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Mobile Ad hoc Networks Working                               I. Chakeres
Group                                                             CenGen
Internet-Draft                                                C. Perkins
Intended status: Standards Track                                WiChorus
Expires: September 23, 2010                               March 22, 2010


                 Dynamic MANET On-demand (DYMO) Routing
                        draft-ietf-manet-dymo-19

Abstract

   The Dynamic MANET On-demand (DYMO) routing protocol is intended for
   use by mobile routers in wireless, multihop networks.  DYMO
   determines unicast routes among DYMO routers within the network in an
   on-demand fashion, offering improved convergence in dynamic
   topologies.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on September 23, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the BSD License.


Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Data Structures  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Route Table Entry  . . . . . . . . . . . . . . . . . . . .  7
     4.2.  DYMO Messages  . . . . . . . . . . . . . . . . . . . . . .  8
       4.2.1.  Generalized Packet and Message Structure . . . . . . .  9
       4.2.2.  Routing Messages (RM) - RREQ & RREP  . . . . . . . . . 10
       4.2.3.  Route Error (RERR) . . . . . . . . . . . . . . . . . . 12
   5.  Detailed Operation . . . . . . . . . . . . . . . . . . . . . . 14
     5.1.  DYMO Sequence Numbers  . . . . . . . . . . . . . . . . . . 14
       5.1.1.  Maintaining A Node's Own Sequence Number . . . . . . . 15
       5.1.2.  Numerical Operations on OwnSeqNum  . . . . . . . . . . 15
       5.1.3.  OwnSeqNum Rollover . . . . . . . . . . . . . . . . . . 15
       5.1.4.  Actions After OwnSeqNum Loss . . . . . . . . . . . . . 15
     5.2.  DYMO Routing Table Operations  . . . . . . . . . . . . . . 15
       5.2.1.  Judging Routing Information's Usefulness . . . . . . . 15
       5.2.2.  Creating or Updating a Route Table Entry with
               Received Superior Routing Information  . . . . . . . . 17
       5.2.3.  Route Table Entry Timeouts . . . . . . . . . . . . . . 18
     5.3.  Routing Messages . . . . . . . . . . . . . . . . . . . . . 18
       5.3.1.  RREQ Creation  . . . . . . . . . . . . . . . . . . . . 18
       5.3.2.  RREP Creation  . . . . . . . . . . . . . . . . . . . . 19
       5.3.3.  Intermediate DYMO Router RREP Creation . . . . . . . . 21
       5.3.4.  RM Handling  . . . . . . . . . . . . . . . . . . . . . 21
       5.3.5.  Adding Additional Routing Information to a RM  . . . . 24
     5.4.  Route Discovery  . . . . . . . . . . . . . . . . . . . . . 25
     5.5.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . 26
       5.5.1.  Active Next-hop Router Adjacency Monitoring  . . . . . 26
       5.5.2.  Updating Route Lifetimes During Packet Forwarding  . . 27
       5.5.3.  RERR Generation  . . . . . . . . . . . . . . . . . . . 27
       5.5.4.  RERR Handling  . . . . . . . . . . . . . . . . . . . . 28
     5.6.  DYMO Identifier (DID)  . . . . . . . . . . . . . . . . . . 29
     5.7.  Unknown Message & TLV Types  . . . . . . . . . . . . . . . 30
     5.8.  Advertising Network Addresses  . . . . . . . . . . . . . . 30
     5.9.  Simple Internet Attachment . . . . . . . . . . . . . . . . 30
     5.10. Multiple Interfaces  . . . . . . . . . . . . . . . . . . . 32



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     5.11. DYMO Control Packet/Message Generation Limits  . . . . . . 32
   6.  Administratively Configured Parameters and Timer Values  . . . 32
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 35
     7.1.  DYMO Message Types Specification . . . . . . . . . . . . . 35
     7.2.  Message and Address Block TLV Type Specification . . . . . 35
     7.3.  Address Block TLV Specification  . . . . . . . . . . . . . 36
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 36
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 37
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 37
     10.2. Informative References . . . . . . . . . . . . . . . . . . 38
   Appendix A.  Shifting Responsibility for an Address Between
                DYMO Routers  . . . . . . . . . . . . . . . . . . . . 39
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39





































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1.  Overview

   The Dynamic MANET On-demand (DYMO) routing protocol enables reactive,
   multihop unicast routing among participating DYMO routers.  The basic
   operations of the DYMO protocol are route discovery and route
   maintenance.

   During route discovery, the originator's DYMO router initiates
   dissemination of a Route Request (RREQ) throughout the network to
   find a route to the target's DYMO router.  During this hop-by-hop
   dissemination process, each intermediate DYMO router records a route
   to the originator.  When the target's DYMO router receives the RREQ,
   it responds with a Route Reply (RREP) sent hop-by-hop toward the
   originator.  Each intermediate DYMO router that receives the RREP
   creates a route to the target, and then the RREP is unicast hop-by-
   hop toward the originator.  When the originator's DYMO router
   receives the RREP, routes have then been established between the
   originating DYMO router and the target DYMO router in both
   directions.

   Route maintenance consists of two operations.  In order to preserve
   routes in use, DYMO routers extend route lifetimes upon successfully
   forwarding a packet.  In order to react to changes in the network
   topology, DYMO routers monitor routes over which traffic is flowing.
   When a data packet is received for forwarding and a route for the
   destination is not known or the route is broken, then the DYMO router
   of source of the packet is notified.  A Route Error (RERR) is sent
   toward the packet source to indicate the route to that particular
   destination is invalid or missing.  When the source's DYMO router
   receives the RERR, it deletes the route.  If this source's DYMO
   router later receives a packet for forwarding to the same
   destination, it will need to perform route discovery again for that
   destination.

   DYMO uses sequence numbers to ensure loop freedom [Perkins99].
   Sequence numbers enable DYMO routers to determine the temporal order
   of DYMO route discovery messages, thereby avoiding use of stale
   routing information.


2.  Applicability Statement

   The DYMO routing protocol is designed for stub or disconnected mobile
   ad hoc networks (MANETs).  DYMO handles a wide variety of mobility
   patterns by dynamically determining routes on-demand.  DYMO also
   handles a wide variety of traffic patterns.  In networks with a large
   number of routers, DYMO is best suited for sparse traffic scenarios
   where routers forward packets to only a small portion of the other



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   DYMO routers, due to the reactive nature of route discovery and route
   maintenance.

   DYMO is applicable to memory constrained devices, since little
   routing state is maintained in each DYMO router.  Only routing
   information related to active sources and destinations is maintained,
   in contrast to most other more proactive routing protocols that
   require routing information to all routers within the routing region
   be maintained.

   DYMO supports routers with multiple interfaces participating in the
   MANET.  DYMO routers can also perform routing on behalf of other
   nodes, attached via participating or non-participating interfaces.

   DYMO routers perform route discovery to find a route to a particular
   destination.  Therefore, DYMO routers MUST be configured to initiate
   and respond to route discovery on behalf of certain nodes, identified
   by address.  When DYMO is the only protocol interacting with the
   forwarding table, DYMO MAY be configured to perform route discovery
   for all unknown unicast destinations.

   At any time within a DYMO routing region only one DYMO router SHOULD
   be responsible for, i.e. "own", a particular address.  Coordination
   among multiple DYMO routers to distribute routing information
   correctly for a shared address (i.e. an address that is advertised
   and can be reached via multiple DYMO routers) is not described in
   this document.  The router behavior for shifting responsibility for
   an address from one DYMO router to another are described in
   Appendix A.

   DYMO MUST only utilizes bidirectional links.  In the case of possible
   unidirectional links, either blacklists ( see Section 7.2) or other
   means (e.g. adjacency establishment with only neighboring routers
   that have bidirectional communication as indicated by NHDP
   [I-D.ietf-manet-nhdp]) of ensuring and monitoring bi-directionality
   should be used.  Otherwise, persistent packet loss may occur.

