VoIP Spear Blog: News & Noise

How to Measure VoIP QoS

Nov 25, 2008 8 Comments

Oftentimes, I hear people mention bandwidth when speaking about VoIP QoS (Quality of Service). There seems to a common misconception that bandwidth is the key factor in determining the quality of voice over a network. In reality, this is not true. It's of course important to have enough bandwidth for your VoIP needs, but there are other important qualities of your Internet connection that affect VoIP QoS -- packet loss, latency, and jitter.

The Internet works by breaking up all data into small groups called packets. Occasionally, some of these packets are lost in the network and don't reach the far-end. This is called packet loss and results in degradation to the quality of your phone call. Ideally, you would want packet loss to be 0% (or at least under 1%), however it's possible for you to experience acceptable VoIP quality with packet loss as high as 5%.

Latency is the amount of time it takes data packets to travel through travel through the network. For most calls in North America, latency is very low (less than 100-150ms even on the public Internet). This is excellent and makes for good quality calls. On the other hand, calls to overseas numbers may have latency in the 250-350ms range or sometimes higher. At these levels of latency, the quality of the call is affected. The callers will start to notice the delay. Fortunately, most overseas callers have been conditioned to expect this type of delay and are comfortable with it.

Jitter is the variation in the inter-arrival time between packets. In other words, jitter is the consistency of the network -- is it consistently feeding packets to the far-end? Jitter of less than 20ms is usually expected for good quality connections. When jitter is high, it means that some packets have higher latency than others. This may cause the packets to arrive too late and be discarded by the other nd of your phone call.

At VoIP Spear, we monitor packet loss, latency, and jitter in order produce the most accurate QoS score we can. Try our Personal plan today. It's free to use and we know you'll find it useful.

8 comments on How to Measure VoIP QoS

Graves On SOHO VoIP » VoIP Spear: New VoIP Q says: Posted on Nov 29, 2008

[...] We’ll see just how useful the monitoring service might be. The companies blog has a interesting initial post describing the significance of various network measurement to VoIP QoS. [...]

VOIP quality at 128kbps - Voxilla VoIP Forum says: Posted on Dec 7, 2008

[...] that affect speech quality. You also need to consider packet loss, latency, and jitter. I have a blog posting going over this at a high level, if you're interested. You can use a service like [...]

KrisBelucci says: Posted on Jun 2, 2009

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sandraraven15 says: Posted on Sep 9, 2009

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