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About the TDRMIM
1.2.5
Support for Passive MAU Workgroups
The TDRMIM's RJ45 lobe ports default to their TCU configuration to
support station connections, but they also offer a Multi Ring Out override
to support connections to passive MAU (Multi-Station Access Unit)
workgroups. Because a passive MAU cannot provide the phantom current
that a station sends down its lobe cable to signal a TCU to open its
interface, the Multi Ring Out configuration directs the port to look for the
presence of data bits rather than for phantom current to determine link
status. Use a management interface to activate the Multi Ring Out
override on selected lobe ports.
The LANVIEW LED output for a Multi Ring Out port is quite
NOTE
different from the output for a TCU port. See Section 4.2 for a
discussion of this and all other LED signal details.
Improved Protection from Beaconing
Multi Ring Out lobe ports provide enhanced reliability for networks that
use passive MAUs by allowing for the separate attachment of each MAU.
Whereas Ring In/Ring Out MAU connection schemes daisy-chain MAUs
together as a single entity and risk their collective isolation in case of
beaconing (see Figure 1-5), the Multi Ring Out method attaches each MAU
individually to its own lobe port. The Beacon Recovery process can then
bypass problematic ring-to-MAU connections individually, leaving all
other workgroups unaffected. The Multi Ring Out configuration thereby
reduces the number of MAU ports that are at risk of collective isolation in
case of beaconing on a MAU port.
1.2.6
Interaction with Other MIMs in the MMAC
When configured with identical ring speed settings, Token Ring MIMs
connect to each other via the continuous FNB rings on the MMAC
backplane.
FNB ring 1 is always available in all MMAC slots, but FNB rings 2, 3, and
4 are extended across the MMAC only where there are multi-ring modules
to carry them. Because single-ring MIMs do not have port-switching
capability and cannot support connections across FNB rings 2, 3, or 4, any
single-ring MIM installed between multi-ring MIMs will break the continuity of
FNB rings 2, 3, and 4. To maintain ring continuity, install all MIMs with
multiple ring access (all port-switching or cluster-switching MIMs) in the
right-most slots of the MMAC where they will have contiguous contact
with each other and with the hub's management module.
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