If you've lived in China, you may have accepted bad call quality when calling overseas via Skype or even a paid SIP service. There are 2 ways you can guarantee excellent call quality from China, within China and overseas with low-cost calls.

Our teams of engineers in Guangzhou have been working on figuring out the issues with most SIP providers, both inside and outside the country when using them to call from China itself and have concluded that it is possible to solve the problem.

From our findings the poor quality SIP, VOIP call traffic, which operates on ports 5060 and 5061 are to do with a progressive throttling of the packets as the call goes on. When the calls start, and this is common among all VOIP providers; the call quality is only good when the IP address that the client is connected to in China has just been issued (the router has been reset, or dynamic ips are usually reset every 24 hours). As time goes on, port 5060 and 5061 traffic is tethered, packets are dropped progressively up to around 40% packet loss meaning call quality degrades too far to make a reasonable call.

It's a clear issue among all the providers we tested, see below:

The above call quality is defined in terms of average packet loss from within China to outside China SIP termination servers. The packet loss effects calls immensely with choppy parts of the call and sometimes a second or two with no voice at all. This happens both on the outgoing and incomming call. It's important to note, this does not happen when we tested calls originating from outside of China, where packet loss was below 5% in most cases.

The issue lies in the China -> Outside China internet connections and can be avoided in the following cases:-

1. China based VOIP company: Ukxin.com They run a commercial tunnelled connection from their China SIP servers to the USA and carefully handle their data lines in either country to ensure good call quality. Their packet loss from our China servers tested over 50x calls was 2.33%. Calls to all parts of the world were acceptable quality.

2. Host your own local SIP/VOIP server and tunnel VOIP traffic over a VPN to your own servers outside of China. Then re-route SIP traffic to the nearest SIP server. We set this up within our own infrastructure and had notably reduced poor call quality.