.  Route Error Generation

   When a data packet is received for a destination without a valid
   routing
   route table entry, a RERR MUST be generated.  When a RREP is being
   transmitted and no active forwarding route to the target TargetNode exists, a RERR
   MUST be generated.  A RERR informs the IP.SourceAddress or
   RREP.OrigNode.Address that the route does not exist, and a route is no longer available, or is now invalid.

   In
   not available through this node.

   When creating a new RERR, the address of first unreachable node
   (IP.DestinationAddress from the data packet) packet or
   RREP.TargetNode.Address) is inserted.  If a value for the unreachable
   node's SeqNum (AddTLV-SeqNum) (AddTLV.UnreachableNode.SeqNum) is known, it SHOULD should be
   placed in the RERR.  The MsgHdr.HopLimit is set to NET_DIAMETER.  The
   MsgHdr.HopCnt is set to one (1).

   Additional unreachable nodes UnreachableNodes that required require the same unavailable link
   (routes with the same Route.NextHopAddress and
   Route.NextHopInterface) MAY may be added to the RERR.  The SeqNum if know
   SHOULD
   known should also be included.  Appending unreachable node UnreachableNode information
   notifies each processing node of additional routes that are no longer
   available.  This option should be administratively configured.

   If SeqNum information is not known or not included in the RERR, all
   nodes processing the routing information RERR will assume their routing information
   associated with the unreachable node UnreachableNode is no longer valid.

   The RERR is sent to the IP.DestinationAddress LL_ALL_MANET_ROUTERS.
   Sending the RERR to the LL_ALL_MANET_ROUTERS address notifies the
   maximum number of nearby
   nodes of that might depend on the now broken link.

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

5.5.4.  Route Error Processing

   When a node processes a RERR, it processes each unreachable UnreachableNode's
   information.  The processing node
   address.  It sets removes the Route.ValidTimeout to forwarding route and
   sets the current time broken flag for each
   Address UnreachableNode.Address found using
   longest prefix matching that meet all of the following conditions:

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

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

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

   Each unreachable node UnreachableNode that did not result in a change to
   Route.ValidTimeout 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 addresses address(es) is also removed.

   If no unreachable node UnreachableNode addresses remain, remain in the RERR, no further other
   processing is
   performed.

   If this RERR's MsgHdr.HopLimit is greater than one (1) required and at least
   one unreachable node address remains in the RERR, then the RERR is
   sent to the IP.DestinationAddress LL_ALL_MANET_ROUTERS.

   Addresses marked with AddTLV-Ignore should remain in the RERR.

5.6.  General DYMO Packet and Message Processing

5.6.1.  Receiving Packets

   When a packet is received, its PktTLV are first examined.  Next each
   message discarded.

   If this RERR's MsgHdr.HopLimit is examined greater than one (1) and processed at least
   one unreachable node address remains in order.

   Each message's headers are first examined.  Next, the MsgTLV are
   examined.  Finally, each message RERR, then the updated
   RERR is processed according sent to its
   MsgHdr.type.

5.6.2.  Processing the IP.DestinationAddress LL_ALL_MANET_ROUTERS.

5.6.  Unknown Message and & TLV Types

   To allow future extensions, DYMO uses bits from the semantics fields
   of PktTLV, Message, MsgTLV, and AddTLV [I-D.ietf-manet-packetbb].
   Note [I-D.ietf-manet-packetbb] does not currently support this
   functionality.

   The semantic bits have the following names and characteristics for
   nodes that do not understand the type.

   Remove

   If the Semantics.Remove-bit a message with an unknown type is set, this information SHOULD be
      removed from the message.

   Discard
      If received, the Semantics.Discard-bit message is set, this
   discarded.

   If a message SHOULD not be
      processed further and it should not be propagated.  In the case contains TLVs of
      PktTLVs if the Semantics.Discard-bit is set, no messages an unknown type, a node ignores these
   during processing.  The processing node can remove these TLVs from the
      packet
   any resulting transmitted messages.  The behavior for unknown TLV
   types should be processed or propagated. administratively configured.

5.7.  Advertising Network Addresses

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

   The meaning of the Prefix field is altered for theroute to an
   Internet gateway; Route.IsInternetGateway is one (1).  If the route
   refers to an Internet gateway, its Prefix in association with the IP
   address indicates that all nodes outside that subnet are reachable
   via the Internet gateway node.  For example, a route to a Internet
   gateway with IP address A.B.C.1 and a prefix of 24 indicates that all
   nodes with an IP address NOT matching A.B.C.X are reachable via this
   node.

5.8.  Simple Internet Attachment and Gatewaying

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

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

   Figure 3: 7: Simple Internet Attachament Example

   MANET

   DYMO nodes wishing to be reachable from nodes in the Internet MUST
   have IP addresses within the gateway's configured and advertised
   MANET subnet.
   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 subnet.

   Since many MANET.

