<P> A link - state routing algorithm optimized for mobile ad hoc networks is the optimized Link State Routing Protocol (OLSR). OLSR is proactive; it uses Hello and Topology Control (TC) messages to discover and disseminate link state information through the mobile ad hoc network . Using Hello messages, each node discovers 2 - hop neighbor information and elects a set of multipoint relays (MPRs). MPRs distinguish OLSR from other link state routing protocols . </P> <P> Distance vector and link state routing are both intra-domain routing protocols . They are used inside an autonomous system, but not between autonomous systems . Both of these routing protocols become intractable in large networks and cannot be used in Inter-domain routing . Distance vector routing is subject to instability if there are more than a few hops in the domain . Link state routing needs huge amount of resources to calculate routing tables . It also creates heavy traffic due to flooding . </P> <P> Path vector routing is used for inter-domain routing . It is similar to distance vector routing . Path vector routing assumes that one node (there can be many) in each autonomous system acts on behalf of the entire autonomous system . This node is called the speaker node . The speaker node creates a routing table and advertises it to neighboring speaker nodes in neighboring autonomous systems . The idea is the same as distance vector routing except that only speaker nodes in each autonomous system can communicate with each other . The speaker node advertises the path, not the metric, of the nodes in its autonomous system or other autonomous systems . Path vector routing is discussed in RFC 1322; the path vector routing algorithm is somewhat similar to the distance vector algorithm in the sense that each border router advertises the destinations it can reach to its neighboring router . However, instead of advertising networks in terms of a destination and the distance to that destination, networks are advertised as destination addresses and path descriptions to reach those destinations . A route is defined as a pairing between a destination and the attributes of the path to that destination, thus the name, path vector routing, where the routers receive a vector that contains paths to a set of destinations . The path, expressed in terms of the domains (or confederations) traversed so far, is carried in a special path attribute that records the sequence of routing domains through which the reachability information has passed . </P> <P> Path selection involves applying a routing metric to multiple routes to select (or predict) the best route . </P>

Global routing algorithm uses a complete graph of the network with all the nodes and links