TD-27 text for h.323

Pete Cordell pete.cordell at BT-SYS.BT.CO.UK
Mon Sep 22 08:29:01 EDT 1997


Generally I think your editorial intervention has been good.  However,
the state reset to when an non-empty capability set is received should
be the state that H.245 is in after H.245 is originally established, NOT
the state before the pause is invoked.  This flushes out any H.245 state
so that you have a known state to which to connect to a new endpoint.
Some attempt at words is:

On reception of a non-empty capability set in this paused state an
endpoint shall
reset its H.245 state to that which it is in just after the H.245
transport connection is made at call establishment time (i.e. the
beginning of phase B).

Hope this helps,

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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