Border Gateway Protocol (BGP) is designed as an exterior gateway protocol used to exchange routing information between different autonomous systems (ASes) on the Internet. BGP operates based on a path vector routing algorithm, where routers exchange network reachability information along with a list of AS numbers that the route traverses. This design allows BGP to make routing decisions based on policies defined by network administrators, such as preferring certain paths over others based on attributes like path length, AS path, and route origin. BGP is critical for maintaining the global routing table and ensuring efficient and reliable routing across the Internet.
BGP (Border Gateway Protocol) operates using the TCP (Transmission Control Protocol) as its underlying transport protocol. TCP provides reliable, connection-oriented communication between BGP routers, ensuring that BGP messages are delivered accurately and in sequence. BGP routers establish TCP connections with neighboring routers, exchanging routing information and keeping these connections open for continuous updates and monitoring. TCP’s reliability and error-checking mechanisms contribute to BGP’s robustness in maintaining accurate and up-to-date routing information across diverse and often complex networks.
BGP supports two main types of protocols: eBGP (External BGP) and iBGP (Internal BGP). eBGP is used between BGP routers in different autonomous systems (ASes) to exchange routing information across organizational boundaries. It facilitates the propagation of routes between different parts of the Internet. iBGP, on the other hand, is used within the same AS to distribute routing information among internal routers. iBGP ensures consistent routing policies and allows ASes to control how traffic flows within their network, including traffic destined for external networks. Together, eBGP and iBGP enable BGP to manage and optimize routing on both inter-AS and intra-AS levels.
TCP (Transmission Control Protocol) is the transport protocol used by BGP (Border Gateway Protocol) for reliable communication between BGP routers. BGP routers establish TCP connections with neighboring routers to exchange routing information, such as network reachability and routing policies. TCP ensures that BGP messages are delivered without errors, in the correct order, and with acknowledgment of receipt. This reliability is crucial for BGP routers to maintain accurate and consistent routing information across diverse networks, ensuring efficient packet forwarding and optimal path selection based on network policies and conditions.