Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                             Boeing
Internet-Draft                                                C. Perkins
Expires: September 6, December 22, 2006                                         Nokia
                                                           March 5,
                                                           June 20, 2006

                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-04
                        draft-ietf-manet-dymo-05

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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 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

   3.
   4.  Data Structures  . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1.  6
     4.1.  Route Table Entry  . . . . . . . . . . . . . . . . . . . .  8
     3.2.  6
     4.2.  DYMO Messages  . . . . . . . . . . . . . . . . . . . . . . 10
       3.2.1.  7
       4.2.1.  Generalized MANET Packet and Message Structure . . . . 10
       3.2.2.  7
       4.2.2.  Routing Message (RM) . . . . . . . . . . . . . . . . . 10
       3.2.3.  8
       4.2.3.  Route Error (RERR) . . . . . . . . . . . . . . . . . . 12

   4. 10
   5.  Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 14
     4.1. 12
     5.1.  DYMO Sequence Numbers  . . . . . . . . . . . . . . . . . . . . . 14
       4.1.1. 12
       5.1.1.  Maintaining a A Node's Own Sequence Number . . . . . . . . . . . . 14
       4.1.2. 12
       5.1.2.  Incrementing a Sequence Number . . . . . . . . . . . . 14
       4.1.3. 13
       5.1.3.  Sequence Number Rollover . . . . . . . . . . . . . . . 14
       4.1.4. 13
       5.1.4.  Actions After Sequence Number Loss . . . . . . . . . . 14
     4.2. 13
     5.2.  DYMO Routing Table Operations  . . . . . . . . . . . . . . 14
       4.2.1.  Creating or 13
       5.2.1.  Judging New Routing Information's Usefulness . . . . . 13
       5.2.2.  Updating a Route Table Entry from with Fresh Routing Message
               Information  . . . . . . . . . . . . . . . . . . . . . 14
       4.2.2.
       5.2.3.  Route Table Entry Timeouts . . . . . . . . . . . . . . 16
     4.3. 15
     5.3.  Routing Message  . . . . . . . . . . . . . . . . . . . . . 16
       4.3.1.  Routing Message 15
       5.3.1.  RREQ Creation  . . . . . . . . . . . . . . . 16
       4.3.2.  Routing Message Processing . . . . . . 15
       5.3.2.  RREP Creation  . . . . . . . . 16
       4.3.3.  Appending Additional Routing Information  to an
               Existing Routing Message . . . . . . . . . . . . 16
       5.3.3.  RM Processing  . . . 17
     4.4.  Route Discovery . . . . . . . . . . . . . . . . . 16
       5.3.4.  Adding Additional Routing Information to a RM  . . . . 18
     4.5.
     5.4.  Route Maintenance Discovery  . . . . . . . . . . . . . . . . . . . . . 18
       4.5.1.  Active Link Monitoring
     5.5.  Route Maintenance  . . . . . . . . . . . . . . . . 18
       4.5.2.  Updating Route Lifetimes . . . . 19
       5.5.1.  Active Link Monitoring . . . . . . . . . . . . . . . . 19
       4.5.3.
       5.5.2.  Updating Route Lifetimes during Packet Forwarding  . . 20
       5.5.3.  Route Error Generation . . . . . . . . . . . . . . . . 19
       4.5.4. 20
       5.5.4.  Route Error Processing . . . . . . . . . . . . . . . . 20
     4.6. 21
     5.6.  General DYMO Packet and Message Processing . . . . . . . . 21
       4.6.1.  Packet Processing
       5.6.1.  Receiving Packets  . . . . . . . . . . . . . . . . . . 21
       4.6.2.  Generic
       5.6.2.  Processing Unknown Message Pre-processing and TLV Types . . . . . . . 21
     5.7.  Network Addresses  . . . . . 21
       4.6.3.  Processing Unknown Message and TLV Types . . . . . . . 21
       4.6.4.  Generic Message Post-processing . . . . . . . . 22
     5.8.  Simple Internet Attachment and Gatewaying  . . . 21
       4.6.5.  DYMO Control Packet Transmission . . . . . 22
     5.9.  Multiple Interfaces  . . . . . . 21
     4.7.  Routing Prefix . . . . . . . . . . . . . 23
     5.10. Packet Generation Limits . . . . . . . . . 21
     4.8.  Simple Internet Attachment and Gatewaying . . . . . . . . 22
     4.9.  Multiple Interfaces 24
   6.  Configuration Parameters . . . . . . . . . . . . . . . . . . . 22
     4.10. Packet Generation Limits 24
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . 23

   5.  Configuration Parameters . . 24
     7.1.  DYMO Message Type Specification  . . . . . . . . . . . . . 25
     7.2.  Packet TLV Type Specification  . . . . 24

   6.  IANA Considerations . . . . . . . . . . 25
     7.3.  Address Block TLV Specification  . . . . . . . . . . . 25
   7. . . 26
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26

   8.
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 27

   9.
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     9.1. 27
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 28
     9.2. 27
     10.2. Informative References . . . . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
   Intellectual Property and Copyright Statements . . . . . . . . . . 30

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 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.  When a data packet is received
   for a route or link that is no longer available 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 the source
   receives the RERR, it can perform route discovery if it still has
   packets to deliver.

   In order to enable extension of the base specification, DYMO uses the
   generalized MANET packet and message format [5].  Additionally, by
   following the defined default behavior for nodes not understanding a
   particular type of information, future enhancements are handled in an
   understood and predetermined fashion.

   DYMO uses sequence numbers as they have been proven to ensure loop
   freedom [3]. [Perkins99].  Sequence numbers enable nodes to determine the
   order of DYMO route discovery messages, thereby avoiding use of stale
   routing information.

   All

2.  Applicability

   The DYMO messages conform routing protocol is designed for mobile ad hoc networks in
   small, medium, and large node populations.  DYMO handles all mobility
   ranges.  DYMO can handle various traffic patterns, but is most suited
   for sparse traffic sources and destinations.  DYMO is designed for
   network where trust is assumed, since it depends on nodes properly
   forwarding traffic to the generalized MANET message and next hop toward the destination on behalf
   of the source.

