"Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. One (DSS1) Protocol; Basic Call Applications Enhancement at the ""b"" Service Entry Point for Virtual Private Network (VPN) Applications; Part 1: Protocol Specification
"The present document specifies the extensions of the protocol for basic call control for the pan-European Integrated Services Digital Network (ISDN). These extensions are applicable at the ""b"" service entry point (as defined in clause 5 of the present document). It is part of the Digital Subscriber Signalling System No. One (DSS1) protocol. The present document contains only additional requirements to those in the main body of ETS 300 403-1 [2]. The present document is applicable only to point-to-point access configurations. The present document specifies additional protocol elements and call control procedures for the handling of calls between users in a Corporate telecommunication Network (CN) at the ""b"" service entry point. The functionality provided by the public network may be: - the emulation of an Originating Private Integrates services Network Exchange (PINX); - the emulation of a Terminating PINX; - the emulation of a Transit PINX; - the emulation of a Relay Node; - the emulation of an Incoming Gateway PINX; - the emulation of an Outgoing Gateway PINX; - the emulation of a combination of two or more of the above. The support of these capabilities is a network option. The present document does not cover the requirements for support of the ""a"" service entry point. The specification included in the present document does not imply any specific implementation technology or platform. NOTE: Calls/connections relating to the ""b"" service entry point are distinguished from calls that are accessing the public network at the T reference point. Calls relating to the T reference point are supported in accordance with the requirements of EN 300 403-1 [2]. Calls relating to the ""b"" service entry point are supported in accordance with the requirements of the present document. The requirements have been defined such that both contexts can coexist on the same access@ and this is expected to be a typical implementation. There is no requirement that when the provisions of the present document are implemented@ calls at the T reference point also need to be implemented on the same access. Where both contexts are implemented@ the access resources are common to both contexts."