INTERNATIONAL  TELECOMMUNICATION  UNION

		     ITU-T RECOMMENDATION SUMMARY


Rec. No. : Q.951.2

Title :	Stage 3 description for number identification supplementary 
	services using DSS 1

Study Group : XI - Switching and Signalling

Version : New

Date of adoption : 1992

Notes :	


		   MULTIPLE SUBSCRIBER NUMBER (MSN)

The Multiple Subscriber Number (MSN) supplementary service provides 
the possibility for assigning multiple ISDN numbers to a single public 
or private access. Note that this allows, e.g.,:

	1)	a calling user to select, via the public network, one 
	or multiple distinct terminals out of a multiple choice (e.g. 
	in a passive bus configuration);

	2)	to identify the terminal to the network for the 
	application of other supplementary services.

It is considered:

	-   that in the case of a basic access, some service providers 
	may not have knowledge or control over what is connected, 
	e.g. private ISDN or a terminal configuration; 

	-   that Administrations have differing numbering methods;

	-   that common international terminal specifications are 
	desired.

The stage 1 description, i.e. the MSN supplementary service description 
as seen from the user, can be found in Recommendation I.251.2.

The stage 2 description, i.e. the information flow for the MSN 
supplementary service, can be found in Recommendation Q.81.2.

Recommendation Q.951.2 specifies the stage 3 description, i.e. the 
protocol requirements for the MSN supplementary service at the 
coincident S and T reference point or at the T reference point (as 
defined in Recommendation I.411).

The MSN supplementary service enables each individual terminal on one 
access to have one or more identities, by which one individual 
terminal (e.g. at a passive bus configuration) can be discriminated 
from the others.

The Multiple Subscriber Number may be either:

	-   the whole ISDN number; or

	-   a part of the ISDN number (the least significant "n" 
	digit(s) where "n" may be a number up to the full length of 
	the ISDN number, and shall be a number large enough to allow 
	all terminals on an access to be assigned an individual 
	number); or

	-   as a service provider option, a number which can be mapped 
	from the ISDN number by the network at the destination network 
	side.

National or international prefixes cannot form part of the Multiple 
Subscriber Number.



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