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)
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
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
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Table of Contents
1. 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
Note that this optimization does not impact interoperability:
implementations that do and do not implement this optimization will
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
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
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
* 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
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
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].
The authors would like to gratefully acknowledge Philippe Jacquet
(Alcatel-Lucent) for intense technical discussions and comments.
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