What is the primary purpose of the BGP protocol?

The Border Gateway Protocol (BGP) is the standardized exterior gateway protocol (EGP) designed to exchange routing and reachability information among different autonomous systems (AS) on the Internet. Its primary purpose is to enable routing between separate administrative domains, making it the core routing protocol of the global Internet. BGP uses a path-vector algorithm and a complex set of attributes to make policy-based routing decisions, determining the best paths for traffic to traverse between autonomous systems.

A. This describes the function of an Interior Gateway Protocol (IGP), such as OSPF or IS-IS, which operates within a single autonomous system.

B. Routing decisions based on hop count are characteristic of distance-vector protocols like RIP, not the path-vector protocol BGP.

D. While BGP has extensions for multicast (MBGP), its primary and fundamental purpose is unicast routing between autonomous systems.

1. IETF RFC 4271

"A Border Gateway Protocol 4 (BGP-4)

" Section 1: Introduction. "The Border Gateway Protocol (BGP) is an inter-Autonomous System routing protocol. The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems."

2. Juniper Networks Documentation

"Junos OS Routing Protocols Library for Routing Devices

" BGP Overview. It states

"BGP is the protocol that runs the Internet... BGP is an exterior gateway protocol (EGP)

which means that it is used to exchange routing information between different organizations."