The frame loss test measures the network’s response in overload conditions—a critical indicator of the network’s ability to support realtime applications in which a large amount of frame loss will rapidly degrade service quality. As there is no retransmission in real-time applications, these services might rapidly become unusable if frame loss is not controlled.
The test instrument sends traffic at maximum line rate and then measures if the network dropped any frames. If so, the values are recorded, and the test will restart at a slower rate (the rate steps can be as coarse as 10%, although a finer percentage is recommended). This test is repeated until there is no frame loss for three consecutive iterations, at which time a results graph is created for reporting. The results are presented as a percentage of frames that were dropped; i.e., the percentage indicates the variable between the offered load (transmitted frames) vs. the actual load (received frames). Again, this test must be performed for all frame sizes.