Figure 5-2 Four-Node, Two-Fiber Blsr Sample Traffic Pattern - Cisco ONS 15327 User Documentation

Chapter 5 SONET Topologies
The SONET K1 and K2 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 reverse direction on the protect bandwidth until it
reaches its destination node. At that point, traffic is switched back to the working bandwidth.
Figure 5-2
Figure 5-2
Node 3
Figure 5-3
All circuits originating on Node 0 carried to Node 2 on Fiber 2 are switched to the protect bandwidth
•
of Fiber 1. For example, a circuit carried on STS-1 on Fiber 2 is switched to STS-25 on Fiber 1. A
circuit carried on STS-2 on Fiber 2 is switched to STS-26 on Fiber 1. Fiber 1 carries the circuit to
Node 3 (the original routing destination). Node 3 switches the circuit back to STS-1 on Fiber 2
where it is routed to Node 2 on STS-1.
Circuits originating on Node 2 that were normally carried to Node 0 on Fiber 1 are switched to the
•
protect bandwidth of Fiber 2 at Node 3. For example, a circuit carried on STS-2 on Fiber 1 is
switched to STS-26 on Fiber 2. Fiber 2 carries the circuit to Node 0 where the circuit is switched
back to STS-2 on Fiber 1 and then dropped to its destination.
June 2002
shows a sample traffic pattern on a four-node, two-fiber BLSR.
Four-node, two-fiber BLSR sample traffic pattern
Node 0
OC-48 Ring
Node 2
shows how traffic is rerouted following a line break between Node 0 and Node 3.
Bidirectional Line Switched Rings
Node 1
Traffic flow
Fiber 1
Fiber 2
Cisco ONS 15327 User Documentation, R3.3
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