Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                             Boeing
Internet-Draft                                          E. Belding-Royer
Expires: April 26, 2006                                 UC Santa Barbara                                                C. Perkins
Expires: September 6, 2006                                         Nokia
                                                        October 23, 2005
                                                           March 5, 2006

                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-03
                        draft-ietf-manet-dymo-04

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Copyright Notice

   Copyright (C) The Internet Society (2005). (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. network on-demand.

Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4

   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5

   3.  Data Structures  . . . . . . . . . . . . . . . . . . . . . . .  7
     3.1  8
     3.1.  Route Table Entry  . . . . . . . . . . . . . . . . . . . .  7
     3.2  8
     3.2.  DYMO Message Elements  . . . Messages  . . . . . . . . . . . . . . .  8
       3.2.1   Generic DYMO Element Structure . . . . . . . . 10
       3.2.1.  Generalized MANET Packet and Message Structure . . . .  9
       3.2.2 10
       3.2.2.  Routing Element (RE) Message (RM) . . . . . . . . . . . . . . . . . 11
       3.2.3 10
       3.2.3.  Route Error (RERR) . . . . . . . . . . . . . . . . . . 14
       3.2.4   Unsupported-element Error (UERR) . . . . . . . . . . . 15 12

   4.  Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 16
     4.1 14
     4.1.  Sequence Numbers . . . . . . . . . . . . . . . . . . . . . 16
       4.1.1 14
       4.1.1.  Maintaining a Sequence Number  . . . . . . . . . . . . 16
       4.1.2 14
       4.1.2.  Incrementing a Sequence Number . . . . . . . . . . . . 16
       4.1.3 14
       4.1.3.  Sequence Number Rollover . . . . . . . . . . . . . . . 16
       4.1.4 14
       4.1.4.  Actions After Sequence Number Loss . . . . . . . . . . 16
     4.2 14
     4.2.  DYMO Routing Table Operations  . . . . . . . . . . . . . . 16
       4.2.1 14
       4.2.1.  Creating or Updating a Route Table Entry from a
               Routing Block  . . . . . . . Message Information  . . . . . . . . . . . . . 16
       4.2.2 14
       4.2.2.  Route Table Entry Timeouts . . . . . . . . . . . . . . 18
     4.3 16
     4.3.  Routing Element Message  . . . . . . . . . . . . . . . . . . . . . 18
       4.3.1 16
       4.3.1.  Routing Element Message Creation . . . . . . . . . . . . . . . 18
       4.3.2 16
       4.3.2.  Routing Element Message Processing . . . . . . . . . . . . . . 18
       4.3.3 16
       4.3.3.  Appending Additional Routing Information  to an
               Existing Routing Element Message . . . . . . . . . . . . . . . 19
     4.4 17
     4.4.  Route Discovery  . . . . . . . . . . . . . . . . . . . . . 19
     4.5 18
     4.5.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . 20
       4.5.1 18
       4.5.1.  Active Link Monitoring . . . . . . . . . . . . . . . . 20
       4.5.2 18
       4.5.2.  Updating Route Lifetimes . . . . . . . . . . . . . . . 21
       4.5.3 19
       4.5.3.  Route Error Generation . . . . . . . . . . . . . . . . 21
       4.5.4 19
       4.5.4.  Route Error Processing . . . . . . . . . . . . . . . . 22
     4.6 20
     4.6.  General DYMO Packet and Message Processing . . . . . . . . 21
       4.6.1.  Packet Processing  . . . . . . . . . 22
       4.6.1   DYMO Control Packet Processing . . . . . . . . . . . . 22
       4.6.2 21
       4.6.2.  Generic Element Message Pre-processing . . . . . . . . . . . . 23
       4.6.3 21
       4.6.3.  Processing Unsupported DYMO Element Unknown Message and TLV Types . . . . . . 23
         4.6.3.1   Generating an Unsupported-element Error  . . . . . 24
       4.6.4 21
       4.6.4.  Generic Element Message Post-processing  . . . . . . . . . . . 24
       4.6.5 21
       4.6.5.  DYMO Control Packet Transmission . . . . . . . . . . . 24
     4.7 21
     4.7.  Routing Prefix . . . . . . . . . . . . . . . . . . . . . . 24
     4.8 21
     4.8.  Simple Internet Attachment and Gatewaying  . . . . . . . . . . . . . . . . . . . 25
     4.9 22
     4.9.  Multiple Interfaces  . . . . . . . . . . . . . . . . . . . 25
     4.10 22
     4.10. Packet Generation Limits . . . . . . . . . . . . . . . . . 25 23

   5.  Configuration Parameters . . . . . . . . . . . . . . . . . . . 26 24

   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27 25
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 28 26

   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 29 27

   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     9.1 28
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 30
     9.2 28
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 30 28

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 30 . . 29
   Intellectual Property and Copyright Statements . . . . . . . . 32 . . 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 re-initiates can perform route discovery if it still has
   packets to deliver.

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

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

   All DYMO packets messages conform to the generalized MANET message and packet
   format [5] and are transmitted via UDP on port TBD.

