Design and investigation of scalable multicast recursive protocols for wired and wireless ad hoc networks

2.4.2.2 Optimized Link State Routing (OLSR)

OLSR [18] is a proactive unicast ad hoc protocol, based on traditional link state algorithm.
At this kind of protocols each node keeps and updates information about the link with the
other nodes stored in a table. The main contribution of OLSR [18] is that it reduces both the
number of re-broadcasting update messages and the size of these messages by setting a multi
point reply (MPR) node strategy. Each node during the update strategy selects a set of one
hop neighbouring nodes as MPRs. The main responsibility of these MPRs is to re-broadcast
the update messages from the node. Other nodes that are not MPRs can read and process
messages without retransmitting.

To select the MPRs, each node periodically sends a list of its one hop neighbours using a
Hello messages, and from the list included in Hello messages, each node selects a set of one
hop neighbours to cover its two hop neighbours in the network.

2.4.3 Reactive routing protocols

Reactive (On-demand) routing protocols attempt to reduce the overhead in proactive routing
protocols, in which a node starts searching for route information only when this node has a
packet to be sent to a specific destination [3]. These kinds of protocols usually consist of two
types of processes: route discovery and route maintenance. This means that a node has
packet(s) to send for a specific destination, it starts a route discovery by flooding a route
request over the network. After a period of time the source node will receive one or more
route reply with information about the routes available to the destination node. The source
node upon receiving these routes will select the one which is suitable for the data to send
according to number of predefined features. The chosen route will be used to transmit the
packets and this route will be maintained by the source during the transmission to ensure that
the packets will reach the destination. Route maintenance occurs after the establishment of
routes, this process continually update the routes until either the destination node becomes
unreachable from any path from the source or the route becomes undesired [58].

According to [3], On-Demand routing protocols can be classified into two types : source
routing [10] and hop-by-hop routing protocols. In the first type of reactive routing protocol,

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