of only 16 hops between two consecutive nodes and it is slow to converge, meaning that it takes a longer time for route changes to be propagated to all nodes. Nowadays there are more sophisticated protocols that are more efficient. Open Shortest Path First (OSPF) The OSPF Protocol was developed to fulfil the need for a high functionality nonproprietory protocol that was superior to the RIP and good for big networks. It is also an Interior Routing Protocol. It also takes the link state into account before taking a routing decision. It is capable of fast re-routing (convergence) and supports variable length subnet masks. In OSPF, an autonomous system is divided into routing areas. A routing area consists of closely related subnets. Link state updates are distributed only inside a routing area and not in the complete network. All routing areas must connect to the backbone area. OSPF follows hierarchical routing in an autonomous system. With OSPF, there is no limitation of hop count, unlike the RIP. OSPF uses IP multicast to send link state updates. Updates are sent only when routing changes occur and not periodically. This results in more efficient bandwidth utilisation. OSPF allows for transfer and tagging of external routes injected into the autonomous system. This keeps track of external routes injected by exterior protocols like BGP. Interior Gateway Routing Protocol (IGRP) The IGRP determines the best path by considering the factors of bandwidth and delay in the networks. The IGRP is fast in distributing routing changes to the nodes, thereby avoiding routing loops caused by disagreement over the next hop to be taken. It does not have hop count limitation. The enhanced IGRP is a new version of the IGRP which combines lease of use of traditional distance vector routing protocols with fast re-routing capabilities of new link state routing protocols. The enhanced IGRP requires less bandwidth as it exchanges only information related to changes in the network. Border Gateway Protocol (BGP) This is an Exterior Gateway