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Cisco ONS 15454 SDH Reference Manual, R5.0
April 2008
Chapter11 SDH Topologies and Up grades
11.2.2 Four-Fiber MS-SPRings
Four-fiber MS-SPRings provide span and ring switching.
Span switching occurs when a working span fails (Figure11-5). Traffic switches to the protect fibers
between the nodes (Node 0 and Node 1 in the Figure 11-5 example) and then returns to the working
fibers that did not fail. Multiple span switches can occur at the same time.
Figure11-5 Four-Fiber MS-SPRing Span Switch
Node 0
Node 1
Node 2
Node 3
Span 1
Span 2Span 3
Span 4
Span 8
Span 7Span 6
Span 5
STM-16 Ring
= Working fibers
= Protect fibers
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