Designing a Network
patterns, you should also draw a network schematic with these patterns indicated to
help you sort it out. Remember the following tips:
Ethernet's CDMA/CD collision handling means that an Ethernet network will
handle only about one-third of its rated speed. In other words, a 100Base-T
segment, which is rated at 100 Mbps, will handle about 33 Mbps of actual data
before starting to degrade.
Whenever possible, use "home-run" wiring (in which each network cable runs
from each workstation to a single location) for all nodes to a single wiring
closet or server room. Doing so enables you to change the network structure
more easily (for example, to break segments into smaller segments) as needs
Except in the smallest networks, plan on installing a network backbone to
which the hubs connect. An Ethernet switch rather than a nonswitching hub
should handle the backbone, so each hub constitutes a single segment or
collision domain. You still must plan to keep each segment's traffic below the
Ethernet saturation point, but this structure will give you plenty of flexibility to
meet this goal.
The physical building might dictate how you structure your network. For
example, a building larger than 200 meters (about 600 feet) in any dimension
probably means you won't be able to employ a home-run wiring scheme
for all your nodes. This is because twisted-pair Ethernet usually reaches
only 100 meters (about 300 feet), which includes routing around building
obstructions, patch cables, and other things that make the actual cable distance
longer than you might measure on a map of the building.
For multifloor buildings that are too big for a home-run wiring scheme,
consider running the backbone vertically from floor to floor, and then have
a wiring closet on each floor that contains the switches to service that floor's
nodes. The wiring from the closet on each floor then fans out to each of the
nodes on that floor.
Consider running the backbone speed at ten times the hub/desktop network
speed. If you're using 100Base-T hubs to connect to the desktop computers,
plan on a 1000Base-T backbone.
Most of the time, most nodes do the majority of their communication to one or
two servers on the network. If you are planning department-specific servers or
if you can identify similar patterns, make sure that each server is on the same
segment as the nodes that it primarily serves.
If your servers tend not to be assigned to support departments and instead
support the entire company, make sure that the servers are directly connected
to the backbone's Ethernet switch.