   When nodes may commonly wish to communicate with the gateway, within the gateway SHOULD indicate MANET want to nodes that it is a gateway by using
   the gateway tlv in any RM transmitted.  The Internet Gateway tlv
   indicates send messages to nodes in the MANET that the Node.Address
   Internet, they simply issue RREQ for those IP.DestinationAddresses.
   The gateway is attached responsible for responding to RREQ on behalf of the
   Internet destinations and is capable of routing data packets to all maintaining their associated sequence
   numbers.

   For an Internet gateway and other nodes
   outside of that maintain the sequence
   number on behalf of other nodes, these routers must be
   administratively configured MANET subnet, defined by to know the Node.Address IP addresses for which they
   must generate DYMO messages and Node.Prefix fields. maintain OwnSeqNum.

5.9.  Multiple Interfaces

   It is likely that

   DYMO will often be used with multiple wireless 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_ALL_MANET_ROUTERS SHOULD send
   the packet on all interfaces that have been configured for DYMO
   operation.

5.10.  Packet  Packet/Message Generation Limits

   To avoid congestion, a node SHOULD NOT transmit more than RATE_LIMIT
   control node's rate of packet/message generation
   should be limited.  The rate and algorithm for limiting messages per second.  RREQ packets SHOULD is
   left to the implementor and should be administratively configured.
   Messages should be discarded before
   RREP or RERR packets. in the following order of preferences
   RREQ, RREP, and finally RERR.

6.  Configuration Parameters and Other Administrative Options

                        Suggested Parameter Values

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

         +------------------------------+------------------------+
         |             Name             |          Value         |
           +------------------------+-------------------------+
         +------------------------------+------------------------+
         |         NET_DIAMETER         |         10 hops        |
         |       RATE_LIMIT      NET_TRAVERSAL_TIME      |            10    1000 milliseconds   |
         |   ROUTE_VALID_TIMEOUT         ROUTE_TIMEOUT        |    5000 milliseconds        5 seconds       |
         |  ROUTE_DELETE_TIMEOUT     ROUTE_AGE_MIN_TIMEOUT    | 5 * ROUTE_VALID_TIMEOUT   NET_TRAVERSAL_TIME   |
         |   ROUTE_DELETE_PERIOD     ROUTE_AGE_MAX_TIMEOUT    | 6       60 seconds       |
         |       ROUTE_NEW_TIMEOUT      |      ROUTE_TIMEOUT     |
         |      ROUTE_USED_TIMEOUT      |      ROUTE_TIMEOUT     |
         |     ROUTE_DELETE_TIMEOUT     |    2 * ROUTE_VALID_TIMEOUT ROUTE_TIMEOUT   |
         |     ROUTE_RREQ_WAIT_TIME     |    1000 milliseconds 2 * NET_TRAVERSAL_TIME |
         |          RREQ_TRIES          |         3 tries        |
         | UNICAST_MESSAGE_SENT_TIMEOUT |
           +------------------------+-------------------------+

                                  Table        1 second        |
         +------------------------------+------------------------+

                                  Table 2
   These suggested values work well for small and medium well connected
   networks with infrequence infrequent topology changes.  For larger networks or  These parameters should
   be administratively configured for the network where DYMO is used.
   Ideally, for networks with frequent topology changes the default DYMO
   parameters should be adjusted using either experimentally determined
   values or dynamic adaptation.  For example, in networks with
   infrequent topology changes ROUTE_VALID_TIMEOUT ROUTE_USED_TIMEOUT may be set to a much
   larger value.

   It is assumed that all nodes in

   In addition to the network share parameters above several administrative options
   exist.  The following table enumerates several of the same parameter
   settings.  Different parameter values options and
   suggested values.

                        Suggested Options Settings

   +-------------------------------------+----------------------------+
   |                 Name                |            Value           |
   +-------------------------------------+----------------------------+
   |        RESPONSIBLE_ADDRESSES        |       Self or Prefix       |
   |           DYMO_INTERFACES           |       User Specified       |
   |         INCLUDE_INFORMATION         |  Yes-SeqNum,HopCnt,Prefix  |
   |            APPEND_ADDRESS           |      Yes - RREQ & RREP     |
   | APPEND_OWN_ADDRESS_INCREMENT_SEQNUM |        Yes for ROUTE_VALID_TIMEOUT or
   ROUTE_DELETE_TIMEOUT in addition to arbitrary packet delays may
   result in frequent route breaks or in extreme cases routing loops. 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.
   DYMO also requires the link-local multicast address
   LL_ALL_MANET_ROUTERS; IPv4 TBD, IPv6 TBD. TBD [I-D.chakeres-manet-iana].

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

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

7.1.  DYMO Message Type Specification

   The following address block TLV.

