The Round Trip Time (RTT) indicates the time that packets need to travel from source to destination and back. High round trip times in audio communication may cause the calling parties to frequently interrupt each other. The test checks if the RTT is within the required limits.
The round trip time is very low and has no impact on the call quality.
The round trip time is higher than expected, but has little impact on the call quality.
The round trip time is too high and will impact the call quality. This may be due to issues with the call routing or severe issues in the network.
The round trip time could not be determined, e.g. because RTCP packets could not be exchanged between the endpoints of the call.