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Voice quality problem

Unanswered Question
Mar 1st, 2012
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Hello Guys,

We have a problem on our voice network, the voice quality for phone 7937G is not good.

Ou network is fully configured to categorized voice with DSCP 34 (AF41) and Cos 5 (Binary 101). We did some traces and test see below:

We sniffed the voice traffic of phone 9951 (work fine) and 7937G

- 9951 --> DSCP 34 (AF41) and Cos 5 (Binary 101) --> voice quality accros wan is excellent.

- 7937G --> DSCP 34 (AF41) and Cos 4 (Binary 100) --> quality not good enough.

Could explain me why the Cos value is different for these kind of phone ? In the enterprise parameters, all is set for DSCP 34.

Could you help me on this ?


Hervé Jacquemin

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Chris Deren Fri, 03/02/2012 - 07:41
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AF41 is only used for Video, so that's what you may be seeing on 9951 phone for a video call.  Regular voice RTP stream is tagged as CS3, so that is what you need to look for. Some older phones may also tag it as AF31.



hjacquemin Mon, 03/05/2012 - 02:15
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Hi Chris,

The customer's network doesn't "support" standard QOS configuration, that's why he configured all the telephony system with AF41 (DSCP 34). All the phones (7940-41, 7960-61) are using the same parameters and works normally.

So do you know a way to force the 7937 to use COS 5 instead of COS 4 with the DSCP 34 ?




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