OLSR – Optimized Link-State Routing

THE Routing Standard for Dynamic, Wireless, Ad hoc, MESH networks

imageThe Optimized Link-State Routing Protocol (OLSR, and its successor OLSRv2) is the IETF standardized routing protocol for Mobile Ad hoc NETworks (MANET).

A link state protocol, OLSR (RFC3626) prototyped several innovative techniques and principles, including the concept of Multi-Point Relays (MPRs) for Flooding Reduction and Topology Reduction, an advanced neighborhood discovery mechanism for detecting and tracking link-bi-directionality in wireless environments and across multiple wireless interfaces. Some of these techniques were later revised, adapted for OSPF and included in the OSPF extension for MANETs (see OSPF for MANETs).

OLSRv2 (RFC7181) and its constituent parts (RFC5148, RFC5444, RFC5497, RFC6130 RFC7181, RFC7182, RFC7183, RFC7184, RFC7185, RFC7186, RFC7187, RFC7188) were built on the 10+ years of experience with OLSR, and offer:

  • High scalability in dense networks by way of Flooding Reduction and Topology Reduction
  • A modular plug-in security architecture
  • Flexible, multi-metric routing
  • Compressed (aggregated) addresses for significantly smaller control messages
  • Built-in extensibility mechanisms, preserving forward and backwards compatibility
  • Native and efficient IPv6 support
  • Flexible and extensive gateway support, for attached networks as well as for global Internet connectivity.

As such, OLSRv2 is more than just a routing protocolOLSRv2 is the platform for Dynamic, Wireless, Ad hoc, MESH network innovation and experimentation.


A Protocol of World-Firsts

OLSR and OLSRv2 have given rise to, numerous “world-firsts”, including:


MPRs: Flooding Reduction & Topology Reduction

MPR Flooding Reduction

MPR Flooding Reduction

OLSR being a link state protocol, the basic concept is that Link State Advertisements (LSAs – in OLSR & OLSRv2 called TC Messages) are flooded through the network, allowing each router to compute a topology map – on which a shortest path algorithm (such as Dijkstra’s algorithm) is run so as to calculate shortest paths to each destination in the network

The “Optimized” in “Optimized Link State Routing” stems, in no small part, from the protocol’s use of MultiPoint Relays, MPRs.

By way of the Neighborhood Discovery Protocol (NHDP – RFC6130), each router will, by way of a periodic and per-interface HELLO message exchange, have learned its local topology: bidirectional links to its immediate neighbors (1-hop neighbors), as well as bi-directional links from its 1-hop neighbors and to their neighbors (2-hop neighbors). For a given router, the 1-hop and 2-hop neighbors form the routers “neighborhood”.

Each router can then, autonomously and without any coordination, select a subset from among its 1-hop neighbors, which forms a dominating set over its neighborhood – that dominating set is the MPR set of that router.

Or, more colloquially, each router selects its MPR set from among its 1-hop neighbors such that a packet transmitted by it, and repeated by only the members of its MPR set, will be received by all 2-hop neighbors. This is signaled in next HELLO message exchange, allowing each router to know for which other routers it is, or is not, an MPR – to construct its “MPR Selector Set” (the set of routers, which have selected it as MPR).

This information is, then, used in two ways:

  • MPR Based Flooding Reduction:
    • When receiving a TC message, forward it if and only if it was received from a MPR Selector
    • (And, of course, don’t forward a TC message more than once)
  • MPR Based Topology Reduction:
    • Only routers which have a non-empty MPR Selector Set generate TC messages.
    • And, when generating a TC message, a router only includes links to destinations listed in the MPR Selector Set

The advantages of this use of MultiPoint Relays, MPRs, is thus fourfold:

