11-3
Cisco ONS 15454 SDH Reference Manual, R5.0
April 2008
Chapter11 SDH Topologies and Up grades
11.2.1 Two-Fiber MS-SPRings
Figure11-1 Four-Node, Two-Fiber MS-SPRing
The SDH K1, K2, and K3 bytes carry the information that governs MS-SPRing protection switches. Each
MS-SPRing node monitors the K bytes to determine when to switch the SDH signal to an alternate
physical path. The K bytes communicate failure conditions and act ions taken between nodes in the ring.
If a break occurs on one fiber, working traffic targeted for a node beyond the break switches t o 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.
Node 0
Node 1
Node 2
Node 3 STM-16 Ring
= Fiber 1
= Fiber 2
71491
VC4s 1-8 (working)
VC4s 9-16 (protect)
VC4s 1-8 (working)
VC4s 9-16 (protect)