Cabletron Systems 100BASE-FX, Cabling Manual

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Full-Duplex Ethernet Network Requirements
6-2 Full-Duplex 10BASE-T
Insertion Loss (Attenuation)
The maximum allowable insertion loss for any 10BASE-T station on the Ethernet
network is 11.5 dB at frequencies from 5 to 10 MHz. This calculation must take all
cabling devices in the cable path into account. A typical insertion loss test must
include the jumper cabling used at the station and at the wiring closet, and any
patch panels, punchdown blocks, and wallplates in the installation.
The insertion loss characteristics of a cable are one of the main determinants of
link length allowed by the Ethernet and 10BASE-T specifications. As long as a
UTP cable does not exceed the total insertion loss of 11.5 dB, it may be any length
up to 200 m (656 ft). The 200 meter maximum total length is based on the total
allowable propagation delay in the network, and cannot be exceeded.
Impedance
Cabletron Systems 10BASE-T equipment requires that 10BASE-T cables in the
Ethernet network have an impedance within the range of 75 to 165
Ω
. Typical UTP
cables used in Ethernet environments have an impedance between 85 and 150
Ω
.
Jitter
Jitter may be caused by intersymbol interference and reflection of signal.
Networking technologies that rely on particular timing or clocking schemes may
be affected by jitter due to excessive signal reflection. Any 10BASE-T cable
installation should not exceed 5.0 ns of jitter. If a cable run meets the 10BASE-T
impedance requirements (detailed above), jitter should not be a concern.
Delay
As Full-Duplex Ethernet operation eliminates the possibility of collisions
occurring, total media length for a Full-Duplex link is determined by signal
strength, noise, and jitter. Delay is not a factor in Full-Duplex Ethernet network
cabling design.
NOTE
As longer cables are more susceptible to other limiting factors,
Cabletron Systems does not recommend the installation of
10BASE-T cabling over 100 m in length.