Single Ring Configuration
6-21
Token Ring
Brief Review of MAUs
The earliest MAUs were dumb boxes, collections of ports and some internal relays
that simply moved the signal along the line and bypassed ports to which no
station was attached. The way that these relays, which performed the bypassing
operations, are activated is through the use of a “phantom current.” The phantom
current is a weak DC charge that is passed along the cable from a Token Ring
station to the MAU. When the MAU detects current coming in through a port, it
opens the relay and allows signals to pass out the cable to the station and back,
rather than bypassing the previously empty port and passing the packet on. In
this way, the Token Ring remains whole when stations are turned on and off.
As MAUs developed, they split into different families, the passive and active
Token-Ring solutions. Passive Token Ring products continued to provide the
same performance as the dumb MAUs, while active Token Ring offered
additional features and functions to enhance speed and reliability. The active
MAUs receive signals and regenerate them, much like repeaters in Ethernet. By
doing this, active Token Ring products allow a single Token Ring to support a
larger number of stations and greater lengths of lobe cabling between the MAU
and the network stations. As you can see, looking at the table of Token Ring
maximums, the active Token Ring MIMs provide longer signal distances than
their cousins the passive MIMs.
Sometimes, however, the active Token Ring technology doesn’t quite go far
enough. If you have a group of users who have offices on the seventh floor and
work areas in the basement of the East wing, and all want to be placed on the
same Token Ring, you have to change the rules a little. The way we accomplish
that is through the use of Ring-In/Ring-Out ports.
Table 6-5. Token Ring RMIMs
Station Port
Media Type
Connector Type
RI/RO Ports
Station
Connectors
Product Name
None
N/A
2 TPIMs
0
TRRMIM-AT
UTP (active)
RJ45
2 TPIMs
12
TRRMIM-2AT
STP (active)
Shielded RJ45
2 TPIMs
12
TRRMIM-4AT
Fiber Optics
(Multimode)
ST Connectors
2 TPIMs
6
TRRMIM-F2T
Fiber Optics
(Single mode)
ST Connectors
2 TPIMs
6
TRRMIM-F3T
Summary of Contents for MMAC-5FNB
Page 1: ...Cabletron Systems Networking Guide MMAC FNB Solutions ...
Page 2: ......
Page 4: ...ii ...
Page 10: ...viii ...
Page 188: ...Expansion Ethernet 8 12 Port Assignment and Virtual LANs ...
Page 194: ...Expansion Token Ring 9 6 Port Assignment ...