TD-27 text for h.323

Pete Cordell pete.cordell at BT-SYS.BT.CO.UK
Tue Sep 23 06:19:30 EDT 1997


I forgot to mention where I thought TD-27 text should go.

I think the best place for it would be 8.4.6 (a new section in the
Sunriver version) after the MC cascading part.  This brings it in as
part of Phase D: Call Services.

Of the other options you mentioned, the first seems a bit tutorially,
and the second is too early in the sequence of events.


Pete Cordell
BT Labs
E-Mail: pete.cordell at
Tel: +44 1473 646436
Fax: +44 1473 645499

>From:  gthom[SMTP:gthom at DELTA-INFO.COM]
>Sent:  19 September 1997 19:47
>To:    ITU-SG16 at
>Subject:       TD-27 text for h.323
>Pete and others,
>I took some editorial liberty with the text of TD-27. It is contained
>below. I expect
>to put this in Capability Exchange. Alternatively, I could put
>it into 8.2.
>Any suggestions, changes, clarifications???
> Gary
>"To allow gatekeepers to re-route connections from endpoints that do
>not support
>supplementary services, endpoints shall support the reception of empty
>sets (i.e. Terminal Capability sets that indicate that the endpoint
>sending the
>message has no receive capabilities).  This feature also allows
>'network' elements
>such as PBXs, call centers, and IVR systems to re-route connections
>of supplementary services and facilitates pre-connect announcements.
>It can also
>be used to delay H.245 media establishment when features such as
>based user location is being used.  It is also highly recommended that
>Version 1
>endpoints support this feature.
>On reception of an empty capability set an endpoint shall enter a
>paused state.  If
>media stream or data logical channels were previously opened by the
>they should be closed.  In this state an endpoint shall accept the
>opening of logical
>channels from the remote end based on the usual rules and continue to
>media from open logical channels from the remote end.  This allows
>endpoints to
>receive announcements (e.g. pre-connect call progress) where the
>entity does not wish to receive media from the endpoint.
>On reception of a non-empty capability set in this paused state an
>endpoint shall
>reset its H.245 state to that which it was in prior to entering the
>paused state.
>This allows an endpoint to be connected to a different endpoint when it
>released from the paused state.  Note that the non-empty capability set
>shall not
>be sent to an endpoint until all its transmit and receive logical
>channels have been
>closed.  A switching entity should also send an H.450 redirection
>indication Facility
>message if the endpoint is being re-routed.  The endpoint shall then
>proceed with
>normal H.245 connection establishment signalling. When leaving the
>paused state
>an endpoint shall take part in master/slave determination signalling,
>and may
>proceed with normal open logical channel signalling procedures.  When
>an MC
>receives a release from the paused state it shall act as if a new
>endpoint has
>entered the conference.
>Unless its capabilities have changed, an endpoint need not resend a
>capability set
>as the gatekeeper will have supplied this to remove any paused state in
>remote endpoint.  This option of not sending a capability set enables
>Name:      Gary Thom
>Company: Delta Information Systems, Inc.
>Phone:     +1-215-657-5270 x23
>Fax    :     +1-215-657-5273
>E-mail:     gthom at
>Date:       09/19/97
>Time:       11:47:19

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