Specifications

Chapter 1 Introduction Installation and Operation Manual
1-22 Functional Description IPmux-24 Ver. 1.5
Figure 1-16. Basic Ring Redundancy Topology – Data Flow during Normal Operation
If a segment, for example, the segment between nodes B and C, breaks (fails),
the ring mechanism automatically moves the blocking nodes to the ends of the
failed segment and reconnects the previously disconnected segment.
The new path of the frames is shown in
Figure 1-17 . Therefore, full connectivity
is restored for any single point of failure. For PW traffic, the redundancy
mechanism ensures that this change takes effect within 50 msec.
Figure 1-17. Basic Ring Redundancy Topology – Data Flow after Recovery from Segment Failure
The method used to achieve fast recovery is based on the use of VLAN tagging.
This approach enables adjacent nodes on the ring to exchange protocol messages
that check the connectivity, and multicast
ring open messages to all the nodes in
case a fault is detected on a segment. Note however that this means the ring
VLAN ID cannot be used for other traffic.
Two VLANs are used by the ring mechanism: one for the multicast messages
(Ring Reject, Ring Open) and one for unicast messages (Link KeepAlive, Ring
Detect, Ring Closed).
VLANs reserved for the ring messages cannot be used for other traffic.
The fast redundancy protection available to the PW traffic within the ring can be
extended to other equipment: such equipment is connected to the USER port of
the IPmux-24 devices, and therefore its traffic is not processed by IPmux-24: it
only passes to the network through the IPmux-24 network ports.
The protected addresses are destination addresses for traffic connected to
IPmux-24 through the user port: this may be traffic from another IPmux-24
device, or from any other type of equipment using IPmux-24 to connect to
remote sites.
Note