BGP (Border Gateway Protocol) is a gateway protocol used to facilitate the exchange of routing information among different Autonomous Systems (AS). BGP enables interconnection and communication between distinct AS networks, allowing them to exchange Internet traffic routing information and decide on data packet forwarding.
BGP allows routers at the edge of AS networks to communicate with one another to determine the best paths for routing traffic to reach its target destination. BGP is designed to operate between autonomous systems, making it an inter-domain routing protocol.
BGP Announcements
BGP Announcements (or BGP updates or BGP Advertisements) are messages between BGP routers to advertise access and traffic information for IP address prefixes (network blocks). BGP announcements inform neighboring BGP routers about the paths to reach specific destinations. This routing information enables routers to make decisions on forwarding traffic across the internet.
BGP announcements provide information about the IP address ranges (prefixes) owned or managed by Autonomous Systems (ASNs). When an ASN advertises its IP address prefixes to neighboring ASes through BGP announcements, it effectively announces the reachability of those address ranges to the wider internet.
Each BGP announcement typically includes one or more IP address prefixes and information about the AS path, which indicates the sequence of ASNs the announcement has traversed. By examining the IP address prefixes in BGP announcements, network operators can determine which address ranges are owned or managed by specific ASNs.