   DYMO is applicable to memory constrained devices, since little
   routing state needs to be maintained.  Only routing information
   related to active destinations must be maintained, as opposed to
   other routing protocols where routing information to all destinations
   or a large population destinations must 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 [5] is required.  The routing algorithm
   need not change.

3.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
   this document are transmitted via UDP on port TBD.

2.  Terminology to be interpreted as described in RFC2119
   [RFC2119].

   This document defines the following terminology:

   DYMO Sequence Number (SeqNum)
      A DYMO Sequence Number is 16-bit number maintained by each
         node, and it node.  This sequence
      number is used to identify the freshness of related routing
      information and to ensure loop-free routes.

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

      IP Destination Address (IPDestinationAddress)

         The destination of a packet, determined by examining the IP
         header.

      IP Source Address (IPSourceAddress)

         The source of a packet, determined by examining the IP header.

      MANETcast

         Packet transmission must
      traverse to all neighboring MANET routers.
         MANETcast packets should be sent with an IPDestinationAddress
         of IPv4 TBD (IPv6 TBD), reach the MANETcastAddress. node holding this information.

   Originator (Orig)
      The Originator originator is the node that created a Routing DYMO Message in an
      effort to disseminate and possibly learn new routing information.

      Prefix

   Route Error (RERR)
      A Prefix indicates node generates a RERR to disseminate that an address is it does not have valid
      route to a network address, rather
         than a host address.  If a Prefix is omitted, the address is
         assumed to be a host address.

      Routing Message (RM)

         A DYMO message that is used to distribute routing information.

      Route Invalidation

         Disabling the use particular destination, or set of a route; causing it to be unavailable for
         forwarding data. destinations.

   Route Reply (RREP)
      Upon receiving a RREQ during route discovery, the target node
      generates a Route Reply (RREP).  A RREP is used to disseeminate disseminate
      routing information information, on how to reach the Target.  A RREP is a RM
         with a unicast IPDestinationAddress, indicating that this RM is target, to be unicast hop-by-hop toward nodes between
      the Target.

      Route Error (RERR)

         A node generates a Route Error (RERR) to disseminate that it
         does not have correct routing information about a particular
         destination, or set of destinations.  A RERR is most often
         generated in response to a request to forward a data packet for
         which target and the current node does not have a valid route. RREQ originator.

   Route Request (RREQ)
      A node generates a Route Request (RREQ) RREQ to discover a valid route to a particular destination (Target).
      destination, called the target.  A RREQ is used to
         disseminate also disseminates routing
      information on how to reach the Originator originator of the RREQ.  A RREQ is simply a RM with the MANETcastAddress
         in the IPDestinationAddress field of the IP packet, causing
         distribution to all neighboring DYMO routers.

   Target
      The Target target node is the ultimate destination of a message.  For
      RREQ
         this will be the target is the desired destination.  For RREP this will be the Originator target
      is the originator of the RREQ.

   Valid Route
      A valid route is a known route where the Route.ValidTimeout is
      greater than the current time.

3.  Valid routes may be used to
      forward data.

   When describing DYMO messages, information found 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.'

4.  Data Structures

3.1.

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.

   o  Route.DestAddress

   o  Route.DeleteTimeout

   o  Route.HopCnt

   o  Route.IsGateway

   o  Route.NextHopAddress

   o  Route.NextHopInterface

   o  Route.Prefix

   o  Route.SeqNum

   o  Route.ValidTimeout

      These fields are defined as follows:

      Route Node Address (Route.DestAddress)  The IP address of the node associated with the routing table
         entry.

      Route Delete Timeout (Route.DeleteTimeout)

         If the time current number
   zero (0) is after Route.DeleteTimeout the
         corresponding reserved and can be used to indicate that the field value
   for this routing entry is unknown or invalid.

   A routing table entry MUST be deleted.

      Route Hop Count (Route.HopCnt) has the following fields:

   Route.Address
      The number IP destination address of intermediate node hops before reaching the
         Route.DestAddress.

      Route Is Gateway (Route.IsGateway)

         1-bit selector indicating whether node associated with the Route.DestAddress is a
         gateway, see Section 4.8.

      Route Next Hop Address (Route.NextHopAddress) 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.DestAddress.

      Route Next Hop Interface (Route.NextHopInterface)
      Route.Address.

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

      Route Prefix (Route.Prefix)

         8-bit field that specifies Route.Address.

   Route.ValidTimeout
      The time at which a route table entry is no longer valid.

   Route.DeleteTimeout
      If the size current time is after Route.DeleteTimeout the corresponding
      routing table entry MUST be deleted.

   The following fields are optional:

   Route.HopCnt
      The number of intermediate node hops traversed before reaching the subnet reachable
         through
      Route.Address node.

   Route.IsInternetGateway
      1-bit selector indicating whether the Route.DestAddress, Route.Address is a an
      Internet gateway, see Section 4.7. 5.8.

   Route.Prefix
      Indicates that the associated address is a network address, rather
      than a host address.  The definition value is the length of the Prefix field netmask/
      prefix.  If prefix is set to zero (0), unknown, or 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.IsGateway
      Route.IsInternetGateway set to one (1), see Section 4.8. seeSection 5.8.

   Route.Used
      1-bit selector indicating whether this Route Sequence Number (Route.SeqNum)

         The sequence number of the Route.DestAddress, zero (0) if
         unknown.

      Route.ValidTimeout

         The time at which a route table entry is scheduled has been used to be
         invalidated.  The routing table entry is no longer considered
         valid if
      forward data toward the current time destination.

   Not including this optional information may result in sub-optimal
   performance, but it is after Route.ValidTimeout.

3.2. not required for correct protocol operation.

4.2.  DYMO Messages

3.2.1.

4.2.1.  Generalized MANET Packet and Message Structure

   All DYMO messages conform to the generalized packet and message
   format as described in [5].

3.2.2.  Routing Message (RM)

   Routing in[I-D.ietf-manet-packetbb].

   All DYMO messages are used to sent using UDP to the destination port TBD.

   All 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 Limit) field for all DYMO messages is set to one
   (1).

