Atec EXFO-FTB-8510G - Manual (Page 4)

Ethernet Performance Validation (Cont'd)
BURST (BACK-TO-BACK)
In this test, fixed-length frames are presented at a rate such that there
is the minimum legal separation for a given medium between frames
over a configurable period of time, starting from an idle state.
The back-to-back value is the number of frames in the longest burst
that the DUT/NUT will handle without the loss of any frames.
FTB-8510G
10 Gigabit Ethernet Test Module
LATENCY
For store and forward devices, latency is the time interval starting when the last bit of the input frame reaches the input port and ending when
the first bit of the output frame is seen on the output port. Roundtrip latency is the time it takes a frame to come back to its starting point.
Variability of latency can be a problem. With technologies like VoIP, a variable or long latency can cause degradation in voice quality.
FRAME LOSS
Frame loss is the percentage of frames that should have been forwarded by a
network device under steady state (constant) loads that were not forwarded due
to lack of resources. This measurement can be used in reporting the
performance of a network device in an overloaded state. This can be a useful
indication of how a device would perform under pathological network conditions
such as broadcast storms.
Metro
Network
Metro
Network
X
Number of bytes
Number of bytes
Burst
Burst
Example of burst (back-to-back) test application.
Burst test procedure:
1.
Send a burst of frames with minimum inter-frame gaps to the DUT/NUT
and count the number of frames forwarded by the DUT/NUT.
2. If the count of transmitted frames is equal to the number of frames forwarded, the length of the burst is increased and the test is rerun.
3. If the number of forwarded frames is less than the number transmitted, the length of the burst is reduced and the test is rerun.
4. The back-to-back value is the number of frames in the longest burst that the DUT/NUT will handle without the loss of any frames.
5. The trial length must be at least 2 seconds and should be repeated at least 50 times with the average of the recorded values being reported.
Frame loss test procedure:
1.
Send a specific number of frames at a specific rate through the DUT/NUT to be tested
and count the frames that are transmitted by the DUT/NUT.
2. The frame loss at a particular line rate is calculated using the following equation:
% Frame loss = Transmitted frames – Received frames X 100
Transmitted frames
3. Measurement should be done for different frame sizes.
Metro
Network
Example of frame loss test application.
Example of frame loss test application.
86% frames lost
at 10 Gbit/s
Metro
Network
74% frames lost
at 9 Gbit/s
Metro
Network
Example of latency test application.
Start time:
Return time:
Latency test procedure:
1.
Determine the throughput of the DUT/NUT for each frame size.
2. Send a stream of frames at a particular frame size through the DUT/NUT at
the determined throughput rate to a specific destination.
3. Send a tagged frame after 60 seconds and store timestamp (A). Capture tag
frame on reception side and store timestamp (B).
4. The latency is timestamp B minus timestamp A.
5. The test must be repeated at least 20 times with the reported value being the
average of the recorded values.