EXFO FTB-8100 Series Transport Blazer for FTB-500 - Manual (Page 439)

Advanced Tabs
SONET/SDH Application 425
Round Trip Delay (RTD)
Round Trip Delay (RTD)
Press TEST, and SDT/RTD.
Round Trip Delay (RTD) measurements are needed to quantify the time it
takes for the signals to reach their destination. Usually, transport delay is
due to two factors: long configured paths and transit times through the
network elements along the path. Therefore, RTD measurements are
significant in systems that require two-way interactive communication,
such as voice telephony, or data systems where the round-trip time directly
affects the throughput rate.
Note: To do Round Trip Delay test, the remote NE should be configured to provide
a loopback. However a local DSn test can be configured to use loopback
codes allowing RTD testing.
Note: Be aware that RTD requires error free operation conditions to provides
reliable results. Therefore, RTD results could be affected by error injection
or error introduced by the network.