Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                             Boeing
Internet-Draft                                                C. Perkins
Intended status: Standards Track                                   Nokia
Expires: August 13, September 3, 2007                                February 9,                                 March 2, 2007

                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-07
                        draft-ietf-manet-dymo-08

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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 in wireless, multihop networks.  It offers
   adaptation to changing network topology and determines unicast routes
   between nodes within the network on-demand. in an on-demand fashion.

Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Applicability  . . . . . Statement  . . . . . . . . . . . . . . . . . . .  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  8
       4.2.2.  Routing 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  Numerical Operations on OwnSeqNum  . . . . . . . . . . . . . . . . 13
       5.1.3.  OwnSeqNum Rollover . . . . . . . . . . . . . . . . . . 13
       5.1.4.  Actions After OwnSeqNum Loss . . . . . . . . . . . . . 13
     5.2.  DYMO Routing Table Operations  . . . . . . . . . . . . . . 13
       5.2.1.  Judging Routing Information's Usefulness . . . . . . . 13
       5.2.2.  Creating or Updating a Route Table Entry with New
               Routing Information  . . . . . . . . . . . . . . . . . 15
       5.2.3.  Route Table Entry Timeouts . . . . . . . . . . . . . . 15
     5.3.  Routing Messages . . . . . . . . . . . . . . . . . . . . . 17
       5.3.1.  RREQ Creation  . . . . . . . . . . . . . . . . . . . . 17
       5.3.2.  RREP Creation  . . . . . . . . . . . . . . . . . . . . 18 17
       5.3.3.  Intermediate Node RREP Creation  . . . . . . . . . . . 18
       5.3.4.  RM Processing  . . . . . . . . . . . . . . . . . . . . 19
       5.3.5.  Adding Additional Routing Information to a RM  . . . . 20
     5.4.  Route Discovery  . . . . . . . . . . . . . . . . . . . . . 21
     5.5.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . 22 21
       5.5.1.  Active Link Monitoring . . . . . . . . . . . . . . . . 22
       5.5.2.  Updating Route Lifetimes during Packet Forwarding  . . 22
       5.5.3.  Route Error Generation . . . . . . . . . . . . . . . . 22
       5.5.4.  Route Error Processing . . . . . . . . . . . . . . . . 23
     5.6.  Unknown Message & TLV Types  . . . . . . . . . . . . . . . 24
     5.7.  Advertising Network Addresses  . . . . . . . . . . . . . . 24
     5.8.  Simple Internet Attachment and Gatewaying  . . . . . . . . 24
     5.9.  Multiple Interfaces  . . . . . . . . . . . . . . . . . . . 26
     5.10. Packet/Message Generation Limits . . . . . . . . . . . . . 26
   6.  Configuration Parameters and Other Administrative Options  . . 26
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
     7.1.  DYMO Message Type Specification  . . . . . . . . . . . . . 28
     7.2.  Packet TLV Type Specification  . . . . . . . . . . . . . . 28
     7.3.  Address Block TLV Specification  . . . . . . . . . . . . . 29
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 29
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 30
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 30
     10.2. Informative References . . . . . . . . . . . . . . . . . . 30
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
   Intellectual Property and Copyright Statements . . . . . . . . . . 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 discovery, the
   originating node initiates dissemination of a Route Request (RREQ)
   throughout the network to find a route to the target node.  During
   this hop-by-hop 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) 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 hop-by-hop
   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 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 source of the packet is
   notified.  A Route Error (RERR) is sent to the packet source to
   indicate the current route to a particular destination is broken.
   When the source receives the RERR, it knows that it must perform
   route discovery if it still has packets to deliver. deliver to that
   destination.

   DYMO uses sequence numbers 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 Statement

   The DYMO routing protocol is designed for stub 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 be maintained. maintained in each node.  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 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 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].

   This

   Additionally, this document uses some terminology from
   [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 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 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 indicate that it does
      not have forwarding route to a one or more particular addresses.

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

   Route Request (RREQ)
      A node (the RREQ OrigNode) generates a RREQ to discover a valid
      route to a particular destination address, called the RREQ
      TargetNode.  When a node 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 currently performing a
      calculation or processing a message.

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

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

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 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.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 traversed before reaching the
      Route.Address node.  Route.HopCnt assists in determining whether
      received routing information is superior to 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] , [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.

   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.

   Most DYMO messages are sent with the IP destination address set to
   the link local multicast address LL_ALL_MANET_ROUTER unless otherwise
   stated.  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 TTL (IP 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 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 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_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 is allowed to traverse.

