[Serusers] Help with attended (consultative) call transfer problem

[Greger Viken Teigre]

Can one Cisco gw do media directly to another gw on the SIP interface?  
I.e. will you see any difference if you proxy the call through your 
rtpproxy?
You don't say anything about how the transfer fails.  As you have an 
existing media session going, it needs to be replaced and you get 
hairpinning of the media.
g-)

Steven C. Blair wrote:
>  
> Hello:
>  
> We have been having persistent problems with consultative (attended) 
> call transfer and I'd like to ask the list for some input.
>  
> We have three Cisco 2821 gateways each with two PRIs connecting to 
> Verizon Centrex service. The route advance sequence defined by Verizon 
> results in all calls entering our VoIP environment entering via 
> gateway #1. If no channels exist calls fail over to gateway #2 and 
> finally #3.
>  
> For load balancing purposes our SER 0.9.7-pre3 proxy will send 
> outbound calls to gateway #3, then #2 and finally #1.
>  
> We are using Cisco 79x0 phones running SIP load 7.3. All other types 
> of calls including blind transfers work.
>  
> Call transfers in which both call legs traverse the same gateway work. 
> Only transfers where each call leg traverses different gateways fail. 
> Given the inbound and outbound routing described above it is easy to 
> see how most transfers fail.
>  
> From a protocol perspective the transfer follows RFCs. I have ethereal 
> traces if anyone needs them.
>  
> Cisco has worked on this problem and is now suspecting that a transfer 
> will only work if both call legs traverse the same gateway. It is 
> unclear if this is technically correct, a configuration issue in our 
> gateway or a mistake.
>  
> To further complicate the issue calls from the PSTN, through a gateway 
> to an IP phone which is transfers to another IP phone on the same 
> proxy work. Failures only happen when the second call leg is to the 
> PSTN and traverse a different gateway.
>  
> Has anyone on this list seen this issue or have any input whatsoever?
>  
> Thanks,Steve
>  
>  
>  
>  
> Senior Network Engineer,
> Information Systems and Computing
> Networking and Telecommunications , Suite 221A /6228
> University of Pennsylvania
> Voice:215-573-8396
> FAX:215-898-9348   
>  
>  
>  
> ------------------------------------------------------------------------
>
> _______________________________________________
> Serusers mailing list
> Serusers at lists.iptel.org
> http://lists.iptel.org/mailman/listinfo/serusers
>   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sip-router.org/pipermail/sr-users/attachments/20080330/d0df482e/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 2844 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://lists.sip-router.org/pipermail/sr-users/attachments/20080330/d0df482e/attachment.bin>