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Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
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Chapter 3 Card Protection
Automatic Protection Switching
The two items above do not apply for a user-initiated soft reset or software upgrade. These resets
are errorless
3.3 Automatic Protection Switching
Unidirectional switching allows traffic on the transmit and receive optical fibers to switch independently.
With nonrevertive 1+1 protection, automatic protection switching (APS) switches a signal after a failure
from the working port to the protect port and the signal stays switched to the protect port until it is
manually switched back. Revertive switching automatically switches the signal back to the working port
when the working port comes back online. 1+1 protection is unidirectional and nonrevertive by default;
revertive switching is easily provisioned using CTC.
3.4 External Switching Commands
The external switching commands on the ONS 15310-MA SDH are Manual, Force, and Lock Out. A
Manual switch will switch traffic if the path has an error rate less than the signal degrade (SD). A Force
switch will switch traffic even if the path has SD or signal fail (SF) conditions. A Force switch has a
higher priority than a Manual switch. In 1+1 mode, however, if there is an SF condition on the protect
line, the SF condition has a higher priority than Force, and Force cannot override the SF condition to
make a switch to the protect line. Lockouts can only be applied to a protect port (in 1+1 configurations)
and prevent traffic from switching to the protect port under any circumstance. Lockouts have the highest
priority. In a 1+1 configuration you can also apply a lock-on to the working port. A working port with a
lock-on applied cannot switch traffic to the protect port in the protection group (pair).