Diversity Routing for the Babel Routing Protocol
draft-chroboczek-babel-diversity-routing-01

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Network Working Group                                      J. Chroboczek
Internet-Draft                         IRIF, University of Paris-Diderot
Intended status: Experimental                          February 15, 2016
Expires: August 18, 2016

            Diversity Routing for the Babel Routing Protocol
              draft-chroboczek-babel-diversity-routing-01

Abstract

   This document defines an extension to the Babel routing protocol that
   allows routing updates to carry radio frequency information, and
   therefore makes it possible to use radio diversity information for
   route selection.

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   This Internet-Draft will expire on August 18, 2016.

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Table of Contents

   1.  Introduction and background . . . . . . . . . . . . . . . . .   2
   2.  Operation of the protocol . . . . . . . . . . . . . . . . . .   3
     2.1.  Changes to data structures  . . . . . . . . . . . . . . .   3
     2.2.  Receiving updates . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Sending updates . . . . . . . . . . . . . . . . . . . . .   4
     2.4.  Metric computation and route selection  . . . . . . . . .   5
     2.5.  Protocol encoding . . . . . . . . . . . . . . . . . . . .   5
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   4.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Appendix A.  The Z3 algorithm . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction and background

   The Babel routing protocol [RFC6126] does not mandate a specific
   algorithm for computing metrics; Appendix A of that document suggests
   using an additive integer metric.  While this works well in many
   topologies, it fails to take into account the possibility of
   interference between radio links, which is important in multi-
   frequency wireless mesh networks.

   Consider for example the following topology, where the solid lines
   use one radio frequency and the dashed lines another, and suppose
   that the solid frequency has very slightly lower packet loss than the
   dashed one:

      B
     / \
    /   \
   A     D
    \   .
     \ .
      C

   When sending data from A to D, Babel will reliably choose the solid
   route through B.  Howerver, this route self-interferes: when B is
   sending a packet to D, it cannot simultaneously be receiving a packet
   from A, which halves the effective throughput.  No such issue arises
   with the route through C, which should therefore be preferred.

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   Interference needs to be taken into account even when it happens
   between non-adjacent links.  Consider the following topology:

      B +++ C
     /       \
    /         \
   A           F
    \         .
     \       .
      D +++ E

   When routing data from A to F, the route through B and C has two
   interfering links: if two packets are sent by A and C at roughly the
   same time, a collision will occur, and both packets will need to be
   resent.  Again, no such issue arises with the route through D and E.

2.  Operation of the protocol
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