User guide

Packet Over SONET Module Installation and User Guide 3-85
Configuring and Monitoring APS Functions
As mentioned earlier, APS can also be applied to the interconnection of bridges.
Figure 3-19 illustrates a configuration where two PoS ports are members of the same
VLAN. Assume that, in this example, both PoS ports are configured to run BCP on the
common VLAN and bridge traffic for the VLAN across the SONET link. Assigning the
two PoS ports to the same APS group improves the resiliency of the bridged network
by enabling faster recovery from SONET line failures relative to that achieved by the
Spanning Tree Protocol (STP). This recovery is accomplished by simply performing a
local APS line switch. Because APS recovers at layer 1, the Spanning Tree Protocol does
not need to be informed of the line failure, and therefore, no time-consuming STP
reconvergence is necessary.
Figure 3-19: APS in bridging configuration
PoS_018
Working line
Group 1
Protection line
Group 1
ADM
VLAN
X
Ethernet