Routing Protocols

Routing protocols perform a vital job in every communication network. In an IP network, the major function of routing protocols is to forward packets received from one network node to another. Routing in a communication network refers to the transmission of data from source to destination by hopping either one hop or multiple hops. Routing protocols work by providing at least two services; selecting best paths between source and destination nodes, and successfully transmitting data to a specified destination. Routing protocol is a combination of processes, algorithms, and messages that enable routers to exchange routing information. Based on routing algorithms, routing protocols are able to discover available routes, construct routing tables, take routing decisions, and exchange information with each other. The routing algorithms use different metrics based on some properties of a path which helps to determine the best route to reach a destination network.

When it comes to larger communication networks, dynamic routing is preferred over static routing. Both static and dynamic routing are just two ways by which routers can learn about remote networks. In static routing, each network location must be entered into the routing table by the network administrator. In dynamic routing, similar routing protocols are configured on routers to enable them discover remote networks. Both routing methods have their advantages and disadvantages. In a smaller network, updating routing tables will be easy for the network administrator. However, on a larger network, doing so will be very difficult and time consuming. Hence dynamic routing protocols must be used. Using dynamic routing protocols on larger networks saves time but it also consumes network resources. Dynamic routing protocols are also more scalable; something that enables them to automatically adapt to any change in network topology. For example when a new network is added to the existing network, dynamic routing protocols are able to discover the new network automatically. Also when there is a node or a route failure, they are able to determine alternative routes and retransmit traffic via these routes with minimal disruption. Scalability is not the same for all routing protocols. Some protocols are more scalable than others. Routing protocol scalability is essential when considering current network growth rate. Therefore when deciding on which routing protocol to implement on a network, the protocol that scales well must be considered.

Routing protocols are grouped into two types. These are interior gateway protocols (IGPs) and exterior gateway protocols (EGPs). Interior gateway protocols are used to enable routers exchange routing information among themselves in the same autonomous systems (AS). An AS consists of a group of networks that are solely managed by a single organization.