   The length of IP addresses (32-bits for IPv4 and 128-bits for IPv6)
   inside DYMO messages are dependent on the IP packet header.  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 (RM)

   Routing Messages (RM) are used to disseminate routing information.  The
   There are two DYMO message types that are RM, RREQ and RREP and they have RREP.  They
   contain the same general
   format. information, but have slightly different processing
   rules.  The fundamental difference between the two messages are that
   RREQ messages require a response, response; while a RREP are responses is the response to
   RREQ.

   Routing message

   RM creation and processing are described in Section 4.3.

   Example Simple RREQ/RREP Routing Message

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   msg-type    |  RSRV |U|N|0|1|           msg-size            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    msg-ttl    |  msg-hopcnt   |      msg-tlv-block-size=0     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Head Length  |             Head              |Number Tails=2 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   TailOrig    |  TailTarget   |        tlv-block-size         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |DYMOSEQNUM-type|          TLV Length           |   Orig.SeqNum.:
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :.Orig.SeqNum   |         Target.SeqNum         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 1

   o 5.3.

   A RM conform to requires the generalized following information:

   IP.DestinationAddress
      The IP address of the packet destination.

   MsgHdr.HopLimit
      The remaining number of hops this message format.

   o  msg-type = DYMO-RREQ or DYMO-RREP

   o  msg-semantics

      *  RM indicate inclusion may traverse.

   AddBlk.Target.Address
      The IP address of msg-ttl and msg-hop-count in msg-
         header-info, by setting bit 1

   o  msg-header-info
      *  RM contains msg-ttl

      *  RM contains msg-hop-count

   o  add-block entries

      *  RM contain 1 and only 1 address marked as Originator - If no
         address is marked as the originator message target.  In RREQ the first address target is
         assumed to be the Originator

      *  if
      unknown destination.  In RREP the RM is unicast (the IPDestinationAddress target is a unicast
         address), RM contain 1 and only 1 the RREQ originator.
      Only one address can be marked as Target
         (Target) - if no the target.

   AddBlk.Orig.Address
      The IP address is marked of the second message originator.  This address is
         assumed in an
      address block and not in the message header to be allow for address
      compression and additional AddTLVs.

   AddTLV.Orig.SeqNum
      The DYMO sequence number of the Target

   o  add-tlv

      * message originator.

   A RM contain may optionally include the following information:

   AddTLV.Target.SeqNum
      The last known DYMO Sequence Number sequence number of the Originator
         (Orig.SeqNum) in a DYMO Sequence Number tlv

      *  RM should contain the SeqNum for each address. target.  If the SeqNum
         is not included a value of Zero (0)
      AddTLV.Target.SeqNum is assumed.  For the Target
         the SeqNum will be the Last Known SeqNum (Target.SeqNum) or
         Zero (0) set to indicate that zero (0), then only the Target can reply

      *  RM should contain the HopCnt for each address.  If HopCnt is
         not included, it is assumed destination
      may respond to this RREQ.

   AddBlk.AdditionalNode.Address
      The IP address of an additional node that can be zero (unknown).  For reached via the
         Target
      node adding this information.  Each AdditionalNode.Address must
      have an associated SeqNum in the HopCnt should be message.

   AddTLV.AdditionalNode.SeqNum
      The DYMO sequence number of the Last Known HopCnt
         (Target.HopCnt)

      *  RM should contain additional node's routing
      information.

   AddTLV.Node.HopCnt
      The number of IP hops to reach the associated Node.Address.

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

   AddTLV.Node.IsGateway
      This AddTLV indicates that the Internet is not a host
         address.  If a reachable via this
      node.  That is, all nodes outside this Node's prefix are reachable
      via the advertising Node.

   AddTLV.Node.IsTarget
      If the target is not included the first address in conjunction with an
         address, it is assumed zero (host address only).  For more
         information on advertising a Prefix see Section 4.7.

      *  RM should contain a Gateway tlv for an the address that blocks, this
      AddTLV is a
         gateway.  If gateway indicator used to indicate the target.

   AddTLV.Node.IsOriginator
      In the event that the originator is not included the second address in association
         with an address, the
      address blocks, this AddTLV is assumed 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 gateway.
         For more route, this flag is set.

   Not including this optional information on gateway operation see Section 4.8.

3.2.3.  Route Error (RERR) may result in sub-optimal
   performance, but it is not required for correct protocol operation.

   Example Simple RERR Message 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | rerr-msg-type   RREQ-type   |  RSRV |U|N|0|1|           msg-size  Resv   |0|0|1|         msg-size=24           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    msg-ttl msg-hoplimit  |  msg-hopcnt   |      msg-tlv-block-size=0     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |
   ...
   Address Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Number Addrs=2 |0|HeadLength=24|             Head Length  |              :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :  Head              |Number Tails=1 (cont)  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  Target.Tail  |     Tail1   Orig.Tail   |       tlv-block-size          |dymo-seqnum-typ|  TLV-blk-size :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       : size=7 (cont) |          TLV Length
       +-+-+-+-+-+-+-+-+
   ...
   Address TLVs
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |DYMOSeqNum-type| Resv  |1|0|0|0| Index Start=1 |          Tail1.SeqNum Index Stop=1  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | tlv-length=16 |          Orig.SeqNum          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 2

   o 1

4.2.3.  Route Error (RERR)

   RERR conform are used to the generalized message format.

   o  msg-type = DYMO-RERR

   o  msg-semantics

      *  RERR indicates inclusion disseminate that a valid route is not available for
   a particular destination, or set of msg-ttl and msg-hop-count in msg-
         header-info, using bit 1

   o  msg-header-info

      *  RERR contain msg-ttl

      * destinations.

   RERR contain msg-hop-count

   o  add-block entries

      *  All addresses creation and processing are considered unreachable unless marked
         otherwise

   o  add-tlvs

      * described in Section 5.5.3 and
   Section 5.5.4.

   A RERR should contain SeqNum for each unreachable node.  If requires the following information:

   IP.DestinationAddress
      The IP address of the packet destination.

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

   AddBlk.Unreachable.Address
      The IP address of an Unreachable Node.  Multiple Unreachable
      Addresses may be included.  If a SeqNum for this address is not included in the message
      included, it is assumed to be zero
         (unknown)

      *  RERR should contain the Last Known HopCnt for each unreachable
         node. unknown.