   The routing algorithm in DYMO may be operated at layers other than
   the network layer, using layer-appropriate addresses.  For operation
   at other layers DYMO's routing algorithm likely will not need to
   change.  Although, modification of the packet/message format may be
   required.


3.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this



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   document are to be interpreted as described in [RFC2119].

   Additionally, this document uses some terminology from [RFC5444].

   This document defines the following terminology:

   Adjacency
      A relationship between selected bi-directional neighboring routers
      for the purpose of exchanging routing information.  Not every pair
      of neighboring routers become adjacent.  Neighboring routers may
      form an adjacency based several different pieces of information or
      protocols; for example, exchange of DYMO routing messages, other
      protocols (e.g.  NDP [RFC4861] or NHDP [I-D.ietf-manet-nhdp]), or
      manual configuration.  Similarly, loss of a routing adjacency may
      also be based upon several pieces of information, and monitoring
      of adjacencies where packets are being forwarded is required (see
      Section 5.5.1).

   Distance (Dist)
      A metric of the distance a message or piece of information has
      traversed.  The minimum value of distance is the number of IP hops
      traversed.  The maximum value is 65,535.

   DYMO Identifier (DID)
      A DID is maintained for each DYMO routing process (ThisNode.DID),
      and the default value is zero (0).  Each routing message is tagged
      with its associated DID (MsgTLV.DID), unless zero (0).  Upon
      receipt of DYMO protocol message a DYMO routing protocol process
      SHOULD only attend to messages with a matching DID value.

   DYMO Sequence Number (SeqNum)
      A DYMO Sequence Number is maintained by each DYMO router process.
      This sequence number is used by other DYMO routers to identify the
      temporal order of routing information generated and ensure loop-
      free routes.

   Forwarding Route
      A route that is used to forward data packets.  Forwarding routes
      are generally maintained in a forwarding information base (FIB) or
      the kernel forwarding/routing table.

   Multihop-capable Unicast IP Address
      A multihop-capable unicast IP address is a unicast IP address that
      when put into the IP.SoureAddress or IP.DestinationAddress field
      is scoped sufficiently to be forwarded by a router.  For example,
      site-scoped or globally-scoped unicast IP addresses.





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   Originating Node (OrigNode)
      The originating node is the source, its DYMO router creates a DYMO
      control message on its behalf in an effort to disseminate some
      routing information.  The originating node is also referred to as
      a particular message's originator.

   Route Error (RERR)
      A RERR message is used to indicate that a DYMO router does not
      have forwarding route to one or more particular addresses.

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

   Route Request (RREQ)
      A RREQ message is issued to discover a valid route to a particular
      destination address, called the RREQ TargetNode.  When a DYMO
      router attends a RREQ, it learns routing information on how to
      reach the RREQ OrigNode.

   Target Node (TargetNode)
      The TargetNode is the ultimate destination of a message.

   This Node (ThisNode)
      ThisNode corresponds to the DYMO router process currently
      performing a calculation or attending to a message.

   Type-Length-Value structure (TLV)
      A generic way to represent information, please see [RFC5444] for
      additional information.

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


4.  Data Structures

4.1.  Route Table Entry

   The route table entry is a conceptual data structure.
   Implementations may use any internal representation that conforms to
   the semantics of a route as specified in this document.

   Conceptually, a route table entry has the following fields:





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   Route.Address
      The (host or network) destination address of the node(s)
      associated with the routing table entry.

   Route.Prefix
      Indicates that the associated address is a network address, rather
      than a host address.  The value is the length of the netmask/
      prefix.

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

   Route.NextHopAddress
      The IP address of the adjacent DYMO router on the path toward the
      Route.Address.

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

   Route.Forwarding
      A flag indicating whether this Route can be used for forwarding
      data packets.  This flag MAY be provided for management and
      monitoring.

   Route.Broken
      A flag indicating whether this Route is broken.  This flag is set
      if the next-hop becomes unreachable or in response to attending to
      a RERR (see Section 5.5.4).

   The following field is optional:

   Route.Dist
      A metric indicating the distance traversed before reaching the
      Route.Address node.

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

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

4.2.  DYMO Messages

   When describing DYMO protocol messages, it is necessary to refer to
   fields in several distinct parts of the overall packet.  These
   locations include the IP header, the UDP header, and fields from
   [RFC5444].  This document uses the following notation conventions.



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   Information found in the table.

             +---------------------------+-------------------+
             |    Information Location   | Notational Prefix |
             +---------------------------+-------------------+
             |         IP header         |        IP.        |
             |         UDP header        |        UDP.       |
             |   RFC5444 message header  |      MsgHdr.      |
             |    RFC5444 message TLV    |      MsgTLV.      |
             |   RFC5444 address blocks  |      AddBlk.      |
             | RFC5444 address block TLV |      AddTLV.      |
             +---------------------------+-------------------+

                                  Table 1

4.2.1.  Generalized Packet and Message Structure

   DYMO messages conform to the generalized packet and message format as
   described in [RFC5444].  Here is a brief description of the format.
   A packet is made up of messages.  A message is made up of a message
   header, message TLV block, and zero or more address blocks.  Each of
   the address blocks may also have an associated address TLV block.

   All DYMO messages specified in this document are sent using UDP to
   the destination port MANET [RFC5498].

   Most DYMO messages are sent with the IP destination address set to
   the link-local multicast address LL-MANET-ROUTERS [RFC5498] unless
   otherwise stated.  Therefore, all DYMO routers SHOULD subscribe to
   LL-MANET-ROUTERS [RFC5498] for receiving control packets.  Note that
   multicast packets MAY be sent via unicast.  For example, this may
   occur for certain link-types (non broadcast mediums), improved
   robustness, or manually configured router adjacencies.

   Unicast DYMO messages (e.g.  RREP) unless otherwise specified in this
   document are sent with the IP destination set to the
   Route.NextHopAddress of the route to the TargetNode.

   The IPv4 TTL (IPv6 Hop Limit) field for all packets containing DYMO
   messages is set to 255.  If a packet is received with a value other
   than 255, it is discarded.  This mechanism helps to ensures that
   packets have not passed through any intermediate routers, and it is
   known as GTSM [RFC5082].

   The length of an address (32 bits for IPv4 and 128 bits for IPv6)
   inside a DYMO message depends on the msg-addr-length (MAL) in the
   msg-header, as specified in [RFC5444].




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   If a packet contains only a single DYMO message and no packet TLVs,
   it need not include a packet-header [RFC5444].

   The aggregation of multiple messages into a packet is not specified
   in this document, but if aggregation does occur the IP.SourceAddress
   and IP.DestinationAddress of all contained messages MUST be the same.

   Implementations MAY choose to temporarily delay transmission of
   messages for the purpose of aggregation (into a single packet) or to
   improve performance by using jitter [RFC5148].

   DYMO control packets SHOULD be given priority queuing and channel
   access.

4.2.2.  Routing Messages (RM) - RREQ & RREP

   Routing Messages (RMs) are used to disseminate routing information.
   There are two DYMO message types that are considered to be routing
   messages (RMs): RREQ and RREP.  They contain very similar information
   and function, but have slightly different handling rules.  The main
   difference between the two messages is that RREQ messages generally
   solicit a RREP, whereas a RREP is the response to RREQ.

   RM creation and handling are described in Section 5.3.

   A RM requires the following information:

   IP.SourceAddress
      The IP address of the node currently sending this packet.  This
      field is generally filled automatically by the operating system
      and should not require special handling.

   IP.DestinationAddress
      The IP address of the packet destination.  For multicast RREQ the
      IP.DestinationAddress is set to LL-MANET ROUTERS [RFC5498].  For
      unicast RREP the IP.DestinationAddress is set to the
      NextHopAddress toward the RREP TargetNode.

   UDP.DestinationPort
      By default, the UDP destination port is set to MANET [RFC5498].

