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Old 01-29-2006, 09:34 PM   #1
Registered: Apr 2003
Location: Vail, CO
Posts: 73

Rep: Reputation: 15
QOS for VOIP on Linux

Hi there,

The Linux machine I have is connected to a University network. I have a layer2 tunnel set up between that and a server I have in New York (Openvpn using tap). My server in New York gets about 83 mbit/s up/down. It's a dedicated server in a co-lo. The connection here at the university is about 30 mbit/s. The problem happens when I upload or download to many clients at once, like with bit torrent; my VOIP calls are very choppy. If I hook up the phone to the University network and use bit torrent on that, it works fine, no choppiness. The university has their own form of QOS on their network on those Juniper routers. The problem is when I use the tunnel; they can no longer see my traffic. This is excacly what I wanted. I had enough eavesdroppers with packet sniffers “testing their tools” on my VOIP calls. So now I encrypt everything. Obviously because of this, they now can't prioritize my VOIP traffic. I have to figure out how to do that on my own. I have root access to both servers, so I can modify both of them. I have spent a lot of time trying to figure out how to use tc, and searching about it on Google. I know how to use iptables fairly well. I also know how to set up multiple route tables using iproute2; using it in conjunction with iptables. tc seems like a very complicated software. I have not been able to figure it out. I looked though piles of scripts people have written for it, but it doesn’t apply to my connection. Most scripts already assume what the maximum upload speed is. Both my upload and download speeds are dynamic. Sometimes I can get 28 mbits; but at other times I get no more then 2-3 mbits/s. I need a script that can give priority to my Vonage devices no matter how much bandwidth I have (the minimum is always over 2 mbits). Maybe a script that can see packet loss and latency and work with that instead of bandwidth. Also I have to control the download speed as well. When I download too fast, it also distorts my voip connection. If there is a way to get this script on one server that would be great. But if I need to run them on both I wouldn’t mind either. Pretty much anything to keep my voip connection clear

If you guy can help me with that I would be very thankful

Old 01-30-2006, 12:37 AM   #2
Registered: Sep 2003
Location: Colorado
Posts: 85

Rep: Reputation: 15
Just so I get this straight. You are routing your Vonage traffice through a VPN tunnel between your linux box on campus and linux box at a colo to stop anyone at your campus from eavesdropping on your calls? Traffic shaping works when the VOIP traffic is outside of the VPN? If so then you can figure out what the campus is using to classify/shape the VOIP traffic. Try setting a TOS or Diff Serv value on your VPN packets using IPtables. Try changing the OpenVPN ports to 5060 or 5061.


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