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Cisco ONS 15454 SDH Reference Manual, R5.0
April 2008
Chapter 7 Card Protection
7.1.2 1:N Protection
Figure 7-2 ONS 15454 SDH Cards in a 1:N Protection Configuration
7.1.2.1 Revertive Switching
1:N protection supports revertive switching. Revertive switching sends the electrical interfaces back to
the original working card after the card comes back online. Detecting an active working card triggers the
reversion process. There is a variable time period for the lag between detection and reversion, called the
revertive delay, which you can set using Cisco Transport Controller (CTC). For instructions, refer to the
Cisco ONS 15454 SDH Procedure Guide. All cards in a protection group share the same reversion
settings. 1:N protection groups default to automatic reversion.
Caution A user-initiated switch (external switching command) overrides the revertive delay, that is, clearing the
switch clears the timer.
7.1.2.2 1:N Protection Guidelines
Several rules apply to 1:N protection groups in the ONS 15454 SDH:
• Working and protect card groups must reside in the same card bank (A or B).
• The 1:N protect card must reside in Slot 3 for side A and Slot 15 for side B.
• Working cards might sit on either or both sides of the protect card.
The ONS 15454 SDH supports 1:N equipment protection for all add/drop multiplexer configurations
(ring, linear, and terminal), as specified by ITU-T G.841.
Timing, Comm., and Control
Cross Connect
AIC-I (optional)
Cross Connect
Timing, Comm., and Control
Working
Working (not electric)
Working
Working
Working
Working (not electric)
Working
Working
Working
Working
1:N Protection
1:N Protection
1:N Protection
83625
FMEC
FMEC
FMEC
FMEC
FMEC
MIC-A/P
MIC-T/C/P
FMEC
FMEC
FMEC
FMEC
FMEC
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