   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 is the RREQ OrigNode.  The TargetNode address is the
      first address in the routing message.

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

   AddTLV.OrigNode.SeqNum

   OrigNode.AddTLV.SeqNum
      The DYMO sequence number of the OrigNode.

   A RM may optionally include the following information:

   AddTLV.TargetNode.SeqNum

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

   AddTLV.TargetNode.HopCnt

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

   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 address TLV block.

   AddTLV.AdditionalNode.SeqNum

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

   AddTLV.Node.HopCnt

   Node.AddTLV.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 TargetNode's HopCnt information.

   AddTLV.Node.Prefix

   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_ALL_MANET_ROUTERS            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...

   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Destination Port=TBD      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RREQ-type   |  Resv   |0|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 |             Head              :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :     (cont)    |  Target.Tail  |   Orig.Tail   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       tlv-block-size=6        |DYMOSeqNum-type|Resv |0|1|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_ALL_MANET_ROUTERS.

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

   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:

   AddTLV.UnreachableNode.SeqNum

   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 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   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...
   Message Body
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      msg-tlv-block-size=0     |Number Addrs=1 |1|HeadLength=4 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       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 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.  Incrementing  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, and
   Route.Broken) and new incoming routing information for a particular
   node in a RM (Node.SeqNum, Node.HopCnt, and RM message type - RREQ/RREP), 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 or Node.HopCnt is unknown or zero (0),
      then the routing information is loop-possible.  If Node.HopCnt >
      Route.HopCnt + 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 is unknown)
       OR (Route.HopCnt is unknown)
       OR (Node.HopCnt > Route.HopCnt +1)) + 1))

   3. Inferior
      If Node.SeqNum == Route.SeqNum the incoming information may be
      inferior; additional information must be examined.  If Node.HopCnt
      >= to Route.HopCnt, the current route is not Broken, and the
      message is a RREQ, then the new information is inferior.  This
      rule will stop RREQ propagation if the HopCnt is not shorter.  If
      Node.HopCnt > Route.HopCnt + 1, the current route is not Broken
      and the message is RREP, then the new information is inferior.
      This rule will stop RREP propagation if the information is
      inferior.  Inferior routes will not cause routing loops if
      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 (RM is RREP)))

   4. Superior
      Routing
      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.  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 == (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)))) true)
           OR ((Node.HopCnt < Route.HopCnt + 1) Route.HopCnt)
              AND (Route.Broken == false)) (RM is RREQ))))

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 is set to the Node.HopCnt,

   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
   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 transmits a RM, other nodes expect the transmitting node
   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 has lost its sequence number (e.g, due to
   daemon reboot or node replacement) the node must wait until routing
   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.  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 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 might not consider this
   information useful if they have better superior information already.

   First, the node adds the AddBlk.TargetNode.Address to the RREQ.

   If a previous value of the TargetNode.SeqNum is known (from a routing
   table entry), it SHOULD be placed in AddTLV.TargetNode.SeqNum TargetNode.AddTLV.SeqNum in all
   but the
   first few last RREQ attempts. attempt.  If a TargetNode.SeqNum is not included,
   it is assumed to be unknown by processing nodes, nodes.  This operation
   ensures that no intermediate nodes reply, and ensures that the
   TargetNode increments its sequence number.

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

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

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

   The MsgHdr.HopCnt is set to zero (0).  The MsgHdr.HopLimit should be
   set to NET_DIAMETER, 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_ALL_MANET_ROUTERS.

5.3.2.  RREP Creation

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

   If ThisNode.SeqNum is included in the RM and ThisNode.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.

   Since RREP messages are not broadcast throughout the network, changes
   to the sequence number are unlikely to reach most nodes in the
   network.  Therefore, it is important to avoid incrementing the
   sequence number when issuing a RREP is an important mechanism to
   reduce the unnecessary devaluing of good routing information, and the
   ability to issue intermediate node replies.  When intermediate node
   replies are coupled with expanding ring search, route discovery cost
   can be reduced.

   ThisNode first adds the RREP AddBlk.TargetNode.Address to the RREP.
   The TargetNode is the ultimate destination of this RREP.

   ThisNode then adds the RREP AddBlk.OrigNode.Address
   (ThisNode.Address) and the RREP AddTLV.OrigNode.SeqNum OrigNode.AddTLV.SeqNum (OwnSeqNum) to
   the RREP.

   Other AddTLVs in the RREP for the OrigNode and TargetNode SHOULD be
   included and set accordingly.  If OrigNode.HopCnt is included it is
   set to zero (0).

