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The use of ARL is intended to simplify network planning. After
calculating the adjusted lobe length, the length of the longest lobe in the
network (or the adjusted lobe length (ALL) as described earlier in this
section) is added to ARL, and the sum is compared to a chart later in this
chapter to determine maximum ring size. See Section 3.2, Calculating
Distances.
Lobe Length
The distance between each LAU or attaching device and its MAU is very
important in network planning. Maximum lobe lengths are a function of
several factors, and they will vary depending on how the network is
configured. See Section 3.2, Calculating Distances.
Cable Type
Type 1, Type 2, Type 3, or Category 5 cabling may be used with Andrew
MAUs. Usually, Type 3 or Category 5 100 ohm cable is used with RJ45-
equipped MAUs, and Types 1 or 2 150 ohm cable are used with data
connector-equipped (DC) MAUs.
MAUs can be used in either 4 Mb or 16 Mb token rings. Maximum
distances will be less in 16 Mb rings.
Repeaters
Andrew Repeaters can vastly increase the geographic distance of a 4 or 16
Mbps network. If there is more than one wiring closet in the ring,
repeaters are recommended between each wiring closet. If they are used,
the length of the main ring can often be disregarded, and maximum lobe
lengths can be achieved. Andrew copper wire repeaters can transmit the
network signal up to 1200 feet on Type 3 cable and up to 2400 feet on
Types 1 or 2 cable. Andrew fiber optic repeaters can transmit the network
signal up to 10,000 feet on fiber optic cable.
If repeaters will be used, it will affect the installation of MAUs. Follow
the installation instructions given in the Andrew Token Ring Repeater
User's Guide or Fiber Optic Token Ring Repeater User's Guide.
Bridges
Bridges can help organize the rings of a network and enhance
performance from the viewpoint of network users.
Installation
19
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