   A Route Error may optionally include the following information:

   AddTLV.Unreachable.SeqNum
      The DYMO sequence number of the Unreachable Node.

   AddTLV.Node.Ignore
      If the HopCnt is information associated with Node.Address should not included in the message it is
         assumed to be zero (unknown)

4. used
      to invalidate routes, this flag is set.

   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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Number Addrs=1 |0|HeadLength=0 |       Unreachable.Addr        :
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       :    Unreachable.Addr (cont)    |        TLV-blk-size=0         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 2

5.  Detailed Operation

4.1.

5.1.  DYMO Sequence Numbers

4.1.1.

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

5.1.1.  Maintaining a A Node's Own Sequence Number

   DYMO requires a each node in the network to maintain its own DYMO
   sequence number (OwnSeqNum), a 16-bit unsigned integer.  The
   circumstances for a node to change incrementing its OwnSeqNum are described
   in Section 4.3.1.

4.1.2. 5.3.

5.1.2.  Incrementing a Sequence Number

   When a node increments its OwnSeqNum (as described in Section 4.3.1
   and Section 4.3.2) 5.3) it
   MUST do so by treating the sequence number value as if it was an
   unsigned number.  The sequence number zero (0) is reserved and is
   used in several DYMO data structures to represent an unknown sequence
   number.

4.1.3.

5.1.3.  Sequence Number 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 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.

4.1.4.

5.1.4.  Actions After Sequence Number Loss

   A node SHOULD can maintain its sequence number in persistent storage. 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 sequence
   number OwnSeqNum
   loss a node MUST wait for at least ROUTE_DELETE_PERIOD 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 RM. DYMO
   messages.  If a data packet is received for forwarding to another
   destination during this waiting period 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 4.5.3. 5.5.3.  At
   the end of the waiting period a node sets its sequence number OwnSeqNum to one (1).

4.2.

5.2.  DYMO Routing Table Operations

4.2.1.  Creating or Updating a Route Table Entry from

5.2.1.  Judging New Routing Message
        Information
   While processing a RM, as described in Section 4.3.2, Information's Usefulness

   Given a node checks
   its routing table for an entry to the Node.Address using longest-
   prefix matching [6].  In the event that no matching entry is found,
   an entry is created.

   If a matching entry is found, the (Route.SeqNum, Route.HopCnt, and
   Route.ValidTimeout) and new routing information about
   Node.Address contained for a particular node
   in this a RM is NOT stale if (Node.SeqNum, Node.HopCnt, and RM message type - RREQ/RREP),
   the result quality of
   subtracting the Route.SeqNum from Node.SeqNum new routing information is equal evaluated to zero (0)
   using determine
   its usefulness.  The following comparisons are performed in order:

   1. Stale
      If Node.SeqNum - Route.SeqNum < 0 (using signed 16-bit arithmetic but it SHOULD be disregarded if:

   o arithmetic)
      the Route.ValidTimeout has not passed and Node.HopCnt information is greater
      than stale.  Using stale routing information is not
      allowed, since doing so might result in routing loops.

   2. Loop-prone
      If Node.SeqNum == Route.SeqNum the information maybe loop-prone,
      additional information must be examined.  If Route.HopCnt is
      unknown or equal set to Route.HopCnt, OR

   o zero (0), then the Route.ValidTimeout has passed and routing information is loop-
      prone.  Likewise, if Node.HopCnt is greater than
      Route.HopCnt plus one (1). unknown or set to zero (0),
      then the routing information is loop-prone.  If Node.HopCnt >
      Route.HopCnt + 1, then the routing information associated with this Node.Address is stale or
   disregarded and this Node.Address loop-prone.
      Using loop-prone routing information is not allowed, since doing
      so might result in routing loops.

   3. Inferior
      If Node.SeqNum == Route.SeqNum the Originator then this DYMO
   message MUST information may be dropped.  For other Node.Addresses that are stale or
   disregarded, the inferior,
      additional information is simply removed from must be examined.  If the RM.  Removing
   stale route is valid
      (by examining Route.ValidTimeout and disregarded routing informations ensures that unused the current time), then the
      new information is not propagated further. inferior if Node.HopCnt > Route.HopCnt.  If the
      route is valid, then the new information for Node.Address is also inferior if
      Node.HopCnt == Route.HopCnt AND this RM is a RREQ.

   4. Fresh
      Routing information that does not stale or
   disregarded, then match any of the following actions occur above criteria
      is loop-free and better than the information existing in the
      routing table.  Only this type of information is used to update
      the route routing table.

5.2.2.  Updating a Route Table Entry with Fresh Routing Information

   If fresh routing information is received, the routing table entry for Node.Address: is
   populated with the following information:

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

   2.  the Route.IsGateway Route.SeqNum is set to the G-bit, Node.SeqNum,

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

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

   5.  the Route.Prefix Route.ValidTimeout is set to Node.Prefix,, the current time +
       ROUTE_VALID_TIMEOUT,

   6.  the Route.SeqNum Route.HopCnt is set to the Node.SeqNum, Node.HopCnt,

   7.  and  the Route.ValidTimeout Route.Prefix is set to the current time +
       ROUTE_TIMEOUT. Node.Prefix,

   8.  the Route.IsInternetGateway is set if address is an Internet
       Gateway.

   Unknown values are set to zero (0).

   If a valid route exists to Node.Address at this point, the route can
   be used to send any queued data packets and to fulfill any
   outstanding route requests.

4.2.2. RREQ.

5.2.3.  Route Table Entry Timeouts

   Before using a routing table entry its timeouts must be examined.

   If the current time is after Route.DeleteTimeout the corresponding
   routing table entry MUST be deleted.

   If the current time is later than a routing entry's
   Route.ValidTimeout, the route is stale and it is not cannot be used to route
   packets.  The information in invalid entries can is still be used for
   filling fields in outgoing RM with last known values.

4.3.  Routing Message

4.3.1.

5.3.  Routing Message

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 4.1.2. (Section 5.1.2).

   Fist, the node adds the AddBlk.Target.Address to the RM.

   If a previous value of the Target.SeqNum is known (from an existing
   routing table entry), it SHOULD be placed in AddTLV.Target.SeqNum.
   If a Target.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.

