Integrated Services Digital Network (ISDN); Digital Subscriber Signalling System No. One (DSS1) Protocol; Generic Functional Protocol for the Support of Supplementary Services for Virtual Private Network (VPN) Applications; Part 1: Protocol Specification
"The present document specifies the generic functional protocol for the pan-European Integrated Services Digital Network (ISDN) applicable at the ""b service entry point"" (as defined in EN 301 060-1 [3]). It is part of the Digital Subscriber Signalling System No. one (DSS 1) protocol. The generic functional protocol is based on the Facility information element and the FACILITY message@ as well as on other specific functional messages. The protocol is symmetrical@ and it is applicable to both basic and primary rate interfaces. The generic functional protocol defined in the present document provides the means to exchange signalling information for the control of supplementary services over a Virtual Private Network (VPN). It does not by itself control any supplementary service but rather provides generic services to specific supplementary service control entities. The application of the present document to individual supplementary services is outside the scope of the present document and is defined in those standards which specify the individual supplementary services. Further part(s) of the present document specify the method of testing required to identify conformance to the present document. The present document is applicable only to point-to-point access configurations. NOTE 1: The exchange of signalling information relating to the VPN ""b service entry point is distinguished from the exchange of signalling information that is used to access public network services at the T reference point. The generic functional protocol applicable in a public network context is supported in accordance with the requirements of EN 300 196-1 [i]. The generic functional protocol specifically applicable in a VPN context is supported in accordance with this standard. 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 this standard is implemented@ the exchange of signalling information relating to 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. NOTE 2: Where both contexts are supported on the same access@ a service provider may support supplementary services applicable for public network calls within a VPN context. In this case the applicability of the individual public network supplementary services to a call with VPN context is beyond the scope of this standard."