Figure 74. Single Link Failure - Alcatel-Lucent 9500 MPR User Manual

Two ERPS Control Processes are instantiated on each ring's node. Each instance selects its own RPL
and RPL Owner.
The ERPS Control Process controls the forwarding function to perform the following actions:
– to disable forwarding over the set of VLANs assigned to the ERPS instance corresponding to blocked
ring links;
– to flush the learned MAC address table.
Only revertive switching mechanism is supported.
The Wait-to-Restore is managed by the RPL Owner, it is configured by the operator in 1 minute steps
between 1 and 12 minutes. The default value is 5 minutes.
Note: In case of a double failure, if the restoring of the two failures takes place at the same time, an out
of service equal to the WTR could occur. To note that a switching off of a single NE causes a double failure
in the Ring.
A Guard Timer is used to prevent ring nodes from receiving outdated R-APS messages. During the dura-
tion of the guard timer, all received R-APS messages are ignored by the ERPS Control Process. The
period of the guard timer may be configured by the operator in 10 ms steps between 10 ms and 2 seconds,
with a default value of 500 ms.
The Holdoff timer is not managed and fixed to 0 since no server layer protection switching mechanism
are present. The Ethernet MAC (ETH) layer, where the ERPS take place, is supported by radio links acting
as Ethernet PHY (ETY) layer in 1+0 configuration.
Since the ERPS instances operate "per VLAN" on a logical ring protecting a set of VLANs, this set must
consequently be configured.
9500 MPR Rel. 3.1
162/980 3DB18809AAAA Issue 1

Figure 74. Single link failure

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