Optimized Link State Routing Protocol

OLSR is a proactive link-state routing protocol, which uses hello and topology control (TC) messages to discover and then disseminate link state information throughout the mobile ad hoc network.

Using Hello messages the OLSR protocol at each node discovers 2-hop neighbor information and performs a distributed election of a set of multipoint relays (MPRs).

Such an algorithm is very difficult to design for ad hoc wireless networks, so OLSR doesn't bother with reliability; it simply floods topology data often enough to make sure that the database does not remain unsynchronized for extended periods of time.

Implementations such as the open source OLSRd (commonly used on Linux-based mesh routers) have been extended (as of v. 0.4.8) with link quality sensing.

Being a proactive protocol, OLSR uses power and network resources in order to propagate data about possibly unused routes.

While this is not a problem for wired access points, and laptops, it makes OLSR unsuitable for sensor networks that try to sleep most of the time.

For small scale wired access points with low CPU power, the open source OLSRd project showed that large scale mesh networks can run with OLSRd on thousands of nodes with very little CPU power on 200 MHz embedded devices.

[citation needed] Being a link-state protocol, OLSR requires a reasonably large amount of bandwidth and CPU power to compute optimal paths in the network.

Key differences are the flexibility and modular design using shared components: packet format packetbb, and neighborhood discovery protocol NHDP.