Datapac X.25 service characteristics

Datapac is a nation-wide public packet switching data communications network operated by the Trans-Canada Telephone System. Datapac, as other networks being developed around the world, allows terminals to access its services by using a standard interface: CCITT Recommendation X.25. Recommendation X.25 defines a set of conventions governing the manner in which packet terminals format control information and data into packets, establish, maintain and clear calls, and manage the transmission and flow of data to and from a packet network. Recommendation X.25 defines a user/network interface; it does not define the end-to-end service provided by the network though clearly there is a close functional correspondence between signalling provided across the interface and across the network. Recommendation X.25 adequately describes the characteristics of the network service allowing manufacturers to provide a single implementation of X.25 which can work on any of the networks supporting X.25. This adequate definition of the end-to-end service allows users to achieve first order benefits of packet networks. For an optimized implementation in a user's equipment, it is necessary to define the service characteristics of national and international services. This paper defines the functional, economic and performance-related characteristics of virtual circuits, specifically those on Datapac.