  1. The cost of a flooding operation is considerably reduced: The number of retransmissions of a single flooded message, especially in a dense network, is considerably lower when using MPR based Flooding Reduction, than when using classic flooding. On the figure above, the top example depicts “classic flooding”, with the bottom example MPR flooding, and the blue nodes” the relays (and thus, retransmissions) involved in a flooding operation.
  2. The packet loss of a flooding operation is considerably reduced: On the figure above, the top example depicts classic flooding, with the bottom example depicting MPR flooding, and the “red nodes” depicting those nodes which receive more than a single copy of a transmission. In a wireless environment, given that all 1-hop neighbors receive the same transmission at the same time, they potentially do the same carrier sense operation and detect at the same time that the channel is idle – and transmit at the same time. Concurrent transmissions entail collisions, which entails packet loss. Thus, MPR flooding limiting the number of relays also limits the number of colissions.
  3. The number of flooding operations is considerably reduced: Only routers with non-empty MPR Selector Sets generate TC messages. As illustrated in the figure above, all the “blue routers” would generate and flood “I have a link to the router in the center” – with the top example being that of a classic link state routing protocol, and the bottom example that of OLSR and OLSRv2.
  4. The size of each flooded message is considerably reduced: Only the subset of destinations listed in a routers MPR Selector Set (i.e., only the destinations on routers that have selected it as MPR) are included in the flooded TC messages, rather than all destinations on all neighboring routers.

The resulting topology graph in each router is a partial graph, including all destinations (of course) and a subset of all links – a subset which contains the links on all shortest paths.


A World-Wide Community

In addition to being “a routing protocol for MANET, OLSR and OLSRv2 is a world-wide community, actively contributing to the protocol specification development, to proposing, developing, and specifying protocol extensions, to implementing the protocol specifications on various platforms — and, of course, to deployments of OLSR & OLSRv2. The map below depicts known deployments of OLSR & OLSRv2.

Known OLSR and OLSRv2 Deployments, world-wide.

Known OLSR and OLSRv2 Deployments, world-wide.

Among the experiments, uses, and deployments of OLSR and OLSRv2 are as diverse scenarios as tactical networking, emergency networking, and community networks.

BAE Systems Tactical Networking Experiments

BAE Systems Tactical Networking Experiments

FunkFeuer.at Community Network Deployment

FunkFeuer.at Community Network Deployment

Several open-source (and, of course, many many proprietary), independent, implementations of OLSR and OLSRv2 exist, a (very partial) list of public implementations includes:


International Interoperability Events

During the development of the core OLSR and OLSRv2 specifications, semi-regular interoperability tests & workshops have occurred, the most structured of which have been:

The technical output of these events have been retained in the OLSR and OLSRv2 (& constituent parts) specifications.


A Flexible, Modular Platform for Experimentation

The OLSRv2 protocol architecture is built around a flexible, modular, platform, intended to facilitate easy development, implementation, and testing of (forward and backwards compatible) routing protocol extensions. This is obtained, in part, by way of OLSRv2 defining and exposing a comprehensive protocol information base, as well as comprehensive constraints enabling and scoping protocol extensions‘ use (consultation, updating) thereof. An other important component of the flexible, modular platform is the use of “The Generalized Mobile Ad hoc NETwork (MANET) Packet/Message Format” RFC5444.

This has given rise to, numerous extensions, experiments, and even world-firsts around OLSRv2:

Other extensions and experiments, enabled by OLSRv2, include:


Related Publications

Clausen, Thomas; Herberg, Ulrich; Yi, Jiazi

RFC8116: Security Threats to the Optimized Link State Routing Protocol Version 2 (OLSRv2) Miscellaneous

RFC 8116, 2017.

Abstract | Links | BibTeX

Yi, Jiazi; Parrein, Benoit

Multipath Extension for the Optimized Link State Routing Protocol Version 2 (OLSRv2) Miscellaneous

RFC 8218, 2017.

Abstract | Links | BibTeX

Herberg, Ulrich; Cole, Robert; Chakeres, Ian; Clausen, Thomas

Definition of Managed Objects for the Neighborhood Discovery Protocol Miscellaneous

IETF - Proposed Standard RFC 7939, 2016, ISSN: 2070-1721.

Abstract | Links | BibTeX

Dearlove, Christopher; Clausen, Thomas

RFC7722: Multi-Topology Extension for the Optimized Link State Routing Protocol Version 2 (OLSRv2) Miscellaneous

IETF - Experimental RFC 7722, 2015, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7722).

