[shownow]

I am in China now,the calls made to north america seems ok,but if I make a call to local phone in Beijing,the latency is noticeable. I can always hear clearly,but the quality of the other end is barely acceptable.
I tried sipphone.com ,it has a one minute free call,I have to say it is much better at least in my situation.I guess the latency problem is from outbound proxy,the calls I made to chines local phones has to travell back to U.S. first then redircted to China.
Is it possible that I don't use OB to make calls ?

[mberlant]

Yes, you will experience latency when your call needs to travel halfway around the world to reach your VoIP service provider and then return halfway around the world to a Chinese telephone. About all you can do is continue to test out other providers in various parts of the world to see which one offers the balance of latency vs. cost that suits you best.

[rizsher]

If you forward hte following ports to the IP of the SPA, you can do away with the Proxy. 5060-5065, 16200-16500; do't know if it has any effect on sound quality, but forwarding these lets u register and make/receive calls with the ob proxy.

[mberlant]

Forwarding ports may help you, but only if you are in complete control over all of the VoIP clients behind the particular NAT router you are using. For example, if you forward ports 5060-5065 and 16200-16500 to device A and device A only uses 5060 and 5061, then device B will not be able to receive any calls when it grabs port 5062 for its registration, nor hear the other party if device B negotiates for a voice channel anywhere between 16200 and 16500.

As long as you have administrative rights to the router you are using and you are the only VoIP device behind that router you wll avoid this conflict.