sundance-communications.com Forums Telephony Discussion Phone & VoIP Systems Toshiba Telephones & Systems voip problems

We are using a CTX 670 with 2 users using ip phones. One in Indianapolis, one in Houston. They are connecting through a broadband cable connection going through a linksys cable/dsl router and are experiencing poor voice quality, especially choppiness. I am not experienced with Voip and our vendor has been no help in resolving our issue. If you can help please respond. Thanks.

I'm don't work on this system but try changing the jitter buffer to a high number if you have a setting for it. Also try changing codec to g.729a if you have that setting. This sends smaller packets so if some are lost it doesn't get so choppy

have you spoken to the installation technician?
m

I have and they don't seem to know a whole lot. Pretty much all they are saying is that it should work. And have no explanations as to why it doesn't. I would even be happy with suggestions to try but can't even get that.

Tony has a great suggestion. Try using the g729 codec. It's simple to change.

are they using VPN?

No we are not using VPN. We were told by our vendor that wouldn't make a difference.

If the BIPU isn't on a public address outside the router, you need to use a VPN. Definitely go with G.729 and increase the jitter buffer. E-mail me and I'll send you a cheat sheet for programming.

Many "broadband" connections really arent that fast. If there is interfering data traffic and the link speed is under 500 kbits/sec then just the time taken to send a data packet can cause significant delay "bumps".

Increasing the jitter buffer size can help however if the jitter is severe then you may have to use a large buffer size which can increase delay too much.

Using G729A reduces the bandwidth taken by the voice packets but would not affect the bandwidth of data traffic - hence if interference from data is the issue then you'd need to fix that first.

Larger routers support prioritization of voice over data however small consumer class routers don't tend to.

The www.voiptroubleshooter.com site has more information, plus a downloadable IP simulator that you can use to set up the scenario and try different codecs and jitter buffer settings to see what would happen

Alan

VPN is the best way to go we have found so far.

The main issue is your going over the Internet. Once it leaves your building you have no control or guarantee on not getting bottleneck in some router 2 states away.