单项选择题

The Border Gateway Protocol (BGP) is an interautonomous system. ______ protocol. The primary function of a BGP speaking system is to exchange network ______ information with other BGP system. This network reachability information includes information on the list of Autonomous System (ASs) that teachability information traverses. BGP-4 provides a new set of mechanisms for supporting ______ interdomain routing. These mechanisms include support for advertising an IP ______ and eliminate the concept of network class within BGP. BGP-4 also introduces mechanisms that allow aggregation of routes, including ______ of AS paths. These changes provide support for the proposed supernettting scheme.
A. confirmless B. connectionless C. answerless D. classless