IS-IS and OSPF are link state routing protocols. Both protocols suggest different procedures for this purpose. Since the procedures are quite different, but targeted to achieve the same goal; it is worthwhile comparing the two according to performance criteria common to both. The following criteria are chosen. • The longest arrival time of an LSU packet at all the routers. Following this measure it can also find if all the LSA packets arrive successfully at all the routers before new instances of the packets are generated. • The average arrival time of LSA packets at all the routers. • The total required bandwidth in each scheme. • The number of memory accesses a router performs in each scheme, which is evidence of the amount of internal work it performs. Clearly, a scheme in which more LSA packets arrive at all the routers more quickly, with a smaller amount of internal work and with the use of a smaller amount of bandwidth and within the routers, is more efficient. In terms of arrival times of routing update packets it find that in our model of broadcast networks the method suggested in OSPF is giving less performance than that of IS-IS. In particular, the OSPF performance in consideration with average arrival time of routing update packets is 2–10 times longer than in IS-IS There are scenarios where OSPF outperforms IS-IS and vice versa, in terms of the bandwidth each scheme consumes as well as the number of routers memory accesses perform in each scheme, IS-IS outperforms OSPF.

Routing Protocol