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20 Description of the Ring Protocol
20.1 Overview of the Ring Protocol
20.1.1 Overview
The Ring Protocol is a Layer 2 network redundancy protocol that detects faults in networks
in which switches are connected in rings, and performs high-speed path switching
accordingly.
Spanning Tree Protocols can be used as a Layer 2 network redundancy protocol, but suffer
from shortcomings such as slow convergence for switching when faults occur. The Ring
Protocol can be used to ensure that the path switching for when faults occur is performed at
high speed. By using ring topology, the need for transmission paths and interfaces is
reduced when compared to a mesh topology.
A switch in a ring topology (where the Ring Protocol is used) can be a master node or a
transit node. The Switch supports the transit node functionality only. This manual describes
the use of the Switch as a transit node. For details about master nodes, see the manuals for
AX series switches that support the master node functionality.
The following figure provides an overview of a ring network based on the Ring Protocol.
Figure 20-1 Overview of the Ring Protocol
Of the nodes constituting a ring, one is the master node and the others are transit nodes.
The two ports connecting each node are called ring ports, and the ring ports of the master
node include a primary port and a secondary port. The master node can divide a ring
configuration by applying a logical block to the secondary port to prevent data frame loops.
The master node regularly sends control frames (health check frames) to monitor the
status within a ring, and determines whether a fault has occurred within the ring based on
whether the sent health check frames have been received or not. Master nodes that detect
a fault or fault restoration set or remove a logical block on the secondary port to switch
paths and restore communication.
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