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Chapter 3: Installation Requirements and Specifications
3-4 SEH100TX User’s Guide
3.2 NETWORK CABLE LENGTHS
This section details the maximum network cable lengths specified by the
IEEE 802.3u standard for a Class I repeater. As stated previously, the
physical size of the network is limited primarily by propagation delay.
The round trip delay cannot exceed 512 bit times or 5.12 µs.
A 100BASE-T network might use all UTP links, all fiber links, or a
combination of both. Figure 3-1 shows a simplified example of a network
with one Class I repeater. Link segments A and B represent the longest
links in the network. In this case, if both segment A and segment B are
UTP, each segment may be up to 100 meters long for a maximum network
length of 200 meters. If segment A is UTP and segment B is fiber optic,
the maximum length of the network is 263 meters (with a maximum UTP
segment length of 100 meters). If both segments A and B are multimode
fiber optic, the maximum length is 274 meters.
If a buffered uplink (EPIM-100FMB) is used, the collision domain is
stopped at the EPIM slot. This allows a full length fiber optic link of 400
meters to be used as an uplink while maintaining 100-meter UTP and
400-meter fiber optic lengths to desktops. So if segment A, shown in
Figure 3-1, is UTP and segment B is fiber optic, the maximum length of
the network is 500 meters. If both segments are fiber optic, the maximum
length is 800 meters.
Figure 3-1 Class I Network
NOTE
A stack of five SEH hubs or four SEH hubs and one SEHI hub
is equivalent to one repeater.
SEH100TX-22
DTE
DTE
A
B