Appendix B: Ethernet Cabling Requirements
B-2
ESX-1320/ESX-1380 Installation Guide
•
Insertion Loss: Between frequencies of 5.0 and 10.0 MHz, the
maximum insertion loss must not exceed 11.5 dB. This includes the
attenuation of the cables, connectors, patch panels, and reflection
losses due to impedance mismatches in the link segment.
•
Impedance: Cabletron Systems 10BASE-T products work on twisted
pair cable with 75 to 165 ohms impedance. Unshielded twisted pair
cables typically have an impedance of between 85 and 110 ohms. You
can also use Shielded Twisted Pair cables, such as IBM Type 1 cable,
but keep in mind that this cable has an impedance of 150 ohms. The
high impedance of the IBM Type 1 cable increases signal reflection.
However, due to cable shielding and the subsequent lack of crosstalk
between shielded pairs, signal reflection has little effect on the quality
of the received signal.
•
Jitter: Intersymbol interference and reflections can cause jitter in the
bit cell timing, resulting in data errors. 10BASE-T links must not
generate more than 5.0 ns of jitter. Make sure your cable meets
10BASE-T link impedance requirements to rule out jitter as a concern.
•
Delay: The maximum propagation delay of a 10BASE-T link segment
must not exceed 1000 ns. This 1000 ns maximum delay limits the
maximum link segment length to no greater than 200 meters.
•
Crosstalk: Signal coupling between different cable pairs within a
multi-pair cable bundle causes crosstalk. 10BASE-T transceiver
design alleviates concerns about crosstalk, provided the cable meets
all other requirements.
•
Noise: Crosstalk, or externally induced impulses, can cause noise.
Impulse noise may cause data errors if the impulses occur at very
specific times during data transmission. Generally, noise is not a
concern. If you suspect noise-related data errors, you may need to
reroute the cable or eliminate the source of the impulse noise.
•
Temperature: Multi-pair PVC 24 AWG telephone cables typically
have an attenuation of approximately 8–10 dB/100 m at 20
°
C (68
°
F).
The attenuation of PVC insulated cable varies significantly with
temperature. At temperatures greater than 40
°
C (104
°
F), we strongly
recommend using plenum-rated cable to ensure that attenuation
remains within specification.
