Contains Bellcore's proposed generic requirements for ISDN X.25 Supplementary Services. The document contains requirements for the following services: 1980 X.25 DTE support, recognized private operating administration selection barred, local charging prevention, one-way logical channel outgoing and incoming, incoming/outgoing calls barred, direct call, default throughput class assignment, nonstandard default packet sizes, nonstandard default window sizes, flow control parameter negotiation, throughput class negotiation, and transit delay.