Optimized Link State Routing (Olsr) Protocol and Comparison of Various Table-Driven Routing Protocols |
Routing table updates areperiodically transmitted throughout the network in order to maintain tableconsistency. To help alleviate the potentially large amount of network trafficthat such updates can generate, route updates can employ two possible types ofpackets: full dump and smaller incremental packets. Each of these broadcastsshould fit into a standard-size of network protocol data unit (NPDU), therebydecreasing the amount of traffic generated. The mobile nodes maintain anadditional table where they store the data sent in the incremental routinginformation packets. New route broadcasts contain the address of thedestination, the number of hops to reach the destination, the sequence numberof the information received regarding the destination, as well as a newsequence number unique to the broadcast. The route labeled with the most recentsequence number is always used. In the event that two updates have the samesequence number, the route with the smaller metric is used in order to optimize(shorten) the path. Mobiles also keep track of the settling time of routes, orthe weighted average time that routes to a destination will fluctuate beforethe route with the best metric is received. By delaying the broadcast of arouting update by the length of the settling time, mobiles can reduce networktraffic and optimize routes by eliminating those broadcasts that would occur ifa better route was discovered in the very near future.