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

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

   Next, the node adds AddBlk.Orig.Address to the RM and the
   AddTLV.Orig.SeqNum (OwnSeqNum) in an address block TLV.  The
   Orig.Address is this node's primary addresses/identifier.  The
   Orig.Address must be a routable IP address.

   Other AddTLVs for the originator SHOULD be set to maximum protocol
   efficiency, but they may be omitted to reduce message size.

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

5.3.2.  RREP Creation

   When a node creates a RREP in response to a RREQ, it MUST increment
   its OwnSeqNum under the following conditions:

   o  Target.SeqNum is greater than OwnSeqNum not included in the message, OR

   o  Target.SeqNum is equal to zero (0), OR

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

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

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

   o  Target.SeqNum is equal to == OwnSeqNum AND Target.HopCnt (the last know hop
      count value) is less than to < Orig.HopCnt (the number of hops traversed by this
      RREQ to reach the target).

   In either case (both RREQ and RREP),

   First, the node MUST add adds the
   Orig.Address AddBlk.Target.Address to the add-block and RM.  The
   Target.Address is copied from the Orig.SeqNum to incoming RREQ AddBlk.Orig.Address.

   Next, the add-tlv-
   block.  It sets node adds the Orig.Address AddBlk.Orig.Address to its own address.  The Orig.SeqNum
   is the node's OwnSeqNum.  The node MAY advertise a prefix using RM and the
   Prefix add-tlv, as described
   AddTLV.Orig.SeqNum (OwnSeqNum) in Section 4.7.  Otherwise, the Prefix
   add-tlv is not included. an address block TLV.  The node MAY advertise it
   Orig.Address is a gateway by
   using a gateway add-tlv, as described in Section 4.8.  Otherwise, copied from the
   gateway add-tlv is not included.  The msg-ttl incoming RREQ AddBlk.Target.Address.

   Other AddTLVs for the originator and target SHOULD be set to
   NET_DIAMETER, maximum
   protocol efficiency, but MAY they may be set smaller. omitted to reduce message size.

   The msg-hopcnt MsgHdr.HopCnt is set to zero (0). the case of RREQ, the msg-ttl MAY be  The MsgHdr.HopLimit is set in accordance with an
   expanding ring search as described in [2] to limit the RREQ
   propagation to a subset of the network and possibly reduce route
   discovery overhead.

4.3.2.  Routing Message
   NET_DIAMETER.

5.3.3.  RM Processing

   After general message pre-processing (Section 4.6.2),

   When a route to the
   Originator RM is then created or updated, as described in Section 4.2.1.

   If a valid route to received the Originator MsgHdr.HopLimit is not created or updated then the
   message MUST be dropped.

   Each additional decremented by one (1)
   and MsgHdr.HopCnt is incremented by one (1).

   For each address in the address block(s) SHOULD be processed RM that includes AddTLV-HopCnt information
   except the Target.  For each of these target and those addresses the Node.HopCnt
   associated tagged with the address AddTLV-Ignore,
   the AddTLV-HopCnt information is incremented by one (1) if it exists
   and is (1).

   Next, this node checks whether its routing table has an entry to the
   AddBlk.Orig.Address using longest-prefix matching [RFC1812].  If a
   route does not zero, then exist, the new routing information is considered fresh
   and a new route table entry is created or and updated as defined described in
   Section 4.2.1.  The updating of the HopCnt occurs after processing.
   Each address resulting in 5.2.2.  If a valid route routing table entry may alleviate a future exists, the new node's
   information is compared with the route discovery.  Any addresses table entry following the
   procedure described in Section 5.2.1.  If the new node's routing
   information is considered fresh, 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 processing of this message is
   performed.

   If the originator's routing information was considered fresh, then
   each address that do is not the target and is not flagged with the
   Ignore address-block-tlv SHOULD 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 other locations can eliminate RREQ for those destination,
   in the event that data needs to be forwarded to these destinations in
   the near future.

   For each of these addresses considered, if the routing table does not yield
   have a valid matching route or
   that are using longest-prefix matching, then a route is
   created and updated as described in Section 5.2.2.  If a routing
   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, the route
   table entry is updated as described in Section 5.2.2.

   If the routing information for an Node.Address is not processed considered
   fresh, then if MUST be removed from the RM.  Only valid
   routing  Removing this
   information ensures that non-fresh information is propagated within RM messages. not propagated.

   If this node is the Target target AND this RM is a RREQ, this node responds
   with a RREP.  The Target  This node creates a new RREP as described in
   Section 4.3.1.  The Target.Address in the new 5.3.2.

   After processing a RM is set or creating a new RM, a node MAY append
   additional routing information to the
   Orig.Address from RM, according to the RM currently being processed.  The
   Target.HopCnt is the hop count for the Orig.Address.  The
   IPDestinationAddress is set to the Route.NextHopAddress for the
   Orig.Address of the current RM being processed.  The Target.SeqNum is
   set to Route.SeqNum for Orig.Address from the current RM being
   processed.  Then the new RM undergoes post-processing, according to
   Section 4.6.4.

   After processing a RM, a node MAY append its routing information to
   the RM, according to the process described in Section 4.3.3. process
   described in Section 5.3.4.  The additional routing information will
   help reduce route discoveries to this
   node.  If all nodes along at the path append their information path
   information will also be available. expense of increased message
   size.

   If this RM's MsgHdr.HopLimit is greater than one (1), this node is
   not the Target.Address and target, AND this RM is a RREQ RREQ, then the current RM (altered
   by the process defined above) SHOULD be MANETcast. 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 Address and target, AND this RM is a RREP RREP, then the current new RM SHOULD be unicast sent
   to the next hop
   address on the route to Route.NextHopAddress for the Target. RREP's Target.Address.

   If this node is the Target.Address, target, the current message is processed,
   but this message RM's information is not forwarded or
   retransmitted.

4.3.3.  Appending

5.3.4.  Adding Additional Routing Information to an Existing Routing
        Message a RM

   Appending routing information will alleviate route discovery attempts
   to this node from the nodes whose information is included, if other nodes that process the resultant RM
   information. use this
   information to update their routing tables.

   Nodes MAY append a their routing information to a RM
   processed RM, if they the node believe
   that this additional routing information will alleviate future RREQ.
   This option should be administratively controlled.

