Latency for VoIP explained-Troubleshooting your Internet to improve VoIP quality [Tutorial]

Today, we continue our discussion on improving the quality of your VoIP experience. In our earlier article on trouble shooting your VoIP connection, we discussed the importance of our Internet connection in determining the quality of your VoIP experience. However, we brushed some details under the carpet. In this post, we will explore some of the parameters related to your Internet connection that are crucial for providing crystal clear voice quality. If you are facing problems with your VoIP connection (feedback, choppy voice, delay, echo, etc.), chances that it is because of some of the factors discussed here. Communication over a network is a complex process made possible by some very intelligent protocols. Fortunately, as a end user, we do not have to worry about the technical details. However, here are few factors that may affect your VoIP experience:

1. Internet connection Speed: This is probably the most obvious factor. In general, higher your Internet connection speed, better your VoIP experience will be. But this does not mean that you need to use the most expensive Internet connection. For a satisfactory VoIP call, you need about 100kbps connection. Obviously, if you use wideband VoIP codecs (e.g., G.722), this figure will go up.

2. Firewall or VoIP Port Blocking: The SIP protocol that is used for VoIP communication uses a fixed set of ports. If for some reason these ports are blocked, you you may not be able to communicate with your VoIP server. This may lead to several problems, including registering with your VoIP provider, one way audio, and no audio, among others. ISPs sometimes block VoIP ports due to legal requirements (e.g., VoIP is not allowed by law in several countries, such as UAE, Dubai), to save bandwidth, or to promote their own VoIP services.

3. Packet Loss: This refers to loss of data packets during transit. When you make a voice call, your voice is converted into packets, which are then transmitted across the network. Each packet consist of a small portion of what you speak. If any of these packets are lost during transmission, that portion of message is lost. Packet loss is not a serious threat for data transmission, as the protocol (e.g., TCP/IP) is designed to take care of such situations by asking the information again. However, this can be a serious issue for voice conversation and may lead to choppy voice or complete loss of audio, depending on the severity of the situation.

4. Latency: In very simple terms latency is the time lapsed from the moment a voice packet leaves the source to the moment it reaches the destination. As can be obvious from the definition, higher latency leads to delays. This delay can ultimately lead to feedback or echo, thereby degrading the quality of voice call. Latency is usually expressed in milliseconds and and in general lower the latency, better the quality. Zero latency, while theoretically possible, is practically not achievable. However, you will start noticing the delay only around 150ms – 200ms. Anything greater than 200ms can be very annoying.

How to diagnose your Internet connection?

There are several tools available on the internet that can provide you the above information. However, I like to use the one provided by Bandwidth.com. Here is the result of the test that I ran on my WiFi network.

As you can see from the above results, there is no firewall problem to the server. My computer can connect to the VoIP server. Further, the latency is well within the acceptable range. There is no packet loss and the speed is also very good for a VoIP call. Thus, from the above results, it seems that I should have good VoIP experience on this network (which I do ).

How to troubleshoot your Internet connection for VoIP?

Fortunately, my Internet connection supports VoIP. What if your results are not as good as the ones above? Here are some tips that could help you get the desired results.

1. If you are using a wireless router, try using a wired connection to your computer or ATA. The interference from other signals may affect your network.
2. If you are behind a router or a switch and facing latency issues, it may help to do a power cycle. Just turn off your router for 10-15 seconds and then turn it back on. This usually works for me.
3. Make sure that your cables or adapters are not damaged. This may lead to high packet loss.
4. You may also want to dedicate all the available bandwidth to your VoIP application. If you are behind a router, you can adjust your QOS settings so as to give priority to your VoIP applications. If you are not using any router or switch, suspend other bandwidth heavy applications, such as online games, streaming media.

If none of these help, try our earlier tutorial on troubleshooting your VoIP connection. If your ISP is blocking your VoIP traffic, you may want to read how to use proxy server to bypass ISP ban on VoIP calls.

Related posts:

1. How to change your Router settings for the best VoIP performance? [Tutorials]
2. How-to troubleshoot your VoIP connection? [Tutorial]
3. Why Mobile Carriers should adopt Mobile VoIP or VoIP over 3G? [Opinion]
4. mVoIP – All you need to know about mobile VoIP [Tutorial]
5. Use VoIP to save money during the admission process [Tutorial]