[Megaco] RE: Glare condition when using embedded descriptors

[John Stock <John.Stock@afc.com>]

Actually I just remember that an offhook event is not sent to the MG in the
case of embedded descriptors.

However this actually exacerbates the problem - there is actually a very
large widow where this glare condition can occur.  I'm certain this must
have been discussed at some point, though couldn't find anything in looking
through past emails.  If such a discussion has taken place, can someone
point me to the email thread?

Thanks.

>  -----Original Message-----
> From: 	John Stock  
> Sent:	Wednesday, January 22, 2003 2:25 PM
> To:	'megaco@ietf.org'
> Subject:	Glare condition when using embedded descriptors
> 
> Hi all,
> 
> I was wondering about handling of this situation:
> 
> - Embedded descriptors are used, such that when a user goes offhook, the
> MG will provide dialtone and begin digit collection without waiting for
> additional signals from the MGC
> - A glare condition happens, such that a ring-in on the phone from the MGC
> side occurs at the same time as the offhook, such that the MG sends the
> offhook notification before receiving the Add command on the ring-in.
> - Thus the MG will begin dial tone before getting the Add, and will cease
> it when connecting the physical termination to the incoming call.
> - The MGC will receive the offhook notification after sending the Add
> command for the ring-in, thus sees it simply as a user answering a
> terminating call.
> 
> My questions are these:
> 
> - Is it proper to handle it this way, such that the subscriber is
> connected to the incoming call, instead of the alternative which is to
> block the incoming call and to provide dial tone and collect digits from
> the subscriber for a separate outgoing call?  I believe this is the way it
> works with other protocols, such as Q.931 in GR303.
> - The odd thing is the brief spurt of dial tone, which may be exacerbated
> by any MGC<->MG messaging delay.  Does anyone know anything that's
> proposed for handling this?  Though it's probably not a big deal since one
> would expect this to happen very very seldomly.  An obvious solution is to
> not use the embedded descriptors, however this then of course removes the
> benefits of doing such.  Another solution may be to have the MG wait for
> the Reply to the offhook before providing dial tone, but this is kind of
> complex because the Reply handling may be in a completely different entity
> and level than event/signal handling.
> 
> Thanks.
> 
> John Stock
> Systems Engineering
> Advanced Fibre Communications
> john.stock@afc.com
> 707-792-6249
> 
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