   Prior to appending their own address to a RM, a node MUST increment
   its OwnSeqNum as defined in Section 4.1.2. 5.1.2.  Then it the node appends its
   IP address (AddBlk-Address) and OwnSeqNum. OwnSeqNum (AddTLV-SeqNum).  It MAY
   also append its Prefix and G-bit other information to its address, such as prefix and/or
   that it is an Internet Gateway.  If included, the RM.  This Node.HopCnt is set
   to one (1) if included.  Several
   length fields MUST (1).

   Routing information about other nodes MAY also be adjusted to include the newly inserted
   information.

4.4.  Route Discovery

   A node generates a Route Request (RREQ) to discover a route to a
   particular destination (Target). added.  If a sequence number this
   information is known for
   the Target included, it is placed in must be flagged with the RREQ.  Otherwise, Target.SeqNum
   assumed to be unknown by processing nodes.  A Target.SeqNum of zero
   (0) MAY be set to indicate that only the destination
   AddTLV.AdditionalNode.IsOffPath.

   Note an address may respond to
   this RREQ.  If appear only once in a previous value of message's address blocks.
   Prior to adding any address, the HopCnt message is known searched for existing
   entries.  If an existing entry exists, this entry will have the Target
   information 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 placed removed.

5.4.  Route Discovery

   A node creates a RREQ (described in Section 5.3.1) to discover a corresponding add-tlv HopCnt.  Otherwise, the
   HopCnt is not included.
   route to a particular destination (target).  The IPDestinationAddress
   IP.DestinationAddress for this RREQ is set to the
   MANETcastAddress.
   LL_ALL_MANET_ROUTERS.  Then the RM is transmitted according to the
   procedure defined in Section 4.6.5. transmitted.

   After issuing a RREQ, the originating node waits for a route to be
   created to the Target. target.  If a route is not found within RREQ_WAIT_TIME
   milliseconds, this node 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 target SHOULD utilize a binary exponential
   backoff.  The first time a node issues a RREQ, it waits
   RREQ_WAIT_TIME milliseconds for a route to the Target. target.  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.  This buffer SHOULD
   have a fixed limited size and discard older data packets first.

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

4.5.

5.5.  Route Maintenance

4.5.1.  Active Link Monitoring

   Before a route can

   A RERR MUST be used for forwarding issued if a packet, data packet is received and it MUST cannot be
   checked
   delivered to make sure that the route is still valid.  If the
   Route.ValidTimeout next hop, RERR generation is earlier than the current time, the packet
   cannot described in
   Section 5.5.3.  A RERR MAY be forwarded, issued immediately after detecting a
   broken link of an active route to quickly notify nodes that a link
   break occurred and certain routes are no longer available.  If a
   route has not been used, a RERR message MUST SHOULD NOT be generated (see
   section Section 4.5.3).  In this case, the Route.DeleteTimeout unless
   generation is set expected to Route.ValidTimeout + ROUTE_DELETE_TIMEOUT.

   If the current time is after Route.DeleteTimeout, then the route MUST
   be deleted, though a route MAY be deleted at any time. reduce future traffic.

5.5.1.  Active Link Monitoring

   Nodes MUST monitor links on active routes. routes that are being used.  This
   may be accomplished by one or several mechanisms.  Including:

   o  Link layer feedback

   o  Hello messages

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

   o  Route timeout

   o  Other monitoring mechanisms or heuristics

   Upon detecting a link break the detecting node MUST set the
   Route.ValidTimeout to the current time for all active routes
   utilizing the broken link.

   A RERR MUST be issued if a data packet is received and it cannot be
   delivered to the next hop.  RERR generation is described in
   Section 4.5.3.  A RERR MAY be issued after detecting a broken link of
   an active route to quickly notify nodes that a link break occurred
   and a route or routes are no longer available.  If a route has not
   been used, a RERR SHOULD NOT be generated unless generation is
   expected to reduce future control traffic.

4.5.2.

5.5.2.  Updating Route Lifetimes during Packet Forwarding

   To avoid route timeouts for active routes, a node MUST SHOULD update the
   Route.ValidTimeout to for the IPSourceAddress IP.SourceAddress to be the current time +
   ROUTE_TIMEOUT
   ROUTE_VALID_TIMEOUT upon receiving a data packet.  This route's
   Route.Used bit is also set, if implemented.

   To avoid route timeouts for active routes, a node SHOULD update the
   Route.ValidTimeout to for the IPDestinationAddress IP.DestinationAddress to be the current
   time + ROUTE_TIMEOUT ROUTE_VALID_TIMEOUT upon successfully transmitting a packet to
   the next hop.

4.5.3.  This route's Route.Used bit is also set.

5.5.3.  Route Error Generation

   When a data packet is received for a destination without a valid
   routing table entry, a Route Error (RERR) RERR MUST be generated by this
   node. generated.  When a RREP is being
   transmitted and no active route to the target exists, a RERR MUST be
   generated.  A RERR informs the source IP.SourceAddress that the route does
   not exist, is no longer available, or is now invalid.

   In a new RERR, the address of first unreachable node (IPDestinationAddress)
   (IP.DestinationAddress from the data packet packet) is inserted.  If a value
   for the unreachable node's SeqNum (AddTLV-SeqNum) is known, it is placed in the RERR; otherwise, if
   unknown it will be assumed to be zero (0).  The msg-ttl SHOULD
   be set
   to NET_DIAMETER, but may be set smaller to limit the scope of placed in the RERR.  The msg-hopcnt MsgHdr.HopLimit is set to zero (0). NET_DIAMETER.
   The IPDestinationAddress MsgHdr.HopCnt is set to the MANETcastAddress.  This option will notify the maximum
   number of nodes of the broken link. one (1).

   Additional unreachable nodes that required the same unavailable link
   (routes with the same Route.NextHopAddress and
   Route.NextHopInterface) MAY be added to the RERR.  For each
   unreachable node the Address is appended.  The SeqNum if know should
   SHOULD also be included.  Appending additional routing unreachable node information
   notifies each processing node of additional routes that are no longer
   available.

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

   The RERR is then processed as described in Section 4.6.5.