Abstract | Links | BibTeX

Clausen, Thomas; Dearlove, Christopher

RFC7631 – TLV Naming in the Mobile Ad Hoc Network (MANET) Generalized Packet/Message Format Miscellaneous

IETF - Proposed Standard RFC 7631, 2015, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7631).

Abstract | Links | BibTeX

Dearlove, Christopher; Clausen, Thomas

RFC7466: An Optimization for the Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP) Miscellaneous

IETF - Proposed Standard RFC 7466, 2015, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7466).

Abstract | Links | BibTeX

Clausen, Thomas; Dearlove, Christopher; Jacquet, Philippe; Herberg, Ulrich

RFC7181: The Optimized Link State Routing Protocol Version 2 Miscellaneous

IETF - Proposed Standard RFC 7681, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7181).

Abstract | Links | BibTeX

Herberg, Ulrich; Clausen, Thomas; Dearlove, Christopher

RFC7182: Integrity Check Value and Timestamp TLV Definitions for Mobile Ad Hoc Networks (MANETs) Miscellaneous

IETF - Proposed Standard RFC 7182, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7182).

Abstract | Links | BibTeX

Herberg, Ulrich; Dearlove, Christopher; Clausen, Thomas

RFC7183: Integrity Protection for the Neighborhood Discovery Protocol (NHDP) and Optimized Link State Routing Protocol Version 2 (OLSRv2) Miscellaneous

IETF - Proposed Standard RFC 7183, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7183).

Abstract | Links | BibTeX

Herberg, Ulrich; Cole, Robert G; Clausen, Thomas

RFC7184: Definition of Managed Objects for the Optimized Link State Routing Protocol Version 2 Miscellaneous

IETF - Proposed Standard RFC 7184, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7184).

Abstract | Links | BibTeX

Dearlove, Christopher; Clausen, Thomas; Jacquet, Philippe

RFC7185: Rationale for the Use of Link Metrics in the Optimized Link State Routing Protocol Version 2 (OLSRv2) Miscellaneous

IETF - Informational RFC 7185, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7185).

Abstract | Links | BibTeX

Dearlove, Christopher; Clausen, Thomas

RFC7187: Routing Multipoint Relay Optimization for the Optimized Link State Routing Protocol Version 2 (OLSRv2) Miscellaneous

IETF - Proposed Standard RFC 7187, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7187).

Abstract | Links | BibTeX

Dearlove, Christopher; Clausen, Thomas

RFC7188: Optimized Link State Routing Protocol Version 2 (OLSRv2) and MANET Neighborhood Discovery Protocol (NHDP) Extension TLVs Miscellaneous

IETF - Proposed Standard RFC 7188, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7188).

Abstract | Links | BibTeX

Yi, Jiazi; Herberg, Ulrich; Clausen, Thomas

RFC7186: Security Threats for the Neighborhood Discovery Protocol (NHDP) Miscellaneous

IETF - Informational RFC 7186, 2014, ISSN: 2070-1721, (http://tools.ietf.org/html/rfc7186).

Abstract | Links | BibTeX

Cordero, Juan Antonio; Yi, Jiazi; Clausen, Thomas; Baccelli, Emmanuel

Enabling Multihop Communication in Spontaneous Wireless Networks Book Chapter

Haddadi, Hamed; Bonaventure, Olivier (Ed.): Recent Advances in Networking, Chapter 9, pp. 413-457, ACM SIGCOMM, 2013.

Links | BibTeX

Clausen, Thomas; Herberg, Ulrich

RFC6622: Integrity Check Value and Timestamp TLV Definitions for Mobile Ad Hoc Networks (MANETs) Miscellaneous

2012, (http://tools.ietf.org/html/rfc6622).

Abstract | Links | BibTeX

Cordero, Juan Antonio; Jacquet, Philippe; Baccelli, Emmanuel

Impact of Jitter-based Techniques on Flooding over Wireless Ad hoc Networks: Model and Analysis Inproceedings

pp. 2059-2067, IEEE Proceedings of the 31st Annual IEEE International Conference on Computer Communications (INFOCOM 2012)., Orlando, FI, United States., 2012, ISSN: 0743-166X.

