Applications
2-16 Issue 8.0 July 2002
In Release 4.1 and later releases, if an incoming DS3 or EC-1 LOS is detected at
the primary node as a result of an incoming signal failure or an interconnecting
node failure in the other ring, the primary node performs an automatic DRI
protection switch. The primary node selects the low-speed signal from the
secondary node as the active low-speed signal, completing the circuit between
the secondary node and the terminating node. In Release 5 and later releases, an
unprotected incoming OC-3 LOS or loss of frame (LOF) also triggers a DRI
protection switch. With Release 7.1 and later releases, an AIS-P will result in a
DRI protection switch.
In Releases 4.1 through 6.0.2, the DRI cross-connection switch takes place at the
STS-3 level. Therefore, if one of the three incoming DS3 or EC-1 low-speed
signals in an STS-3 tributary fails, the DRI protection switch affects all three
low-speed signals of an STS-3 tributary. In Release 7 and later releases, the DRI
protection switch may take place at the STS-1 level. Therefore, if one of the three
incoming DS3 or EC-1 low-speed signals fails in an STS-3 tributary, the DRI
protection switch will only affect the failed STS-1 tributary.
The primary node does not monitor the condition of the incoming low-speed signal
at the secondary node before performing a DRI protection switch. In Release 6
and later releases, the DRI protection switch time is less than 100 milliseconds for
unprotected (0x1) OC-3 interfaces and less than 200 milliseconds for unprotected
failures in 1+1 protected OC-3 interfaces. For more information about DRI
protection switching, refer to Volume I, Section 9, “Maintenance Description.”
If the primary node in the line-switched ring fails, the FT-2000 OC-48
Add/Drop-Rings Terminals adjacent to the primary node perform two-fiber ring
protection switching. Traffic is rerouted to/from the termination node in the
line-switched ring through the secondary node to the other ring.
If the secondary node in the line-switched ring fails, the FT-2000 OC-48
Add/Drop-Rings Terminals adjacent to the secondary node perform two-fiber ring
protection switching. However, traffic continues to be routed to/from the
termination node in the line-switched ring through the primary node to the other
ring. For information about two-fiber ring protection switching, refer to Volume I,
Section 9, "Maintenance Description."
Cross-connections can be made, using the CIT or message-based operations
system interface. The message-based operations system interface uses X.25
protocol and TL1 messages. For more information about cross-connections, refer
to Volume I, Section 8, “Administration and Provisioning.”
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