User`s guide

18 Metrobility 10/100Mbps Delta Class AutoTwister
Auto-Recovery Application Example
A set of four AutoTwisters can be used to provide the redundancy
necessary to ensure that data from a 100Mbps device reaches its
destination in a 10Mbps device, as illustrated in the diagram below. In
this example, the main link, which includes AutoTwisters A1 and A2, must
be seen as a single connection. If any of the cables in the main link fails,
both switch/hubs must be notified of the failure so they can activate the
backup link, which includes AutoTwisters B1 and B2.
Since the entire main link
must appear down if any of
its connecting segments fails,
the copper ports of
AutoTwisters A1 and A2 must
be able to indicate a no-link
condition to their correspond-
ing switch/hubs. To do this,
auto-recovery must be enabled on the two AutoTwisters.
To enable auto-recovery on the AutoTwisters, make sure that on each
unit, AN1 is disabled, LLR2 is enabled, and LLCF is enabled.
The diagram below illustrates how the two switch/hubs are alerted to a
broken fiber cable in the main link, thus activating the backup link with
AutoTwisters B1 and B2.
Sequence of events:
• AutoTwister A1 stops trans-
mitting data to AutoTwister
A2.
• AutoTwister A2 senses the
loss of link and stops trans-
mitting link pulses to Auto-
Twister A1 and the 10Mbps
switch/hub.
• AutoTwister A1 receives the no link condition and stops transmitting
link pulses to the 100Mbps switch.
• The 100Mbps and 10Mbps switch/hubs detect that the main link is
down and switch traffic to the backup link.
•Traffic resumes via the backup path with AutoTwisters B1 and B2.
• Because auto-recovery is enabled, AutoTwisters A1 and A2 try to
reestablish the fiber link by periodically sending out pulses from their
fiber ports.
100Mbps
Switch/Hub
10Mbps
Switch/Hub
AutoTwister A1 AutoTwister A2
LED lit = established link LED unlit = no link
Fiber
Cable
AutoTwister B1 AutoTwister B2
Fiber
Cable
100Mbps
Switch/Hub
10Mbps
Switch/Hub
AutoTwister A1 AutoTwister A2
Link Loss
Carried Forward
Link Loss
Returned
Link Loss
Carried Forward
AutoTwister B1
AutoTwister B2
Fiber
Cable
LED unlit = no linkLED lit = established link