What is network jitter?
How Does Network Jitter Impact Application Performance?
Network jitter, a.k.a. packet delay variation (PDV), is a stuttering like effect in signal quality because of inconsistent packet delays in a data transmission. Each packet in the transmission may be routed differently to its destination causing packets to arrive out of order or not at all (called packet loss). Though technology will handle this situation and put the packets back in order, it does cause delays. To illustrate the impact, in cases of high jitter video calls or VoIP, users will experience stuttering video, intermittent voice or dropped calls when speaking to others over the internet.
How is network jitter measured?
Closely related to network latency, jitter is a measurement of variation of delay in a data transmission characteristic of packet-switched networks. Jitter is measured in milliseconds (ms). A simple way to calculate jitter is with the following formula:
For example, we could calculate the following seven data point ping sample to find the AvgJitter:
Ping sample set (ms): 115, 136, 184, 163, 127, 177, 192
First, find the differences between each consecutive ping sample.
|Latency 1||Latency 2||Difference (ms)|
Second, average the differences. Remember to divide the total of the differences by 6 not 7 for the correct average (7 is the number of ping samples, but there are only 6 differences):
21+48+21+36+50+15 = 191 ms total of differences
191/6 = 31.83 ms
What is a good average jitter?
In Microsoft’s view an average network jitter exceeding 30 ms is considered a “poor call”. So comparing our sample above, we see that 31.82 ms is a poorly performing network.
Application Performance and Network Jitter
Poor network jitter is a real concern for real-time application performance. The quality of a VoIP experience, for instance, quickly deteriorates when jitter is high. This results in choppy calls, and if packet loss is too great, delayed or dropped signals.
Packet loss is when there is overload of network traffic and routers begin discarding data packets in an attempt to manage network latency. Dropped packets will then need to be requested again adding to the delay.
Network congestion is the main cause of packet loss. When routers are unable to direct the flow of network data they buffer packets to relieve traffic. If congestion increases then the overloaded routers begin dropping packets, usually when latency exceeds a delay of 100-200 ms.Any or all of the following can contribute to network congestion:
- Exceeding the network’s bandwidth: e.g. simultaneous downloading, streaming, and multiple VoIP sessions
- Inadequate hardware: incompatible, outdated, or damaged network hardware can cause bottlenecks
- WiFi’s signal: walls and other impediments block radio signals causing packet loss
- Software configurations: bugs and improper configuration of network hardware software can cause packet loss