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

   AddBlk.TargetNode.Address
      The IP address of the message TargetNode.  In a RREQ the
      TargetNode is the destination address for which route discovery is
      being performed.  In a RREP the TargetNode is the RREQ OrigNode



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      address.  The TargetNode address is the first address in a routing
      message.

   AddBlk.OrigNode.Address
      The IP address of the originator and its associated prefix length.
      In a RREQ the OrigNode is the source's address and prefix.  In a
      RREP the OrigNode is the RREQ TargetNode's address and prefix for
      which a RREP is being generated.  This address is the second
      address in the message for RREQ.

   OrigNode.AddTLV.SeqNum
      The DYMO sequence number of the originator's DYMO router.

   A RM may optionally include the following information:

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

   TargetNode.AddTLV.Dist
      The last known Distance to the TargetNode.

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

   AdditionalNode.AddTLV.SeqNum
      The DYMO sequence number associated with this routing information.

   OrigNode.AddTLV.Dist
      A metric of the distance to reach the associated OrigNode.Address.
      This field is incremented by at least one at each intermediate
      DYMO router.

   AdditionalNode.AddTLV.Dist
      A metric of the distance to reach the associated
      AdditionalNode.Address.  This field is incremented by at least one
      at each intermediate DYMO router.












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   Example IPv4 RREQ

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   IP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     IP.SourceAddress                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         IP.DestinationAddress = LL-MANET-ROUTERS              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    IP TTL/HopLimit = 255      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

                                 Figure 1

4.2.3.  Route Error (RERR)

   A RERR message is used to disseminate the information that a route is
   not available for one or more particular addresses.

   RERR creation and handling are described in Section 5.5.



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   A RERR requires the following information:

   IP.SourceAddress
      The IP address of the DYMO router that sent this packet.  This
      field is generally filled automatically by the operating system
      and should not require special handling.

   IP.DestinationAddress
      For multicast RERR messages, The IP address is set to LL-MANET-
      ROUTERS [RFC5498].  For unicast RERR messages, the IP address is
      set to the NextHopAddress.

   UDP.DestinationPort
      By default, the UDP destination port is set to MANET [RFC5498].

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

   AddBlk.UnreachableNode.Address
      The address of an UnreachableNode and its associated prefix
      length.  Multiple unreachable addresses may be included in a RERR.

   A Route Error may optionally include the following information:

   UnreachableNode.AddTLV.SeqNum
      The last known DYMO sequence number of the unreachable node.  If a
      SeqNum for an address is not included, it is assumed to be
      unknown.  This case occurs when a node receives a message to
      forward to a destination for which it does not have any
      information in its routing table.





















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   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.SourceAddress                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         IP.DestinationAddress = LL-MANET-ROUTERS              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    IP.TTL/HopLimit = 255      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   UDP Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Destination Port = MANET    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Header
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   RERR-type   |0|1|0|0| MAL=3 |         msg-size=15           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | msg-hoplimit  |
       +-+-+-+-+-+-+-+-+
   Message TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     msg-tlv-block-size=0      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block
                                       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                       |Number Addrs=1 |0|0|0|0|0| Rsv |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     UnreachableNode.Address                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Message Body - Address Block TLV Block
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        TLV-blk-size=0         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2


5.  Detailed Operation

5.1.  DYMO Sequence Numbers

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





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5.1.1.  Maintaining A Node's Own Sequence Number

   DYMO requires that each DYMO router in the network maintain its own
   DYMO sequence number (OwnSeqNum) on behalf of the addresses for which
   it is responsible.  OwnSeqNum a 16-bit unsigned integer.  The
   circumstances for ThisNode to incrementing its OwnSeqNum are
   described in Section 5.3.

5.1.2.  Numerical Operations on OwnSeqNum

   When ThisNode increments its OwnSeqNum (as described in Section 5.3)
   it MUST do so by treating the sequence number value as an unsigned
   number.

5.1.3.  OwnSeqNum Rollover

   If the sequence number has been assigned to be the largest possible
   number representable as a 16-bit unsigned integer (i.e., 65,535),
   then the sequence number SHOULD be set to one (1) incremented.

5.1.4.  Actions After OwnSeqNum Loss

   A DYMO router SHOULD maintain its sequence number in persistent
   storage.

   If a DYMO router's OwnSeqNum is lost, it MUST take certain actions to
   avoid creating routing loops.  To prevent this possibility after
   OwnSeqNum loss a DYMO router MUST wait for at least
   ROUTE_DELETE_TIMEOUT before fully participating in the DYMO routing
   protocol.  If a DYMO control message is received during this waiting
   period, the DYMO router SHOULD handle it normally but MUST NOT
   transmit or retransmit any DYMO messages.  If a data packet is
   received for forwarding to another destination during this waiting
   period, the DYMO router MUST generate a RERR message indicating that
   this route is not available and reset its waiting timeout.  At the
   end of the waiting period the DYMO router sets its OwnSeqNum to one
   (1) and begins participating.

   The longest a node need wait is ROUTE_SEQNUM_AGE_MAX_TIMEOUT.  At the
   end of the maximum waiting period a node SHOULD set its OwnSeqNum to
   one (1) and begins participating.

5.2.  DYMO Routing Table Operations

5.2.1.  Judging Routing Information's Usefulness

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



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   node in a RM (Node.SeqNum, Node.Dist, and RM message type - RREQ/
   RREP), the quality of the new routing information is evaluated to
   determine its usefulness.  Incoming routing information is classified
   as follows:

   1. Stale
      If Node.SeqNum - Route.SeqNum < 0 (using signed 16-bit arithmetic)
      the incoming information is stale.  Using stale routing
      information is not allowed, since doing so might result in routing
      loops.

      (Node.SeqNum - Route.SeqNum < 0)
          using signed 16-bit arithmetic

   2. Loop-possible
      If Node.SeqNum == Route.SeqNum the incoming information may cause
      loops if used; in this case additional information MUST be
      examined.  If Route.Dist or Node.Dist is unknown or zero (0), then
      the routing information is loop-possible.  If Node.Dist >
      Route.Dist + 1, then the routing information is loop-possible.
      Using loop-possible routing information is not allowed, otherwise
      routing loops may be formed.

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

   3. Inferior
      In case of known equal SeqNum, the information is inferior in
      multiple cases: (case i) if Node.Dist == Route.Dist + 1 (it is a
      greater distance route) AND Route.Broken == false; (case ii) if
      Node.Dist == Route.Dist (equal distance route) AND Route.Broken ==
      false AND this RM is a RREQ.  The inferior condition stops
      forwarding of RREQ with equivalent distance.

      ((Node.SeqNum == Route.SeqNum) AND
       (((Node.Dist == Route.Dist + 1) AND (Route.Broken == false)) OR
        ((Node.Dist == Route.Dist) AND
         (RM is RREQ) AND (Route.Broken == false))))

   4. Superior
      Incoming routing information that does not match any of the above
      criteria is loop-free and better than the information existing in
      the routing table.  Information is always superior if Node.SeqNum
      - Route.SeqNum > 0 (using signed 16-bit arithmetic).  In the case
      of equal sequence numbers, the information is superior in multiple
      cases: (case i) if Node.Dist < Route.Dist; (case ii) if Node.Dist



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      == Route.Dist + 1 AND Route.Broken == true (a broken route is
      being repaired); (case iii) if Node.Dist == Route.Dist AND it is a
      RREP (RREP with equal distance are forwarded) OR Route.Broken ==
      true (a broken route is being repaired).  For completeness, we
      provide the following (optimized) pseudo-code.

      (Node.SeqNum - Route.SeqNum > 0) OR
          using signed 16-bit arithmetic
      ((Node.SeqNum == Route.SeqNum) AND
       ((Node.Dist < Route.Dist) OR
        ((Node.Dist == Route.Dist + 1) AND (Route.Broken == true)) OR
        ((Node.Dist == Route.Dist) AND
         ((RM is RREP) OR (Route.Broken == true)))))

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

   The route table entry is populated with the following information:

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

   2.  the Route.Prefix is set to the Node.Prefix.

