X.25 and Related Recommendations in IBM Products

This paper describes ISM'S use of Recommendation X.25 and related recommendations of the International Telegraph and Telephone Consultative Committee. After reviewing the development history of X.25 and some of the motivations for using it, the paper gives an overview of packet-switched data networks. The reader is then given a brief technical description of Recommendation X.25 and some other recommendations used in conjunction with X.25. The architectural relationships between X.25 and ISM'S Systems Network Architecture (SNA) are described for packet-switched X.25 connections between SNA nodes and for X.25 connections between SNA and non-SNA nodes. Specific elements of Recommendation X.25 used in SNA nodes are defined. After several ISM products that support X.25 and some of the related recommendations are described, ISM'S equipment for testing the X.25 interface is discussed.