Cisco Cisco ONS 15454 SONET Multiservice Provisioning Platform (MSPP) Guía De Diseño
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Protection Modes
Optical protection switching occurs automatically in response to detected faults, as well as
manual requests initiated by local or remote users. The Cisco ONS 15454 supports 50
milliseconds (ms) 1+1 unidirectional or bi-directional protection switching upon detecting a signal
failure or condition such as LOS, LOF, AIS-L or high BER on one or more of the optical card’s
ports. Revertive and nonrevertive switching options are available down to the circuit level.
The protection modes supported by the Cisco ONS 15454 are described in Table 7-24.
Table 7-24: Protection Modes
Mode Description
Unidirectional
Each ONS 15454 node bridges it’s transmit information on the working and protect lines.
When traffic is switched from a bad line, only the receiving node performs a switch. The
APS channel (which is carried in the K1 and K2 bytes of the signal on the protection line) is
used to indicate the local switch action and the mode of operation. Path Protection
Configuration is the default mode for 1+1 protection groups in the ONS 15454.
When traffic is switched from a bad line, only the receiving node performs a switch. The
APS channel (which is carried in the K1 and K2 bytes of the signal on the protection line) is
used to indicate the local switch action and the mode of operation. Path Protection
Configuration is the default mode for 1+1 protection groups in the ONS 15454.
Bi-directional
Each ONS 15454 node monitors it’s receive bit stream on the currently active path. When a
problem is detected, both nodes transfer their transmit bit stream to the protection line.
Switching of only one direction is not allowed. Head end to tail end signaling is
accomplished using the APS channel. The ONS 15454 Bi-directional Path Switched Ring
(BLSR) protection mode is configured by the user during initial turn up of the ring.
problem is detected, both nodes transfer their transmit bit stream to the protection line.
Switching of only one direction is not allowed. Head end to tail end signaling is
accomplished using the APS channel. The ONS 15454 Bi-directional Path Switched Ring
(BLSR) protection mode is configured by the user during initial turn up of the ring.
Revertive
In revertive mode, a failure is detected and the working line temporarily switches to the
protect line using the K1/K2 bytes. When the working line is restored and meets the BER
criteria, a wait-to-restore (WTR) timer is initiated in the ONS 15454 to prevent “switch
bouncing.” Traffic is switched back to the working line at both ONS 15454 nodes when the
working line has recovered from the failure and the WTR interval has been met, or the
manual switch command is cleared. Traffic will revert back to the working line again using
the K1/K2 bytes. Revertive protection is illustrated in Figure 2-27.
protect line using the K1/K2 bytes. When the working line is restored and meets the BER
criteria, a wait-to-restore (WTR) timer is initiated in the ONS 15454 to prevent “switch
bouncing.” Traffic is switched back to the working line at both ONS 15454 nodes when the
working line has recovered from the failure and the WTR interval has been met, or the
manual switch command is cleared. Traffic will revert back to the working line again using
the K1/K2 bytes. Revertive protection is illustrated in Figure 2-27.
Non-Revertive
In non-revertive mode, the ONS 15454 detects a failure and switches the working line to the
protect line using the K1/K2 bytes. The protect line now becomes the working line and the
previous working line will become the protect line. If the line that failed is restored, traffic will
not switch back. There is no WTR setting for non-revertive switching. Traffic will not be
switched back unless the current working line develops trouble. Non-revertive protection is
illustrated in Figure 2-28.
protect line using the K1/K2 bytes. The protect line now becomes the working line and the
previous working line will become the protect line. If the line that failed is restored, traffic will
not switch back. There is no WTR setting for non-revertive switching. Traffic will not be
switched back unless the current working line develops trouble. Non-revertive protection is
illustrated in Figure 2-28.
The ONS 15454 provides less than 50 ms automatic path, line, and Path Protection Configuration
dual ring interconnect switching as described in GR-1400-CORE and GR-253-CORE.
Electrical Card Protection
The ONS 15454 provides the following electrical card protection methods:
1:1
1:N
1x0
1:1 Protection
In 1:1 protection, a working card is paired with a protect card of the same type. If the working
card fails, the traffic from the working card switches to the protect card. You can provision 1:1 to
be revertive or nonrevertive. If revertive, traffic automatically reverts to the working card after the
failure on the working card is resolved. Figure 7-22 shows the ONS 15454 in a 1:1 protection
configuration.