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DSCP for Softphone (Charmed)

Unanswered Question

I want to implement QoS on a LAN with sotfphones attached. The Softphones are actually provided by the CTI bridge application, Charmed, but are use the Cisco TSP utility to link to Windows 2000.


The problem is that the softphone does not mark the TOS or DSCP bits to allow me to identify the voice traffic and prioritise it in the LAN switches. I have had to make a work-around using an IP access-list to identify RTP streams going to the Voice Gateway and the prioritise based on this ACL.


This is not ideal. Does anyone know how to get the softphone to set the DSCP or TOS bits with Windows 2000? I don't know if it is an issue only with Charmed or if this also happens with the Cisco softphone.


Thanks.

Michael

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mowour Tue, 05/20/2003 - 05:33
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Hi Michael,


The Cisco IP Softphone does not mark signalling traffic and this is documented in CSCdz27923. However, Cisco IP SoftPhone should set DSCP for RTP packets to 'ef' (backwards compatible TOS = 5).


Which version of the Cisco TSP are you using?


Regards.

Thanks for the reply,


The control traffic is less of a problem. As for the TSP version, it is the version that came with Call Manager 3.1, I think (I did not set that part up). I mentioned this to the Call Manager administrator, but he thought that he could not use a newer version of TSP with an older version of Call Manager. I thought this was nonsense, but we didn't have a newer version anyway.


Which version would you recommend? Will the Charmed softphone also work with the newer TSP, and will it set the DSCP?


Thanks.

Regards,

Michael

mowour Tue, 05/20/2003 - 09:12
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Hi Michael,


I can't speak to the compatibility between the Charmed Softphone and the Cisco CallManager TSP, but it is true that the Cisco TSP version needs at a minimum to be at the same major version as the CallManager in order to match the CTIManager that will control the softphone. Testing would have to be done in order to verify compatibility. For the kind of interoperability assistance you need, you would likely be best served by opening a TAC case in order to have the opportunity to have the traces and debugs evaluated.


Regards.

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