British telecom ccitt no.7 network experience and direction

British Telecom (BT) has embarked upon a major modernisation programme to replace its existing analogue Public Switched Telephone Network with an Integrated Digital Switching and Signalling Network. This paper gives an overview of the BT CCITT No.7 (CCS7) digital signalling network architecture and explores BT's experiences of interworking to different implementations of CCS7 both within the BT Network and to other network operators. The paper also examines the need for interworking validation prior to interconnect and the procedures BT has instigated to ensure BT's network integrity. The evolution of CCS7 in relation to future new services and the introduction of Intelligent Networks are discussed.