2.  Terminology

      IP Destination Address (IPDestinationAddress)

         The destination of a packet, indicated

      DYMO Sequence Number (SeqNum)

         A DYMO Sequence Number is 16-bit number maintained by examining the IP
         header.

      IP each
         node, and it is used to ensure loop-free routes.

      Hop Count (HopCnt)

         The number of 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, indicated determined by examining the IP header.

      DYMOcast

      MANETcast

         Packet transmission to all DYMO neighboring MANET routers.  DYMOcast
         MANETcast packets should be sent with an IPDestinationAddress
         of IPv4 TBD (IPv6 TBD), the DYMOcastAddress. MANETcastAddress.

      Originator (Orig)

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

      Prefix

         A Prefix indicates that an address is a network address, rather
         than a host address.  If a Prefix is omitted, the address is
         assumed to be a host address.

      Routing Element (RE) Message (RM)

         A DYMO message element that is used to distribute routing information.

      Route Invalidation

         Disabling the use of a route, route; causing it to be unavailable for
         forwarding data.

      Route Reply (RREP)

         Upon receiving a RREQ, RREQ during route discovery, the target node
         generates a Route Reply (RREP).  A RREP is used to disseeminate
         routing information on how to reach the Target.  A RREP is a RE RM
         with a unicast IPDestinationAddress, indicating that this RE RM is
         to be unicast hop-by-hop toward the
         TargetAddress. 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 the current node does not have a valid route.

      Route Request (RREQ)

         A node generates a Route Request (RREQ) to discover a valid
         route to a particular destination (TargetAddress). (Target).  A RREQ is used to
         disseminate routing information on how to reach the Originator
         of the RREQ.  A RREQ is simply a RE RM with the DYMOcastAddress MANETcastAddress
         in the IPDestinationAddress field of the IP packet.  Also, the A-bit
         is set to one (A=1) packet, causing
         distribution to indicate that all neighboring DYMO routers.

      Target

         The Target is the TargetNode must
         respond with ultimate destination of a RREP. message.  For RREQ
         this will be the desired destination.  For RREP this will be
         the Originator of the RREQ.

      Valid Route

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

3.  Data Structures

3.1

3.1.  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 is after Route.DeleteTimeout the
         corresponding routing table entry MUST be deleted.

      Route Hop Count (Route.HopCnt)

         The number of intermediate node hops before reaching the
         Route.DestAddress.

      Route Is Gateway (Route.IsGateway)

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

      Route Next Hop Address (Route.NextHopAddress)

         The IP address of the next node on the path toward the
         Route.DestAddress.

      Route Next Hop Interface (Route.NextHopInterface)

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

      Route Prefix (Route.Prefix)

         6-bit

         8-bit field that specifies the size of the subnet reachable
         through the Route.DestAddress, see Section 4.7.  The definition
         of the Prefix field is different for gateways; entries with
         Route.IsGateway set to one (1). (1), see Section 4.8.

      Route Sequence Number (Route.SeqNum)

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

      Route.ValidTimeout

         The time at which a route table entry is scheduled to be
         invalidated.  The routing table entry is no longer considered
         valid if the current time is after Route.ValidTimeout.

3.2

3.2.  DYMO Messages

3.2.1.  Generalized MANET Packet and Message Elements

3.2.1  Generic DYMO Element Structure

   All DYMO message elements MUST messages conform to the fixed data structure
   below.

   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 generalized packet and message
   format as described in [5].

3.2.2.  Routing Message (RM)

   Routing messages are used to disseminate routing information.  The
   two message types are RREQ and RREP and they have the same general
   format.  RREQ messages require a response, while RREP are responses
   to RREQ.

   Routing message 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |          Len          |    TTL    |I|Reserved |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .          NotifyAddress (Only Types with M-bit set)            .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   . TargetAddress (for non-DYMOcastAddress IPDestinationAddresses).
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                             Data                              .
   .                     Type-Specific Payload                     .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

      Element Type (Type)

                  0                          0
                  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8
                  +-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+ 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type   msg-type    |     =    |M| H  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 2

         The Type field identifies 1

   o  RM conform to the element generalized message format.

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

   o  msg-semantics

      *  RM indicate inclusion 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 well Originator - If no
         address is marked as the handling
         by nodes that do not implement or understand the element.  The
         most significant bit, originator the M-bit, denotes whether first address is
         assumed to be the element
         requires notification via an Unsupported-element Error (UERR)
         when Originator

      *  if the element RM is unicast (the IPDestinationAddress is not understood or handled by a particular
         node.  The next two bits, H-bits, identify how unicast
         address), RM contain 1 and only 1 address marked as Target
         (Target) - if no address is marked the Type second address is
         assumed to be handled by nodes not implementing the Type, regardless of
         UERR delivery.  Section 4.6.3 describes Target

   o  add-tlv

      *  RM contain the handling behavior
         based on DYMO Sequence Number of the Type.

      I-bit (I)

         1-bit selector indicating whether Originator
         (Orig.SeqNum) in a DYMO Sequence Number tlv

      *  RM should contain the element has been ignored
         by some node that has relayed this element. SeqNum for each address.  If I=1 the element
         has been ignored.

