management transit switching centre T-SGW transport signalling gateway transit serving node time to customer time to market time to service universal description, discovery and integration user datagram protocol user-network interface universal mobile telecommunication system uniform resource identifier universal subscriber identity module UTRAN universal terrestrial radio access network value-added service provider virtual container at level 4 (140Mbit/s in PDH, plesiochronous digital hierarchy) very high bit rate digital subscriber line virtual home environment visited location register vector mark-up language VoATM voice over ATM voice over frame relay Glossary voice over IP virtual private network vertical service provider wide area network (as opposed to local area network) wireless application protocol wireless application service provider WCDMA wideband code division multiple access wired equivalent privacy wireless Internet WAP identity module wireless Internet service provider wireless local area network web services description language web services flow language wireless session protocol wireless transport layer security world wide web (any) digital subscriber line eXtensible Markup Language XHTML HTML reformulated as an XML application Introduction 1.1 THE BOOK IN BRIEF This book is follow-up of Understanding Telecommunications 1 and 2, published in 1996-98 by Telia and Ericsson. The main author of all the books is Anders Olsson. The basics of various networks (PLMN, PSTN/ISDN, ATM, Internet etc.) are not repeated here. This book instead provides an integrated holistic view of users, telecom business and networks at a time when telecom, datacom and media industries are converging. See Figure 1.1. It offers the reader a cross-scientific, generic and well-structured overview of the tele- com area. A main objective is to understand what competencies are required to become successful within the converging telecom world of today. The technical content is fairly generic but with the main focus on an all-acc