Routing Multipoint Relay Optimization for the Optimized Link State Routing Protocol Version 2 (OLSRv2)
BAE Systems Advanced Technology Centre
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+44 1245 242194
chris.dearlove@baesystems.com
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LIX, Ecole Polytechnique
+33 6 6058 9349
T.Clausen@computer.org
http://www.ThomasClausen.org/
Mobile Ad hoc Networking (MANET)
MANET
OLSRv2
link metric
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.
The Optimized Link State Routing Protocol version 2
is a proactive link state routing protocol designed for use in mobile ad hoc
networks (MANETs) . This document improves one area
of the OLSRv2 specification.
One improvement included in OLSRv2, compared to its predecessor described in
, is the use of link metrics, rather than minimum-hop routing. A
rationale for how link metrics were included in OLSRv2 is documented in
. However, one aspect of the use of link metrics described in
, the removal of some unnecessarily selected routing multipoint relays
(MPRs), was not included in . 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.
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
.
This specification updates . 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.
defines the properties for the selection of
routing MPRs from among a router's symmetric 1-hop
neighbors. The properties are
the selected MPRs must consist of a set of symmetric 1-hop
neighbors that cover all the symmetric 2-hop neighbors, and
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 indicates that
this requirement is overly prescriptive for routing MPR selection.
The update to
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.
A set of routing MPRs created as specified in MAY be optimized in the following manner. Note that this uses the notation of Section 18.2 of :
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 .
The update to OLSRv2 does not introduce any new
protocol signals, nor does it change the processing of any received protocol signals.
This update to OLSRv2 permits an
implementation that is compliant with OLSRv2 to (potentially) eliminate some
unneeded routers from the routing MPR sets generated as described in , 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 does not present any additional security considerations,
beyond those described in .
The authors would like to gratefully acknowledge Philippe Jacquet (Alcatel-Lucent) for intense technical discussions and comments.
Key words for use in RFCs to Indicate Requirement Levels
Harvard University
Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP)
Ecole Polytechnique, France
Naval Research Laboratory, USA
BAE Systems Advanced Technology Centre, UK
The Optimized Link State Routing Protocol version 2
Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations
Naval Research Laboratory
University of Maryland
The Optimized Link State Routing Protocol
Ecole Polytechnique, France
Project Hipercom, INRIA Rocquencourt, France
Rationale for the Use of Link Metrics in the Optimized Link State Routing Protocol Version 2 (OLSRv2)