scope:

This European Telecommunication Standard (ETS) specifies the Synchronization and Co-ordination Function (SCF) which provides for the OSI Connection-mode Network Service according to CCITT Recommendation X.213 [2] in a Control- and User-plane, or Management- and User-plane, as appropriate, ISDN environment. The SCF specified in this ETS is to be implemented in endsystems conforming to OSI principles for connection to the pan-European Narrowband or Broadband Integrated Services Digital Network (N-ISDN/B-ISDN) as provided by European Public Telecommunications Operators.

The SCF is identified in the protocol reference model according to CCITT Recommendation I.320 [1].

The SCF for the provision of the OSI Connection-mode Network Service is specified in terms of the interrelationship between Network primitives at its upper and lower boundaries. The SCF performs the synchronization between C-plane, or M-plane if appropriate, and U-plane on a per network connection basis and is not concerned with any functionality which is required, if multiplexing within U-plane underlying layers is used.

This ETS is applicable to an ISDN customer access using an ISDN access signalling system such as the Digital Subscriber Signalling System No. one (DSS1) protocol within the C-plane for the provision of a Switched Virtual Circuit (SVC), and Permanent Virtual Circuit (PVC) arrangements. It does not require a particular protocol within the U-plane, but rather relies on Service Data Units (SDUs) to be exchanged between the SCF as service user and the U-plane as service provider.

This ETS is applicable to equipment conforming to OSI principles to be attached at the user side of N-ISDN, or B-ISDN, as appropriate, User-Network Interface (UNI).