Subject: [Megaco] Handling of terminations for call forwarding scenarios

From: "Colin Smith" <[email-masked]>
Date: Thu, 26 Apr 2007 16:06:33 +0100

Hi,

I would appreciate your insight into the correct procedures to be followed
in managing terminations for PSTN-originated calls that have been forwarded
from the IMS domain to the PSTN.

My thinking is that, since the SIP session remains the same, the existing
context should be maintained. The termination representing the forwarding
leg should be subtracted and on receipt of the re-targeted INVITE a new term
added to reserve the PCM resources out to the PSTN for the forwarded leg.

Does this align with the procedure you envisage or do you have an
alternative proposal? Is there documentation any where that references the
correct procedures in this instance?

Cheers,

Colin Smith

21COM Systems

Tel: +44 7782 333 314

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From: [email-masked]
Date: Fri, 27 Apr 2007 17:41:57 +0200

Colin,

see my responses inline.

Albrecht

                      "Colin Smith"                                                                                                     
                      <colin.smith@21c         To:      <[email-masked]>                                                               
                      om.co.uk>                cc:                                                                                      
                                               Subject: [Megaco] Handling of terminations for call forwarding scenarios                 
                      26.04.2007 17:06                                                                                                  

Hi,

My thinking is that, since the SIP session remains the same, the existing
context should be maintained.

[ABS] Yes. Also because the half call from PSTN-originated side may remain
in the context ("no need to move that TDM Termination to a 2nd context").

The termination representing the forwarding leg should be subtracted and on
receipt of the re-targeted INVITE a new term added to reserve the PCM
resources out to the PSTN for the forwarded leg.

[ABS] Yes. The ephemeral Termination is subtracted and a new TDM
Termination is added.

[ABS] Don't know. You may have a look at TISPAN IMS or 3GPP IMS specs,
perhaps 29.163 could be a starting point ...

Cheers,

Colin Smith

21COM Systems

Tel: +44 7782 333 314

specifically stated.   All liability for loss or damage caused by viruses
is excluded.

---

From: "Colin Smith" <[email-masked]>
Date: Mon, 30 Apr 2007 09:22:39 +0100

Albrecht,

Thanks for the quick response. Prior to my e-mailing the Megaco group I had
searched the TISPAN and 3GPP standards for an answer to the forwarding
conditions at the MGCF. Unfortunately TS 29.163 and others do not yet extend
to cover the forwarding cases - possibly because CDIV remains fluid in the
standards?

A further reasonable assumption I have to make is that the trigger for the
subtraction of the forwarding termination is the receipt of the 181 response
code at the MGCF - does this make sense to you also?

Having gone so far to fill what appears to be a gap in the definition, would
it also make sense to document our discussion publicly and submit to the
appropriate body for consideration?

Cheers,
 
Colin Smith
 
21COM Systems
 
Tel: +44 7782 333 314

-----Original Message-----
From: [email-masked]
[mailto:[email-masked]] 
Sent: Friday, April 27, 2007 4:42 PM
To: Colin Smith
Cc: [email-masked]
Subject: Re: [Megaco] Handling of terminations for call forwarding scenarios

Colin,

see my responses inline.

Albrecht

                      "Colin Smith"

                      om.co.uk>                cc:

                                               Subject: [Megaco] Handling of
terminations for call forwarding scenarios                 
                      26.04.2007 17:06

Hi,

Cheers,

Colin Smith

21COM Systems

Tel: +44 7782 333 314