Re: Switching to H.245

18 May 2001

      Or something like "H.323 entities shall only process the first fastStart
element it receives for a call".
Thanks guys.
...
-----Original Message-----
From: Sasha Ruditsky [mailto:sasha@RADVISION.COM]
Sent: Friday, May 18, 2001 12:16 PM
To: ITU-SG16@mailbag.cps.intel.com
Subject: Re: Switching to H.245
Hi François
Probably I'll try to state you question in more generic way.
We know that it is possible to perform OLC operations after fast start
completed
and before another Q.931 message (like ALERTING or CONNECT) 
with fast start
is sent.
(the simplest probably is to close channel opened using fast start)
(3rd party pause and redirection is of course procedure of this kind)
What is the meaning of the fast start in such CONNECT message?
And here I agree with Chris that such fast start elements 
should be ignored.
So probably the text that may solve this and should be added 
should state
something like:
"H.323 entity shall process fast start elements only once 
during the call."
BTW Probably the same statement should be done about 
h245Address. I just
know one H.323 endpoint that established 3 H.245 connections 
when got the
h245Address in CALL PROCEEDING, ALERTING and CONNECT.
Sasha
-----Original Message-----
From: Chris Wayman Purvis [mailto:cwp@ISDN-COMMS.CO.UK]
Sent: Friday, May 18, 2001 6:56 AM
To: ITU-SG16@mailbag.cps.INTEL.COM
Subject: Re: Switching to H.245
Francois,
Good catch!  My suggestion would be to add some text saying 
that anything
exchanged via H.245 overrides anything done by fastStart, even if the
fastStart happens to arrive later.
Now what happens if there's a possible scenario someone can 
devise where you
manage to get tunnelled and "separate connection" H.245 
contradicting each
other is a thornier problem - can anyone see that happening?
Regards,
Chris
Francois Audet wrote:
...
Hum, interesting.
My follow up question is then:
* A sends SETUP to B with fast start with h245Address and
  tunnelling. ALERTING responds to FS, and the whole TCS and M/S
  process takes place. Then A wants to forward the call 

(internally)
...
  before answer (i.e., in the ALERTING phase). It thus 

sends TCS=0,
...
  TCS=full, OLCs and all that. Then B answers and sends 

the CONNECT
...
  (with the same fastStart as the ALERTING as per earlier
  discussions we had ;^)  Wouldn't the content of the fastStart
  contradict what the actual forwarded connections is 

really? Would
...
  it be a problem?

Seems pretty tricky...
-----Original Message-----
From: Paul Long [mailto:plong@IPDIALOG.COM]
Sent: Thursday, May 17, 2001 11:52 AM
To: ITU-SG16@MAILBAG.INTEL.COM
Subject: Re: Switching to H.245

Francois,

I realize how this could be confusing, but I don't 

necessarily see a
...
conflict since they all say, "may." For example, if I 

say, "X may do
...
A or B," and, "X may do B," that does not preclude "X may do A."
Conversely, if I said "shall" instead of "may," I think 

there would
...
be real conflicts. I've worked on EPs that are very aggressive
during call establishment. For example, Setup contains an
h245Address and indicates support for Fast Connect and H.245
Tunneling. Other than all the non-compliant EPs out 

there, it worked
...
just fine. The EPs also support third-party pause, but I don't
remember ever testing that particular scenario. As long 

as an EP is
...
implemented correctly, I don't see anything in the 

Recommendation
...
that would prevent this from working.

Paul Long

ipDialog, Inc.

    -----Original Message-----
    From: Mailing list for parties associated with 

ITU-T Study Group
...
    16 [mailto:ITU-SG16@mailbag.cps.INTEL.COM]On Behalf 

Of Francois
...
    Audet
    Sent: Thursday, May 17, 2001 1:07 PM
    To: ITU-SG16@mailbag.cps.INTEL.COM
    Subject: Switching to H.245

    Guys,

    H.323/8.1.7.2 says :

        After establishment of a call using the Fast Connect
        procedure, either endpoint may determine that it is
        necessary to invoke call features that require 

the use of
...
        H.245 procedures. Either endpoint may initiate 

the use of
...
        H.245 procedures at any point during the call, using
        tunnelling as described in 8.2..1 (if 

h245Tunnelling remains
...
        enabled) or a separate H.245 connection. The process for
        switching to a separate H.245 connection is described in

8.2.3.
...
    8.2..3 says:

        When H.245 encapsulation or Fast Connect is being used,
        either endpoint may choose to switch to using 

the separate
...
        H.245 connection at any time.

    There seem to be some contradiction in there: is it "after
    establishment" or "at any time"?

    Do you have to wait for after CONNECT to establish 

a separate
...
    H.245 channel or not?

    The case I'm interested in would be to send SETUP with
    fastStart, then receive ALERTING with fastStart. 

Then can either
...
    end initiate H.245  before CONNECT? If so, what if 

third party
...
    pause and redirection  is initiated before CONNECT?

    ----

    François AUDET, Nortel Networks

    mailto:audet@nortelnetworks.com, tel:+1 408 495 3756

--
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
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