Traffic Shaping for VOIP on Airport Extreme Router?

[Madhattan]

Hey Everyone,

We have around 20 VOIP phones in our office, and sometimes when everyone is busy, calls seem to get a metallic noise to them.

I contacted the phone company (8x8) and they said that some ports should be opened in the router to help with this problem.

The router is an Apple Airport Extreme. In the advanced tab, there is an area for port mapping, but it looks like you can only open ports for one IP at a time.

Is there a way that I can open 7 UDP ports for the entire DHCP IP Range?

--Thanks

 

[kevnich2]

What kind of internet connection do you have? How many simultaneous calls do you have going during your busiest times? I don't think you need ports forwarded, sounds like you need QOS to give your VOIP packets priority over other traffic. And yes, you can't forward the same port to more than one IP address.

If it's absolutely needed you could use port triggering, but if more than once device is in use at the same time, that also wouldn't do you any good.

 

[Madhattan]

At our busiest, we could have 15 or so simultaneous calls going on at a time. We have business class DSL, i believe it is around 10mb/sec down and 1 or 2 up.

I think you are right about looking into QOS rather than port forwarding.

I think this means that I will have to go with a different router altogether right?

 

[drebo]

QoS isn't going to do you a damn bit of good because your ISP isn't going to honor whatever QoS tagging you employ. What you can do is look in to prioritization.

That said, 20 phones is a lot for a SOHO-class router. Also, whoever told you that forwarding ports would help is a moron. It's more likely to CAUSE problems than to fix them in a hosted PBX environment. But, that's par for the course with 8x8.

You're likely running into jitter issues as you get more and more people on the phone. Priority queuing for RTP packets can help minimize jitter on a busy router, but I wouldn't expect a SOHO router to be able to keep up with it for 15 simultaneous calls.

That said, all the prioritization in the world isn't going to help you if this is just a good ol' case of network congestion. VoIP is not an exact science unless you control the entire network end-to-end.

Grab an ASA5505. You won't be disappointed.

 

[Madhattan]

So I put the Cisco ASA5505 in between the modem and router and configure it to give priority to RTP packets?

 

[drebo]

You get rid of your Airport Extreme and use the ASA as your NAT device.