Appendix C: More Details of the ISDN Signalling Access Protocols

In Chapter 5 the protocols associated with the operation of an ISDN connection are summarized so that the main principles of their operation are made clear. Inevitably this has meant that there has been a loss of completeness and rigour. This Appendix is an extension to give more details of the operation of the protocols for those that need this information. The layer l relates to the Basic Rate Access only. Layers 2 and 3 also relate to the Primary Rate interface. It is extracted from BT Network Requirement (BTNR) 191, which describes an implementation of the ETSI (European Telecommunication Standards Institute) standards and the approval requirements as set out in NETS (Normes Europhes de TklCcommunication). Other implementations may have detail differences but owing to a common origin in the relevant ITU-T recommendations, these differences are likely to be small. The protocols described have not been restricted to those currently implemented by BT as these are being extended on a regular basis. The extracts quoted are chosen to illustrate the operation of the interfaces. However, in the space available it has not been possible to include all situations or give a complete coverage of the protocols involved. For those requiring more information, the full BTNR may be obtained from BTNR Technical Secretariat, BT plc, Post Point 1 G42, 2 City Forum, 250258 City Road, London, EClV 2TL. To assist further reference the original paragraph numbering of the Recommendations has been retained; some detailed rewriting has been done to bridge deleted text.