Abstract | Links | BibTeX

Herberg, Ulrich; Clausen, Thomas

Delay Tolerant Routing with OLSRv2 Inproceedings

Proceedings of the The 9th IEEE/IFIP International Conference on Embedded and Ubiquitous Computing (EUC), 2011.

Abstract | Links | BibTeX

Clausen, Thomas; Dearlove, Christopher; Dean, Justin

RFC6130: Mobile Ad Hoc Network (MANET) Neighborhood Discovery Protocol (NHDP) Miscellaneous

2011, (http://tools.ietf.org/html/rfc6130).

Abstract | Links | BibTeX

Herberg, Ulrich; Clausen, Thomas; Cole, Robert G

MANET Network Management and Performance Monitoring for NHDP and OLSRv2 Inproceedings

Proceedings of the 6th International Conference on Network and Services Management, 2010.

Abstract | Links | BibTeX

Clausen, Thomas; Herberg, Ulrich

Router and Link Admittance Control in the Optimized Link State Routing Protocol version 2 (OLSRv2) Inproceedings

Proceedings of the 4th International Conference on Network and System Security (NSS 2010), 2010, ISBN: 978-1-4244-8484-3.

Abstract | Links | BibTeX

Herberg, Ulrich; Clausen, Thomas; Milan, Jerome

Digital Signatures for Admittance Control in the Optimized Link State Routing Protocol version 2 Inproceedings

Proceedings of the International Conference on Internet Technology and Applications (iTAP 2010), 2010, ISBN: 978-1-4244-5142-5.

Abstract | Links | BibTeX

Clausen, Thomas; Herberg, Ulrich

Vulnerability Analysis of the Optimized Link State Routing Protocol version 2 (OLSRv2) Inproceedings

Proceedings of the IEEE International Conference on Wireless Communications, Networking and Information Security (WCNIS2010), 2010, ISBN: 978-1-4244-5850-9.

Abstract | Links | BibTeX

Herberg, Ulrich; Clausen, Thomas

Security Issues in the Optimized Link State Routing Protocol Version 2 (OLSRV2) Journal Article

International Journal of Network Security & Its Applications (IJNSA), 2010.

Abstract | Links | BibTeX

Clausen, Thomas; Dearlove, Christopher

RFC5497: Representing Multi-Value Time in MANETs Miscellaneous

2009, (http://www.rfc-editor.org/rfc/rfc5497.txt).

Abstract | Links | BibTeX

Clausen, Thomas; Dearlove, Christopher; Dean, Justin; Adjih, Cedric

RFC5444 - Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format Miscellaneous

2009, (http://www.ietf.org/rfc/rfc5444.txt).

Abstract | Links | BibTeX

Clausen, Thomas; Dearlove, Christopher; Adamson, Brian

RFC5148: Jitter Considerations in Mobile Ad Hoc Networks (MANETs) Miscellaneous

2008, (http://tools.ietf.org/html/rfc5148).

Abstract | Links | BibTeX

Baccelli, Emmanuel; Clausen, Thomas; Garnier, Julien

Duplicate Address Detection in OLSR Networks Inproceedings

IEEE Conference on Wireless Personal Multimedia Communications (WPMC), Aalborg, Denmark, Sept. 2005, 2005.

Abstract | Links | BibTeX

Baccelli, Emmanuel; Clausen, Thomas

A Simple Address Autoconfiguration Mechanism for OLSR Inproceedings

IEEE International Symposium on Circuits and Systems (ISCAS), Kobe, Japan, May 2005, 2005.

Abstract | Links | BibTeX

Baccelli, Emmanuel; Clausen, Thomas; Wakikawa, Ryuji

Route Optimization in Nested Mobile Networks (NEMO) using OLSR Inproceedings

International Conference on Networks and Communication Systems (NCS), Krabi, Thailand, April 2005, 2005.