                            DYMO Message Types

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

                                  Table 2 4

7.2.  Packet TLV Type Specification

                             Packet TLV Types

   +-------------------+------+--------+-------------------------------+
   |        Name       | Type | Length | Value                         |
   +-------------------+------+--------+-------------------------------+
   |  Unicast Response |  TBD | 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 3 5

7.3.  Address Block TLV Specification

                          Address Block TLV Specification Overview

   +----------------------+------+--------+----------------------------+ Types

   +----------------+------+---------+---------------------------------+
   |      Name      | Type |  Length | Value                           |
   +----------------------+------+--------+----------------------------+
   +----------------+------+---------+---------------------------------+
   |   DYMOSeqNum   | 10 - | 16 bits | The DYMO sequence num           |
   |                |  TBD |  bits         | associated with this address.   |
   |                |      |         | address. The sequence     |
   |                      |      |        | number may be the last  |
   |                |      |         | last known sequence number.     |
   |    HopCount    | 11 - |  8 bits | The number of hops         |
   |                      |  TBD |        | traversed by the |
   |                |  TBD |         | the information associated with |
   |                |      |         | with this address.                   |
   |   IsInternetGateway     MaxAge     | 12 - | 0 bits | Usde to indicate that this |
   |                      |  TBD |        | node is an Internet        |
   |                      |      |        | Gateway                    |
   |     IsOriginator     | 13 - | 0 bits | Used to indicate that this |
   |                      |  TBD |   Any   | node is the Originator The maximum number of           |
   |                |      |        | the RM.                    |
   |       IsTarget       | 14 - | 0 bits | Used to indicate this node |
   |                      |  TBD |  length | is the target of the DYMO  |
   |                      |      |        | message                    |
   |        Ignore        | 15 - |    0   | Used to indicate milliseconds that this |
   |                      |  TBD |        | addresses should not be the           |
   |                |      |         | processed normally; associated routing information  |
   |                |      |         | instead it should can be kept before being        |
   |                |      |         | ignored. deleted.                        |
   +----------------------+------+--------+----------------------------+
   +----------------+------+---------+---------------------------------+

                                  Table 4 6

8.  Security Considerations

   Currently, DYMO does not specify any special security measures.
   Routing protocols, however, are prime targets for impersonation
   attacks.  In networks where the node membership is not known, it is
   difficult to determine the occurrence of impersonation attacks, and
   security prevention techniques are difficult at best.  However, when
   the network membership is known and there is a danger of such
   attacks, DYMO messages must be protected by the use of authentication
   techniques, such as those involving generation of unforgeable and
   cryptographically strong message digests or digital signatures.
   While DYMO does not place restrictions on the authentication
   mechanism used for this purpose, IPsec Authentication Message (AH) is
   an appropriate choice for cases where the nodes share an appropriate
   security association that enables the use of AH.

   In particular, RM messages SHOULD be authenticated to avoid creation
   of spurious routes to a destination.  Otherwise, an attacker could
   masquerade as that destination and maliciously deny service to the
   destination and/or maliciously inspect and consume traffic intended
   for delivery to the destination.  RERR messages, while slightly less
   dangerous, messages SHOULD be
   authenticated in order to prevent malicious nodes from disrupting
   active routes between communicating nodes.

   If the mobile nodes in the ad hoc network have pre-established
   security associations, the purposes for which the security
   associations are created should include that of authorizing the
   processing of 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.

9.  Acknowledgments

   DYMO is a descendant of the design of previous MANET reactive
   protocols, especially AODV [RFC3561] and DSR [Johnson96].  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, and Thomas Clausen Clausen, Christopher Dearlove, and Seung Yi for
   reviewing of DYMO, as well as several specification suggestions.

10.  References

10.1.  Normative References

   [I-D.ietf-manet-packetbb]
              Clausen, T., "Generalized MANET Packet/Message Format",
              draft-ietf-manet-packetbb-02 (work in progress),
              July 2006.

   [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.

   [RFC3513]  Hinden, R. and S. Deering, "Internet Protocol Version 6
              (IPv6) Addressing Architecture", RFC 3513, April 2003.

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

10.2.  Informative References

   [I-D.ietf-manet-nhdp]
              Clausen, T., Dearlove, C., and J. Dean,

   [I-D.chakeres-manet-iana]
              Chakeres, I., "MANET
              Neighborhood Discovery Protocol", draft-ietf-manet-nhdp-00 IANA Needs",
              draft-chakeres-manet-iana-01 (work in progress), June
              September 2006.

   [I-D.ietf-manet-packetbb]

   [I-D.ietf-manet-nhdp]
              Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized MANET Packet/Message Format",
              draft-ietf-manet-packetbb-01 "MANET Neighborhood Discovery Protocol
              (NHDP)", draft-ietf-manet-nhdp-00 (work in progress),
              June 2006.

   [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.

Authors' Addresses

   Ian Chakeres
   Boeing Phantom Works
   The Boeing Company
   P.O. Box 3707 Mailcode 7L-49
   Seattle, WA  98124-2207
   USA

   Email: ian.chakeres@gmail.com

   Charlie Perkins
   Nokia Research Center
   313 Fairchild Drive
   Mountain View, CA  94043
   USA

   Phone: +1-650-625-2986
   Fax:   +1-650-625-2502
   Email: charlie.perkins@nokia.com charles.perkins@nokia.com

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