Why is BGP a highly applicable routing protocol for the Internet?

• A. The Internet uses only the hop-by-hop routing paradigm and BGP can support any policy that conforms to that paradigm
• B. It uses distance-vector routing
• C. It floods all networks
• D. It ignores policies

Answer: (A)

The mechanism that makes BGP highly applicable is its policy-based approach to interdomain routing. BGP is designed to exchange reachability between autonomous systems and to carry policy information that operators use to control which paths traffic should take. As a path-vector protocol, it tracks the route’s journey through ASes (AS_PATH) and uses attributes like LOCAL_PREF, MED, and communities to influence path selection. This lets networks encode business relationships (who is a peer, who is a transit provider) and perform traffic engineering, all while scaling to the Internet’s size. This fits the hop-by-hop style of Internet routing, with decisions made at each border between ASes. The other options don’t fit because BGP isn’t distance-vector, it doesn’t flood the network, and it is designed to enforce rather than ignore policies.