Subject: [Megaco] Provisional Responses.

From: Venkataramana cuddapah <[email-masked]>
Date: Mon, 26 Nov 2001 10:15:53 +0530

Hi,

I am working on MGCP implementation in CallAgent. Can any one please 
clarify me this
queri :

The queri goes like this :

1. Can Call Agent send provisional response to any of the messages 
received from the
gateways controlled by this Agent. ?

2. If so, Do I need to maintain any time out once the call Agent sends 
the provsional response till it sends the final response ?

3. In RFC2705 under the section 3.6.5, I dont find any clear note for 
how long I need to wait once after  provisional response...is sent . 
(this case araises in case of network failures  or any such problem , 
for example, if provisional response is not received by the gateway, it 
will send out the request once again...then how should the call Agent 
respond to it ?

Your valuable feedback on this will help me a lot to understand RFC in a 
better way .

Thanks
Venkat

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From: Flemming Andreasen <[email-masked]>
Date: Mon, 26 Nov 2001 11:50:14 -0500

Venkataramana cuddapah wrote:

> Hi,
>
> I am working on MGCP implementation in CallAgent.

For future reference, please send MGCP questions to "[email-masked]"

> Can any one please

Yes.

> the provsional response till it sends the final response ?

Yes. There is still transaction-level timeouts (look for "LONGTRAN-TIMER"
2705bis-01).

> will send out the request once again...then how should the call Agent

See 2705bis instead (currently draft-andreasen-mgcp-rfc2705bis-01.txt).
Basically, you simply repeat the last response.

-- Flemming

--
Flemming Andreasen
Cisco Systems

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From: Flemming Andreasen <[email-masked]>
Date: Mon, 26 Nov 2001 11:50:14 -0500

Yes.

-- Flemming

--
Flemming Andreasen
Cisco Systems

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From: Venkataramana cuddapah <[email-masked]>
Date: Tue, 27 Nov 2001 10:09:32 +0530

Hi Flemming Andreasen ,

Let me first thank you for the explanation. Please see in line for my 
 doubt..

>Yes. There is still transaction-level timeouts (look for "LONGTRAN-TIMER"
But  "LONGTRAN-TIMER" is for the mgcp entity( call agent or gateway) to 
start, when it receives the provisional response for its request, such 
that it could wait for the final response..This timer value will be 
higher than the normal retransmition timer. Please correct if I am wrong 
in my understanding...  But, I doubt , if the same timer could be used 
by the mgcp entity which sends out the provisional response. In the 
first track, is it required to maintain the timer for the mgcp entity 
when ever it sends out provisional response...?

The answer for the above question can have two posible cases :
1.  May be yes, timer need to be considered, because there is always 
doubt on the network relaibility/endpoint state...and like wise...issues..

2. Or even I feel I need not have any timer when I send out the 
provisional response , because the same entity is going to send the 
final response...which also includes the whole of the provisonal 
response and the timer is well( max of 30 sec) defined for this final 
response in the RFC .

Flemming ! which could be the optimal and correct way that you suggest 
in this regard .

Please send me your comments on my understanding of this concept.

Thanks
Venkat

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From: Venkataramana cuddapah <[email-masked]>
Date: Tue, 27 Nov 2001 10:09:32 +0530

Hi Flemming Andreasen ,

Thanks
Venkat

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From: Flemming Andreasen <[email-masked]>
Date: Tue, 27 Nov 2001 22:19:33 -0500

Venkataramana cuddapah wrote:

> But  "LONGTRAN-TIMER" is for the mgcp entity( call agent or gateway)
> to start, when it receives the provisional response for its request,
> such that it could wait for the final response..This timer value will
> be higher than the normal retransmition timer. Please correct if I am
> wrong in my understanding...

You are correct.

> But, I doubt , if the same timer could be used by the mgcp entity
> which sends out the provisional response. In the first track, is it
> required to maintain the timer for the mgcp entity when ever it sends
> out provisional response...?
>

Correct again. The only transaction timer the entity sending the
provisional response needs to maintain is the maximum transaction time
which you can reasonably approximate as T-HIST minus T-MAX. If the
transaction execution time exceeds this, you will have to abort it and
send back an error response (which of course has to be sent reliably).

> doubt on the network relaibility/endpoint state...and like

See above. Also, once the final response is sent following a provisional
response, time-out and retransmission apply to the final response since
it is sent reliably (requires a response acknowledgement).

> response and the timer is well( max of 30 sec) defined for this final

Right.

-- Flemming

--
Flemming Andreasen
Cisco Systems

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From: Flemming Andreasen <[email-masked]>
Date: Tue, 27 Nov 2001 22:19:33 -0500

You are correct.

Right.

-- Flemming

--
Flemming Andreasen
Cisco Systems