Evolving Standards for Packetized Communications in the ISDN

During the July, 1986 meeting of CCITT Study Group XVIII in Geneva, Switzerland, a four step approach to the evolution of standards for packetized data transfer services was defined. This four step approach starts with the simple overlay of X. 25 onto the ISDN (X.31), the addition of LAPD to the B-channel for multiplexing purposes (step 2), the use of the LAPD multiplexing information for routing (frame-relay or frame-switching - step 3), and the use of very high speed communication interfaces (broadband ISDN) for ISDN data (step 4).