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

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

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

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

   Fields without known values are not populated with any value.

   Previous timers for this route table entry are removed.  A timer for
   the minimum delete timeout (ROUTE_AGE_MIN) is set to
   ROUTE_AGE_MIN_TIMEOUT.  A timer for the maximum delete timeout
   (ROUTE_SEQNUM_AGE_MAX).  ROUTE_SEQNUM_AGE_MAX is set to
   Node.AddTLV.VALIDITY_TIME [RFC5497] if included; otherwise,
   ROUTE_SEQNUM_AGE_MAX is set to ROUTE_SEQNUM_AGE_MAX_TIMEOUT.  The
   usage of these timers and others are described in Section 5.2.3.

   At this point, a forwarding route should be created and the
   Route.Forwarding flag set.  Afterward, the route can be used to send
   any queued data packets and forward any incoming data packets for
   Route.Address.  This route also fulfills any outstanding route
   discovery attempts for Node.Address.



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5.2.3.  Route Table Entry Timeouts

5.2.3.1.  Minimum Delete Timeout (ROUTE_AGE_MIN)

   When a DYMO router transmits a RM, other DYMO routers expect the
   transmitting DYMO router to have a forwarding route to the RM
   originator.  After updating a route table entry, it should be
   maintained for at least ROUTE_AGE_MIN.  Failure to maintain the
   information might result in lost messages/packets, or in the worst
   case scenario several duplicate messages.

   After the ROUTE_AGE_MIN timeout a route can safely be deleted.

5.2.3.2.  Maximum Sequence Number Delete Timeout (ROUTE_SEQNUM_AGE_MAX)

   Sequence number information is time sensitive, and MUST be deleted
   after a time in order to ensure loop-free routing.

   After the ROUTE_AGE_MAX timeout a route's sequence number information
   MUST be discarded.

5.2.3.3.  Recently Used Timeout (ROUTE_USED)

   When a route is used to forward data packets, this timer is set to
   expire after ROUTE_USED_TIMEOUT.  This operation is also discussed in
   Section 5.5.2.

   If a route has not been used recently, then a timer for ROUTE_DELETE
   is set to ROUTE_DELETE_TIMEOUT.

5.2.3.4.  Delete Information Timeout (ROUTE_DELETE)

   As time progresses the likelihood that old routing information is
   useful decreases, especially if the network nodes are mobile.
   Therefore, old information should be deleted.

   After the ROUTE_DELETE timeout, the routing table entry should be
   deleted.  If a forwarding route exists, it should also be removed and
   the Route.Forwarding flag unset.

5.3.  Routing Messages

5.3.1.  RREQ Creation

   Before a DYMO router creates a RREQ it SHOULD increment its OwnSeqNum
   by one (1) according to the rules specified in Section 5.1.2.
   Incrementing OwnSeqNum will ensure that all nodes with existing
   routing information will consider this new information superior to



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   existing routing table information.  If the sequence number is not
   incremented, certain DYMO routers might not consider this information
   superior, if they have existing better routing information.

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

   If a previous value of the TargetNode.SeqNum is known (from a routing
   table entry using longest-prefix matching), it SHOULD be placed in
   TargetNode.AddTLV.SeqNum in all but the last RREQ attempt.  If a
   TargetNode.SeqNum is not included, it is assumed to be unknown by
   handling nodes.  This operation ensures that no intermediate DYMO
   routers reply, and ensures that the TargetNode's DYMO router
   increments its sequence number.

   Next, the node adds AddBlk.OrigNode.Address, its prefix, and the
   OrigNode.AddTLV.SeqNum (OwnSeqNum) to the RM.

   The OrigNode.Address is the address of the source for which this DYMO
   router is initiating this route discovery.  The OrigNode.Address MUST
   be a unicast address.  This information will be used by nodes to
   create a route toward the OrigNode, enabling delivery of a RREP, and
   eventually used for proper forwarding of data packets.

   If OrigNode.Dist is included it is set to a number greater than zero
   (0).

   The MsgHdr.HopLimit SHOULD be set to MSG_HOPLIMIT.

   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 local network and possibly reduce
   route discovery overhead.

   The IP.DestinationAddress for multicast RREQ is set to LL-MANET-
   ROUTERS.  For links that do not support multicast or situations in
   which unicast messaging is preferred, the IP.DestinationAddress for
   unicast RREQ is set to the NextHopAddress.

   Each DYMO routing protocol message SHOULD contain ThisNode.DID's
   value in a message TLV (MsgTLV.DID).  If ThisNode.DID value is zero
   (0) it MAY be omitted.

5.3.2.  RREP Creation

   First, the AddBlk.TargetNode.Address is added to the RREP.  The
   TargetNode is the ultimate destination of this RREP; the RREQ



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   OrigNode.Address.

   Next, AddBlk.OrigNode.Address and prefix are added to the RREP.  The
   AddBlk.OrigNode.Address is the RREQ TargetNode.Address.  The
   AddBlk.OrigNode.Address MUST be a unicast IP address.  ThisNode
   SHOULD advertise the largest known prefix containing
   AddBlk.OrigNode.Address.

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

   If TargetNode.SeqNum is included in the RM and TargetNode.SeqNum -
   OwnSeqNum < 0 (using signed 16-bit arithmetic), OwnSeqNum SHOULD be
   incremented by one (1) according to the rules specified in
   Section 5.1.2.

   If TargetNode.SeqNum is included in the RM and TargetNode.SeqNum ==
   OwnSeqNum (using signed 16-bit arithmetic) and Dist will not be
   included in the RREP being generated, OwnSeqNum SHOULD be incremented
   by one (1) according to the rules specified in Section 5.1.2.

   If OwnSeqNum is not incremented the routing information might be
   considered stale.  In this case, the RREP might not reach the RREP
   Target.

   After any of the sequence number operations above, the RREP
   OrigNode.AddTLV.SeqNum (OwnSeqNum) MUST also be added to the RREP.

   Other AddTLVs in the RREP for the OrigNode and TargetNode SHOULD be
   included and set accordingly.  If OrigNode.Dist is included it is set
   to a number greater than zero (0) and less than 65,535.  The Distance
   value will influence judgment of the routing information
   (Section 5.2.1) against known information at other DYMO routers that
   handle this RM.

   The MsgHdr.HopLimit is set to MSG_HOPLIMIT.

   The IP.DestinationAddress for RREP is set to the IP address of the
   Route.NextHopAddress for the route to the RREP TargetNode.

   Each DYMO routing protocol message SHOULD contain ThisNode.DID's
   value in a message TLV (MsgTLV.DID).  If ThisNode.DID value is zero
   (0) it MAY be omitted.






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5.3.3.  Intermediate DYMO Router RREP Creation

   Sometimes a DYMO router other than the TargetNode's DYMO router (call
   it an "intermediate DYMO router") has routing information that can
   satisfy an incoming RREQ.  An intermediate DYMO router can issue a
   intermediate DYMO router RREP on behalf of the TargetNode's DYMO
   router.

   Before creating a intermediate DYMO router RREP, OwnSeqNum SHOULD be
   incremented by one (1) according to the rules specified in
   Section 5.1.2.

   If OwnSeqNum is not incremented the routing information about
   ThisNode might be considered stale by a handling DYMO router.  In
   this case, the RREP would not reach the RREP TargetNode.

   When an intermediate DYMO router originates a RREP in response to a
   RREQ on behalf of the TargetNode's DYMO router, it sends the RREP to
   the RREQ OrigNode with additional routing information (Address,
   Prefix, SeqNum, Dist, etc.) about the RREQ TargetNode.  Appending
   additional routing information is described in Section 5.3.5.

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

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

5.3.4.  RM Handling

   First, ThisNode decides whether to attend to this message.  If the
   message contains a MsgTLV.DID it SHOULD match ThisNode.DID's value.
   If the message does not contain a MsgTLV.DID it is assumed to be zero
   (0) and SHOULD be discarded if ThisNode.DID's value is not zero (0).

