1Cnf S4/op1Req AM2 behaviour S4/op1Req S4/op1Cnf in AP1 OS/servRelReq((S2)) OS/servReIReq({Srix) x-op1Req x-op1Cnf OS/relServRelOrd(x) x-op1Ref OS/relServRelOrd(y) OS/relServRelOrd(x) y-op1Ref OS/servReIReq((S3)) OS/servReIReq((Srivy) S4/op1Ref OS/relServRelOrd(y) y-op1Req S4/op1Req S4/op1Req S4/op1Cnf y-op1Cnf Fig. 7.67 Abstract protocols are based on service and object behaviours Thus, when abstract networks are based on service networks, abstract protocols need not to be designed, they can be generated. This is probably one of the greatest advantages of separating service networks from abstract networks, especially when we consider how complex abstract protocols can easily become, compared to the relative simplicity of service behaviours and object behaviours. Appendix 1: List of Standards ITU-T recommendations (date of latest version): ITU-T E.163 (11/88) Numbering Plan for the International Telephone Service ITU-T E.164 (05/97) The International Public Telecommunication Numbering Plan ITU-T G.707 (to be published 10/00) Network Node Interface for the SDH ITU-T G.708 (06/99) Sub STM-0 Network Node Interface for the SDH ITU-T G.732 (11/88) Characteristics of Primary PCM Multiplex Equipment Operating at 2048 kbit/s ITU.T G.733 (11/88) Characteristics of Primary PCM Multiplex Equipment Operating at 1544 kbit/s ITU-T G.803 (03/00) Architecture of Transport Networks Based on the SDH ITU-T I.113 (06/97) Vocabulary of Terms for Broadband Aspects of ISDN ITU-T I.121 (04/91) Broadband Aspects of ISDN ITU-T I.150 (02/99) BISDN ATM Functional Characteristics ITU-T I.211 (03/93) BISDN Service Aspects ITU-T 1.320 (11/93) ISDN Protocol Reference Model ITU-T I.321 (04/91) BISDN Protocol Reference Model and its Application ITU-T I.324 (10/91) ISDN Network Architecture ITU-T 1.327 (03/93) BISDN Network Functional Architecture ITU-T I.330 (11/88) ISDN Numbering and Addressing Principles ITU-T 1.340 (11/88) ISDN Connection Types ITU-T I.350 (03/93) General Aspects of Quality of Service and Network Performance in Digital Network