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Internet Engineering Task Force (IETF)                       C. DearloveRequest for Comments: 7187                               BAE Systems ATCUpdates:7181                                                 T. ClausenCategory: Standards Track                       LIX, Ecole PolytechniqueISSN: 2070-1721                                               April 2014Routing Multipoint Relay Optimization forthe 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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7187.Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (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 Simplified BSD License.Dearlove & Clausen           Standards Track                    [Page 1]

RFC 7187             OLSRv2 Routing MPR Optimization          April 2014Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .23.  Applicability Statement . . . . . . . . . . . . . . . . . . .24.  Routing MPR Selection . . . . . . . . . . . . . . . . . . . .35.  Security Considerations . . . . . . . . . . . . . . . . . . .46.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .47.  References  . . . . . . . . . . . . . . . . . . . . . . . . .47.1.  Normative References  . . . . . . . . . . . . . . . . . .47.2.  Informative References  . . . . . . . . . . . . . . . . .41.  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 toDearlove & Clausen           Standards Track                    [Page 2]

RFC 7187             OLSRv2 Routing MPR Optimization          April 2014   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 ofSection 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   ofSection 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].Dearlove & Clausen           Standards Track                    [Page 3]

RFC 7187             OLSRv2 Routing MPR Optimization          April 20145.  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.  References7.1.  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",RFC7181, 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.Dearlove & Clausen           Standards Track                    [Page 4]

RFC 7187             OLSRv2 Routing MPR Optimization          April 2014Authors' 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/Dearlove & Clausen           Standards Track                    [Page 5]