JDS Uniphase IP Video Test Option HST-3000, User Manual

Page: 109 / 356

Chapter 3 Ethernet Testing
Loopback testing
HST-3000 Ethernet Testing User’s Guide
87
Loopback testing
Loopback testing allows you to transmit Ethernet, IP, or TCP/
UDP traffic from one HST-3000 (or another JDSU Ethernet
test set), and then loop the traffic back through a second unit
on the far end of a circuit.
When configuring a loopback test, you can now select a
Unicast loopback type to loop up a specific test instrument on
the far end, or a Broadcast loopback type to loop up the first
instrument on the network that responds.
Using the Local
Loopback
feature
You can manually perform a local loopback by selecting the
LLB action on the far end unit to loop frames back to the traffic
originating HST.
The loopback unit always uses the labels specified for the
transmitted traffic; therefore:
– If your near-end unit is in LLB mode and is configured to
transmit traffic with a second MPLS label, but the unit’s
link partner is configured to transmit traffic with a single
label, the out of sequence and lost frames counts
reported by the module's link partner may increment if the
incoming frame rate is too high.
– If your near-end module is in LLB mode, and is configured
to transmit traffic with a single MPLS label, but the
module's link partner is configured to transmit traffic with
more than one label, the near-end module’s receive band-
width utilization will exceed its transmit bandwidth utiliza-
tion.
NOTE:
You can not start an RFC script, or generate traffic when
your instrument is in LLB mode. Your instrument simply
loops received traffic back to the source test instrument.