eMDI Detection Indicators

Packet Loss Rate

As shown in Figure 1, eMDI detects packets with sequence numbers 1 to 20. The packets with sequence numbers 4 and 6 are two consecutive packets. That is, the packet with sequence number 5 is lost. The packets with sequence numbers 9 and 12 are two consecutive packets. That is, the packets with sequence numbers 10 and 11 are lost.

During the detection period, 17 packets are received and the total number of lost packets is 3. Therefore, the packet loss rate is (3/20) x 100% = 15%.

Figure 1 Packet loss

Out-of-Order Rate

As shown in Figure 2, eMDI detects packets with sequence numbers 1 to 20. The packets with sequence numbers 6 and 5 are two consecutive packets. That is, the packet with sequence number 5 is out of order. The packets with sequence numbers 13, 10, 11, and 12 are four consecutive packets. That is, the packets with sequence numbers 10, 11, and 12 are out of order.

During the detection period, 20 packets are received and the total number of out-of-order packets is 4. Therefore, the out-of-order rate is (4/20) x 100% = 20%.

Figure 2 Packet out-of-order

Jitter

Currently, eMDI supports collection of the jitter indicator in all scenarios. However, the collected jitter indicator is sent to uTraffic only in some specified scenarios. The analysis result of the jitter indicator can be displayed in a trend chart.

Figure 3 Jitter calculation

Jitter indicates the average deviation of the interval over which a packet is sent and received. The jitter is calculated based on the timestamp in an RTP packet header. As shown in Figure 3, S indicates the timestamp in an RTP packet header and R indicates the time when a packet arrives. For packet i and packet j, the calculation formula for deviation is D(i, j) = (Rj - Sj) - (Ri - Si). The calculation formula for the jitter (J) is as follows:

J = J + (|D (i - 1, i)| - J)/16