review copy of H.225.0 version 2 available

Glen Freundlich ggf at
Fri Sep 19 16:01:37 EDT 1997

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???



"To allow gatekeepers to re-route connections from endpoints that do not support
supplementary services, endpoints shall support the reception of empty capability
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 independent
of supplementary services and facilitates pre-connect announcements.  It can also
be used to delay H.245 media establishment when features such as Gatekeeper
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 endpoint,
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 receive
media from open logical channels from the remote end.  This allows endpoints to
receive announcements (e.g. pre-connect call progress) where the announcing
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 is
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 the
remote endpoint.  This option of not sending a capability set enables faster

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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