BGP (Border Gateway Protocol) uses TCP (Transmission Control Protocol) as its transport layer protocol for several reasons. TCP provides reliable, connection-oriented communication between BGP peers, ensuring that BGP messages are delivered accurately and in sequence. BGP relies on TCP’s mechanisms such as error detection, retransmission of lost packets, and flow control to maintain a stable and robust communication channel. This reliability is crucial for BGP, as it deals with critical routing information that must be transmitted accurately and efficiently across the internet.
BGP uses TCP instead of UDP (User Datagram Protocol) primarily due to the reliability and connection-oriented nature of TCP. UDP, in contrast, is a connectionless protocol that does not guarantee delivery or order of packets. BGP requires a reliable transport mechanism to ensure that routing information, including updates and advertisements of network reachability, is consistently and correctly propagated between BGP peers. By using TCP, BGP can establish and maintain reliable connections, handle network congestion more effectively through TCP’s congestion control mechanisms, and ensure the integrity of routing updates exchanged between routers.
The TCP port used by BGP for establishing connections between neighbors is port 179. BGP peers initiate TCP connections on this port to exchange routing information, establish BGP sessions, and synchronize routing tables. The use of a specific port (179) allows routers and BGP speakers to identify and communicate with each other over TCP, enabling the exchange of routing updates and maintaining consistent network reachability information across the internet.
BGP operates as an exterior gateway protocol that facilitates the exchange of routing and reachability information between different autonomous systems (ASes) on the internet. When a BGP session is established between two routers or BGP-speaking devices, they exchange routing updates known as BGP updates. These updates contain information about network prefixes (IP address ranges) and associated attributes such as AS paths, metrics, and policies. BGP uses this information to determine the best paths to reach specific destinations across the internet, allowing routers to make informed routing decisions and update their routing tables accordingly. BGP’s scalability and policy-based routing capabilities make it suitable for managing large-scale networks and complex routing policies in the global internet infrastructure.
BGP uses TCP (Transmission Control Protocol) as its transport layer protocol. TCP operates at Layer 4 of the OSI model and provides reliable, connection-oriented communication between BGP peers. TCP ensures that BGP messages, including routing updates and keep-alive messages, are transmitted accurately, in sequence, and with error checking. This reliable communication is essential for BGP to maintain stable routing sessions between routers or BGP-speaking devices across different autonomous systems (ASes) on the internet.