The ISDN user part (ISUP) has been designed for use in the circuit-switched part of ISDN networks (see Fig. ). It includes messages and procedures for the control of interexchange calls between two (analog) subscribers, two ISDN users, and between an ISDN user and a subscriber [ 1,2]. As in TUP signaling, ISUP call-control signaling is primarily link-by-link, but also includes procedures for end-to-end signaling. Telecoms that have installed TUP signaling in their networks are gradually converting to ISUP signaling | Signaling in Telecommunication Networks. John G. van Bosse Copyright 1998 John Wiley Sons Inc. ISBNs 0-471-57377-9 Hardback 0-471-22415-4 Electronic ISDN USER PART This chapter resumes the discussion of SS7 signaling and describes the ISDN integrated digital services network user part of SS7. INTRODUCTION The ISDN user part ISUP has been designed for use in the circuit-switched part of ISDN networks see Fig. . It includes messages and procedures for the control of interexchange calls between two analog subscribers two ISDN users and between an ISDN user and a subscriber 1 2 . As in TUP signaling ISUP call-control signaling is primarily link-by-link but also includes procedures for end-to-end signaling. Telecoms that have installed TUP signaling in their networks are gradually converting to ISUP signaling. The telecoms in the . have chosen to bypass TUP and are moving directly from multi-frequency and CCIS signaling Chapters 4 and 6 to ISUP. ISUP Call-control Requirements The major difference between TUP and ISUP is that ISUP also supports signaling in calls in which one or both parties are ISDN users. ISUP has been designed to meet the signaling requirements for ISDN-related services. Support of Bearer Services. The bearer service requested by a calling user can impose restrictions on the network equipment that can be used for the call. 269 270 ISDN USER PART Table Trunk transmission exchange and signaling types allowed in connections for individual bearer services. Speech Bearer Service kHz Audio 64 kb s Data Analog FDM trunk group A A N 64 kb s digital trunk group A A A Trunk group with ISUP signaling A A A Trunk group with other signaling A A N Circuit multiplication equipment A N N Echo control A N N Exchange with analog switchblock A A N Exchange with digital switchblock A A A A allowed. N not allowed. These limitations are listed in Table . For example speech calls can be carried on analog or digital PCM trunks that may