      Reserved (Reserved, Reservd, Res, R)

         Reserved bits.  These bits are set to zero SeqNum
         is not included a value of Zero (0) is assumed.  For the Target
         the SeqNum will be the Last Known SeqNum (Target.SeqNum) or
         Zero (0) during element
         creation and ignored during processing.

      Element Time to Live (TTL)

         6-bit field indicate that identifies only the maximum number of times Target can reply

      *  RM should contain the
         element HopCnt for each address.  If HopCnt is
         not included, it is assumed to be retransmitted.  The TTL field operates similar
         to IPTTL (MaxCount) and is decremented at each hop.  When TTL
         reaches zero (0) the element is dropped.

      Element Length (Len)

         12-bit field that indicates (unknown).  For the size of
         Target the element in bytes,
         including HopCnt should be the fixed portion.

      Element Notify Address (NotifyAddress)

         The node to send Last Known HopCnt
         (Target.HopCnt)

      *  RM should contain a UERR if the Element Type Prefix for each address that is unsupported or not handled by the processing node.  The NotifyAddress field a host
         address.  If a prefix is
         only present if the Type field has the M-bit not included in conjunction with an
         address, it is set to one (1).

      Element Target Address (TargetAddress)

         The node assumed zero (host address only).  For more
         information on advertising a Prefix see Section 4.7.

      *  RM should contain a Gateway tlv for an address that is the ultimate destination of the element.  This
         field a
         gateway.  If gateway indicator is only required if not included in association
         with an address, the IPDestinationAddress address is assumed to not the
         DYMOcastAddress.  During hop-by-hop transmission of be a DYMO
         packet the IPDestinationAddress is filled with the
         Route.NextHopAddress of the route table entry associated with
         the TargetAddress.

      Element Data (Data)

         Type-specific payload.

3.2.2  Routing Element (RE) gateway.
         For more information on gateway operation see Section 4.8.

3.2.3.  Route Error (RERR)

   Example Simple RERR 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     Type      |          Len rerr-msg-type |    TTL    |I|A|S| Res  RSRV |U|N|0|1|           msg-size            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                         TargetAddress                         .
       |    msg-ttl    |  msg-hopcnt   |      msg-tlv-block-size=0     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          TargetSeqNum  Head Length  |             Head              |Number Tails=1 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  THopCnt  |Res|                                               .
   +-+-+-+-+-+-+-+-+                                               .
   .                                                               .
   .                    Routing Block 1 (RBlock1)                  .
   .                                                               .     Tail1     |       tlv-block-size          |dymo-seqnum-typ|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                    Additional Routing Blocks                  .
   .                                                               .
       |          TLV Length           |          Tail1.SeqNum         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Figure 3

      A-bit (A)

         1-bit selector indicating whether this RE requires a RREP by 2

   o  RERR conform to the TargetAddress.  If A=1 a RREP is required.  The
         instructions for generating a RREP are described in
         Section 4.3.2.

      S-bit (S)
         1-bit selector indicating whether this RE requires a unicast generalized message be sent to format.

   o  msg-type = DYMO-RERR

   o  msg-semantics

      *  RERR indicates inclusion of msg-ttl and msg-hop-count in msg-
         header-info, using bit 1

   o  msg-header-info

      *  RERR contain msg-ttl

      *  RERR contain msg-hop-count

   o  add-block entries

      *  All addresses are considered unreachable unless marked
         otherwise

   o  add-tlvs

      *  RERR should contain SeqNum for each unreachable node.  If the previous hop address.  This message MAY
         used by
         SeqNum is not included in the previous hop message it is assumed to ensure that be zero
         (unknown)

      *  RERR should contain the link traversed Last Known HopCnt for each unreachable
         node.  If the HopCnt is not unidirectional.  The handling instructions for included in the S-bit message it is
         explained
         assumed to be zero (unknown)

4.  Detailed Operation

4.1.  Sequence Numbers

4.1.1.  Maintaining a Sequence Number

   DYMO requires each node in Section 4.3.2.

      Element Target Address (TargetAddress) the network to maintain its own DYMO
   sequence number (OwnSeqNum), a 16-bit unsigned integer.  The
   circumstances for a node that is the ultimate destination of the Routing
         Element.

      Target to change its OwnSeqNum are described in
   Section 4.3.1.

4.1.2.  Incrementing a Sequence Number (TargetSeqNum)

   When a node increments its OwnSeqNum (as described in Section 4.3.1
   and Section 4.3.2) it MUST do so by treating the sequence number
   value as if it was an unsigned number.  The sequence number of the ultimate destination of this Routing
         Element.  If the Sequence Number zero (0)
   is unknown for this particular
         Route.DestAddress then TargetSeqNum reserved and is set used in several DYMO data structures to zero (0).

      Target Hop Count (THopCnt)

         6-bit field that identifies represent
   an unknown sequence number.

4.1.3.  Sequence Number Rollover

   If the sequence number of intermediate nodes
         through which a packet traversed on the route has been assigned to this
         particular TargetAddress be the last time largest possible
   number representable as a route was available.
         The THopCnt is the Route.HopCnt of 16-bit unsigned integer (i.e., 65535), then
   the TargetAddress, stored in sequence number MUST be set to 256 when incremented.  Setting the routing table of the RREQ originator.  If the hop count
         information is not available at the originating node then the
         THopCnt is set to zero (0).

