GSM1000 Gigabit Converter
13
9 – LST (Link Segmentation Test)
The LST in the GSM1000 is used to notify one Network device upon a link failure in the
other Network device, or in the opposite direction (Fault Propagation).
The setting of the LST switches has absolutely no effect as long as no link failure is
detected. Thus, data is communicated normally.
The LST DIP switches have two positions per data link direction.
S3 controls LST signals from the F/O port 1(1000Base-SX/LX) to Fiber port 2
(1000Base-LX). (See Figure 1 below).
When S3 is in its down position (LST OFF), a link down at the Fiber port 1 switches off
the Fiber output port 2, thus, signaling the other device upon the failure.
When S3 is in its up
position (LST ON), a link down at the Fiber port 1 generates an
idle signal that is transmitted at the fiber output port 2 which does not affect the other
attached device. (provided that the tested link is intact and functional)
S4 controls LST signals from the Fiber port 2 to Fiber TP port 1.
When S4 is in its down position (LST Off), a link down at the Fiber port 2 switches off
the Fiber output port 1, thus, signaling the attached device upon the failure. When S4 is
in its up position (LST ON), a link down at the Fiber port 2 generates an idle signal that
is transmitted at the F/O output port 1 which does not affect the attached device.
(provided that the link is intact and functional)
Default Operation Mode: LST ON (“TEST” mode)
Users that do not require real time alert (Fault Propagation) upon a failure from one
Network device to the other Network device, should set S3 and S4 switches of both
converters in their Up position (LST ON).
Users requiring real time alert (Fault Propagation) upon a failure may define/setup one
direction of alert, or both directions. This can be from Network Device B to Network
Device A
or/and
the other way.
LST Operation
Figure –1 depicts a typical installation when Fault Propagation (LST OFF) from
Network device B to Network Device A is selected.
Switch position: Device C – S3 Down, S4 Up; Device D – S4 Down, S3 Up
Figure-1 Using LST (Link failure notification)
When a link failure is detected between Network device B and device C, it turns off the
transmission of device C, thus, turning Off the Fiber link input of device D. This turns
off the transmission of device D, thus, turning Off the F/O link input of Network device
A. Same events will take place in case the link between Network device A and
GSM1000D has failed (provided that DIP switches S3 (GSM1000D) and S4
(GSM1000C) are in LST OFF mode.
