BGP Routing Protocol

Abstract

Border Gateway Protocol is the protocol which makes the Internet work. It is used at the Service provider level which is between different Autonomous Systems (AS). An Autonomous System is a single organization which controls the administrative part of a network. Routing with in an Autonomous System is called as Intra-Autonomous routing and routing between different Autonomous Systems is called as Inter-Autonomous System routing. The routing protocols used within an Autonomous System are called Interior Gateway Protocols (IGP) and the protocols used between the Autonomous Systems are called Exterior Gateway Protocols. Routing Information Protocol (RIP), Open Short Path First (OSPF) and Enhanced Interior Gateway Routing Protocol (EIGRP) are the examples for IGP protocols and Border Gateway Protocol (BGP) is the example for EGP protocols.

Every routing protocol use some metric to calculate the best path to transfer the routing information. BGP rather than using a particular metric, it uses BGP attributes to select the best path. Once it selects the best path, then it starts sending the updates in the network. Every router implementing BGP in the network, configures this best path in its Routing Information Base. Only one best route is selected and forwarded to the whole network. [17] Due to the tremendous increase in the size of the internet and its users, the convergence time during link failure in the protocol is very high.