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INTERNATIONAL TELECOMMUNICATION UNION
ITU-T RECOMMENDATION SUMMARY
Rec. No. : Q.951.8
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 :
SUB-ADDRESSING (SUB)
The Sub-addressing (SUB) supplementary service allows the called
(served) user to expand his addressing capacity beyond the one given
by the ISDN number.
The sub-addressing possibility offers an additional addressing
capacity independent from the ISDN number.
A called party sub-address, if presented by a calling user is delivered
unaffected to the called user. The called party sub-address may form
part of the compatibility checking by the called user. Only the served
user defines the significance of the sub-address.
The functions offered by the SUB supplementary service can be used to
identify a particular endpoint of a call beyond the ISDN access.
If a calling user wants to transfer called party sub-address
information to the called user, the calling user shall insert the
called party sub-address information into the SETUP message as part of
the basic service.
The sub-address information is transferred transparently through the
network from the originating to the destination user-network
interface. At the called user side, the called party Sub-address shall
be offered to the served user within the SETUP message, if the called
user has subscribed to this supplementary service.
Note 1 - Other sub-address information elements, e.g. calling party
sub-address or Connected party sub-address information elements are
not the subject of the SUB supplementary service and hence are
described in the appropriate supplementary service specifications
(e.g., in the Calling Line Identification Presentation and Connected
Line Identification Presentation supplementary services
specifications).
Note 2 - The maximum size of the called party sub-address is 20
octets. However, for a certain period of time, the size of the
sub-address may be less than 20 octets either within certain networks
or between networks.
To order the complete text of this Recommendation, please use the
Order Form for ITU-T Recommendations. An electronic version of this
form is available on ITUDOC (Winword 2.0: UPI=ITU-5265; ASCII: UPI=ITU-2488).