      Routing Block (RBlock)

         Data structure that describes routing information related to a
         particular IP address, RBNodeAddress.

      Routing Block (RBlock)

   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
                                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                   |G|  RBPrefix   |Res| RBHopCnt  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                          RBNodeAddress                        .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          RBNodeSeqNum                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                   Figure 4

         G-bit (G)

            1-bit selector to indicate whether the RBNodeAddress is a
            gateway.  If G=1 RBNodeAddress is a gateway.  For more
            information on gateway operation see Section 4.8.

         Prefix Size (Prefix)

            7-bit field that specifies the size of the subnet reachable
            through the associated node, see Section 4.7.  The
            definition of Prefix is different for gateways.

         Routing Block Hop Count (RBHopCnt)

            6-bit field that identifies the number of intermediate nodes
            through which the associated RBlock has passed.

         Routing Block Node Address (RBNodeAddress)

            The IP address of the node associated with this RBlock.

         Routing Block Node Sequence Number (RBNodeSeqNum)
            The sequence number of the node associated with this RBlock.

3.2.3  Route Error (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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |          Len          |    TTL    |I|Reserved |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                          UNodeAddress1                        .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          UNodeSeqNum1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .               Additional UNodeAddressN (if needed)            .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Additional UNodeSeqNumN (if needed)             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 5

      Unreachable Node Address (UNodeAddress)

         The IP address of the unreachable node.

      Unreachable Node Sequence Number (UNodeSeqNum)

         The sequence number of the unreachable node, if known;
         otherwise, zero (0).  RERR generation is described in
         Section 4.5.3.

3.2.4  Unsupported-element Error (UERR)

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |          Len          |    TTL    |I|Reserved |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                          TargetAddress                        .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                       UElemTargetAddress                      .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                        UERRNodeAddress                        .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   UElemType   |
   +-+-+-+-+-+-+-+-+

                                 Figure 6

      Element Target Address (TargetAddress)

         The node that is the ultimate destination of the element,
         NotifyAddress.

      Unsupported-element Target Address (UElemTargetAddress)

         Address of the destination of the element that caused
         generation of this UERR; TargetAddress from the offending fixed
         DYMO element.

      Unsupported-element Node Address (UERRNodeAddress)

         The IP address of the node that created the UERR.

      Unsupported-element Type (UElemType)

         The Type that required generation of the UERR.

4.  Detailed Operation

4.1  Sequence Numbers

4.1.1  Maintaining a Sequence Number

   DYMO requires each node in the network to maintain its own
   sequence number (OwnSeqNum).  The circumstances for a node to change its
   OwnSeqNum are described in Section 4.3.1.

4.1.2  Incrementing a Sequence Number

   When a node increments its OwnSeqNum (as described in Section 4.3.1
   and Section 4.3.2) 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 256 allows other nodes to represent
   an unknown sequence number.

4.1.3  Sequence Number Rollover

   If detect that the sequence number
   has been assigned to be the largest possible
   number representable as a 32-bit unsigned integer (i.e., 4294967295),
   then rolled over and the node has not lost its sequence number MUST be set to one (1) when incremented.

4.1.4 number.

4.1.4.  Actions After Sequence Number Loss

   A node SHOULD maintain its sequence number in persistent storage.

   If a node's OwnSeqNum is lost, it must take certain actions to avoid
   creating routing loops.  To prevent this possibility after sequence
   number loss a node MUST wait for at least ROUTE_DELETE_PERIOD before
   transmitting any
   fully participating in the DYMO packet other than RERR generated by this node. routing protocol.  If a DYMO control packet
   message is received during this waiting period, the node SHOULD
   process it normally but MUST not transmit or retransmit any DYMO control
   packets. RM.  If a
   data packet is received for forwarding to another destination during
   this waiting period the node MUST send generate a RERR message to the IPSourceAddress with the
   UNodeSeqNum set to zero (0) indicating
   that this route is not available and restart reset its waiting period before
   transmitting any DYMO control packets except period.  RERR generated by this
   node.

4.2
   generation is described in Section 4.5.3.  At the end of the waiting
   period a node sets its sequence number to one (1).

4.2.  DYMO Routing Table Operations

4.2.1

4.2.1.  Creating or Updating a Route Table Entry from a Routing Block Message
        Information
   While processing a RE, RM, as described in Section 4.3.2, a node checks
   its routing table for an entry to the RBNodeAddress Node.Address using longest-
   prefix matching. matching [6].  In the event that no matching entry is found,
   an entry is created.

   If a matching entry is found, the routing information about
   RBNodeAddress contained in this RBlock is NOT stale if the result of
   subtracting the Route.SeqNum from RBNodeSeqNum is greater than zero
   (0) using signed 32-bit arithmetic.

   If a matching entry is found, the routing information about
   RBNodeAddress
   Node.Address contained in this RBlock RM is NOT stale if the result of
   subtracting the Route.SeqNum from RBNodeSeqNum Node.SeqNum is equal to zero (0)
   using signed 32-bit 16-bit arithmetic but it SHOULD be disregarded if:

   o  the Route.ValidTimeout has not passed and RBHopCnt Node.HopCnt is greater
      than or equal to Route.HopCnt, OR

   o  the Route.ValidTimeout has passed and RBHopCnt Node.HopCnt is greater than
      Route.HopCnt plus one (1).

