[Robustness] conference call today Jan 6 -- final reminder

Maureen Stillman Maureen.Stillman at NOKIA.COM
Thu Jan 6 08:17:57 EST 2000


Boaz,

This is a missing point in this discussion.  The proposal is to close the
Call Signaling channel because it is anticipated that there is no additional
use for the channel.  If this anticipation is wrong, a procedure is required
to reopen the call signaling channel and to resynchronize all the state
information.

What is the proposed procedure for reopening this channel?

Please do not state that your application does not use H.450 or any other
subsequent use of the call signaling channel.  Even though your gatekeeper
does not use H.450, my endpoint does and interworking is required.

Bob

------------------------------------------------------------------
Robert Callaghan
Siemens Information and Communication Networks
Tel: +1.561.997.3756    Fax: +1.561.997.3403
Email:  Robert.Callaghan at ICN.Siemens.com
------------------------------------------------------------------


-----Original Message-----
From: Boaz Michaely [mailto:Boaz_Michaely at VOCALTEC.COM]
Sent: Wednesday, January 05, 2000 4:47 PM
To: ITU-SG16 at mailbag.cps.intel.com
Subject: Re: Closing Q.931 TCP connection..


Hi Chris,
Glad I caught your interest ...
Let me clarify some points which seem to have been misunderstood:
(I'll try shorthand this time :-)

1. The case is NOT made for the GK not being the point for SETUP to call.
Quite the reverse:
I propose that the GK *is* the single point to call, and that it executes
load balancing logic to distribute the H.245 negotiations elsewhere.

2. Varying the address given in AnnexG defetes no 1.

3. H.450.2 has nothing to do with it as the call is NOT being redirected.
It is merely being decomposed.

4. You are NOT required to remove the call signalling at all.
I'm afraid my point has been completely missed : I call for ALLOWING the
close of the "Q.931" TCP signalling channel, while maintaining only the
MEDIA CONTROL (h.245) channel open.

5. I too suspect that this scenario "just works", which is why I find it
attractive to continue to allow closing of the Q.931
channel mid-call, WITHOUT killing the call . (again - this is perfectly
legal today).
We may need to update the standard, though, in order to solve the problems
that Paul identified !

Thanks for your thoughts,
     Boaz

-------- On 04/01/2000 06:27 PM GMT  Chris Wayman Purvis
<cwp at ISDN-COMMS.CO.UK>  wrote:




Boaz,

The beast you describe is very strange and, as Paul says, interesting.

Permit me to copy a para from your mail, in order to take issue with it!

>> Once a SETUP message comes in, the GK replies with an H.245 address of
the
>> applicable MG. Note that the GK has to be the point of call for SETUP,
>> since it may use the information in the SETUP message for finding the
>> applicable MG (i.e. using CLI and/or DNIS), as well as it performs load
>> balancing on the MGs.
I'm not convinced the case is made here for the GK not being the point for
SETUP to call.  As you postulate the use of "SendSetup" Annex G messages,
load
balancing can be achieved adequately by varying the address given there.
I'm
hazy about how much information Annex G gives you as to the source of a
call,
but would hope that the sort of information that will be useful here (such
as
country of origin of the call) would be available (maybe an Annex G expert
can
help here?)?

Even given the GK as the destination for the original setup message,
H.450.2(?
I think it's 2!) would allow the call to be redirected elsewhere once the
GK
has looked at that message.

What I'm saying in general is that I'd hope to be able to achieve your
application without requiring the removal of the call signalling channel,
and
I'm sure there are at least two ways of doing it, depending on precisely
what
you require, without any new standards needing to be written.

In most cases I'm agnostic about Paul's point of a gatekeeper routing call
control (H.225.0) but not connection control (H.245).  In my view
everything
just works.  BUT I believe that in order for everything to "just work" the
assumption has to be there that the call control channel doesn't die
mid-call.

