Cisco ONS 15600 Reference Manual page 155

Chapter 8 SDH Topologies and Upgrades
Figure 8-2
Node 3
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 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 8-3
78-18400-01
Four-Node, Two-Fiber MS-SPRing
Node 0
STM-16 Ring
Node 2
shows a traffic pattern sample on a four-node, two-fiber MS-SPRing.
VC4s 1-8 (working)
VC4s 9-16 (protect)
VC4s 1-8 (working)
VC4s 9-16 (protect)
Node 1
Cisco ONS 15600 SDH Reference Manual, Release 9.0
8.3.1 Two-Fiber MS-SPRings
= Fiber 1
= Fiber 2
8-3