   If the information in associated with this RBlock Node.Address is stale or
   disregarded and this
   RBlock Node.Address is the first RBlock in a RREQ Originator then this DYMO packet
   message MUST be dropped.  For other RBlocks containing Node.Addresses that are stale or disregarded routing
   information,
   disregarded, the RBlock information is simply removed from this RE and the RELen
   adjusted. RM.  Removing
   stale and disregarded RBlocks routing informations ensures that unused
   information is not propagated further.

   If the route information for RBNodeAddress Node.Address is not stale, disregarded stale or a disregarded RREP,
   disregarded, then the following actions occur to the route table
   entry for RBNodeAddress: Node.Address:

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

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

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

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

   5.  the Route.Prefix is set to RBPrefix, Node.Prefix,,

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

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

   If a valid route exists to RBNodeAddress, 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

4.2.2.  Route Table Entry Timeouts

   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 be used to route
   packets.  The information in invalid entries is can still be used for
   generating RREQ messages.

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

4.3
   filling fields in outgoing RM with last known values.

4.3.  Routing Element

4.3.1 Message

4.3.1.  Routing Element Message Creation

   When a node creates a RREQ it SHOULD increment its OwnSeqNum by one
   according to the rules specified in Section 4.1.2.  When a node
   creates a RREP, then RREP in response to a RREQ, it increments MUST increment its OwnSeqNum
   under the following conditions:

   o  TargetSeqNum  Target.SeqNum is greater than OwnSeqNum OR

   o  TargetSeqNum  Target.SeqNum is equal to OwnSeqNum AND Target.HopCnt is unknown
      OR

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

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

   In either case (for (both RREQ or and RREP), the node MUST create add the first
   RBlock.
   Orig.Address to the add-block and the Orig.SeqNum to the add-tlv-
   block.  It sets the RBNodeAddress Orig.Address to its own address.  The
   RBNodeSeqNum Orig.SeqNum
   is the node's OwnSeqNum.  The node may MAY advertise a prefix using the
   Prefix field, add-tlv, as described in Section 4.7.  Otherwise, the Prefix field
   add-tlv is set to zero (0). not included.  The node may MAY advertise it is a gateway by setting the G-bit if it is
   using a gateway, gateway add-tlv, as described in Section 4.8.  Otherwise, the G-bit
   gateway add-tlv is set to zero (0). not included.  The TTL msg-ttl SHOULD be set to
   NET_DIAMETER, but MAY be set smaller.  For  The msg-hopcnt is set to zero
   (0). the case of RREQ, the TTL msg-ttl MAY be set in accordance with an
   expanding ring search as described in [2].

4.3.2 [2] to limit the RREQ
   propagation to a subset of the network and possibly reduce route
   discovery overhead.

4.3.2.  Routing Element Message Processing

   After general DYMO element message pre-processing (Section 4.6.2), the
   RBHopCnt for the first RBlock is incremented by one (1).  A a route to the first RBlock
   Originator is then created or updated, as described in Section 4.2.1.

   If this RBlock does not result in a valid route to the
   packet Originator is not created or updated then the
   message MUST be dropped.

   Each additional RBlock address in the address block(s) SHOULD be processed. processed
   except the Target.  For each RBlock of these addresses the Node.HopCnt
   associated with the
   RBHopCnt address is incremented by one (1), (1) if it exists
   and is not zero, then a route is created or updated as defined in
   Section 4.2.1.  The updating of the HopCnt occurs after processing.
   Each RBlock address resulting in a valid route entry may alleviate a future
   route discovery.  Any
   RBlocks addresses that do not result in yield a valid route update or
   that are not processed MUST be removed from the RE. RM.  Only valid
   routing information is propagated within RM messages.

   If this node is the TargetAddress Target AND the A-bit this is set (A=1), a RREQ, this node MUST respond responds
   with a RREP.  The target node Target creates a new RE RREP as described in
   Section 4.3.1.  The TargetAddress Target.Address in the new RE RM is set to the RBNodeAddress1
   Orig.Address from the RE RM currently being processed.  The
   THopCnt
   Target.HopCnt is the hop count for the TargetAddress.  The A-bit is set to
   (A=0). Orig.Address.  The
   IPDestinationAddress is set to the Route.NextHopAddress for the TargetAddress.
   Orig.Address of the current RM being processed.  The TargetSeqNum Target.SeqNum is
   set to Route.SeqNum for Orig.Address from the TargetAddress. current RM being
   processed.  Then the new RE RM undergoes post-processing, according to
   Section 4.6.4.

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

   If this node is not the TargetAddress, Target.Address and this is a RREQ the current RE
   RM SHOULD be
   handled according to Section 4.6.4. MANETcast.  If this node is not the TargetAddress, the current packet Target Address and any
   additional elements are processed, but
   this packet is not
   retransmitted.