   Next, ThisNode MAY selectively attend to messages based upon
   information in the message.  ThisNode SHOULD only handle messages
   from adjacent DYMO routers.  If ThisNode chooses not to handle this
   message, the message is discarded and further processing stopped.

   ThisNode checks if the AddBlk.OrigNode.Address is a valid multihop-
   capable (e.g. site or global scope) unicast address.  If the address
   is not a valid unicast address, the messages is discarded and further
   processing stopped.

   ThisNode also checks whether AddBlk.OrigNode.Address is an address



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   handled by this DYMO router.  If this node is the originating DYMO
   router, the RM is dropped.

   ThisNode checks if the AddBlk.TargetNode.Address is a valid multihop-
   capable unicast address.  If the address is not a valid unicast
   address, the messages is discarded and further processing stopped.

   Next, ThisNode checks whether its routing table has an entry to the
   AddBlk.OrigNode.Address using longest-prefix matching [RFC1812].  If
   a route with a valid Route.SeqNum does not exist, then the new
   routing information is considered fresh and a new route table entry
   is created and updated as described in Section 5.2.2.  If a route
   table entry does exists and it has a valid Route.SeqNum, the incoming
   routing information is compared with the route table entry following
   the procedure described in Section 5.2.1.  If the incoming routing
   information is considered superior, the route table entry is updated
   as described in Section 5.2.2.

   For each address (except the TargetNode) in the RM that includes
   AddTLV.Dist information, the AddTLV.Dist information MAY be
   incremented.  The updated Distance value will influence judgment of
   the routing information (Section 5.2.1).

   If the resulting Distance value for the OrigNode is greater than
   65,535, the message is discarded.  If the resulting Distance value
   for another node is greater than 65,535, the associated address and
   its information are removed from the RM.

   After handling the OrigNode's routing information, then each address
   that is not the TargetNode MAY be considered for creating and
   updating routes.  Creating and updating routes to other nodes can
   eliminate RREQ for those IP destinations, in the event that data
   needs to be forwarded to the IP destination(s) now or in the near
   future.

   For each of the additional addresses considered, ThisNode first
   checks the that the address is a multihop-capable unicast address.
   If the address is not a unicast address, the address and all related
   information MUST be removed.

   If the routing table does not have a matching route with a valid
   Route.SeqNum for this additional address using longest-prefix
   matching, then a route is created and updated as described in
   Section 5.2.2.  If a route table entry exists with a valid
   Route.SeqNum, the incoming routing information is compared with the
   route table entry following the procedure described in Section 5.2.1.
   If the incoming routing information is considered superior, the route
   table entry is updated as described in Section 5.2.2.



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

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

   If the ThisNode is the DYMO router responsible for the TargetNode and
   this RM is a RREQ, then ThisNode responds with a RREP to the RREQ
   OrigNode (the new RREP's TargetNode).  The procedure for issuing a
   new RREP is described in Section 5.3.2.  At this point, ThisNode need
   not perform any more operations for the RM being processed.

   As an alternative to issuing a RREP, ThisNode MAY choose to
   distribute routing information about ThisNode (the RREQ TargetNode)
   more widely.  That is, ThisNode MAY optionally perform a route
   discovery; by issuing a RREQ with ThisNode listed as the TargetNode,
   using the procedure in Section 5.3.1.  At this point, ThisNode need
   not perform any more operations for the RM being processed.

   If ThisNode is not the TargetNode, this RM is a RREQ, the RREQ
   contains the TargetNode.AddTLV.SeqNum, and ThisNode has a forwarding
   route to the TargetNode with a SeqNum where Route.TargetNode.SeqNum -
   RREQ.TargetNode.AddTLV.SeqNum >= 0 (using signed 16-bit arithmetic);
   then ThisNode MAY respond with an intermediate DYMO router RREP.  The
   procedure for performing intermediate DYMO router RREP is described
   in Section 5.3.3.  If an intermediate DYMO router RREP is sent,
   ThisNode need not perform any more operations for the RM being
   processed.

   After handling a RM or creating a new RM, ThisNode MAY append
   additional routing information to the RM prior to redistributing this
   information, according to the procedure described in Section 5.3.5.
   The additional routing information can help reduce route discoveries
   at the expense of increased message size.

   For each address (except the TargetNode) in the RM that includes
   AddTLV.Dist information, the AddTLV.Dist information is incremented
   by at least one (1).  The updated Distance value will influence
   judgment of the routing information (Section 5.2.1) against known
   information at other DYMO routers that handle this RM.

   If the resulting Distance value for the OrigNode is greater than
   65,535, the message is discarded.  If the resulting Distance value
   for another node is greater than 65,535, the associated address and
   its information are removed from the RM.




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   Next, the MsgHdr.HopLimit is decremented by one (1).  If this RM's
   MsgHdr.HopLimit is greater than or equal to one (1), ThisNode is not
   the TargetNode, AND this RM is a RREQ, then the current RM (altered
   by the procedure defined above) SHOULD be sent to the
   IP.DestinationAddress LL-MANET-ROUTERS [RFC5498].  If the RREQ is
   unicast, the IP.DestinationAddress is set to the NextHopAddress.

   If this RM's MsgHdr.HopLimit is greater than or equal to one (1),
   ThisNode is not the TargetNode, AND this RM is a RREP, then the
   current RM is sent to the Route.NextHopAddress for the RREP's
   TargetNode.Address.  If no forwarding route exists to Target.Address,
   then a RERR SHOULD be issued to the OrigNode of the RREP.

   By sending the updated RM ThisNode is advertising that it will
   provide routing for addresses contained in the outgoing RM based on
   the information enclosed.  ThisNode MAY choose not to send the RM,
   though not resending this RM could decrease connectivity in the
   network or result in a non-shortest distance path.

   Some examples of why ThisNode might choose to not re-issue a RM are:
   if ThisNode does not want to advertise routing for the contained
   addresses because it is already heavily loaded; if ThisNode has
   already issued nearly identical routing information (e.g.  ThisNode
   had recently issued a RM with nearly the same distance); or if
   ThisNode is low on energy and does not want to expend energy for
   control message sending or packet forwarding.  These types of
   advanced behavior are not defined in this specification.

5.3.5.  Adding Additional Routing Information to a RM

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

   DYMO routers can append routing information to a RM.  This option
   (APPEND_INFORMATION) should be administratively configurable or
   intelligently controlled.

   Prior to appending an address controlled by this DYMO router to a RM,
   ThisNode MAY increment its OwnSeqNum as defined in Section 5.1.2.  If
   OwnSeqNum is not incremented the appended routing information might
   not be considered superior, when received by nodes with existing
   routing information.  Incrementation of the sequence number when
   appending information to an RM in transit (APPEND_INFORMATION_SEQNUM)
   should be administratively configurable or intelligently controlled.

   If an address controlled by this DYMO router includes ThisNode.Dist,
   it is set to a number greater than zero (0).



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   For added addresses (and their prefixes) not controlled by this DYMO
   router, Route.Dist can be included if known.  If Route.Dist is not
   known, it MUST NOT be included.

   MaxAge information about the appended address(es) MUST be included.

   Additional information (e.g.  SeqNum and Dist) about any appended
   address(es) SHOULD be included.

   Note that, the routing information about the TargetNode MUST NOT be
   added.  Also, duplicate address entries SHOULD NOT be added.
   Instead, only the best routing information (Section 5.2.1) for a
   particular address SHOULD be included.

5.4.  Route Discovery

   When a source's DYMO router needs to forward a data packet on behalf
   of an attached node and it does not have a forwarding route to the
   data packet's unicast IP destination address, ThisNode sends a RREQ
   (described in Section 5.3.1) to discover a route to the particular
   destination (TargetNode).

