K1/K2 Byte strycture:
At any point of time, each node will be knowing the current status of the ring ( normal or protected). When the protection switches are not active, each node sends K-bytes in each direction indicating "no bridge request". At the time of failure in the ring between two adjacent nodes, two paths may exist for communication. Short path is the one, which directly connects both the nodes. Longer path connects these two nodes via all other nodes on the ring. When a node receives a non-idle K-byte message containing a destination ID of another node on the ring, that node will change to pass through mode.
Let us read about types of ring protection in next post