   If the S-bit is set to one (1) in the RE, then a unicast message RREP the current RM SHOULD be sent or have been sent unicast to the previous next hop within
   UNICAST_MESSAGE_SENT_TIMEOUT.  Any unicast packet will serve this
   purpose, but it MAY be an ICMP REPLY message.
   address on the route to the Target.

   If a message this node is not
   sent, then the previous hop may assume that Target.Address, the link current message is
   unidirectional and may blacklist processed,
   but this node.

4.3.3 message is not forwarded or retransmitted.

4.3.3.  Appending Additional Routing Information  to an Existing Routing
       Element
        Message

   Appending routing information will alleviate route discovery attempts
   to this node from other nodes that process the resultant RE. RM
   information.  Nodes MAY append a RBlock their routing information to RE a RM
   processed if the believes they believe that this additional routing information
   will alleviate future RREQ.

   Prior to appending a RBlock their address to a RE, RM, a node MUST increment its
   OwnSeqNum as defined in Section 4.1.2.  Then it appends its IP
   address, OwnSeqNum,
   address and OwnSeqNum.  It MAY also append its Prefix and G-bit to
   the RE in a RBlock.  The
   RBHopCnt RM.  This Node.HopCnt is set to zero (0).  The RE Len is one (1) if included.  Several
   length fields MUST also be adjusted according to include the number of RBlocks in the RE.

4.4 newly inserted
   information.

4.4.  Route Discovery

   A node generates a Route Request (RREQ) to discover a valid route to a
   particular destination (TargetAddress).  A RREQ is a RE with the
   A-bit is set to one (A=1) to indicate that the TargetNode must
   respond with a RREP. (Target).  If a sequence number is known for
   the
   TargetAddress Target it is placed in the TargetSeqNum field. RREQ.  Otherwise,
   TargetSeqNum is set Target.SeqNum
   assumed to zero (0). be unknown by processing nodes.  A TargetSeqNum Target.SeqNum of zero
   (0) MAY be set to indicate that only the destination may respond to
   this RREQ.  If a
   hop count previous value of the HopCnt is known for the TargetAddress Target
   it is placed in the THopCnt
   field. a corresponding add-tlv HopCnt.  Otherwise, the THopCnt
   HopCnt is set to zero (0). not included.  The IPDestinationAddress is set to the DYMOcastAddress.
   MANETcastAddress.  Then the RE RM is
   then transmitted according to the
   procedure defined in Section 4.6.5.

   After issuing a RREQ, the originating node waits for a route to be
   created to the TargetNode. Target.  If a route is not received 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 TargetNode 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 TargetNode. 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 for a route SHOULD be buffered.

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

4.5

4.5.  Route Maintenance

4.5.1

4.5.1.  Active Link Monitoring

   Before a route can be used for forwarding a packet, it MUST be
   checked to make sure that the route is still valid.  If the
   Route.ValidTimeout is earlier than the current time, the packet
   cannot be forwarded, and a RERR message MUST be generated (see
   section Section 4.5.3).  In this case, the Route.DeleteTimeout is set
   to Route.ValidTimeout + ROUTE_DELETE_TIMEOUT.

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

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

   o  Link layer feedback

   o  Hello messages

   o  Neighbor discovery

   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 routes 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 SHOULD 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.

4.5.2 generated unless generation is
   expected to reduce future control traffic.

4.5.2.  Updating Route Lifetimes

   To avoid route timeouts for active routes, a node MUST update the
   Route.ValidTimeout to the IPSourceAddress to be the current time +
   ROUTE_TIMEOUT upon receiving a data packet.

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

4.5.3

4.5.3.  Route Error Generation

   When a data packet is received for a destination without a valid
   routing table entry, a Route Error (RERR) MUST be generated by this
   node.  A RERR informs the source that the current route does not exist, is no
   longer
   available. available, or is now invalid.

   In the a new RERR, the UNodeAddress1 field is the address of the unreachable node (IPDestinationAddress)
   from the data packet. packet is inserted.  If a value for the
   UNodeSeqNum unreachable
   node's SeqNum is known, it is placed in the RERR; otherwise, if
   unknown it will be assumed to be zero (0)
   is placed in the UNodeSeqNum field of the RERR. (0).  The TTL msg-ttl SHOULD be set
   to NET_DIAMETER, but may be set smaller.  The
   IPDestinationAddress is set smaller to limit the DYMOcastAddress.

   Additional unreachable nodes that required the same unavailable link
   (routes with the same Route.NextHopAddress and
   Route.NextHopInterface) as the UNodeAddress1 SHOULD be appended to scope of the
   RERR.  For each unreachable node the UNodeAddress and UNodeSeqNum
   are appended.  The Len msg-hopcnt is set accordingly. to zero (0).  The RERR IPDestinationAddress
   is then processed as described in Section 4.6.5.

4.5.4  Route Error Processing

   When a node processes a RERR after generic element pre-processing
   (Section 4.6.2), it SHOULD set the Route.ValidTimeout to the current
   time for each route to a UNodeAddress that meets all of the following
   conditions:

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

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

   3.  The UNodeSeqNum is zero (0) OR MANETcastAddress.  This option will notify the result maximum
   number of subtracting
       Route.SeqNum from UNodeSeqNum is less than or equal to zero using
       signed 32-bit arithmetic.