   After issuing a RREQ, the OrigNode DYMO router waits for a route to
   be created to the TargetNode.  If a route is not created within
   RREQ_WAIT_TIME, ThisNode may again try to discover a route by issuing
   another RREQ using the procedure defined in Section 5.3.1 again.
   Route discovery SHOULD be considered failed after
   DISCOVERY_ATTEMPTS_MAX and the final RREQ's corresponding
   RREQ_WAIT_TIME.

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

   For example, the first time a DYMO router issues a RREQ, it waits
   RREQ_WAIT_TIME for a route to the TargetNode.  If a route is not
   found within that time, the DYMO router MAY send another RREQ.  If a
   route is not found within two (2) times the current waiting time,
   another RREQ MAY be sent.  No more than DISCOVERY_ATTEMPTS_MAX route
   discovery attempts SHOULD be made before considering route discovery
   for this destination to have failed.  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 by the source's DYMO
   router.  This buffer SHOULD have a fixed limited size
   (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES) and older data packets
   SHOULD be discarded first.



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   Buffering of data packets can have both positive and negative
   effects, and therefore buffer settings (BUFFER_DURING_DISCOVERY)
   SHOULD be administratively configurable or intelligently controlled.

   If a route discovery attempt has failed (i.e. an attempt or multiple
   attempts have been made without receiving a RREP) to find a route to
   the TargetNode, any data packets buffered for for the corresponding
   TargetNode are dropped and a Destination Unreachable ICMP message
   SHOULD be delivered to the source.

5.5.  Route Maintenance

   A RERR SHOULD be issued if a data packet is to be forwarded and it
   cannot be delivered to the next-hop because no forwarding route for
   the IP.DestinationAddress exists; RERR generation is described in
   Section 5.5.3.

   Upon this condition, an ICMP Destination Unreachable message SHOULD
   NOT be generated unless this router is responsible for the
   IP.DestinationAddress and that IP.DestinationAddress is known to be
   unreachable.

   In addition to inability to forward a data packet, a RERR SHOULD be
   issued immediately after detecting a broken link (see Section 5.5.1)
   of a forwarding route to quickly notify DYMO routers that a that
   certain routes are no longer available.  If a newly unavailable route
   has not been used recently (indicated by ROUTE_USED), the RERR SHOULD
   NOT be generated.

5.5.1.  Active Next-hop Router Adjacency Monitoring

   Nodes MUST monitor connectivity to adjacent next-hop DYMO routers on
   forwarding routes.  This monitoring can be accomplished by one or
   several mechanisms, including:

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

   o  Route timeout

   o  Lower layer feedback that a particular adjacent router is no
      longer reachable

   o  Other monitoring mechanisms or heuristics

   Upon determining that a next-hop DYMO router is unreachable, ThisNode
   MUST remove the affected forwarding routes (those with an unreachable
   next-hop) and unset the Route.Forwarding flag.  ThisNode also flags
   the associated routes in DYMO's routing table as Broken.  For each



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   broken route a timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT.

5.5.2.  Updating Route Lifetimes During Packet Forwarding

   To avoid removing the forwarding route to reach the IP.SourceAddress,
   ThisNode SHOULD set a timeout (ROUTE_USED) to ROUTE_USED_TIMEOUT for
   the route to the IP.SourceAddress upon receiving a data packet.  If a
   timer for ROUTE_DELETE is set, it is removed.

   To avoid removing the forwarding route to the IP.DestinationAddress
   that is being used, ThisNode SHOULD set a timeout (ROUTE_USED) to
   ROUTE_USED_TIMEOUT for the route to the IP.DestinationAddress upon
   sending a data packet.  If a timer for ROUTE_DELETE is set, it is
   removed.

5.5.3.  RERR Generation

   A RERR informs DYMO routers that a route to certain destinations is
   not available through ThisNode.

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

   Additional UnreachableNodes that require the same unavailable link
   (routes with the same Route.NextHopAddress and
   Route.NextHopInterface) SHOULD be added to the RERR, as additional
   AddBlk.UnreachableNode.Address entries with their associated prefix.
   The SeqNum if known SHOULD also be included.  Appending
   UnreachableNode information notifies each node that handles this
   message of additional routes that are no longer available.  This
   option (APPEND_EXTRA_UNREACHABLE) SHOULD be administratively
   configurable or intelligently controlled.

   If SeqNum information is not known or not included in the RERR, all
   nodes handling the RERR will assume their routing information
   associated with the UnreachableNode is no longer valid and flag those
   routes as broken.

   Each DYMO routing protocol message SHOULD contain ThisNode.DID's
   value in a message TLV (MsgTLV.DID).  If ThisNode.DID value is zero
   (0) it MAY be omitted.



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   A multicast RERR is sent to the IP.DestinationAddress LL-MANET-
   ROUTERS [RFC5498].  Sending the RERR to the LL-MANET-ROUTERS address
   notifies all nearby DYMO routers that might depend on the now broken
   link.  If the RERR is unicast, the IP.DestinationAddress is set to
   the NextHopAddress.

   At this point, the packet or message that forced generation of this
   RERR SHOULD be discarded.

5.5.4.  RERR Handling

   First, ThisNode decides whether to handle this message.  If the
   message contains a MsgTLV.DID it SHOULD match ThisNode.DID's value.
   If the message does not contain a MsgTLV.DID it is assumed to be zero
   (0) and SHOULD be discarded if ThisNode.DID's value is not zero (0).

   Next, ThisNode MAY selectively handle messages based upon information
   in the message.  ThisNode MAY choose to only handle messages from
   adjacent DYMO routers.  If ThisNode chooses not to handle this
   message, the message is discarded and further processing stopped.

   When a DYMO router handles a RERR, it examines each UnreachableNode's
   information.  The attending DYMO router removes the forwarding route,
   unsets the Route.Forwarding flag, sets the Route.Broken flag, and a
   timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT for each
   UnreachableNode.Address found using longest prefix matching that meet
   all of the following conditions:

   1.  The UnreachableNode.Address is a multihop-capable unicast
       address.

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

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

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

   During handling if Route.SeqNum is zero (0) or unknown and
   UnreachableNode.SeqNum exists in the RERR, then Route.SeqNum MAY be
   set to UnreachableNode.SeqNum.  Setting Route.SeqNum can reduce
   future RRER handling and forwarding.

   Each UnreachableNode that did not result in a broken route is removed
   from the RERR, since propagation of this information will not result



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   in any benefit.

   Each UnreachableNode that did result in a broken route SHOULD remain
   in the RERR.

   If any UnreachableNode was removed, all other information (AddTLVs)
   associated with the removed address(es) MUST also removed.

   After handling if Route.SeqNum is known and an UnreachableNode.SeqNum
   is not included in the RERR, then Route.SeqNum (i.e.
   UnreachableNode.SeqNum) MAY be added to the RERR.  Including
   UnreachableNode.SeqNum can reduce future RRER handling and
   forwarding.

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

   If handling continues, the MsgHdr.HopLimit is decremented by one (1).
   Further, if this RERR's new MsgHdr.HopLimit is greater than one (1)
   and at least one unreachable node address remains in the RERR, then
   the updated RERR SHOULD be sent.

   A multicast RERR is sent to the IP.DestinationAddress LL-MANET-
   ROUTERS [RFC5498].  If the RERR is unicast, the IP.DestinationAddress
   is set to the NextHopAddress.

5.6.  DYMO Identifier (DID)

   Each DYMO routing protocol process MUST have an associated DYMO
   Identifier (DID).  The DID allows multiple DYMO routing protocol
   processes to operate over the same links and on the same device
   independently.  This function may also be used to administratively
   separate DYMO processes with incompatible options, timers, or
   extensions.

   The DID is similar in function to OSPF Instance ID [RFC5340]
   [I-D.ietf-ospf-multi-instance], OSPF Area ID [RFC2328] [RFC5340],
   and/or the MANET_ID TLV [I-D.chakeres-manet-manetid].

