X.25

X.25 is a CCITT standard developed by ITU- TSS for WAN (wide area networks). It defines the interface between an end user computer and packet switching network. This is an international standard used for many worldwide corporations. It also has two parts. Packet layer protocol (PLP) is the routing protocol that manages the network layer and X.3 controls the transport layer.

ITU-TSS

This is an abbreviation of International Telecommunications Union-Telecommunications Standardization Sector.

CCITT

It refers Consulative Committee for International Telephony and Telegraphy. CCITT is an international organization for communications standard.