H.323 (8.1) Phase A - Call Setup

Chris Wayman Purvis cwp at isdn-comms.co.uk
Fri Jul 20 09:02:19 EDT 2001


Ah!  The reasoning becomes clear - thanks Paul!
Nevertheless, Pete is right.  Given that the term "endpoints" can include 
answering machines this needs some careful rewording!

Regards,
Chris

Paul E. Jones wrote:

> 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 at VEGASTREAM.COM>
> To: <ITU-SG16 at 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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> 
> 
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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
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