Users Guide

Ethernet Ring Protection 1045
Ethernet Ring Protection Switching Port Role
Ethernet Ring Protection Switching (ERPS) defines three port roles: the RPL
owner port, the RPL neighbor port, and the Normal port.
Under normal conditions, the RPL is blocked (not used for data traffic), thus
preventing loops. The ports at each end of the RPL are called
RPL owner and
RPL neighbor .
RPL Owner Port
It is the RPL owner that provides the main control for protection switching.
The owner generates R-APS No Request RPL-Blocked (NR, RB) messages
continuously and is in charge of the RPL's blocking and forwarding states.
Under normal operation, when there are no failures, the RPL owner generates
R-APS (NR, RB) messages. It periodically sends these, every five seconds, over
both of its ring ports. These messages indicate which of its ring ports is being
blocked.
RPL Neighbor Port
The port adjacent to the RPL owner is the RPL neighbor port. Both the RPL
owner port and the RPL neighbor ports are blocked in normal situations to
prevent loops. Under the Signal Fail condition, both the RPL owner and
neighbor ports are unblocked. Configuration of a RPL neighbor port is
optional.
Normal Port
A normal port monitors the status of the directly connected ring link and
sends R-APS PDUs to notify the other ports of its link status changes.
R-APS Channel
R-APS messages require a separate ring-wide VLAN known as the R-APS
VLAN or R-APS Channel. Each ERP instance uses an R-APS VLAN for
sending and receiving R-APS messages.
The function of the R-APS VLAN is to support a path for monitoring the ring
and maintaining its operational functions. R-APS VLAN must have all ERP
ring ports as members. Nodes receiving the R-APS message must send a copy