Maintenance Description
Issue 8.0 July 2002
9-31
Protection Switching 9
High-Speed Protection 9
General 9
The FT-2000 OC-48 Add/Drop-Rings Terminal performs 2-fiber ring protection
switching in response to automatically detected faults in the OC-48 high-speed
lines, as well as external commands from a technician at a local/remote CIT or
operations system. Refer to the FAULT-Switch-Line input in Volume I,
Section 11, "Craft Interface Terminal Usage."
Table 9-3 shows the standard protection switching priorities in descending order
of priority used by the FT-2000 OC-48 Add/Drop-Rings Terminal.
The FT-2000 OC-48 Add/Drop-Rings Terminal uses bidirectional revertive 2-fiber
ring protection switching. Bidirectional refers to when protection switching is
performed in the transmit and receive directions. In revertive 2-fiber ring
protection switching, the traffic switches from the service STS-3 tributaries of an
OC-48 high-speed line to the protection STS-3 tributaries of the other OC-48
high-speed line when a fault occurs. When the fault clears, the traffic switches
back (reverts) to the service STS-3 tributaries.
There are eight STS-3 tributaries carrying service on OC-48 high-speed line 1W
and eight STS-3 tributaries carrying service on OC-48 high-speed line 1E. The
Table 9-3. 2-Fiber Ring Protection Switching Priorities
Switch Priority (Descending Order) Source of Request
Reset* CIT/OS
Automatic protection switch (APS) channel failure†Automatic
Protection hardware failure†Automatic
Lockout of protection CIT/OS
Forced switch CIT/OS
Signal fail Automatic
Signal degrade Automatic
Manual switch CIT/OS
Wait to restore Automatic
* Resetting the line switch priority (FAULT-Switch-Line-Priority:Reset)
has no effect on any automatic switch priority except wait to restore.
†An APS channel failure and a protection hardware failure are the same
priority.
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