Application of ISDN User Part (ISUP) Version 3 for the Integrated Services Digital Network (ISDN) - Public Land Mobile Network (PLMN) signalling interface; Part 1: Protocol specification
The present document specifies the third version of the Integrated Services Digital Network (ISDN) - Global System for Mobile communications (GSM) Public Land Mobile Network (PLMN) signalling interface. The present document is applicable to the interconnection of PLMN and ISDN.
The ISUP interface defined is the trunk signalling interface between the PLMN and the ISDN. It is assumed that the interface between PLMN and ISDN can occur at any point in a national network, provided that the exchange in the national network has this ISDN-PLMN signalling interface.
This signalling interface is based on ISUP version 3 (as given in EN 300 356-1 [1] to EN 300 356-20 [19]). The functionality in the GSM system is based on GSM Phase 2+ Release 1998.
NOTE 1:	Support of new functionality in the GSM system applicable for this interface may be included in subsequent versions of the present document or may be published as a new EN.
Connection types:
The following ISUP version 3 connection types can be supported:
-	speech;
-	3,1 kHz audio;
-	64 kbit/s unrestricted;
-	64 kbit/s unrestricted preferred;
-	2  64 kbit/s unrestricted;
-	384 kbit/s unrestricted;
-	1 536 kbit/s unrestricted;
-	1 920 kbit/s unrestricted.
NOTE 2:	2  64 kbit/s, 384 kbit/s, 1 536 kbit/s, 1 920 kbit/s unrestricted and 64 kbit/s unrestricted preferred connection types are not supported by the GSM access, however the connection types may be used in order to support other access methods via the GSM network.
Supplementary services:
The following ISUP version 3 supplementary services can be supported:
-	Calling Line Identification Presentation (CLIP)/
Calling Line Identification Restriction (CLIR);
-	Connected Line Identification Presentation (COLP)/
Connected Line Identification Restriction (COLR);
-	Terminal portability (TP);
-	User-to-User Signalling (UUS);
-	Closed User Group (CUG);
-	Subaddressing (SUB);
-	Malicious Call Identification (MCID);
-	Conference call, add-on (CONF);
-	Explicit Call Transfer (ECT);
-	Call Forwarding Unconditional (CFU)/
Call Forwarding on Busy (CFB)/
Call Forwarding on No Reply (CFNR);
-	Call Deflection (CD);
-	Call Hold (HOLD);
-	Call Waiting (CW);
-	Completion of Calls to Busy Subscriber (CCBS);
-	Completion of Calls on No Reply (CCNR);
-	Three party (3PTY).
The support of supplementary services on this interface does not necessarily imply that the supplementary services are supported in one or the other of the networks interconnected.
The Direct Dialling In (DDI) supplementary service and Multiple Subscriber Number (MSN) supplementary service have no impact on this interface.
This interface can be used within national networks, however messages and parameters that are marked for national use in EN 300 356-1 [1] are not described in the present document.