Alternatives for interconnection of public packet switching data networks

Abstract

CCITT has proposed Recommendation X.75 as a technique for interconnecting public data networks in a standard way. However, this is not the only or necessarily the best approach. This paper focuses on two major factors in determining the merits of different network interconnection approaches, and compares the X.75 approach to a few alternatives in each of these areas.One of the determining factors for interconnection is the willingness of each network to cooperate. X.75 requires a high degree of cooperation and uniformity of each network's operations.Another determining factor in interconnection is the degree of gateway participation in providing various levels of end-to-end service, such as virtual circuit and terminal handling services. The gateway may fully participate in and “terminate” the protocol for a given service, or may not participate in the protocol at all. The former leads to a stepwise implementation of an end-to-end service while the latter results in an endpoint approach. CCITT has chosen a largely terminating approach for virtual call service, but an endpoint approach for terminal handling. The degree of participation is examined for three alternatives: the X.75 gateway, the subscriber gateway and the datagram gateway.