Cabletron Systems MICROMMAC-22T, User Manual

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CABLING
4-3
4.2.1 Signal Interference
This section describes some of the conditions that can degrade Token
Ring signals and related corrective measures.
Crosstalk
Crosstalk is interference caused by signal coupling between different
cable pairs contained within a multi-pair cable bundle. Multi-pair cabling
jackets should not be used for routing Token Ring trunk cabling,
especially at 16 Mbps. Avoid mixing Token Ring cabling with other
cabling systems (e.g., telephone) within the same multi-pair jacket.
Noise
Noise can be caused by crosstalk or externally imposed impulses. If
noise-induced errors are suspected, ensure that the electrical wiring in the
area is properly wired and grounded and/or try re-routing cabling away
from potential noise sources (motors, switching equipment, fluorescent
lighting, high amperage equipment).
Temperature
The attenuation level of PVC-insulated cable varies significantly with
temperature. Check the cable manufacturer’s specifications. Plenum-rated
cables are strongly recommended in areas where temperatures exceed
40˚C. Under such conditions, plenum-rated cables ensure that cable
attenuation tolerance remains within specifications.
4.2.2 Determining The Station Count
Assuming optimal conditions resulting from a well-designed cabling and
cabling component installation, the Token Ring can consist of 250
stations when STP type 1 or 2 lobe cabling is used throughout the entire
installation. The count decreases to 150 stations when UTP is used for
any segment in the installation.
!
CAUTION
When calculating the station count for an installation that
includes multiple MicroMMAC-Ts interconnected by ring-trunk
cabling, consider that each MicroMMAC-T is equivalent to
three stations on the ring, even though the MicroMMAC-T has
a single MAC address. The management agent is a station and
the two ring ports that are in service account for the other two
stations. Exceeding the recommended station-count
undermines the ring’s performance capacity.