User Manual Managed Switches
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If the chain is healthy the O-Chain Edge port of the switch with lowest MAC address always
becomes the blocking (discarding) state and the other Edge port will be the forwarding one.
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BPDU control packets which will be sent cyclic from RSTP network to the O-Chain Edge ports
will be blocked by both Edge ports as long as the chain is healthy. As result the RSTP network
does not recognize any loop and sets for both RSTP ports the forwarding state.
•
When learning new MAC addresses for unknown traffic sent via both RSTP ports, only the one
connected to forwarding O-Chain Edge port will learn the path to devices connected to the
O-Chain. The other RSTP port, though also having forwarding status, never will participate in any
traffic due to the blocked O-Chain Edge port. This ensures a unique traffic flow via the forwarding
O-Chain Edge port.
•
In case of a broken chain (means any interruption in the chain behind the O-Chain Edge switches)
both O-Chain Edge ports go to state forwarding and send additionally a TCN BPDU packet
(Topology Change Notification) to their connected RSTP ports. This will trigger a fast network
topology change of the RSTP network resulting in fast renewed accessibility of devices at both
parts of the broken chain. In this case, both RSTP ports stay in state forwarding. Only for an
interrupted connection between O-Chain Edge port and RSTP port the state on both sides will
change to link down.
Recovery time for O-Chain connected to any non-redundant Daisy Chain network or to a
proprietary 3
rd
party network
For connections to unmanaged switches, to a non-redundant daisy chain network or to a redundant
proprietary 3
rd
party network the overall network topology recreation time depends worst case on the
remaining MAC address aging time of the 3
rd
party switches (when the chain becomes broken). For
those devices there is no mechanism to inform them about a broken chain and to flush their MAC
address tables immediately. Only the O-Chain switches flush their MAC address tables after around
30 ms providing all devices connected to O-Chain switches, immediately an update path for Ethernet
communication to any target device. However already established communication relations,
originally initiated from 3
rd
party network devices to O-Chain connected devices, do not longer work
until the MAC address tables of the 3
rd
party switches will be renewed after the remaining aging-time
has been expired.
How O-Chain generally works
How to configure O-Chain generally:
1. Enable the Chain Redundancy in all the switches of the daisy chain.
2. Determine the switches that shall be used as edge switches.
3. Configure at all the switches of the daisy Chain the ports that will be part of the chain.
4. In the two edge switches, additionally configure the edge port (port which is connected to the
counterpart part of the other network).
There is no need to change anything in the configuration of the network on which the O-Chain
switches will be attached.