   All DYMO routers with the same DID that come in contact with each
   other MUST operate with a compatible set of configuration options,
   timing parameters (see Section 6), and protocol extensions.  In cases
   with non-default options, the DID value SHOULD be administratively
   chosen.

   The default DID value is zero (0), and using this value requires that
   the implementation utilize options and timing parameters compatibly
   with those defined in Section 6.



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   Each DYMO routing protocol message sent MUST contain its associated
   DID in a message TLV; unless the DID value is zero (0), in which case
   it MAY be omitted.

   Upon receipt of DYMO protocol message a DYMO routing protocol process
   SHOULD only process messages with a DID (MsgTLV.DID) value matching
   its own DID (ThisNode.DID).

5.7.  Unknown Message & TLV Types

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

   For handling of messages that contain unknown TLV types, the default
   behavior is to leave the information in control messages unmodified.
   Although, this behavior (UNKNOWN_TYPES) MAY be be administratively
   controlled.

5.8.  Advertising Network Addresses

   DYMO routers specify the prefix length for each advertised address.
   Any nodes (other than the advertising DYMO router) within the
   advertised prefix MUST NOT participate in the DYMO protocol directly.
   For example, advertising 192.0.2.1 with a prefix length of 24
   indicates that all nodes with the matching 192.0.2.X are reachable
   through this DYMO router.

5.9.  Simple Internet Attachment

   Simple Internet attachment consists of a stub network of DYMO routers
   connected to the Internet via a single Internet DYMO router (IDR).
   The Internet may be connected via multiple DYMO routers, but such
   behavior is not specified in this document.

   The IDR is responsible for responding to RREQs for DYMO routers on
   behalf of addresses on the Internet, as well as discovering routes to
   addresses within the DYMO Region on behalf of nodes on the Internet.














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         /--------------------------\
        /          Internet          \
        \                            /
         \------------+-------------/
                      |
       Routable &     |
       Topologically  | 192.0.2.0/24
       Correct        |
       Prefix         |
                +-----+------+
                |  Internet  |
         /------|  DYMO      |-------\
        /       |  Router    |        \
       /        |192.0.2.1/32|         \
       |        +------------+         |
       |         DYMO Region           |
       |                               |
       | +--------------+              |
       | |  DYMO Router |              |
       | |  192.0.2.2/32|              |
       | +--------------+              |
       |              +--------------+ |
       |              |  DYMO Router | |
       |              |  192.0.2.3/32| |
       \              +--------------+ /
        \                             /
         \---------------------------/

               Figure 3: Simple Internet Attachment Example

   DYMO routers, and hosts behind these routers, wishing to be reachable
   from hosts on the Internet MUST have IP addresses within the IDR's
   routable and topologically correct prefix (e.g. 192.0.2.0/24).  Given
   a node in the DYMO Region with a routeable address handled by the
   IDR, the IDR is responsible for discovering routes and forwarding
   packets received from the Internet destined for these nodes inside
   the DYMO Region prefix(es).  The IDR SHOULD advertize the largest
   known prefix for any addresses on the Internet, when advertising
   routing information in RMs.

   When a DYMO router within the DYMO Region wants to forward packets to
   a node on the Internet, they simply issue RREQ for those IP
   Destination Addresses; using normal DYMO route discovery.  The IDR is
   responsible for properly responding to RREQ on behalf of the Internet
   destinations.






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5.10.  Multiple Interfaces

   DYMO may be used with multiple interfaces; therefore, the particular
   interface over which packets arrive MUST be known whenever a packet
   is received.  Whenever a new route is created, the interface through
   which the Route.Address can be reached is also recorded in the route
   table entry.

   When multiple interfaces are available, a node transmitting a
   multicast packet with IP.DestinationAddress set to LL-MANET-ROUTERS
   SHOULD send the packet on all interfaces that have been configured
   for DYMO operation.

   Similarly, DYMO routers should subscribe to LL-MANET-ROUTERS on all
   their DYMO interfaces.

5.11.  DYMO Control Packet/Message Generation Limits

   To ensure predictable control overhead, DYMO router's rate of packet/
   message generation SHOULD be limited.  The rate and algorithm for
   limiting messages (CONTROL_TRAFFIC_LIMITS) is left to the implementor
   and should be administratively configurable or intelligently
   controlled.  DYMO control messages SHOULD be discarded in the
   following order of preferences RREQ, RREP, and finally RERR.


6.  Administratively Configured Parameters and Timer Values

   DYMO contains several parameters which MUST be administratively
   configured.  The list of these follows:

              Required Administratively Configured Parameters

   +------------------------+------------------------------------------+
   |          Name          |                Description               |
   +------------------------+------------------------------------------+
   |           DID          |  All DYMO routers with the same DID that |
   |                        |   come in contact with each other MUST   |
   |                        |     operate with a compatible set of     |
   |                        |       configuration options, timing      |
   |                        | parameters, and protocol extensions.  If |
   |                        |   non-default potentially incompatible   |
   |                        |  options, timing parameters or protocol  |
   |                        |  extensions are utilized the DID MUST be |
   |                        |         set to a non-zero value.         |
   |  RESPONSIBLE_ADDRESSES |  List of addresses, and their associated |
   |                        |   prefix, for which this DYMO router is  |
   |                        |               responsible.               |



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   |     DYMO_INTERFACES    |  List of the interfaces participating in |
   |                        |          DYMO routing protocol.          |
   +------------------------+------------------------------------------+

                                  Table 2

   DYMO contains a number of timers.  The default timing parameter
   values follow:

                      Default Timing Parameter Values

           +------------------------------+-------------------+
           |             Name             |       Value       |
           +------------------------------+-------------------+
           |         ROUTE_TIMEOUT        |     5 seconds     |
           |     ROUTE_AGE_MIN_TIMEOUT    |      1 second     |
           | ROUTE_SEQNUM_AGE_MAX_TIMEOUT |     60 seconds    |
           |      ROUTE_USED_TIMEOUT      |   ROUTE_TIMEOUT   |
           |     ROUTE_DELETE_TIMEOUT     | 2 * ROUTE_TIMEOUT |
           |     ROUTE_RREQ_WAIT_TIME     |     2 seconds     |
           | UNICAST_MESSAGE_SENT_TIMEOUT |      1 second     |
           +------------------------------+-------------------+

                                  Table 3

   The above timing parameter values work well for small and medium
   well-connected networks with moderate topology changes.

   The timing parameters SHOULD be administratively configurable for the
   network where DYMO is used.  Ideally, for networks with frequent
   topology changes the DYMO parameters should be adjusted using either
   experimentally determined values or dynamic adaptation.  For example,
   in networks with infrequent topology changes ROUTE_USED_TIMEOUT may
   be set to a much larger value.

                         Default Parameter Values

   +------------------------+-------+----------------------------------+
   |          Name          | Value |            Description           |
   +------------------------+-------+----------------------------------+
   |      MSG_HOPLIMIT      |   10  | This value should be larger than |
   |                        |  hops |  the DYMO network diameter.  If  |
   |                        |       |  this value is not large enough, |
   |                        |       |  routing messages may not reach  |
   |                        |       |   their intended destinations.   |






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   | DISCOVERY_ATTEMPTS_MAX |   3   |   The number of route discovery  |
   |                        |       |      attempts to make before     |
   |                        |       |   indicating that a particular   |
   |                        |       |     address is not reachable.    |
   +------------------------+-------+----------------------------------+

                                  Table 4

   In addition to the above parameters and timing values, several
   administrative options exist.  These options have no influence on
   correct routing behavior, although they may potentially reduce DYMO
   routing control messaging in certain situations.  The default
   behavior is to NOT enable any of these options; and although many of
   these options can be administratively controlled, they may be better
   served by intelligent control.  The following table enumerates
   several of the options.

