单选题 The Border Gateway Protocol (BGP) is an interautonomous system {{U}}(28) {{/U}} protocol. The primary function of a BGP speaking system is to exchange network {{U}}(29) {{/U}} information with other BGP system. This network reachability information includes information on the list of Autonomous System (ASs) that reachability information traverses. BGP-4 provides a new set of mechanisms for supporting {{U}}(30) {{/U}} interdomain routing. These mechanisms include support for advertising an IP {{U}}(31) {{/U}} and eliminate the concept of network class within BGR BGP-4 also introduces mechanisms that allow aggregation of routes, including. {{U}}(32) {{/U}} of AS paths. These changes provide support for the proposed supernettting scheme.