   Each UNodeAddress that did not result in a change to
   Route.ValidTimeout SHOULD be removed from the RERR.

   Prior to generic post processing a node MAY remove any UNodeAddressN,
   UNodeSeqNumN pairs except UNodeAddress1 to decrease the element size.

   If at least one UNodeAddress remains and at least one route remains
   in the RERR it SHOULD be handled as described in Section 4.6.4 to
   continue notification nodes of the broken link.

   Additional unreachable nodes effected by that required the broken link.
   Otherwise, same unavailable link
   (routes with the RERR is dropped.

4.6  General DYMO Processing

4.6.1  DYMO Control Packet Processing

   A DYMO packet may consist of multiple DYMO elements.  Each element is
   processed individually same Route.NextHopAddress and in sequence, from first to last.  An
   incoming DYMO packet MUST
   Route.NextHopInterface) MAY be completely processed prior added to any DYMO
   packet transmissions.

   The length of IP addresses (32-bits for IPv4 and 128-bits for IPv6)
   inside DYMO elements is dependent on the IP packet header. RERR.  For
   example, if each
   unreachable node the IP header Address is IPv6 then all DYMO elements contained in
   the payload use IPv6 addresses.

   Unless specific element appended.  The SeqNum if know should
   also be included.  Appending additional routing information notifies
   each processing requires dropping the DYMO packet,
   it node of additional routes that are no longer
   available.

   The RERR is retransmitted after processing, according to the method then processed as described in Section 4.6.5.

4.6.2  Generic Element Pre-processing

   Each element in

4.5.4.  Route Error Processing

   When a DYMO packet undergoes pre-processing before the
   element specific processing occurs.  During pre-processing, node processes a RERR, it SHOULD set the TTL
   is decremented by one (1).

4.6.3  Processing Unsupported DYMO Element Types

   This section describes Route.ValidTimeout to
   the processing current time for unsupported DYMO element
   Types.  The Type field identifies the handling by nodes each Address that do not
   implement, support or understand a particular Element Type. meets all of the following
   conditions:

   1.  The most
   significant bit (M-bit) indicates whether an Unsupported-element
   Error (UERR) SHOULD be sent to Route.NextHopAddress is the same as the NotifyAddress. RERR IPSourceAddress.

   2.  The next two bits
   (H-bits) identify how Route.NextHopInterface is the element should be handled.

                  0                          0
                  0 1 2 3 4 5 6 7 8          0 1 2 3 4 5 6 7 8
                  +-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+
                  |     Type      |     =    |M| H |         |
                  +-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+

   If same as the interface on which
       the RERR was received.

   3.  The Node.SeqNum is zero (0), unknown, OR the M-bit result of
       subtracting Route.SeqNum from Node.SeqNum is set in a DYMO element being processed by a node less than or equal
       to zero using signed 16-bit arithmetic.

   Each Node.Address that
   does did not support this Element Type result in a UERR change to
   Route.ValidTimeout SHOULD be sent to the
   NotifyAddress.  This is accomplished by following removed from the instructions in
   Section 4.6.3.1.

   Regardless RERR, since propagation
   of whether or this information should not a UERR is sent result in response any benefit.

   Prior to this
   unsupported Element Type, the post processing a node MUST also examine the
   H-bits to determine how this unsupported element is handled.  The
   unsupported element Type MUST be handled as follows:

   o  If H == 00 skip the element MAY remove any unreachable node
   address and continue as if its associated information to decrease the packet did not
      contain this element.

   o message size.

   If H == 01 remove the unsupported element (using the Len field)
      from this node is the packet Target and continue as if the packet did not include this
      element.

   o IPDestinationAddress is its own
   Address then it may stop processing.

   If H == 10 set at least one unreachable node address remains in the ignored bit (I-bit) skip this element and
      continue, RERR it
   SHOULD be handled as if described in Section 4.6.4 to continue
   notification of nodes effected by the packet did not contain this element.

   o  If H == 11 drop broken link.  Otherwise, the packet without processing any other DYMO
      elements.

4.6.3.1  Generating an Unsupported-element Error

   When an unsupported element type
   RERR is received with the M-bit set, the
   processing node SHOULD generate an Unsupported-element Error (UERR). dropped.

4.6.  General DYMO Packet and Message Processing

4.6.1.  Packet Processing

   The TargetAddress is set to length of IP addresses (32-bits for IPv4 and 128-bits for IPv6)
   inside DYMO messages are dependent on the NotifyAddress.  The
   IPDestinationAddress is set to IP packet header.  For
   example, if the Route.NextHopAddress toward IP header uses IPv6 addresses then all messages and
   addresses contained in the
   NotifyAddress.  The UElemTargetAddress is set to payload use IPv6 addresses.

4.6.2.  Generic Message Pre-processing

   Each message undergoes pre-processing before the TargetAddress
   from message specific
   processing occurs.  During pre-processing, the unsupported element.  The UERRNodeAddress msg-ttl is set to decremented
   by one (1) and the node
   address generating this UERR.  The UElemType msg-hopcnt is incremented by one (1).

