Cisco ONS 15454 - Page 384

12-4
Cisco ONS 15454 Reference Manual, R7.0.1
OL-9217-01
Chapter 12 SONET Topologies and Upgrades
12.2 12.2.1 Two-Fiber BLSRs
Figure 12-1 Four-Node, Two-Fiber BLSR
The SONET K1, K2, and K3 bytes carry the information that governs BLSR protection switches. Each
BLSR node monitors the K bytes to determine when to switch the SONET signal to an alternate physical
path. The K bytes communicate failure conditions and actions taken between nodes in the ring.
If a break occurs on one fiber, working traffic targeted for a node beyond the break switches to the protect
bandwidth on the second fiber. The traffic travels in a reverse direction on the protect bandwidth until it
reaches its destination node. At that point, traffic is switched back to the working bandwidth.
Figure 12-2 shows a traffic pattern sample on a four-node, two-fiber BLSR.
Node 0
Node 1
Node 2
Node 3 OC-48 Ring
= Fiber 1
= Fiber 2
61938
STSs 1-24 (working)
STSs 25-48 (protect)
STSs 1-24 (working)
STSs 25-48 (protect)