 expected, resulting in a International Switching Symposium (ISS '90), 1, .105. network end-end delay variation of a few milliseconds. Gard, I., Rooth, J. (1990) An ATM switch implementation - technique and technology. In Proceedings of the X111 Interna- tional Switching Symposium (ISS '90), 4, p. 23. 41.5.1.5 End to end transfer delay Haduong, T., Stavenow, B., Dejean, J. (1990) Stratified reference model - an open architecture approach for B-ISDN. In Pro- This is the one way propagation time between two S/T interfaces. It ceedings of the X111 International Switching Symposium (ISS excludes Cell assembly/disassembly time and is not applied to '90), 1, p. 105. lost/misrouted cells. It is therefore confined to the delay caused by Hui, J. (1988) Resource allocation for broadband networks, IEEE the transmission links and by the transit delays of the switches. Journal on Selected Areas in Communications, 6 (9) Dec. Schaffer, B. (1990) ATM switching in the developing telecommuni- 41.5.2 Call Control Parameters cation networks. In Proceedings of the X111 International Switching Symposium (ISS '90) 1, p.105. These are as follows: Wernik, M.R., Munter, E. (1990) Broadband public network and switch architecture. In Proceedings of the X111 International Connection set-up delay, which is the interval between the Switching Symposium (ISS '90), 1, p. 15. event of the call set-up message transfer and receipt of its The Synchronous Digital Hierarchy (SDH) Mark Matthews Northern Telecom Europe Contents 42.1 Introduction 42/3 PDH deficiencies 42/3 The basis of SDH 42/5 42.4 The SDH standards 42/8 42.5 Control and management 42/18 SDH based networks 42/19 42.7 Impact of broadband standards 42/26 42.8 Future technologies 42/26 42.9 Conclusion 42/27 42.10 References 42/27 This page intentionally left blank Introduction 42/3 42.1 Introduction cant competition into several of these former monopoly markets, especially in the USA, UK and Japan. This competition to supply high quality telecom services to business customers is forcing PTO