Vigor 2800G and Skype QoS


Could do with some help. I'm trying to setup QoS on my Vigor 2800G ADSL router to prioritize Skypein and Skypeout traffic. I've set Skype to use port 41726 for incoming connections and I don't see an option for outgoing connections.

On my router I have setup QoS however when I receive a Skypein call it doesn't appear to be using the port that I specified and I can see the traffic coming in as "other" rather than on the port 41726 as expected. I really can't see what I doing wrong?

To complticate things a bit I have a Smoothwall firewall (Express 3) between me and the router. On the router I am forwarding port 41726 to the red interface on the firewall which in turn forwards into onto my pc. I am able to make and receive calls so I assume that this is working correctly as I am not seeing any blocks in the log but I guess skype may be port jumping for some reason.

Can anyone come up with a few ideas to help me troubleshoot this a bit, i'm running out of ideas.


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There is no point trying to configure QoS on incoming traffic as the traffic has already gone over the low speed network so configuring QoS wony have any benefit.
For outgoing Skype uses a random port so you cannot really configure QoS on this.

If you need QoS then your only real alternative is to switch to a standard VoIP provider.
emailjwsAuthor Commented:
Right, OK thats for the feedback.

I agree in part what you are saying about QoS on incoming traffic however I still think it would be useful. There is a lot of P2P traffic on this LAN segment and I think it would be useful to prioritize the traffic to ensure that skype has enough bandwidth to operate correctly. as a side point, why do you think I am not seeing the incoming traffic on the port that I specify in skype?

For outgoing is no way you know off to force Skype to use a particular port? no registry setting or something?

If you applied QoS on incoming traffic you would only be able to control the data flowing onto your network from the internet connection. Since the internet connection is slower than the network QoS will have no effect because it will have no reason to restrict some data flow.
You can apply QoS to outbound data and generally this works well as typically the upstream badowidth is less than the downstream.
However even with this it is still possible for a few people doing large downloads to use up the downstream bandwidth and therefore cause problems. It is possible for a router to detect this and start dropping or delaying response packets to slow down the transfer but this only works for the TCP protocol and is a bandwidth shaping feature and not specifically QoS.

Lots of people are recomended to upgrade their routers to ones which support QoS. Normally it is a much better idea to instead get another internet connection and dedicate it just for VoIP. That way you dont have problems with being unable to control the inbound data rate and dont need QoS at all since it is a dedicated link.

Defining a port for inbound calls should work for calls someone else establishes to you. Skype uses P2P using practically random ports so there is no way of identifying the traffic. In addition they dont appear to support ToS (Type of Service - not terms of service) so you cannot even use that for QoS. Skype is designed to work through firewalls etc... so it does its best to work through proxy servers and hide the data so it cannot be easily blocked.

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emailjwsAuthor Commented:
So basically there isn't anything I can do without getting another DSL link for VOIP then. Unfortunatley not the answer I wanted to hear but what your saying makes sense and you answered my question so thanks very much for that.

All points to you.
emailjwsAuthor Commented:
Just as an after thought, do you have any experience with pfsense? It looks like it can do traffic shaping, might be useful no?
Sorry I have not seen it before. The problem is though how do you define the skype traffic in order to shape it.
emailjwsAuthor Commented:
Yeah good point, ok fair enough, thanks for all your help.
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