Jitter Calculation

In networking, jitter refers to the variation in the forwarding delay of consecutive packets in a stream. In other words, if packet 1 and packet 2 take a similar amount of time to arrive at the destination, then their jitter is low. If they take very different amounts of time to arrive, then jitter is higher.

Catchpoint's Jitter metric represents the average jitter for consecutive pairs of packets during a test run.

How Jitter is Calculated in Catchpoint

Data from Catchpoint's Ping monitor is used to calculate jitter by comparing the Round Trip Time (RTT) for a series of pings. We take the absolute difference in RTT for each pair of consecutive samples, and then find the average of these differences.

Note that in the event of dropped packets, the dropped packets are skipped and Jitter is calculated using only packets that received a response, as long as they total at least three. (E.G. If Packets A, B, C, D, and E are sent, but packet C is dropped, then the Jitter calculation is performed using just packets A, B, D, and E.) If only two or fewer packets received a response, then Jitter will not be calculated.

Example

Suppose a test run sends five ping packets to the destination, and the RTT values for the five samples are as follows:

9 ms, 5 ms, 3 ms, 6 ms, 7 ms

First, we will find the absolute difference in roundtrip time for each pair of consecutive samples:

We then calculate the average of these differences (divide the sum of the differences by the number of differences)

So for this test run, Jitter would be 2.5 ms.

Additional Examples

The following table shows Jitter calculations for several example scenarios:

Case 4 - no Jitter calculation because only two packets were not dropped
Case 5 - no Jitter calculation because all packets were dropped