DIGITAL SUBSCRIBER SIGNALING SYSTEM NO. 1 Digital subscriber signaling system No. 1 (DSSl) is used for signaling between an ISDN (integrated services digital network) subscriber and his local exchange. This chapter is a brief excursion from the description of signaling system (SS7), which has been the subject of Chapters 7 through 9, and will continue in Chapter 11, with the description of the integrated services digital network user part (ISUP). This order of presentation has been chosen because DSSl can be discussed without references to ISUP, and because it is helpful to be familiar with DSSl when exploring ISUP, which is. | 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 10 DIGITAL SUBSCRIBER SIGNALING SYSTEM NO. 1 Digital subscriber signaling system DSS1 is used for signaling between an ISDN integrated services digital network subscriber and his local exchange. This chapter is a brief excursion from the description of signaling system SS7 which has been the subject of Chapters 7 through 9 and will continue in Chapter 11 with the description of the integrated services digital network user part ISUP . This order of presentation has been chosen because DSS1 can be discussed without references to ISUP and because it is helpful to be familiar with DSS1 when exploring ISUP which is the interexchange signaling system for the control of ISDN interexchange calls. INTRODUCTION TO ISDN AND DSS1 This section presents a broad-brush introduction to ISDN focusing primarily on its signaling aspects. More details on ISDN architecture and technology can be found in a number of texts 1-4 . Circuit-mode and Packet-mode Networks So far we have discussed circuit-mode telecommunication networks in which two subscribers communicate over a temporary and dedicated circuit consisting of the subscriber lines and possibly one or more trunks. Connections are set up by exchanges at the start of a call and released when the call has ended. During the 1970s a new network architecture was developed for data communications. These networks which have been installed in a number of 224 INTRODUCTION TO ISDN AND DSS1 225 countries consist of nodes that are interconnected by data links. The users of these network have data terminals DTE at their premises which are attached to one of the nodes. Users communicate by sending packets consisting of a header and a limited amount of data say up 100 octets . The packets are transferred on the data links and each node uses the address information in the packet .
