CUBE router not sending Reject on G711.codec

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Aug 5th, 2009
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Hello we are running Verizon SIP into CUBE gateways and have run into the following issue:

Verizon's techs are testing with this sequence:

- Call gets connected with G729 codec. Both parties hear each other fine

- Verizon tech sends a fax tone through the line.

- Verizon's gateway sends a G711 request to CUBE gateway, and the call gets distorted.

- If we remove the G711 option, the CUBE gateway doesnt respond to the G711 request and the call will drop after 2 minutes.

So on our end, what needs to happen is:

- If Verizon sends us a G711 request, our CUBE router/gateway should send a REJECT back to Verizon, so that the call stays G729, however what the CUBE gateway is doing is just sitting there and not responding, causing Verizon to disconnect the call after 2 minutes because it is not getting a response.

- Upon doing further research, Cisco had come back and told us that the renegotiation issue was fixed in 12.4.20.T2, which is what we are running on all the CUBE gateways.

Any assistance would be much appreciated.

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Nicholas Matthews Wed, 08/05/2009 - 19:53
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Hard to say - the correct configuration would look something like this:

voice service voip

dtmf-interworking rtp-nte

and also either:





midcall-signaling passthru

depending on sip-sip or sip-h323.

then your outgoing dial peers to verizon should look like:

dial-peer voice 100 voip

destination pattern....

session protocol sip

session target...

(no codec listed, as g729 is default)

no vad

fax protocol none

dtmf-relay rtp-nte

incoming called-number.....

For a fax call, the terminating gateway is responsible for sending the switchover request. Thus, it doesn't make sense for Verizon to both generate the tone and send the re-invite request from their side. They should only send a switchover request if the tone is generated from your side of the equipment and you placed the call outbound. Otherwise the gateway may act a little strange to an inbound switchover request for a call it terminated.

ccsip message debugs would clarify.


brandoncheah Wed, 08/05/2009 - 20:45
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I will attach the debug and config tomorrow. The reason Verizon is generating a fax tone is for troubleshooting purposes. They can reproduce the call distortion by sending the fax tone.

I understand for a fax call, the gateway is responsible for sending the switchover request, however in the debugs, it shows the codec renegotiation when they generate the tone.

What i dont get is why the call gets connected successfully at the G729 codec and even though there is a fax tone generated, verizon is sending a G711 codec for renegotiation? Shouldn't a connected call at G729 stay G729, regardless of whatever tone generated after?

Nicholas Matthews Thu, 08/06/2009 - 12:38
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Hi Brandon,

There's nothing in the logs that would indicate that there is a fax switchover going on. Whatever your devices are that have DSPs in this call flow (the PSTN gateway in the SIP provider network and the IP phone) are causing this problem.

Likely, it will be the SIP provider's equipment that is causing the voice quality problem.



brandoncheah Thu, 08/06/2009 - 13:02
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I appreciate your time, Here is the bug ID that i found. Bugs CSCsm34933 and CSCsq01966. However, cisco said it was corrected in IOS 12.4.20.T2

Im trying to get the provider to realize that everything was working fine for at least a few months before the distortion started happening. I am almost positive that Vz patched something on thier gateways, but im stuck here.

Nicholas Matthews Thu, 08/06/2009 - 15:20
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Hi Brandon,

Both of those bugs require for a re-INVITE to be sent. I don't see either in your case, as all I see is a standard call setup that is torn down later.

I'm curious if this upgrade actually does anything for you.


brandoncheah Thu, 08/06/2009 - 15:32
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We already did the upgrade to that version and it was working correctly until Vz did something on their gateways recently, but the previous issues we had were corrected in the IOS i had mentioned.


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