UDP Jitter Test (NQA)

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A UDP jitter test is used to calculate the packet delay, jitter, and packet loss ratio using timestamps carried in UDP packets. Jitter is time offset of the interval between the receipts of two consecutive packets minus the interval between the transmissions of the two packets. Figure 2-6 illustrates a network on which a UDP jitter test is performed. The UDP jitter test process is as follows:

The NQA client (Router A) sends packets to the NQA server (Router B) at a specified interval.
Upon receipt, the server adds a timestamp to each packet and loops the packets to the client.
The client subtracts the interval at which packets are sent from the interval at which packets are received. The client then obtains the jitter time.

The following indexes can be calculated by the client:

Maximum, minimum, and average jitter values of the packets exchanged between the client and server
Maximum one-way delay time of the packets that the client sends to the server or the server sends to the client

The jitter time reflects the network status.

In a UDP jitter test, you can set the number of packets to be sent at one time in each test instance to simulate a specific service. For example, configure the client to send 3,000 UDP packets every 20 ms to simulate G.711 traffic.

Figure UDP jitter test networking: