Line protection switching (1+1) occurs automatically in response to detected faults, as well as in response to external commands from technicians at a local or remote CIT or OS. Alcatel-Lucent 1850 TSS-5 provides SONET/SDH standard line protection switching on optical interfaces as a user-provisionable option.
Alcatel-Lucent 1850 TSS-5 supports non-revertive, unidirectional 1+1 line switching protection on the VLNC50/52/55 OC-3/STM-1, OC-12/STM-4, or OC-48/STM-16 interfaces.
When PROT (equipment-protection-allowed) is enabled on the shelf, 1+1 is a supported application and each pair of lines across the boards may be a different rate. The two pairs of lines can have different applications (either 1+1 or UPSR/SNCP).
Alcatel-Lucent 1850 TSS-5 uses standard protection switching priorities as follows:
Lockout of protection
Forced switch (FS)
Automatic switch: signal fail (SF)
Automatic switch: signal degrade (SD)
Manual switch (MS)
Alcatel-Lucent 1850 TSS-5 uses unidirectional, non-revertive 1+1 line switching. Automatic protection switch procedures as specified by the SONET/SDH standards are used.
Automatic line switches are initiated by signal fail and signal degrade conditions on the received OC-n/STM-n signal. This signal's BER is calculated from violations in the SONET/SDH line overhead B2 parity byte. Signal fail is declared for incoming loss of signal, loss of frame, line AIS, or a BER exceeding a provisionable 10-3 to 10-5 threshold, while a BER exceeding a provisionable 10-5 to 10-9 threshold causes the signal degrade condition. A line protection switch is completed within 50 milliseconds of the onset of a hard failure such as a fiber cut.
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