On our office network (26 people), some users have complained of poor Skype call quality, particularly in the upstream direction. I wanted to ask, how do I identify Skype traffic, considering that it uses a random port, in order that I might prioritise it at the router level?
If your computers are on a Windows domain , you can use group policy QoS settings to assign DSCP values to traffic generated by the Skype executable file (skype.exe)(actually, you can do the same with local policy on a workgroup computer, you just might need a registry key added too). DSCP 46 I believe is what's usually used for expedited forwarding. Then you'd need to get QoS setup on any switches and routers the traffic will traverse so that it will honor the DSCP ef markings.
You can match skype traffic in a class-map using the configuration below on Cisco routers. To do this, the router uses a feature called NBAR (it looks at layer 4 and higher information in the packet to determine the application.)
Once matched, you can then give that class higher priority like this:
I'm sure other vendors offer similar functionality, but I can't really say for sure.
I think you are right; Skype uses random non-common outbound ports (greater than 1024) for each session which makes QoS tagging problematic
But you can use QoS for SIP and provide voice data priority as long as you have SIP Quality of Service-based hardware.
protected by Sven♦ Jun 15 at 8:54
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