Roni,
I agree that 6.2.8 may be "somewhat vague" in stating exactly when the
H.245 Control Channel must be established. Nevertheless, it states that
it shall be established and this is considered to be irrespective of the
channel actually being used! I.e. it does not matter whether fast connect,
H.245 tunnelling or "normal H.245" is going to be used.
8.1.7.2 is no great help in answering the "when" question either, because
it is left up to the Endpoint's discretion ("...at the time an endpoint
deems it necessary...") to decide. I would consider this text to be
misleading, because according to 6,2,8 the Endpoint must establish this
connection.
Frank
Roni_e@ACCORD.CO.IL@SMTP@MAILBAG.INTEL.COM on 22-03-2001 10:37:35
Please respond to Roni_e@ACCORD.CO.IL@SMTP
Sent by: ITU-SG16@MAILBAG.INTEL.COM
To: ITU-SG16@MAILBAG.INTEL.COM@SMTP
cc:
Subject: Re: Conflicting text in H.323 concerning the requirement for esta blishing a H.245 control channel??
Classification:
Chris,
About your comments
1. B can make A start H.245 by using facility message with reason
startH.245. See H.323 8.2.3 Switching to a separate H.245 connection.
2. About 6.2.8 I agree that it states the H.245 shall be established, it
does not say when. The when is mentioned in 8.1.7.2.
Roni Even
-----Original Message-----
From: Chris Wayman Purvis [mailto:cwp@ISDN-COMMS.CO.UK]
Sent: Wednesday, March 21, 2001 3:31 PM
To: ITU-SG16@MAILBAG.INTEL.COM
Subject: Re: Conflicting text in H.323 concerning the requirement for
esta blishing a H.245 control channel??
Roni,
H.323 mandates the support of H.245 for end points that comply with the
standard. It does not mean, when using fast connect that it must be open
immediately but can be opened at a later stage by any side.
Except that it states exactly the opposite in the section under discussion.
Also, consider the following scenario:
Two endpoints, A and B. B does not support tunnelled H.245. A calls B,
without giving any H.245 address in its Setup message. B accepts the call
on the basis of fastStart. No H.245 channel is set up, as you suggest.
Suppose now B wishes to send a UII (or any H.245 message) to A. It can't.
It can't set up the H.245 channel. A could set it up, but doesn't see the
need.
The reason for
mandating H.245 is to supply a control channel and is important for
gateways
and MCUs as well as for control functions in point to point calls such as
Video fast updates. H.323 annex F defines a simple end point that has
H.245
support as optional.
I do not see the conflict between 6.2.8 and 8.1.7 if 6.2.8 means that you
have to support it but not to actually open it as in simple fast connect
calls.
But 6.2.8 does not mean that. It clearly states that an H.245 channel SHALL
be opened.
As for DTMF you can use the DTMF RTP payload to have it in band instead of
H.245.
If the person you're talking to happens to support this. Of course you
don't know whether or not it does if you haven't exchanged TCS.
-----Original Message-----
From: Agboh, Charles [mailto:charles.agboh@EBONE.COM]
Sent: Tuesday, March 20, 2001 6:59 PM
To: ITU-SG16@MAILBAG.INTEL.COM
Subject: Re: Conflicting text in H.323 concerning the requirement for
esta blishing a H.245 control channel??
Chris,
Part of establishing a "point-to-point" call involves opening 2 TCP
connnections using the Fast Connect procedure as you described it. If
Please let's not break this!
Regards,
Chris
that
is the case, then the extract from H.323v2 below is misleading(I believe).
H.323v2: 8.1.7 Fast Connect Procedure
"..... The Fast Connect procedure allows the endpoints to establish a
basic
point-to-point call with as few as one round-trip message exchange,
enabling
immediate media stream delivery upon call connection."
BR,
Charles
-----Original Message-----
From: Chris Wayman Purvis [mailto:cwp@ISDN-COMMS.CO.UK]
Sent: Tuesday, March 20, 2001 5:47 PM
To: ITU-SG16@MAILBAG.INTEL.COM
Subject: Re: Conflicting text in H.323 concerning the requirement for
esta blishing a H.245 control channel??
Charles,
It does NOT defeat ANY of the stated aims of FastConnect.
These aims were to get agreed media channels in both
directions open as
quickly as possible. Doing FastStart AND H.245 gives you your media
quickly, and means you have the power of H.245 thereon.
In-band DTMF transfer may be used. If you happen to be using
a codec that
supports it. If you assume it when you're using an
unsuitable codec you'll
have a problem. Which is a reason for using H.245 capability
negotiation.
Regards,
Chris
Agboh, Charles wrote:
which defeats the whole point of having a Fast Connect
procedure (FS +
H.245). Why isn't in-band- DTMF transfer used instead (in FS)?
-Charles
-----Original Message-----
From: Frank Derks [mailto:frank.derks@PHILIPS.COM]
Sent: Tuesday, March 20, 2001 4:40 PM
To: ITU-SG16@MAILBAG.INTEL.COM
Subject: Re: Conflicting text in H.323 concerning the
requirement for
establishing a H.245 control channel??
Chris,
I thought I was being clear enough, so let me try again.
6.2.8/H.323 states
that an enpoint must open one (and exactly one) H.245 control
channel. When
Fast Connect is being used, I assume that the intention is
that no such control
channel is opened.
To be compliant with 6.2.8/H,323 I would have to open a H.245
control channel
irrespective of which type of H.245 procedures I will be
using. So if I intend
to use Fast Start (and assuming that the other party also
supports this), I
still have to open a H.245 control channel.
Frank
cwp@isdn-comms.co.uk on 20-03-2001 15:17:14
To: Frank Derks/HVS/BE/PHILIPS@EMEA2
cc: ITU-SG16@mailbag.cps.INTEL.COM@SMTP
Subject: Re: Conflicting text in H.323 concerning the
requirement for establishing a H.245 control channel??
Classification:
Frank,
Why do you consider this text to be "conflicting"?
Specifically, with what does it conflict?
Regards,
Chris
6.2.8/H.323 states: "The endpoint shall establish exactly
one H.245
Control Channel for each call that the endpoint is
participating in."
8.1.7/H.323 never states that when Fast Connect is being
used such a
control channel should be established. As far as I understand the
mechanism this is only required to switch to "normal" H.245
procedures.
It would seem that section 6.2.8 should be rephrased to
make clear that
the H.245 control channel shall only be established when
"normal" H.245
procedures are being followed and not in the fast connect case.
Frank
--
Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
Winkfield Row, Berkshire. RG42 6LY ENGLAND
Phone: +44 1344 899 007
Fax: +44 1344 899 001
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--
Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
Winkfield Row, Berkshire. RG42 6LY ENGLAND
Phone: +44 1344 899 007
Fax: +44 1344 899 001
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
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--
Dr Chris Purvis -- Development Manager
ISDN Communications Ltd, The Stable Block, Ronans, Chavey Down Road
Winkfield Row, Berkshire. RG42 6LY ENGLAND
Phone: +44 1344 899 007
Fax: +44 1344 899 001
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
listserv@mailbag.intel.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
listserv@mailbag.intel.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For help on this mail list, send "HELP ITU-SG16" in a message to
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Frank Derks