4.5.4. sent to the IP.DestinationAddress LL_ALL_MANET_ROUTERS.
   Sending the RERR to the LL_ALL_MANET_ROUTERS address notifies the
   maximum number of nodes of the 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 SHOULD set processes each unreachable node
   address.  It sets the Route.ValidTimeout to the current time for each
   Address that meets found using longest prefix matching that meet all of the
   following conditions:

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

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

   3.  The Node.SeqNum Route.SeqNum is zero (0), unknown, OR the result of
       subtracting Route.SeqNum from Node.SeqNum is less than or equal
       to zero using
       (0), unknown, OR Node.SeqNum - Route.SeqNum <= 0 (using signed
       16-bit arithmetic. arithmetic).

   Each Node.Address unreachable node that did not result in a change to
   Route.ValidTimeout SHOULD be is removed from the RERR, since propagation of
   this information should will not result in any benefit.

   Prior to post processing a node MAY remove any unreachable node
   address and its associated  Any information to decrease
   associated with the message size. removed addresses is also removed.

   If this no unreachable node addresses remain, no further processing is the Target and the IPDestinationAddress is its own
   Address then it may stop processing.
   performed.

   If this RERR's MsgHdr.HopLimit is greater than one (1) and at least
   one unreachable node address remains in the RERR, then the RERR it
   SHOULD be handled as described in Section 4.6.4 is
   sent to continue
   notification of nodes effected by the broken link.  Otherwise, IP.DestinationAddress LL_ALL_MANET_ROUTERS.

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

4.6. RERR.

5.6.  General DYMO Packet and Message Processing

4.6.1.  Packet Processing

   The length of IP addresses (32-bits for IPv4 and 128-bits for IPv6)
   inside DYMO messages are dependent on the IP

5.6.1.  Receiving Packets

   When a packet header.  For
   example, if the IP header uses IPv6 addresses then all messages is received, its PktTLV are first examined.  Next each
   message is examined and
   addresses contained processed in the payload use IPv6 addresses.

4.6.2.  Generic Message Pre-processing order.

   Each message undergoes pre-processing before message's headers are first examined.  Next, the MsgTLV are
   examined.  Finally, each message specific
   processing occurs.  During pre-processing, the msg-ttl is decremented
   by one (1) and the msg-hopcnt is incremented by one (1).

4.6.3. processed according to its
   MsgHdr.type.

5.6.2.  Processing Unknown Message and TLV Types

   We expect

   To allow future extensions, DYMO uses bits from the next version semantics fields
   of the generalized MANET packet PktTLV, Message, MsgTLV, and
   message format [5] to include message 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 tlv semantic
   bits to control characteristics for
   nodes that do not understand the behavior of unknown types.

4.6.4.  Generic Message Post-processing type.

   Remove
      If the msg-ttl of any message Semantics.Remove-bit is zero (0) after processing it MUST set, this information SHOULD be
   dropped.

4.6.5.  DYMO Control Packet Transmission

   Packet transmission and re-transmission are controlled by
      removed from the
   IPDestinationAddress. message.

   Discard
      If the IPDestinationAddress is a unicast
   address, the packet IPDestinationAddress Semantics.Discard-bit is replaced by the
   Route.NextHopAddress from a route table lookup for set, this message SHOULD not be
      processed further and it should not be propagated.  In the Target.  If a
   route for case of
      PktTLVs if the Target Semantics.Discard-bit is unknown or invalid set, no messages from the
      packet is dropped and
   a RERR SHOULD be generated.

   For all currently defined DYMO packets the IPTTL (IPMaxCount) SHOULD should be set to 1 (IPTTL=1), since all DYMO packet communications are
   exchanged between direct neighbors only.

4.7.  Routing Prefix processed or propagated.

5.7.  Network Addresses

   Any node MAY advertise connectivity to a subset of node addresses
   within its network address space by using a Prefix tlv [5].  The
   [I-D.ietf-manet-packetbb].  Any nodes (other than the advertising
   node) within the advertised Prefix SHOULD NOT participate in the
   MANET and these nodes MUST be reachable by forwarding packets to the
   node advertising connectivity.  For example, 192.168.1.1 A.B.C.1 with a prefix
   length of 16 24 indicates all nodes with the prefix 192.168.X.X matching A.B.C.X are
   reachable through 192.168.1.1. the node with address A.B.C.1.

   The meaning of the Prefix field is altered for routes theroute to the an
   Internet gateway;
   Route.IsGateway Route.IsInternetGateway is one (1).  If the G-bit is set the route
   refers to an Internet gateway, its Prefix in association with the IP
   address indicates that all nodes outside the that subnet are reachable
   via the Internet gateway node.  For example, a route to a Internet
   gateway with IP address 192.168.1.1 A.B.C.1 and a prefix of 16 24 indicates that all
   nodes with an IP address NOT matching 192.168.X.X A.B.C.X are reachable via this
   node.

4.8.

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 targets outside
   its configured MANET subnet, as well as delivering packets to
   destinations outside the MANET.

         /--------------------------\
        /          Internet          \
        \                            /
         \------------+-------------/
         MANET Subnet | A.B.C.X
                +-----+-----+
                |   MANET   |
         /------|  Internet |------\
        /       |  Gateway  |       \
       /        |  A.B.C.1  |        \
       |        +-----------+        |
       |            MANET            |
       |                             |
       | +------------+              |
       | | MANET Node |              |
       | |  A.B.C.2   |              |
       | +------------+              |
       |              +------------+ |
       |              | MANET Node | |
       |              |   A.B.C.3  | |
       \              +------------+ /
        \                           /
         \-------------------------/

   Figure 3: Simple Internet Attachament Example

   MANET nodes wishing to be reachable from nodes in the Internet MUST
   have IP addresses within the gateway's configured and advertised
   MANET subnet.  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 nodes may commonly wish to communicate with the gateway,
   the gateway SHOULD indicate to nodes that it is a gateway by using
   the gateway tlv in any RM created or processed. transmitted.  The gateway Internet Gateway tlv
   indicates to nodes in the MANET that the Node.Address is attached to
   the Internet and is capable of routing data packets to all nodes
   outside of the configured MANET subnet, defined by the Node.Address
   and Node.Prefix fields.

