Implementation For Bxm Cards; Tiered Management Control; Table 26-1 Bxm Sonet Aps - Cisco BPX-BXM-155-8DX Installation And Configuration Manual

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 26-1 and shown
in Figure 26-2 and Figure 26-3, respectively. APS 1+1 Annex B has the same general layout as shown
in Figure 26-2, except that the active line is called the primary, and the standby line is referred to as the
secondary.

Table 26-1 BXM SONET APS

Tiered Management Control
SONET is defined across three elements, section, line, and path as shown in Figure 26-1 and described
in Table 26-2. 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.
Cisco BPX 8600 Series Installation and Configuration
26-2
APS 1+1 The APS 1+1 redundancy provides card and line redundancy, using the same
numbered ports on adjacent BXM backcards.
APS 1:1 The APS 1:1 redundancy provides line redundancy, using adjacent lines on the same
BXM backcard.
APS 1+1 The APS 1+1 Annex B redundancy provides 1+1 high-speed protection, which can
Annex B be configured only for bi-directional, non-revertive 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.
Chapter 26 Configuring SONET Automatic Protection System
Release 9.3.0, Part Number 78-10674-01 Rev. D0, July 2001