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MANET Working Group                                         Sanghyun Ahn
Internet Draft                                       University of Seoul
Expires: June 13, 2016                                 December 22, 2015


                    DSR Extensions for Multipath Routing
                    draft-ahn-manet-multipath-dsr-00.txt

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Abstract

   This document describes how DSR [1] can be extended for the support
   of MANET multipath routing. Since DSR uses the source routing
   approach, it can be appropriate for multipath routing.
   Therefore, in this draft, we describe how we can extend DSR for
   finding multiple routes from the source to the destination.


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Extensions on DSR Options Header . . . . . . . . . . . . . . .  3
   3.1 Extensions on DSR Route Request Option . . . . . . . . . . . .  4
   4.  Other Considerations . . . . . . . . . . . . . . . . . . . . .  5
   References . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . .  5

































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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  Introduction

   The mobile ad hoc network (MANET) is composed of a number of mobile
   nodes which can communicate with each other through multiple wireless
   links without the help of a wired infrastructure. Therefore,
   in the MANET, the route connectivity tends to be very unstable.
   This route unstability can be mitigated by providing more than
   one route to a source and destination node pair. In recent years,
   there have been intensive studies done on multipath routing protocols
   for the MANET [1]. Also, multipath routing protocols may have the
   advantage of providing load balancing by distributing data traffic
   to a number of routes. On the other hand, it may incur more control
   message overhead to set up multiple routes.

   The DSR protocol [2] works based on the source routing mechanism
   and support multiple routes between a pair of the source and the
   destination nodes by maintaining several routes in the route cache
   of the source node. That is, DSR basically support multipath routing
   and the source routing capability makes the support of multipath
   routing easier. However, in DSR, a route reply (RREP) message
   with a route information is sent back to the source by an
   intermediate node with a fresh route to the destination or
   by the destination itself. By doing this way, the source can
   collect a random number of the routes to the destination.
   And this may cause higher route discovery overhead.

   The route discovery overhead can be reduced by allowing the source
   to specify the maximum number of routes between the source and the
   destination and by making the destination to select that number of
   routes from the routes obtained from the route request (RREQ)
   messages received at the destination. This type of route selection
   can be achieved by disabling the C bit in the DSR Route Request
   option [3] (i.e., the cached route reply capability is disabled)
   and specifying the number of routes as defined in this document.

   In this draft, we describe how the DSR Options header has to be
   extended to support the source to specify the number of routes
   it needs.


3.  Extensions on DSR Options Header



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3.1 Extensions on DSR Route Request Option

   The Route Request option in the DSR Options header is extended as
   follows:


 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option Type  |  Opt Data Len |     Identification    |C| Pt|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Target Address                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Address[1]                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Address[2]                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Address[n]                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


IP fields: the same as described in [2]

Route Request fields: the same as described in [3] except for the
                      R bit and the Pt field

   Pt
      The maximum allowable number of paths (routes) between the source
      and the destination which is specified in the Target Address
      field. The source specifies the value of the Pt field.
      The number of routes is the value of the Pt field plus 1
      (i.e., the value 0 in the Pt field is the default value and
      implies a single route between the source and the destination).
      Thus, the maximum allowable number of routes between a pair of
      source and destination nodes is 4 and this is usually expected
      to be enough. When the C bit is 1, the value in the Pt field
      has to be ignored. In other words, the value in the Pt field is
      meaningful only when the C bit value is 0. When the destination
      receives an RREQ message with the C bit value of 0 in its Route
      Request option, it has to send back upto that number of RREP
      messages to the source. The mechanism to select those routes
      sent back to the source is out of the scope of this draft.

   R
      R bit is a reserved bit for further extension of DSR Route
      Request option.



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4.  Other Considerations

   TBD.


References

   [1] M. Tarique, K. E. Tepe, S. Abidi and S. Erfani, "Survey of
       Multipath Routing Protocols for Mobile Ad Hoc Networks," Journal
       of Network and Computer Applications, November 2009.
   [2] D. Johnson, Y. Hu and D. Maltz, "The Dynamic Source Routing
       Protocol," RFC 4728, February 2007.
   [3] S. Ahn, "DSR Extensions for the Resolution of Cached Route
       Reply Implosion," IETF draft-ahn-manet-dsr-crri-00.txt,
       December 2015.


Author's Address

   Sanghyun Ahn
   University of Seoul
   90, Cheonnong-dong, Tongdaemun-gu
   Seoul 130-743
   Korea
   Email: ahn@uos.ac.kr


























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