Protection Switching Chapter 13
RADWIN 2000 User Manual Release 2.6.40 13-6
Protection Switching
Protection switching occurs upon failure in the ring.
The Ethernet service restoration time depends on the number of hops in the ring. With four
hops the Ethernet service is restored in less than 50 ms.
In single and dual homed topologies the service restoration may take longer due to the aging
time of the external switches. Switches that are immediately aware of routing changes reduce
the restoration time.
Hardware Considerations
Ethernet Ring Protection is supported by the IDU-C, IDU-E and PoE.
A typical Ring Protection Link consists of an IDU-C or new style IDU-E, a PoE and two ODUs
as shown in Figure 13-2. Hence one end of the RPL and of ring controlled links, as shown in
Figure 13-2 has to be an IDU. It is recommended to have an IDU at each node to have the
flexibility to change the RPL.
A ring node is built from two ODUs from adjacent links. The ODUs can be connected to either
an IDU or to a PoE device as in Figure 13-2. Port names in the IDU are shown.
Figure 13-2: Node with IDU and PoE device
The switching function is carried out by the IDU-Cs and IDU-Es, both of which provide Layer
2 support (see Chapter 14).
Special Case: 1 + 1 Ethernet Redundancy
The same device may be used to provide economic 1 +1 redundancy for a single link.
A 1+1 Ethernet is a ring with two nodes. One of the links is RPL.
Note
Connect the switch at the site only to one IDU.
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