OLSR is a proactive routing protocol that obtain the strength of link state algorithm. By proactive, it means that the entire topology of the network is maintained by every node. Some of the OLSR functionalities include: 1. It declares only links with its multipoint relay selectors. 2. Every node select from its neighbor, who can read or who can broadcast messages, those nodes are termed as multipoint relays (MPRs). 3. The link state information is partially distributed in the network, where the link is obtained only between an MPR and its MPR selectors. Only MPR can retransmit in this protocol. For instance, consider a node A having nodes B, C, and D as its neighbors. So, if A considers C as MPR, then whatever packet A sends is received by all the other three nodes. However, only C can rebroadcast that packet. Hence, this protocol significantly reduces the number of retransmissions in a broadcast procedure and can play a significant role for dense ad hoc networks.
OLSR is not a central entity based but works on a completely distributed manner. Since the nodes send periodic control messages, it is not compulsory to have a reliable transmission of messages.