Chapter 1 Getting Started
Test scenarios
18
HST-3000 Ethernet Testing User’s Guide
loopback must be established by issuing a loop up command
on the unit on the near end, or by initiating a local loopback
(LLB) on the far end unit. See Figure 11.
Depending on the application you are running, the far end unit
does the following for each received frame or packet:
– If you are running a layer 2 application, it swaps the
source and destination MAC addresses.
– If you are running a layer 3 application, it swaps the
source and destination MAC and IP addresses
– If you are running a layer 4 application, it swaps the
source and destination MAC and IP addresses, and the
source and destination port numbers.
After swapping the addresses (or port numbers), the unit then
sends the frame or packet back to the near end unit for anal-
ysis.
Terminate tests are typically performed after the loopback is
established to verify connectivity, measure frame and packet
loss, measure round trip delay (latency), and insert and
observe errors.
Figure 11 Soft Loopback at far end
Transport
Network
Location A
Access Element
Location B
Access Element
HST-3000
R/T 2R/T 1
Rx Tx Rx Tx
HST-3000
R/T 2R/T 1
Rx Tx Rx Tx
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