Information Technology Reference
In-Depth Information
Station
signal
Data connector
colors
Modular jack
8-pin
Pinouts
6-pin
Transmit -
Black
3
2
Receive +
Red
4
3
Receive -
Green
5
4
Transmit +
Orange
6
5
SHORTING
BARS
FIGURE 2.9
Token-Ring wiring patterns for the data connector, 8-pin modular (RJ-45 type) connector, and
the 6-pin modular (RJ-11 type) connector.
4, or 5 wire will carry either the 4 Mbps or 16 Mbps data rates, although the
Category 5e standards offer future growth to 100 Mbps networking. The standard
distance limits for station cable in TIA/EIA-568-C will take care of Token-Ring net-
works in most instances, because each workstation acts as a repeater to the next
workstation. However, if you wish to calculate the actual working distances accord-
ing to IBM's recommendations, you must include a complex series of derating fac-
tors that take into account the number of wiring closets and MSAUs. These
calculations yield the maximum allowable station cable lengths and the allowable
cable lengths between wiring closets. Table 2.1 shows a typical planning table for
type 1 STP cable at 16 Mbps. For a relatively simple network that involves only one
or two wiring closets or, if you use repeaters or bridges between closets, you may be
able to bypass the calculations. However, if your network is complex, you should
consult one of the network planning guides from IBM and other Token-Ring MSAU
component vendors.
Because Token-Ring may be run on either 150-ohm STP or 100-ohm UTP,
potential impedance-matching problems will exist if you have a mixed-media net-
work. For example, the Token-Ring network interface card (NIC) generally has a 9-
pin d-shell connector with a 150-ohm interface.
If your station cable (from the wall jack to the wiring closet) is 100-ohm UTP,
you will have to use a “media filter” cable from the NIC to the wall jack to trans-
late from the 150-ohm NIC interface to the 100-ohm cable. Figure 2.10 shows a
typical media filter. The media filter actually contains an impedance transformer
(balun) that compensates for the impedance difference. Operating without a media
filter can cause serious problems that will limit lobe distances and cause unwanted
signal reflections.
Wiring-related problems that may be encountered with Token-Ring networks
include excessive distance between workstations and MSAUs or between wiring
