"Once the call is answered, your PSTN gateway shouldn't be involved in
the transfer process."

 

Well, I understand it works like this (actually, I checked with my test
system and it does :-). Devices: Snom300, Cisco 2651 ISDn router)

1.      PSTN gateway sends an INVITE to target1.
2.      Target1 answers with OK to the PSTN gateway and establishes the
call
3.      Transfer starts. Target1 sends a REFER to the PSTN gateway with
target2 as Refer-To.
4.      The PSTN gateway INVITEs target2.

 

Since I sent the mail, we made it working with the Cisco. The solution
involved a new dial peer matching the short internal numbers. If the
destination pattern matches the internal numbering plan, the dial peer
sends back the call to SipX. This way the Cisco gateway can handle the
internal SipX users when they are targeted with Refer-To.

 

Funny how much the Cisco gateway does not care about domains.

 

I am interested in experiences with SIP trunks. Do I understand
correctly that the Ingate device handles REFER if the trunk is not able
to?

 

Regards,

Gabor

 

________________________________

From: Tony Graziano [mailto:[email protected]] 
Sent: 25 February 2009 11:08
To: [email protected]; Gabor Paller
Subject: Re: [sipx-users] Best practices for transfer

 

Once the call is answered, your PSTN gateway shouldn't be involved in
the transfer process. When a call is transferred it is handled by the
proxy, and your UA's (phones, target1/target2) should be able to handle
this procedure.

If ANY call comes in from the PSTN and hits an AA, and then can transfer
to an extension successfully, it means your PSTN gateway handles the
refer properly. Once audio is established with a target, you should be
able to tarnsfer repeatedly.

If it is a siptrunking device, Ingate for example, you should make sure
the ITSP supports the feature, and your SBC or siptrunk gateway does as
well.

I has "subsequent transfer failures" with an Ingate using a siptrunk,
but solved it here: http://track.sipfoundry.org/browse/XECS-2098

>>> "Gabor Paller" <[email protected]> 02/25/09 3:58 AM >>>
Hi,

I am curious about the best practices for transferring external incoming
calls.

The scenario is very common: Source (an external number) calls target1
(an internal number, SipX user). Target1 transfers the call to target2
(another internal number). This models a common case of a secretary
transferring calls.

I understand that SIP-wise, the scenario depends on REFER request sent
from target1 device to the device representing the source. As the source
is a PSTN number, the device representing the source is either a gateway
or a SIP trunking equipment which don't know about the target2 internal
number. What is the best way of getting the gateway/trunking equipment
to know about target2?

Regards,
Gabor
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