In LMA, the DL/UL RTP Packet Headers parameters can be extremely useful in analyzing RTP communications, but the difference between parameters under the All tab and Event tab is not immediately obvious.

The difference between these tabs is that the parameters under All are generated for every RTP packet sent/received by the device, whereas the parameters under Event are only generated when a specific event occurs. These events are usually issues with the RTP packets, such as when packets arrive out of order or when packets go missing. If there are no such events during a test, then none of the parameters will populate, and the Event tab will be greyed out.

Lets watch this in action. Below are four RTP DL packets from a real world test case. Because of physical layer issues, packet 56438 was never received by the device, triggering a Packet Missing event.

The RTP Gap (All) (sec) parameter, under the All tab, calculates the RTP gap for every received packet, meaning it calculates the gap between the incoming packets every time one is received. In contrast, the RTP Gap (sec) parameter only populates when a missing packet event occurs, so it only populates for packet 56439, since that is the next packet after packet 56438 was skipped.