Providing QoS in OSPF based best effort network using load sensitive routing

In an open shortest path first (OSPF) based best effort network, when a packet experiences congestion, the routing subsystem cannot send it through an alternate path. Thus, it fails to provide desired quality of service (QoS) during congestion. In order to provide QoS we have reported three different load sensitive routing (LSR) protocols in [A. Sahoo, An OSPF based load-sensitive QoS routing algorithm using alternate paths, in: IEEE International Conference on Computer Communication Networks, October 2002; A. Tiwari, A. Sahoo, Providing QoS support in OSPF based best effort network, in: IEEE International Conference on Networks, November 2005; A. Tiwari, A. Sahoo, A local coefficient based load sensitive routing protocol for providing QoS, in: IEEE International Conference on Parallel and Distributed Systems, July 2006]. The LSR protocol forwards packets through alternate paths in case of congestion. The number of alternate paths at any node depends on the value of operating parameter or coefficient used for alternate path calculation. Though the basic protocol in these cases was the same, the methods of choosing operating parameter were different. We referred to these three methods as LSR [A. Sahoo, An OSPF based load-sensitive QoS routing algorithm using alternate paths, in: IEEE International Conference on Computer Communication Networks, October 2002], E-LSR [A. Tiwari, A. Sahoo, Providing QoS support in OSPF based best effort network, in: IEEE International Conference on Networks, November 2005] and L-LSR [A. Tiwari, A. Sahoo, A local coefficient based load sensitive routing protocol for providing QoS, in: IEEE International Conference on Parallel and Distributed Systems, July 2006] coefficient methods. In this paper, we present the LSR protocol along with the three coefficient calculation methods pointing out the reason for going from one method to the next. The main strength of our LSR protocol is that it provides loop free alternate paths in the event of congestion and can interwork with routers running vanilla OSPF protocol. We show through simulation that the LSR protocol based on any of the three different coefficient calculation methods performs much better than OSPF and that out of the three methods proposed by us, L-LSR performs the best.