Acronyms
The following acronyms are used in the discussion about Ethernet ring protection switching
(ERPS):
•
MA—Maintenance association
•
MEP—Maintenance association end point
•
OAM—Operations, administration, and management (Ethernet ring protection switching
uses connectivity fault management daemon)
•
FDB—MAC forwarding database
•
STP—Spanning Tree Protocol
•
RAPS—Ring automatic protection switching
•
WTB—Wait to block
•
WTR—Wait to restore
•
RPL—Ring protection link
Ring Nodes
Multiple nodes are used to form a ring. There are two different node types:
•
Normal node—The node has no special role on the ring.
•
RPL owner node—The node owns the RPL and blocks or unblocks traffic over the RPL.
Ring Node States
The following are the different states for each node of a specific ring:
•
init—Not a participant of a specific ring.
•
idle—No failure on the ring; the node is performing normally. For a normal node, traffic
is unblocked on both ring ports. For the RPL owner or RPL neighbor, traffic is blocked
on the ring port that connects to the RPL and unblocked on the other ring port.
•
protection—A failure occurred on the ring. For a normal node, traffic is blocked on the
ring port that connects to the failing link and unblocked on working ring ports. For the
RPL owner, traffic is unblocked on both ring ports if they connect to non-failure links.
•
pending—The node is recovering from failure or its state after a clear command is used
to remove the previous manual command. When a protection group is configured, the
node enters the pending state. When a node is in pending state, the WTR or WTB timer
will be running. All nodes are in pending state till WTR or WTB timer expiry.
•
force switch—A force switch is issued. When a force switch is issued on a node in the
ring all nodes in the ring will move into the force switch state.
•
manual switch—A manual switch is issued. When a manual switch is issued on a node
in the ring all nodes in the ring will move into the manual switch state.
113Copyright © 2017, Juniper Networks, Inc.
Chapter 4: Configuring Interfaces and Chassis
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