How is BGP classified in the context of routing protocols?

BGP, or Border Gateway Protocol, is classified as a path-vector routing protocol, which is the correct classification based on its operational characteristics and functionality. Unlike link-state or distance-vector protocols, BGP maintains a table of network paths, which include not only the next hop but also the path information that allows for loop prevention and policy-based routing decisions.

Path-vector protocols like BGP utilize AS (Autonomous System) paths as their key mechanism for maintaining the routing information. Each BGP router maintains a list of ASes that a route has traversed, thus providing it with the ability to enforce routing policies and make intelligent routing decisions based on various attributes tied to path selection. This design is critical for the functioning of the internet itself, as it maintains stability and scalability across numerous interconnected networks.

While link-state and distance-vector protocols have their own mechanisms—such as creating a complete view of the network topology in the case of link-state or using distance metrics in the case of distance-vector—BGP's unique approach with path vectors sets it apart, making it effectively suited for inter-domain (between different networks) routing. The hybrid routing protocol classification is typically reserved for protocols that combine features of both link-state and distance-vector, and thus does not