Abstract | Links | BibTeX

Clausen, Thomas; Baccelli, Emmanuel; Rodolakis, Georgios; Adjih, Cedric; Jacquet, Philippe

Fish-Eye OLSR Scaling Properties Journal Article

IEEE Journal on Communications Networks (JCN), Special Issue on Ad Hoc Networking, Dec 2004, 2004.

Abstract | Links | BibTeX

Clausen, Thomas; Jacquet, Philippe; Viennot, Laurent

Analyzing Control Traffic Overhead versus Mobility and Data Traffic Activity in Mobile Ad Hoc Network Protocols Journal Article

ACM Journal on Wireless Networks (Winet) July 2004, volume 10 no. 4, 2004.

Abstract | Links | BibTeX

Raffo, Daniele; Adjih, Cédric; Clausen, Thomas; Mühlethaler, Paul

An advanced signature system for OLSR Inproceedings

workshop on security of ad hoc and sensor networks, pp. 10–16, 2004.

Abstract | Links | BibTeX

Clausen, Thomas

Combining Temporal and Spartial Partial Topolgy for MANET Routing - Merging OLSR and FSR Inproceedings

Proceedings of the IEEE conference on Wireless Personal Multimedia Communications (WPMC), 2003.

Abstract | Links | BibTeX

Clausen, Thomas; Jacquet, Philippe

RFC3626: The Optimized Link State Routing Protocol Miscellaneous

2003, (http://tools.ietf.org/html/rfc3626).

Abstract | Links | BibTeX

Adjih, Cedric; Clausen, Thomas; Laouiti, Anis; Mühlethaler, Paul; Raffo, Daniele

Securing the OLSR protocol Inproceedings

In 2nd IFIP Annual Mediterranean Ad Hoc Networking Workshop (Med-Hoc-Net 2003), Mahdia, pp. 25–27, 2003.

Abstract | Links | BibTeX

Clausen, Thomas; Qayyum, Amir; Jacquet, Philippe; Toor, Y; Muhlethaler, Paul

Sleep mode operation of a routing protocol in mobile ad hoc networks Inproceedings

The proceedings of the joint International Conference on Wireless LANs and Home Networks (ICWLHN 2002) and Networking (ICN 2002), 2002, ISBN: 9812381279.

Links | BibTeX

Clausen, Thomas; Jacquet, Philippe; Viennot, Laurent

Investigating the impact of partial topology in proactive MANET routing protocols Inproceedings

Wireless Personal Multimedia Communications, 2002. The 5th International Symposium on, pp. 1374-1378 vol.3, 2002, ISSN: 1347-6890.

Abstract | Links | BibTeX

Clausen, Thomas; Jacquet, Philippe; Viennot, Laurent

Comparative Study of Routing Protocols for Mobile Ad-hoc NETworks Inproceedings

Proceedings of the IFIP MedHocNet, September 2002, Sardinia, Italy, 2002.

Abstract | Links | BibTeX

Viennot, Laurent; Jacquet, Philippe; Clausen, Thomas

Analyzing Control Traffic Overhead in Mobile Ad-hoc Network Protocols versus Mobility and Data Traffic Activity Inproceedings

In Proceedings of the 1st IFIP Annual Mediterranean Ad Hoc Networking Workshop (MedHocNet’02, 2002.

Abstract | Links | BibTeX

Jacquet, Philippe; Muhlethaler, Paul; Clausen, Thomas; Laouiti, Anis; Qayyum, Amir; Viennot, Laurent

Optimized link state routing protocol for ad hoc networks Inproceedings

Multi Topic Conference, 2001. IEEE INMIC 2001. Technology for the 21st Century. Proceedings. IEEE International, pp. 62-68, 2001.

Abstract | Links | BibTeX

Clausen, Thomas; Hansen, Gitte; Christensen, Lars; Behrmann, Gerd

The Optimized Link State Routing Protocol Evaluation through Experiments and Simulation Inproceedings

IN PROCEEDING OF WIRELESS PERSONAL MULTIMEDIA COMMUNICATIONS, IEEE, 2001.

Abstract | Links | BibTeX

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