Regards,
Chris

"Paul E. Jones" wrote:
>
> Boaz,
>
> I do consistently argue against closing the call signaling channel.  But
> there are good reasons for this:
> 1) Many devices out there clear the call when the channel is closed (yes,
> this is wrong, but it's a fact of life :-)
> 2) Closing the call signaling channel prohibits (or complicates) the use
of
> supplementary services and other in-band signaling.
>
> The text to which Chris Purvis refers is section 6.1.  Here is an
extraction
> of that text:
> ``For the gatekeeper mediated call signalling case (see Figure 8/H.323),
the
> terminals shall keep the reliable port active throughout the call.
However,
> the gatekeeper may choose to close this signalling channel, but should
keep
> the channel open for calls that involve gateways. This will allow the
> end-to-end transmission of Q.931 information elements such as display
> information.''
>
> What you propose below is interesting and may yield a more scalable
> solution.  Perhaps this should be explored.  I might note, though, that
at
> the moment, such a configuration is "undefined".  According to H.323,
> routing the call signaling through a Gatekeeper, but not the H.245, is
"for
> further study".  It might be interesting to read contributions from you
that
> might open this area for study.
>
> Best Regards,
> Paul
>
> ----- Original Message -----
> From: "Boaz Michaely" <Boaz_Michaely at vocaltec.com>
> To: "Paul E. Jones" <paul.jones at ties.itu.int>
> Cc: <h323implementors at imtc.org>; <itu-sg16 at mailbag.cps.intel.com>
> Sent: Thursday, December 30, 1999 7:40 PM
> Subject: Re: Closing Q.931 TCP connection..
>
> > Happy new Y2K !
> > Your consistent argueing against closing the Q.931 sig. channel, is
> > appreciable, and I share your concern for many service scenarios. (I
guess
> > we'll talk more about this in February, which is why the ITU-SG16 list
is
> > copied)
> > However, in the following scenario, it seems highly desireable to be
able
> > to close the sig. channel:
> > (if this has been described before, please forgive my ignorance)
> >
> > Think of a scaleable IVR server farm which is implemented using
multiple
> > MG's, each capable of H.245, RTP/RTCP, and a very simple control
protocol
> > (H.248 ?). A single GRC GK, which is also an AnnexG Border Element is
used
> > as the single entry into this port-dense system.
> > This GK may be addressed using LRQ from another domain (e.g. that of an
> > ITSP). In addition, it publishes its own address using "SendSetup" type
of
> > addressing in the AnnexG templates that it publishes.
> >
> > Once a SETUP message comes in, the GK replies with an H.245 address of
the
> > applicable MG. Note that the GK has to be the point of call for SETUP,
> > since it may use the information in the SETUP message for finding the
> > applicable MG
> > (i.e. using CLI and/or DNIS), as well as it performs load balancing on
the
> > MGs.
> > Now the audio session is connected and the call takes place, while the
MG
> > handles the DTMFs and all the logic.
> > Let's assume that there are no changes in the call routing from this
point
> > on (which is typically the case in, say, automatic banking systems
etc.)
> > GK intervention is not required any more until the call is done.
> >
> > It would be nice if the GK could get rid of the dangling Q.931 TCP
> > connection, while the RTP call continues until it is disconnected by
the
> > human caller. If I understand correctly, this is a perfectly legitimate
> > behaviour using the existing standard. (I trust this is true for all
> > versions ?)
> >
> > Assuming this scenario is valid (have I overlooked anything ?) can we
find
> > a way to continue to support it while reducing the mess for other
services
> > ?
> > Reinitiating the sig. channel in some way may not be a bad idea ?
> >
> > Finally, I must admit I do not understand Chris's comment about making
> sure
> > the other party is not a GW.
> > Why is that so?
> >
> >
> > Boaz Michaely
> > VocalTec Communications Ltd.
> > +972 (9) 970-7869
> > email: boaz at vocaltec.com
> > http://people.itu.int/~michaely
> >
> >
> >
> >
> >
> >
> > "Paul E. Jones" <paul.jones at ties.itu.int> on 02/01/2000 12:04:50 AM
> >
> > Please respond to "Paul E. Jones" <paul.jones at ties.itu.int>
> >
> > To:   "Chris Wayman Purvis" <cwp at isdn-comms.co.uk>, "Satya T"
> >       <satyat at MIEL.MOT.COM>
> > cc:   h323implementors at imtc.org (bcc: Boaz Michaely)
> > Subject:  Re: Closing Q.931 TCP connection..
> >
> >
> >
> >
> > Folks,
> >
> > I would like to second Chris' comments.  It really is a very bad idea
to
> > close the call signaling channel.  This might have been important prior
to
> > H.245 tunneling and Fast Connect, but in my opinion, this just isn't
> > necessary any longer.
> >
> > My chief complaint is that once the channel is closed, there's no
> guarantee
> > one can re-open it.  This is especially true on the receiving end-- the
> > called endpoint may not know the call signaling address to which to try
to
> > re-establish a socket connection, and it cannot assume 1720.  Reverse
call
> > setup may not even be possible, given some network arrangements
(including
> > the usage of devices to traverse firewalls).
> >
> > There are several reasons to keep the channel open, too.  This gives
the
> > endpoint the ability to perform supplementary services.  If the channel
is
> > closed, the endpoints lose that functionality-- unless we can guarantee
a
> > way of re-establishing that channel.
> >
> > So, my advise to all implementers: never, never close the call
signaling
> > channel.
> >
> > Paul
> >
> > ----- Original Message -----
> > From: "Chris Wayman Purvis" <cwp at isdn-comms.co.uk>
> > To: "Satya T" <satyat at MIEL.MOT.COM>
> > Cc: <h323implementors at imtc.org>
> > Sent: Tuesday, December 21, 1999 8:52 AM
> > Subject: Re: Closing Q.931 TCP connection..
> >
> >
> > > Satya,
> > >
> > > This is the subject of much current discussion, but the group within
ITU
> > SG16
> > > discussing robustness.  Currently:
> > > ReleaseComplete closes the call.
> > > Closing the Q.931 TCP connection without ReleaseComplete does not
close
> > the
> > > call if there is a separate active H.245 connection.
> > > However, consideration is being given to the possibility of changing
> this
> > rule,
> > > if no implementations can be found that deliberately close the Q.931
TCP
> > > connection during a call.
> > >
> > > I strongly advise against deliberately closing the Q.931 TCP
connection
> > without
> > > terminating the call, but as things currently stand
> > > a) you are permitted do so as long as there is no gateway involved in
> the
> > call
> > > (which you may or may not be able to know!!!)
> > > b) you should cope with other parties in the call doing this (unless
you
> > or
> > > they are a gateway!!!!!).
> > >
> > > Regards,
> > > Chris
> > >
> > > Satya T wrote:
> > > >
> > > > Hi all,
> > > >     There's a gatekeeper routed call,
> > > > and if the GK closes down the Q931 TCP connection,
> > > > does it mean the call is closed? Consider the following cases :
> > > >
> > > >      1. When GK sends RELEASE complete before breaking
> > > >          down the TCP
> > > >      2. When GK does NOT send RELEASE complete before
> > > >          breaking down TCP
> > > >
> > > > H.245 connection is established & ON directly between the EPs in
> > > > both cases when the Q931 TCP is broken down.
> > > >
> > > > Is it considered closed in both the scenarios? or only in the
former?
> > > >
> > > > regards
> > > > Satya T
> > > >
> > >
> > >
> >
--------------------------------------------------------------------------
> > >
> > > --
> > > 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



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