[cisco-voip] Forwarded Calls drop after 29 secs

[Mark Holloway]

The issue with 'call drops on forwarded calls' is usually a result of the PBX treating the forwarded portion of the call as a totally separate call leg from the originating call into the PBX and the PBX is not providing a progress indicator to the telco switch for the original call leg until the second call leg is answered.  The telco switch will timeout if it doesn't receive a progress message and drop the call because there has been no acknowledgement to the original call setup.  The reason it may not happen 100% of the time is if the forwarded call to the PSTN is setup or answered fast enough, the PBX will notify the original call leg know the call has been answered or there is ring back.  Depending on the far end carrier your are forwarding calls to, it may work in some instances but not others.  Proper PBX behavior is when calls are forwarded from the PBX to the PSTN, the PBX should provide SIP Diversion or ISDN Progress Indicator on the original call leg so the telco switch does not timeout.  Carriers who are using Sonus, Broadsoft, Metaswitch, often make static changes in their switch to work around this problem, but the PBX is still doing it wrong. 



On Jan 23, 2010, at 3:20 PM, James Buchanan wrote:

> I had the same issue once. The SIP provider’s provider was killing the call at thirty seconds.
>  
> James Buchanan, CCIE #25863
> Senior Network Engineer
> Coleman Technologies, Inc.
> 12 Cadillac Drive, Suite 130
> Brentwood, TN 37017
> (615) 866-5729
>  
> From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Jim Skelton
> Sent: Friday, January 22, 2010 2:46 PM
> To: Joel Perez
> Cc: cisco-voip at puck.nether.net
> Subject: Re: [cisco-voip] Forwarded Calls drop after 29 secs
>  
> Hi Joel,  I had a similar issue.  I would see our calls drop after exactly 30 seconds.  It turned out to be an issue with our carrier TimeWarner telecom and thier Oakland SIP switch.  We repointed to thier North Carolina SIP switch and everything cleared up.   TW is running Sonus switches.
>  
>  Our setup with twtelecom is Carrier---sip---CUBE----h323---CUCM
>  
> Hope this helps.
>  
>  
>  
> Jim Skelton
> Halliburton
>  
> 
> 
>  
> On Fri, Jan 22, 2010 at 1:13 PM, Joel Perez <tman701 at gmail.com> wrote:
> Hey Guys,
>  
> I have a customer that is experiencing a weird issue.
> Currently some of their forwarded calls are failing after 29 secs. I believe it is only happening when the calls are forwarded to 2 specific carriers, but cant confirm that yet.
> I have a ticket open with the carrier so that they can take a look at the traces we have captured.
> The issue happens the following way. Inbound call to main company DID goes to an AA, if no choice is used by the caller then it goes to a live person. However afterhours this live person forwards their call to an offsite #. When that offsite # receives the forwarded call they are only able to stay on for 29 secs then the call dies on both ends.
>  
> THe set up is as follows:
> Carrier---sip---CUBE----sip---CUCM---sccp---IPT
> CUCM is 7.0
> Unity is 7.0
> CUBE is 12.4.(20T4)
>  
> I have tried capturing debugs on the CUBE but havent been able to see any SIP (BYE) messages from either side.
> This only happens when Unity is involved. Normal CFW doesnt have this problem.
>  
>  
> Thanks,
>  
> Joel P
> 
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