OLSRv2 MPR: Routing Multipoint Relay Optimization for the Optimized Link State Routing Protocol Version 2 (OLSRv2)

Internet Engineering Task Force (IETF)                       C. Dearlove
Request for Comments: 7187                               BAE Systems ATC
Updates: 7181                                                 T. Clausen
Category: Standards Track                       LIX, Ecole Polytechnique
ISSN: 2070-1721                                               April 2014


               Routing Multipoint Relay Optimization for
      the Optimized Link State Routing Protocol Version 2 (OLSRv2)

Abstract

   This specification updates the Optimized Link State Routing Protocol
   version 2 (OLSRv2) with an optimization to improve the selection of
   routing multipoint relays.  The optimization retains full
   interoperability between implementations of OLSRv2 with and without
   this optimization.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7187.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Applicability Statement . . . . . . . . . . . . . . . . . . .   2
   4.  Routing MPR Selection . . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   4

1.  Introduction

   The Optimized Link State Routing Protocol version 2 [RFC7181] is a
   proactive link state routing protocol designed for use in mobile ad
   hoc networks (MANETs) [RFC2501].  This document improves one area of
   the OLSRv2 specification.

   One improvement included in OLSRv2, compared to its predecessor
   described in [RFC3626], is the use of link metrics, rather than
   minimum-hop routing.  A rationale for how link metrics were included
   in OLSRv2 is documented in [RFC7185].  However, one aspect of the use
   of link metrics described in [RFC7185], the removal of some
   unnecessarily selected routing multipoint relays (MPRs), was not
   included in [RFC7181].  This specification updates OLSRv2 to include
   this optimization.

   Note that this optimization does not impact interoperability:
   implementations that do and do not implement this optimization will
   interoperate seamlessly.

2.  Terminology

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

   Additionally, this document uses the terminology of [RFC7181].

3.  Applicability Statement

   This specification updates [RFC7181].  As such, it is applicable to
   all implementations of this protocol.  The optimization presented in
   this specification is simply permissive; it allows an additional
   optimization, and there is no requirement for any implementation to
   include it.  However, inclusion of this optimization is advised; it
   can, in some cases, create smaller and fewer messages, without ever
   having the opposite effect.

   [RFC7181] defines the properties for the selection of routing MPRs
   from among a router's symmetric 1-hop neighbors.  The properties are

   o  the selected MPRs must consist of a set of symmetric 1-hop
      neighbors that cover all the symmetric 2-hop neighbors, and

   o  the selected MPRs must do so retaining a minimum distance route
      (1-hop, if present, or 2-hop) to each symmetric 2-hop neighbor.

   The discussion in the latter part of Section 6.2 of [RFC7185]
   indicates that this requirement is overly prescriptive for routing
   MPR selection.  The update to [RFC7181] described in this
   specification permits a router to use the described optimization,
   while still being considered compliant with OLSRv2.

   Note that whether or not a router is considered compliant, a router
   that implements the optimization described in this specification will
   interoperate successfully with routers that are not implementing this
   optimization.

4.  Routing MPR Selection

   A set of routing MPRs created as specified in [RFC7181] MAY be
   optimized in the following manner.  Note that this uses the notation
   of Section 18.2 of [RFC7181]:

   1.  If there is a sequence x_0, ..., x_n of elements of N1 such that:

       *  x_0 is a routing MPR,

       *  x_1, ... , x_n have corresponding elements y_1, ..., y_n of
          N2, and

       *  d1(x_0) + d2(x_0,y_1) + ... + d2(x_m-1,y_m) < d1(x_m) for m =
          1, ... , n,

       then x_1 to x_n may be removed from the set of routing MPRs, if
       selected.

   Note that "corresponding elements" in N1 and N2 means that these
   elements represent the same router.  All of this information is
   available from information gathered by NHDP [RFC6130].

5.  Security Considerations

   The update to OLSRv2 [RFC7181] does not introduce any new protocol
   signals, nor does it change the processing of any received protocol
   signals.

   This update to OLSRv2 [RFC7181] permits an implementation that is
   compliant with OLSRv2 to (potentially) eliminate some unneeded
   routers from the routing MPR sets generated as described in
   [RFC7181], which also eliminates the need to include the
   corresponding information in generated Topology Control (TC)
   messages.  Because this information is not used when included, this
   update to OLSRv2 [RFC7181] does not present any additional security
   considerations, beyond those described in [RFC7181].

6.  Acknowledgments

   The authors would like to gratefully acknowledge Philippe Jacquet
   (Alcatel-Lucent) for intense technical discussions and comments.

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC6130]  Clausen, T., Dean, J., and C. Dearlove, "Mobile Ad Hoc
              Network (MANET) Neighborhood Discovery Protocol (NHDP)",
              RFC 6130, April 2011.

   [RFC7181]  Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
              "The Optimized Link State Routing Protocol Version 2", RFC
              7181, April 2014.

7.2.  Informative References

   [RFC2501]  Macker, J. and S. Corson, "Mobile Ad hoc Networking
              (MANET): Routing Protocol Performance Issues and
              Evaluation Considerations", RFC 2501, January 1999.

   [RFC3626]  Clausen, T. and P. Jacquet, "The Optimized Link State
              Routing Protocol", RFC 3626, October 2003.

   [RFC7185]  Clausen, T., Dearlove, C., and P. Jacquet, "Rationale for
              the Use of Link Metrics in the Optimized Link State
              Routing Protocol Version 2 (OLSRv2)", RFC 7185, April
              2014.

Authors' Addresses

   Christopher Dearlove
   BAE Systems Advanced Technology Centre
   West Hanningfield Road
   Great Baddow, Chelmsford
   United Kingdom

   Phone: +44 1245 242194
   EMail: chris.dearlove@baesystems.com
   URI:   http://www.baesystems.com/


   Thomas Heide Clausen
   LIX, Ecole Polytechnique

   Phone: +33 6 6058 9349
   EMail: T.Clausen@computer.org
   URI:   http://www.ThomasClausen.org/