Expansion - Ethernet
8-4
Simple Ethernet
The modules produced for these functions are the EMME and EMM-E6. The
EMME and EMM-E6 provide repeating for Ethernet Channel A, supply extensive
management functions for all Ethernet modules in the chassis, and interconnect
all three backplane buses using the customer’s choice of bridging or routing. Also,
these Multichannel Ethernet management modules provide bridged or routed
connections to external networks. The EMME supports one front panel
segmented connection to an external network (Channel D), while the EMM-E6
supports the four connections the EMME is capable of, as well as connection to an
external network through the use of Bridge/Router Interface Modules (BRIMs).
So, to expand the capabilities of the example simple Ethernet hub presented in
Chapter 5, we need to replace the IRM3 module that is providing repeating and
management for the Media Interface Modules on Ethernet Channel A with a
management module that performs the necessary bridging functions. In the case
of this expansion, since there are no expressed requirements for connections to
other network types, we utilize the EMME. If a connection to, say, a wide area
network link or an FDDI backbone was required, the EMM-E6 would have
allowed us to use Bridge/Router Interface Modules to make the required
connection.
After replacing the IRM3 with the EMME, we need to place users on Ethernet
Channels B and C. We do this through the use of RMIMs, as previously discussed.
As RMIMs provide their own repeating functionality, we need not supply any
additional modules to allow them to operate. We divide the new users into
distinct groups, paying close attention to their expected network utilization, and
choose the correct number and type of RMIMs from the RMIM table to supply the
connectivity needs of each group. Remember that stations on an RMIM are all
assigned to the same backplane channel of the hub; there is no individual
assignment. All users on each module will be assigned to Channel B, Channel C,
or operate as a standalone network without a connection to the backplane bus.
If we assume that we are continuing to utilize the same media and connector
types for the users being added to the new segments in the example chassis, and
further assume that each new segment must provide support for 40 Ethernet
stations, we can narrow the RMIM choices down by an examination of the Table
of RMIM modules in Chapter 5:
- Our required media eliminates the CXRMIM (thin coaxial cable), and
FORMIM-22 (multimode fiber optics) from consideration.
- Our required connector type further eliminates the TPRMIM-33 and
TPRMIM-36 (RJ21 connectors) from consideration.
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