Soft phone QoS

Unanswered Question
Oct 29th, 2007
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Dear Sir,

We have two network to separate data and voice traffic. But if users have soft phone installed, how can we provide QoS for the voice. And how can we screen the voice and data traffic from the desktop?


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Overall Rating: 4.5 (2 ratings)
sadbulali Fri, 11/02/2007 - 07:11
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The short answer is yes Softphone and IPC will both set the IP DSCP vlaues for RTP packets leaving the PC. It is possible that your switches are configured to not trust the packets leaving the PC and thus the DSCP is being set to 0.

The IP QoS SRND discusses switch qos configuration with untrusted endpoints and softphone. Check out page 2-8 in the pdf at

Aaron Harrison Sat, 11/03/2007 - 04:49
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If you are using any softphone application this leaves you only two options:

1) Trust DSCP in packets from the PCs

2) Mark traffic on ingress with appropriate DSCPs

If using option 1), you will likely still want to use an ingress policy in order to police the QoS assured traffic and mark down excessive traffic from end user PCs.

If using option 2), you can be more strict about markings but should still police ingress traffic using a policy.

AutoQos in recent software releases has the option of using the 'auto qos voip cisco-softphone' command to set up a policy that matches the appropriate traffic and polices it to sensible levels.

Hope this helps.


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