                    Administratively Controlled Options

   +---------------------------+---------------------------------------+
   |            Name           |              Description              |
   +---------------------------+---------------------------------------+
   |     APPEND_INFORMATION    |  Whether to append ThisNode's routing |
   |                           |          information to a RM.         |
   | APPEND_INFORMATION_SEQNUM |    Whether to increment ThisNode's    |
   |                           |    OwnSeqNum when append ThisNode's   |
   |                           |      routing information to a RM.     |
   |  BUFFER_DURING_DISCOVERY  |  Whether and how much data to buffer  |
   |                           |        during route discovery.        |
   |  APPEND_EXTRA_UNREACHABLE |      Whether to append additional     |
   |                           |    Unreachable information to RERR.   |
   |       UNKNOWN_TYPES       |  What action to take when an unknown  |
   |                           |   TLV type is received.  The default  |
   |                           | action is to forward this information |
   |                           |  unmodified.  Another action would be |
   |                           |      to remove this information.      |
   |   CONTROL_TRAFFIC_LIMITS  |    DYMO control messaging should be   |
   |                           |   limited to avoid consuming all the  |
   |                           |           network bandwidth.          |
   +---------------------------+---------------------------------------+

                                  Table 5

   Note: several fields have limited size (bits or bytes) these sizes
   and their encoding may place specific limitations on the values that
   can be set.  For example, MsgHdr.HopLimit is a 8-bit field and
   therefore MSG_HOPLIMIT cannot be larger than 255.




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7.  IANA Considerations

   In its default mode of operation, DYMO uses the UDP port MANET
   [RFC5498] to carry protocol packets.  DYMO also uses the link-local
   multicast address LL-MANET-ROUTERS [RFC5498].

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

7.1.  DYMO Message Types Specification

                            DYMO Message Types

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

                                  Table 6

7.2.  Message and Address Block TLV Type Specification

                             Message TLV Types

   +-------------------+------+--------+-------------------------------+
   |        Name       | Type | Length | Value                         |
   +-------------------+------+--------+-------------------------------+
   |  Unicast Response | 10 - |    0   | Indicates to the processing   |
   |      Request      |  TBD | octets | 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 can assume that  |
   |                   |      |        | the link is unidirectional    |
   |                   |      |        | and MAY blacklist the link to |
   |                   |      |        | this node.                    |
   +-------------------+------+--------+-------------------------------+

                                  Table 7





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7.3.  Address Block TLV Specification

                          Address Block TLV Types

   +---------------+-----------+-----------+---------------------------+
   |      Name     |    Type   |   Length  | Value                     |
   +---------------+-----------+-----------+---------------------------+
   |      DYMO     |  9 - TBD  |    DID    | ThisNode.DID's value.     |
   |   Identifier  |           |   length  | More information can be   |
   |     (DID)     |           |           | found in Section 5.6      |
   | DYMO Sequence |  10 - TBD |  up to 2  | The DYMO sequence num     |
   |     Number    |           |   octets  | associated with this      |
   |  (DYMOSeqNum) |           |           | address.  The sequence    |
   |               |           |           | number may be the last    |
   |               |           |           | known sequence number.    |
   |    Distance   |  11 - TBD |  up to 2  | A metric of the distance  |
   |               |           |   octets  | traversed by the          |
   |               |           |           | information associated    |
   |               |           |           | with this address.        |
   | VALIDITY_TIME |    TBD    |           | The maximum amount of     |
   |  - AKA MaxAge | [RFC5497] |           | time that information can |
   |               |           |           | be maintained before      |
   |               |           |           | being deleted.  The       |
   |               |           |           | VALIDITY_TIME TLV is      |
   |               |           |           | defined in [RFC5497].     |
   +---------------+-----------+-----------+---------------------------+

                                  Table 8


8.  Security Considerations

   This document does not mandate any specific security measures.
   Instead, this section describes various security considerations and
   potential avenues to secure DYMO routing.

   The most important security mechanisms for DYMO routing are
   integrity/authentication and confidentiality.

   In situations where routing information or router identity are
   suspect, integrity and authentication techniques SHOULD be applied to
   DYMO messages.  In these situations, routing information that is
   distributed over multiple hops SHOULD also verify the integrity and
   identity of information based on originator of the routing
   information.

   A digital signature could be used to identify the source of DYMO
   messages and information, along with its authenticity.  A nonce or



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   timestamp SHOULD also be used to protect against replay attacks.
   S/MIME and OpenPGP are two authentication/integrity protocols that
   could be adapted for this purpose.

   In situations where confidentiality of DYMO messages is important,
   cryptographic techniques SHOULD be applied.

   In certain situations, like sending a RREP or RERR, a DYMO router
   could include proof that it has previously received valid routing
   information to reach the destination, at one point of time in the
   past.  In situations where routers are suspected of transmitting
   maliciously erroneous information, the original routing information
   along with its security credentials SHOULD be included.

   Note that if multicast is used, any confidentiality and integrity
   algorithms used must permit multiple receivers to handle the message.


9.  Acknowledgments

   DYMO is a descendant of the design of previous MANET reactive
   protocols, especially AODV [RFC3561] and DSR [RFC4728].  Changes to
   previous MANET reactive protocols stem from research and
   implementation experiences.  Thanks to Elizabeth Belding-Royer for
   her long time authorship of DYMO.  Additional thanks to Luke Klein-
   Berndt, Pedro Ruiz, Fransisco Ros, Koojana Kuladinithi, Ramon
   Caceres, Thomas Clausen, Christopher Dearlove, Seung Yi, Romain
   Thouvenin, Tronje Krop, Henner Jakob, Alexandru Petrescu, Christoph
   Sommer, Cong Yuan, Lars Kristensen, and Derek Atkins for reviewing of
   DYMO, as well as several specification suggestions.


10.  References

10.1.  Normative References

   [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.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, October 2007.

   [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized Mobile Ad Hoc Network (MANET) Packet/Message



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              Format", RFC 5444, February 2009.

   [RFC5497]  Clausen, T. and C. Dearlove, "Representing Multi-Value
              Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497,
              March 2009.

   [RFC5498]  Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
              (MANET) Protocols", RFC 5498, March 2009.

10.2.  Informative References

   [I-D.chakeres-manet-manetid]
              Chakeres, I., "MANET_ID TLV",
              draft-chakeres-manet-manetid-03 (work in progress),
              February 2008.

   [I-D.ietf-manet-nhdp]
              Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
              Network (MANET) Neighborhood Discovery Protocol (NHDP)",
              draft-ietf-manet-nhdp-11 (work in progress), October 2009.

   [I-D.ietf-ospf-multi-instance]
              Lindem, A., Roy, A., and S. Mirtorabi, "OSPF Multi-
              Instance Extensions", draft-ietf-ospf-multi-instance-01
              (work in progress), October 2009.

   [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.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

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

   [RFC4728]  Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
              Routing Protocol (DSR) for Mobile Ad Hoc Networks for
              IPv4", RFC 4728, February 2007.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC5148]  Clausen, T., Dearlove, C., and B. Adamson, "Jitter
              Considerations in Mobile Ad Hoc Networks (MANETs)",



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              RFC 5148, February 2008.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.


Appendix A.  Shifting Responsibility for an Address Between DYMO Routers

   Only one DYMO router within a routing region SHOULD be responsible
   for a particular address at any time.  If two DYMO routers
   dynamically pass responsibility of an address correct DYMO routing
   behavior must be observed.  The DYMO router adding the new address
   must wait for any exiting routing information about this address to
   be purged from the network.  Therefore, it must wait at least
   ROUTER_SEQNUM_AGE_MAX after the previous DYMO router for this address
   stopped participating and advertising routing information on its
   behalf.


Authors' Addresses

   Ian D Chakeres
   CenGen
   9250 Bendix Road North
   Columbia, Maryland  21045
   USA

   Email: ian.chakeres@gmail.com
   URI:   http://www.ianchak.com/


   Charles E. Perkins
   WiChorus Inc.
   3590 North First Street, Suite 300
   San Jose, CA  95134
   USA

   Phone: +1-408-421-1172
   Email: charliep@computer.org












Chakeres & Perkins     Expires September 23, 2010              [Page 39]


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