In large-scale networks, routing protocols play a vital role to keep the network up and running. Routers use dynamic protocols to first learn about the directly connected routers, then learn about routes that have been advertised from other routers and finally build its own list (Routing Table) to be able to determine the best path to destination networks.
A Routing Protocol is a set of procedures based on algorithm that the router uses to exchange routing information with other routers. It provides dynamic reaction mechanism for network topology changes as well as notifying other routers of a change. In addition, dynamic routing protocols will find an alternate path around topology changes to keep the network in operation.
The most common classes of dynamic routing protocols are Distance Vector routing protocols and Link State routing protocols. In Distance Vector protocols, routes are advertised as vectors of distance and direction (Graziani & Johnson, 2009) . Distance normally measured by hop count, on the other hand, Direction means the next hop. Some of the well-known Distance Vector protocols are Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP) and Enhanced Interior Gateway Routing Protocol (EIGRP). Routers using Distance Vector protocols periodically send their routing table to neighbouring nodes and then use Bellman-Ford algorithm to process the updates for bath determination. By using this algorithm, routers are not aware of the entire topology of the network; instead, they will only know about the adjacent routers.
In contrast, Link State routing protocol build up a complete view of the network by accumulating information from all the network routers. All routers know the entire map for the network; therefore, they will be able to determine the best path to all destination networks. Routers using Link State protocol do not send periodic updates as is the case with Distance Vector, alternatively, updates are sent whenever there is a change in the topology after the network has been converged. The most common link state protocols are Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS).
These routing protocols have evolved over the years to meet the demands of changing network requirements. Hence, after the IPv6 innovation, many of these routing protocols developed an enhanced version that support IPv6 routing such as Routing Information protocol Next Generation (RIPng), OSPFv3 and IS-IS (for IPv6).
In the next post, I am going to talk about every and each o the mentioned protocols.
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