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

   Sometimes a node other than the TargetNode (call it an "intermediate
   node") has routing information that can satisfy an incoming RREQ.
   When an intermediate node originates a RREP in response to a RREQ, 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 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 creates a gratuitous 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 checks the IP.Destination to ensure
   that it is a link local packet.

   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, the AddTLV.HopCnt information is
   incremented by one (1).

   Next, this node checks whether its routing table has an entry to the
   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 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 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 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 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
   superior, the route table entry is updated as described in
   Section 5.2.2.

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

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

   If the ThisNode is 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 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 AddBlk.TargetNode.SeqNum, TargetNode.AddTLV.SeqNum, and ThisNode has an forwarding
   route to the TargetNode with a SeqNum (Route.TargetNode.SeqNum)
   greater than or equal to the RREQ AddBlk.TargetNode.SeqNum; TargetNode.AddTLV.SeqNum; then this
   node MAY respond with an intermediate node RREP.  The procedure for
   performing intermediate node 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.

   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 sent to the
   LL_ALL_MANET_ROUTERS IP.DestinationAddress.

   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 use this
   information to update their routing tables.

   Nodes can append routing information to a RM, and should if ThisNode
   believes that the RM.  Appending additional
   routing information will can help alleviate future RREQ.  This option
   should be administratively configurable.

   Prior to appending its own address 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 included the Node.HopCnt for ThisNode is included, 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

   A node creates and sends a RREQ (described in Section 5.3.1) to
   discover a route to a particular destination (TargetNode) for which
   it does not currently have a forwarding route.

   After issuing a RREQ, the OrigNode 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 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 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. buffered at the source.  This
   buffer should have a fixed limited size (BUFFER_SIZE_PACKETS or
   BUFFER_SIZE_BYTES) and older data packets SHOULD be discarded first.

   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.

5.5.  Route Maintenance

   A RERR MUST be issued if a data packet is received and it cannot be
   delivered to the next 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 SHOULD be
   issued immediately after detecting a broken link of an forwarding
   route to quickly notify nodes 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 forwarding routes that are being used, 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 forwarding routes that are 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 that the
   route does not exist, and a route is not available through this node.

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

   The RERR is sent to the IP.DestinationAddress LL_ALL_MANET_ROUTERS.
   Sending the RERR to the LL_ALL_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.  Route Error Processing

   Before processing a RERR, a node checks the IP.Destination to ensure
   that it is a link local packet.

   When a node processes a RERR, it processes each UnreachableNode's
   information.  The processing node 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 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
       UnreachableNode.SeqNum is zero (0), unknown, OR
       UnreachableNode.SeqNum - Route.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_ALL_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 a network address by using a PREFIX_LENGTH TLV
   [I-D.ietf-manet-packetbb].  Any nodes (other than the advertising
   node) within the advertised prefix SHOULD NOT participate in the 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.

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 TargetNodes
   outside its configured DYMO prefix, as well as delivering packets to
   destinations outside the MANET.

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

               Figure 7: Simple Internet Attachament Example

   DYMO nodes 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 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.

   For an Internet gateway and other nodes 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 will often 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_ALL_MANET_ROUTERS SHOULD send
   the packet on all interfaces that have been configured for DYMO
   operation.

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         |
         +------------------------------+------------------------+
         |         NET_DIAMETER         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  |
   |            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.
   DYMO also requires the link-local multicast address
   LL_ALL_MANET_ROUTERS; IPv4 TBD, IPv6 TBD [I-D.chakeres-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 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 |         | associated with this address.   |
   |                |      |         | The sequence number may be the  |
   |                |      |         | last known sequence number.     |
   |    HopCount    | 11 - |  8 bits | The number of hops traversed by |
   |                |  TBD |         | the information associated with |
   |                |      |         | this address.                   |
   |     MaxAge     | 12 - |   Any   | The maximum number of           |
   |                |  TBD |  length | milliseconds that the           |
   |                |      |         | associated routing information  |
   |                |      |         | can be kept before being        |
   |                |      |         | deleted.                        |
   +----------------+------+---------+---------------------------------+

                                  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 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 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, Thomas Clausen, Christopher Dearlove, and Seung Yi Yi, and Romain
   Thouvenin 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
              draft-ietf-manet-packetbb-03 (work in progress),
              July 2006.
              January 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 (work in progress),
              October 2006.

   [I-D.ietf-manet-nhdp]
              Clausen, T., "MANET Neighborhood Discovery Protocol
              (NHDP)", draft-ietf-manet-nhdp-00 draft-ietf-manet-nhdp-01 (work in progress),
              June 2006.
              February 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.

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

   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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