Dissemination of routing information in broadcast networks: OSPF versus IS-IS

OSPF and IS-IS are two main standard link state routing protocols designed to operate in various complex network topologies. One aspect that both prot ocols handle is the reliable dissemination of routing information over broa dcast networks such as Ethernet and FDDI. Both protocols suggest different schemes for this purpose, and in this article we compare the two. The perfo rmance criteria being checked are: the longest arrival time of routing upda te packets at all the routers; the total required bandwidth; and the number of memory accesses a router performs, which is evidence of the amount of i nternal work ii performs. We find that in our model of broadcast networks t he scheme suggested in IS-IS is more efficient than that of OSPF in terms o f the arrival times of routing update packets. In particular, the average a rrival time of routing update packets in OSPF is 2-10 time; longer than in IS-IS. In terms of the bandwidth each scheme consumes, there are scenarios where OSPF outperforms IS-IS and vice verse. In terms of the number of memo ry accesses routers perform in each scheme, IS-IS out-performs OSPF.