4.6.3.  Processing Unknown Message and TLV Types

   We expect the Type from next version of the
   unsupported element.  The TTL SHOULD be set generalized MANET packet and
   message format [5] to NET_DIAMETER, but MAY
   be set smaller.  The Len is set include message semantic bits and tlv semantic
   bits to control the total number behavior of bytes in this
   UERR.  The element is then processed as described in Section unknown types.

4.6.4.

4.6.4  Generic Element Message Post-processing

   If the first element TTL is zero (0) the DYMO packet is dropped after
   processing of all elements.  If the TTL of the first element is
   greater than zero the DYMO packet is re-transmitted after processing
   of all elements.  If the TTL msg-ttl of any element message is zero (0) after processing it MUST be removed from the DYMO packet prior to
   transmission.

4.6.5
   dropped.

4.6.5.  DYMO Control Packet Transmission

   DYMO packet

   Packet transmission and re-transmission is are controlled by the
   IPDestinationAddress.  If the IPDestinationAddress is a unicast
   address, the packet IPDestinationAddress is replaced by the
   Route.NextHopAddress from a route table lookup for the TargetAddress. Target.  If a
   route for the TargetAddress Target is unknown or invalid the packet is dropped and
   a RERR SHOULD be generated.

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

4.7 neighbors only.

4.7.  Routing Prefix

   Any node can MAY advertise connectivity to a subset of other nodes node addresses
   within its address space by using the prefix field in RE. a Prefix tlv [5].  The nodes (other
   than the advertising node) within the advertised prefix Prefix SHOULD NOT
   participate in the MANET and MUST be reachable by forwarding packets
   to the node advertising connectivity.  For example, 192.168.1.1 with
   a prefix of 16 indicates all nodes with the prefix 192.168.X.X are
   reachable through 192.168.1.1.

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

4.8 node.

4.8.  Simple Internet Attachment and Gatewaying

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

   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 setting using
   the gateway bit (G-bit) tlv in any RE RM created or processed.  The G-bit
   flag gateway tlv
   indicates to nodes in the MANET that the RBNodeAddress Node.Address is attached to
   the Internet and is capable of routing data packets to all nodes
   outside of the configured MANET subnet, described defined by the
   RBNodeAddress Node.Address
   and RBPrefix Node.Prefix fields.

4.9

4.9.  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.DestAddress Route.Address can
   be reached is also recorded into in the route table entry.

   When multiple interfaces are available, a node transmitting a
   DYMOcast
   MANETcast packet SHOULD send the packet on all interfaces that have
   been configured for operation in the MANET.

4.10 DYMO operation.

4.10.  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.  Configuration Parameters

   Here are some default parameter values for DYMO:

      Parameter Name Suggested Value

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

      NET_DIAMETER 10

      RATE_LIMIT 10

      ROUTE_TIMEOUT                   3000 5000 milliseconds

      ROUTE_DELETE_TIMEOUT 5*ROUTE_TIMEOUT

      RREQ_WAIT_TIME 1000 milliseconds

      RREQ_TRIES 3

   For large 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 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 or
   ROUTE_DELETE_TIMEOUT in addition to arbitrary packet delays may
   result in frequent route breaks or routing loops.

6.  IANA Considerations

   DYMO defines a Type field for each element within a packet sent to
   port TBD. several message-types and tlv-types.  A new registry
   will be created for the values for this
   Type field, the various type fields, and the
   following values will be assigned:

      Type

      msg-type Value

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

      Routing Element (RE)                 1 -------

      Route Request (DYMO-RREQ) 8 - TBD

      Route Reply (DYMO-RREP) 9 - TBD

      Route Error (RERR)                   2

      Unsupported-element Error (UERR)     3 (DYMO-RERR) 10 - TBD

      address-tlv Value

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

      DYMO SeqNum (multivalue) 20 - TBD

      HopCnt (multivalue) 21 - TBD

      Prefix (multivalue) 0 [5]

      Gateway (zero length) 22 - TBD

      Originator 23 - TBD

      Target 24 - TBD

   Future values of the Type will be allocated using standard actions as
   described in [1].  For future Types with the M-bit set NotifyAddress
   MUST be included.  Similarly for future Types that are unicast hop-
   by-hop hop-by-hop
   (packets not sent to the DYMOcastAddress), MANETcastAddress), these Types MUST include
   the TargetAddress Target.Address field.

7.  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 elements 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 Element Message (AH) is
   an appropriate choice for cases where the nodes share an appropriate
   security association that enables the use of AH.

   In particular, RE 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.  Acknowledgments

   DYMO is a descendant of the design of previous MANET reactive
   protocols, especially AODV [2] and DSR [4].  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 and Koojana Kuladinithi for reviewing of DYMO, as
   well as several specification suggestions.

9.  References

9.1

9.1.  Normative References

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

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

9.2

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

9.2.  Informative References

   [3]  Perkins, C. Perkins 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. Johnson 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

   Elizabeth Belding-Royer
   University of California Santa Barbara
   Dept. of Computer Science
   Santa Barbara, CA  93106-5110
   USA

   Phone: +1-805-893-3411
   Fax:   +1-805-893-8553
   Email: ebelding@cs.ucsb.edu

   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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