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Chapter 5
SONET Topologies
5.2.3 BLSR Bandwidth
BLSR nodes can terminate traffic that is fed from either side of the ring. Therefore, BLSRs are suited
for distributed node-to-node traffic applications such as interoffice networks and access networks.
BLSRs allow bandwidth to be reused around the ring and can carry more traffic than a network with
traffic flowing through one central hub. BLSRs can also carry more traffic than a UPSR operating at the
same OC-N rate.
capacity is the OC-N rate divided by two, multiplied by the number of nodes in the ring minus the
number of pass-through STS-1 circuits.
four-fiber BLSRs.
Table 5-2
OC Rate
OC-12
OC-48
OC-192
1. N equals the number of ONS 15454 nodes configured as BLSR nodes.
2. PT equals the number of STS-1 circuits passed through ONS 15454 nodes in the ring (capacity can vary
Table 5-3
OC Rate
OC-48
OC-192
Figure 5-7
simultaneously on different spans on the ring: one set from Node 3 to Node 1, one from Node 1 to Node
2, and another from Node 2 to Node 3.
November 2001
Table 5-2
shows the bidirectional bandwidth capacities of two-fiber BLSRs. The
Two-Fiber BLSR Capacity
Working Bandwidth
STS1-6
STS 1-24
STS 1-96
depending on the traffic pattern).
Four-Fiber BLSR Capacity
Working Bandwidth
STS 1-48 (Fiber 1)
STS 1-192 (Fiber 1)
shows an example of BLSR bandwidth reuse. The same STS carries three different traffic sets
Table 5-3
shows the bidirectional bandwidth capacities of
Protection Bandwidth
Ring Capacity
STS 7-12
6 x N
STS 25-48
24 x N - PT
STS 97-192
96 x N - PT
Protection Bandwidth
Ring Capacity
STS 1-48 (Fiber 2)
48 x N - PT
STS 1-192 (Fiber 2)
192 x N - PT
Cisco ONS 15454 Installation and Operations Guide
Bidirectional Line Switched Rings
1
2
- PT
5-7
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