User's Manual

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Chapter 41 Introduction of Fast Ethernet Ring
Protection
41.1 Overview
Ethernet ring protection protocol is a special type of link-layer protocol specially designed for constructing the
ring Ethernet topology. The Ethernet protection protocol can shut down one link in a complete ring topology,
preventing the data loop from forming the broadcast storm. If a link is broken, the protocol immediately resumes
the link that is previously shut down. In this way, the nodes among the ring network can communicate with
each other.
The ring protection protocol and STP are both used for topology control on the link layer. STP is suitable for
all kinds of complicated networks, which transmits the change of network topology hop by hop. The ring
protection protocol is used for ring topology and adopts the pervasion mechanism to transmit the change of
network topology. Therefore, the convergence of the ring protection protocol in the ring network is better than
STP. In a sound network, the ring protection protocol can resume network communication within less than
50ms.
Remarks:
EAPS supports setting a switch to be a node of multiple physical rings so as to be able to
construct a complicated topology.
41.2 Related Concepts of Fast Ether-Ring Protection
Figure 1.1 EAPS Ethernet ring
41.2.1 Roles of Ring’s Nodes
Each switch on an Ethernet ring is a ring node. The ring nodes are classified into master nodes and transit
nodes. Only one switch on the Ethernet ring can serve as a mere master node and other switches are worked
as transit nodes.