GSM1010M Gigabit Converter
14
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 TP link input of Network Device A.
The user may verify the integrity of the link segments by switching the LST command
TP>>FO to ON at device C. An idle signal is transmitted to device D that turns ON the
links at devices D and A. (setting LST FO>>TP to ON at device D alone turns On the link
at Network Device A). This scenario is depicted in Fig –2.
The LST ON may be thus used to verify that the tested link segments are intact and
operative and determine the failed link as shown in Figure-2.
The Link alert (Fault Propagation) can be also selected for both directions simultaneously.
(in both devices D and C the LST commands FO>>TP and TP>>FO are set to LST OFF).
If the 1000Base-LX link fails, when the LST is OFF, appropriate signals are transmitted to
both remote Network Devices A and B alerting them that a link failure has occurred.
Figure – 2 LST ON operation (Test Mode =Link Segmentation Test)
The LST operates in the same manner when a GSM1010/MA unit is attached as a
remote device in the above configuration (see Figure –3 next page). In this case
the GSM1010M will behave as a Master Unit, the GSM1010/MA as a remote
managed unit, and the MA management is functional and operative between the
two devices.
The LST commands are set from the management and override the DIP switches
setting. In GSM1010/MA, the LST TP to FO function is not allowed to avoid MA
management failure if the user will inadvertently (or due to malfunction) disconnect
the TP link between Devices C and B. (The DIP switches S3 and S4 in GSM1010/MA
are by default preset to Test Mode (LST ON) to preserve the MA link Integrity).
If the configuration of Figure-3 is in LST OFF mode (via MA LST commands) and
the main FO link fails (1000Base-LX link), the LST OFF will cause a link down
condition at both Network Devices. From the system management we
can set the LST commands to ON for GSM1010M unit, but for the GSM1010/MA,
