2.3.4 X.25

2.3.4 X.25
X.25 is a packet-switching standard widely used in WANs. The X.25 standard was developed by the International Telegraph and Telephone Consultative Committee (CCITT), which has been renamed the International Telecommunications Union (ITU). The standard, referred to as Recommendation X.25, was first introduced in 1974, and it provides to networks the options of permanent or switched virtual circuits. X.25 is required to provide reliable service and end-to-end flow control. Because each device on a network can operate more than one virtual circuit, X.25 must provide error and flow control for each virtual circuit.
A big advantage of X.25 is that it is used internationally, while the major drawback is that error checking and flow control slow down X.25. Traditionally, networks utilizing it are implemented with line speeds of up to 64Kbps. These speeds are inadequate to provide most LAN services, which typically require speeds of 10Mbps or better. X.25 networks, therefore, are poor choices for providing LAN application services in a WAN environment.