4.9.

5.9.  Multiple Interfaces

   It is likely that DYMO will 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
   MANETcast packet
   with IP.DestinationAddress set to LL_ALL_MANET_ROUTERS SHOULD send
   the packet on all interfaces that have been configured for DYMO
   operation.

4.10.

5.10.  Packet Generation Limits

   To avoid congestion, a node SHOULD NOT transmit more than RATE_LIMIT
   control messages per second.  RREQ packets SHOULD be discarded before
   RREP or RERR packets.

5.

6.  Configuration Parameters

   Here are some default parameter values for DYMO:

                        Suggested Parameter Values

           +------------------------+-------------------------+
           |          Name Suggested          |          Value

      --------------------------- ---------------          |
           +------------------------+-------------------------+
           |      NET_DIAMETER      |            10           |
           |       RATE_LIMIT       |            10

      ROUTE_TIMEOUT           |
           |   ROUTE_VALID_TIMEOUT  |    5000 milliseconds    |
           |  ROUTE_DELETE_TIMEOUT 5*ROUTE_TIMEOUT

      RREQ_WAIT_TIME  | 5 * ROUTE_VALID_TIMEOUT |
           |   ROUTE_DELETE_PERIOD  | 6 * ROUTE_VALID_TIMEOUT |
           |  ROUTE_RREQ_WAIT_TIME  |    1000 milliseconds    |
           |       RREQ_TRIES       |            3            |
           +------------------------+-------------------------+

                                  Table 1

   These suggested values work well for small and medium well connected
   networks with infrequence topology changes.  For large larger networks or
   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_TIMEOUT ROUTE_VALID_TIMEOUT may be set to a much larger
   value.

   It is assumed that all nodes in the network share the same parameter
   settings.  Different parameter values for ROUTE_TIMEOUT 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.

6.

7.  IANA Considerations

   DYMO defines 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.

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

   Future types will be created for the values for the various type fields, and the allocated using standard actions as described in
   [RFC2434].

7.1.  DYMO Message Type Specification

   The following values will be assigned:

      msg-type Value

      -------------------------------- ------- address block TLV.

                            DYMO Message Types

                   +------------------------+----------+
                   |          Name          |   Type   |
                   +------------------------+----------+
                   |  Route Request (DYMO-RREQ) 8 (RREQ)  | 10 - TBD |
                   |   Route Reply (DYMO-RREP) 9 (RREP)   | 11 - TBD |
                   |   Route Error (DYMO-RERR) (RERR)   | 12 - TBD |
                   +------------------------+----------+

                                  Table 2

7.2.  Packet TLV Type Specification

                             Packet TLV Types

   +-------------------+------+--------+-------------------------------+
   |        Name       | Type | Length | Value                         |
   +-------------------+------+--------+-------------------------------+
   |  Unicast Response |  TBD |  10 -  | Indicates to the processing   |
   |      Request      |      |   TBD

      address-tlv  | 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 this node.  |
   +-------------------+------+--------+-------------------------------+

                                  Table 3

7.3.  Address Block TLV Specification

                 Address Block TLV Specification Overview

   +----------------------+------+--------+----------------------------+
   |         Name         | Type | Length | Value

      -------------------------------- -----

      DYMO SeqNum (multivalue) 20                      |
   +----------------------+------+--------+----------------------------+
   |      DYMOSeqNum      | 10 - |   16   | The DYMO sequence num      |
   |                      |  TBD

      HopCnt (multivalue) 21 |  bits  | associated with this       |
   |                      |      |        | address.  The sequence     |
   |                      |      |        | number may be the last     |
   |                      |      |        | known sequence number.     |
   |       HopCount       | 11 - | 8 bits | The number of hops         |
   |                      |  TBD

      Prefix (multivalue) |        | traversed by the           |
   |                      |      |        | information associated     |
   |                      |      |        | with this address.         |
   |   IsInternetGateway  | 12 - | 0 [5] bits | Usde to indicate that this |
   |                      |  TBD |        | node is an Internet        |
   |                      |      |        | Gateway (zero length) 22                    |
   |     IsOriginator     | 13 - | 0 bits | Used to indicate that this |
   |                      |  TBD |        | node is the Originator 23 - TBD

      Target 24 of  |
   |                      |      |        | the RM.                    |
   |       IsTarget       | 14 - | 0 bits | Used to indicate this node |
   |                      |  TBD

   Future values |        | is the target of the Type will be allocated using standard actions as
   described in [1].  For future Types DYMO  |
   |                      |      |        | message                    |
   |        Ignore        | 15 - |    0   | Used to indicate that are unicast hop-by-hop
   (packets this |
   |                      |  TBD |        | addresses should not sent to the MANETcastAddress), these Types MUST include
   the Target.Address field.

7. be    |
   |                      |      |        | processed normally;        |
   |                      |      |        | instead it should be       |
   |                      |      |        | ignored.                   |
   +----------------------+------+--------+----------------------------+

                                  Table 4

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, 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.

8.

9.  Acknowledgments

   DYMO is a descendant of the design of previous MANET reactive
   protocols, especially AODV [2] [RFC3561] and DSR [4]. [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, Klein-
   Berndt, Pedro Ruiz, Fransisco Ros and Ros, Koojana Kuladinithi Kuladinithi, Ramon
   Caceres, and Thomas Clausen for reviewing of DYMO, as well as several
   specification suggestions.

9.

10.  References

9.1.

10.1.  Normative References

   [1]

   [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", RFC 2434, BCP 26, RFC 2434,
              October 1998.

   [2]

   [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 On-
              Demand Distance Vector (AODV) Routing", RFC 3561,
              July 2003.

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

9.2.

10.2.  Informative References

   [3]

   [I-D.ietf-manet-nhdp]
              Clausen, T., Dearlove, C., and J. Dean, "MANET
              Neighborhood Discovery Protocol", draft-ietf-manet-nhdp-00
              (work in progress), June 2006.

   [I-D.ietf-manet-packetbb]
              Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized MANET Packet/Message Format",
              draft-ietf-manet-packetbb-01 (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.

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

   [5]  Clausen, T., Dearlove, C., and J. Dean, "Generalized MANET
        Packet/Message Format", February 2006.

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

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