AW: H.323 (8.1) Phase A - Call Setup
Hi all, I would recommend to read Q.931. This gives a lot of background information about the use of the different messages. Guntram
-----Ursprüngliche Nachricht----- Von: Peter Price [mailto:PeterP@VEGASTREAM.COM] Gesendet: Freitag, 20. Juli 2001 15:37 An: ITU-SG16@MAILBAG.INTEL.COM Betreff: Re: H.323 (8.1) Phase A - Call Setup
Paul,
in fact, on further reflection, your second paragaraph highlights the error in (8.1) We both agree Alerting should be sent to the caller as soon as the callee's phone is ringing but the text opens the door for someone to send Call Proceeding and then not ever send Alerting.
It becomes clearer to me that the original intent was almost certainly "If an endpoint can respond to a Setup message with a Connect within 4 seconds, it is not required to send the Alerting message." Reference to Call Proceeding is incorrect and to Release Complete irrelevent.
I'm not sure what should be done to clarify the purpose of Call Proceeding. I think it being optional for terminal devices has led people to ignore its correct use in gateways which are an important part of the network. Perhaps this need a separate thread.
Peter
-----Original Message----- From: Peter Price [mailto:PeterP@VEGASTREAM.COM] Sent: 20 July 2001 14:05 To: ITU-SG16@mailbag.cps.INTEL.COM Subject: Re: H.323 (8.1) Phase A - Call Setup
Paul,
I forgot to say that I agree with your second paragraph with the proviso that it might take more than 4 seconds to send the Alerting. Call Proceeding is not a substitue for Alerting its just an indication that the caller should not give up too quickly.
Pete
-----Original Message----- From: Paul E. Jones [mailto:paulej@PACKETIZER.COM] Sent: 20 July 2001 12:48 To: ITU-SG16@mailbag.cps.INTEL.COM Subject: Re: H.323 (8.1) Phase A - Call Setup
Peter,
Alerting was the intent. Call Proceeding not produce a ringing sound in the caller's ear. H.323 devices have to be able to send an Alerting, though they're not required to do so if they can send a Connect within 4 second. The 4 seconds is the T303 timeout and the T303 timer is
disabled when
receiving Alerting, too... not just Call Proceeding.
The ideas are related, but independent. What we have seen some folks do is send a Call Proceeding to the caller and then nothing
else until the
connect. The result is that the calling party hears silence for a very long time: that's not good.
Paul
----- Original Message ----- From: "Peter Price" PeterP@VEGASTREAM.COM To: ITU-SG16@mailbag.cps.INTEL.COM Sent: Friday, July 20, 2001 6:54 AM Subject: H.323 (8.1) Phase A - Call Setup
Hi folks,
I think I may have found some incorrect text in H.323 8.1
The same text appears in both V3 and V4 so I suspect nobody
has commented
before.
In the paragraph beginning: "An endpoint shall be capable of sending the Alerting
message. ..."
it goes on to say: "If an endpoint can respond to a Setup message with a
Connect, Call
Proceeding, or Release Complete within 4 seconds, it is not
required to send
the Alerting message. An endpoint sending the Setup message
can expect to
receive either an Alerting, Connect, Call Proceeding, or
Release Complete
message within 4 seconds after successful transmission."
I believe the first sentence here should really be
discussing the
requirement to send a Call Proceeding (not Alerting) message. The period of 4 seconds in the last sentence is related to
T303 which is
specifically terminated by a Call Proceeding message in
order to extend the
timeout for the sending endpoint.
I think the sentence should read: "If an endpoint can respond to a Setup message with a
Connect, Alerting, or
Release Complete within 4 seconds, it is not required to
send the Call
Proceeding message."
This is then consistent with the use of Call Proceeding
described in
8.1.8.2
(second para).
Peter Price
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Guntram Diehl