INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : Q.85.1

Title :	Stage 2 description for community of interest supplementary 
	services

Study Group : XI - Switching and Signalling

Version : Revised

Date of adoption : 1992

Notes :	


			CLOSED USER GROUP (CUG)

Recommendation Q.85.1 defines the stage 2 of the integrated services 
digital network (ISDN) as provided by telecommunications operators for 
the Closed User Group (CUG) supplementary service. Stage 2 identifies 
the functional capabilities and the information flows needed to 
support the service description. The Stage 2 description also 
identifies user operations not directly associated with a call 
(see Recommendation I.130).

Recommendation Q.85.1 is specified according to the methodology 
specified in Recommendation Q.65.

Recommendation Q.85.1 does not formally describe the relationship 
between this supplementary service and the basic call, but where 
possible, this information is included for guidance.

In addition, Recommendation Q.85.1 does not specify the requirements 
where the service is provided to the user via a private ISDN. 
Recommendation Q.85.1 does not specify the requirements for the 
allocation of defined functional entities within a private ISDN, it 
does however, define which functional entities may be  allocated to 
a private ISDN.

Recommendation Q.85.1 does not specify the additional requirements 
where the service is provided to the user via a telecommunications 
network that is not an ISDN.

The CUG supplementary service enables users to form groups to and from 
which access is restricted. A specific user may be a member of one or 
more closed user groups. Members of a specific Closed User Group can 
communicate among themselves but not, in general, with users outside 
the group.

The CUG supplementary service is applicable to all telecommunication 
services.

Recommendation Q.85.1 is applicable to the stage 3 Recommendations for 
the ISDN CUG supplementary service. The term "stage 3" is also 
defined in Recommendation I.130.



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