Cisco BPX 8650, Installation And Configuration Manual

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25-2
Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 25 Configuring SONET Automatic Protection System
Tiered Management Control
If the “Revertive” option is enabled, ( cnfapsln command), the hardware automatically switches back to
the working line from the protection line after a configured time period called “Wait to Restore”
(
cnfapsln command) has elapsed. The working line must be in a clear state for this to occur. The
revertive option is the default for APS 1:1 but not for APS 1+1.
Coordination between the two ends of the line is accomplished using the in-band protocol.
During setup, the commands addapsln , cnfcdaps , and cnfapsln are used to create the line-redundant
pair. Also, appropriate front cards, back cards, and a special RDNT-BP daughter backplane are required
for APS 1+1 configurations.
During operation, signal failure or signal degradation can cause APS “switchovers”. A switchover is
when the line that was active gives up control to its partner line. This partner line now becomes the
“active” line, while the original active line becomes the “standby” line.
Implementation for BXM Cards
Automatic Protection Switching provides a standards based line-redundancy for BXM OC-3 and OC-12
cards. With Release 9.2, the BXM OC-3 and BXM OC-12 cards support the SONET APS 1+1 and APS
1:1 standards for line redundancy which is provided by switching from the working line to the protection
line.
The working line is normally the active line, and the protection line is normally the standby line.
The APS 1+1 and APS 1:1 protocols that are supported by the BXM are listed in Table 25-1 and shown
in Figure 25-2 and Figure 25-3, respectively. APS 1+1 Annex B has the same general layout as shown
in Figure 25-2, except that the active line is called the primary, and the standby line is referred to as the
secondary.
Tiered Management Control
SONET is defined across three elements, section, line, and path as shown in Figure 25-1 and described
in Table 25-2. An advantage of this tiered approach is that management control can be exercised at each
level, for example at the section level independent of the line or path level.
Note
APS on the BPX requires the use of single mode fiber, not multi-mode fiber, on both ends of the
trunk. The PXM cards on any connected MGXs should also be single mode fiber.
Table 25-1 BXM SONET APS
Protocol Description
APS 1+1 The APS 1+1 redundancy provides card and line redundancy, using the same
numbered ports on adjacent BXM back cards.
APS 1:1 The APS 1:1 redundancy provides line redundancy, using adjacent lines on the same
BXM back card.
APS 1+1
Annex B The APS 1+1 Annex B redundancy provides 1+1 high-speed protection, which can be
configured only for bidirectional, nonrevertive protection switching. For Annex B, the
active line is referred to as the “primary section” and the standby line is referred to as
the “secondary section”. Manual switching (switchapsln) is not allowed in the APS
1+1 Annex B implementation.