D-Link DES-815 User Manual - Network

4

Overview

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 The EIA/TIA 568 Wiring Standard does not support the use

of coaxial cables for horizontal wiring.

Network

Network diameter, which is the distance between two end-stations

in the same collision domain, is the primary difference between

traditional Ethernet and Fast Ethernet.  Due to the increased

speed in Fast Ethernet and adherence to the EIA/TIA 568 wiring

rules, the network diameter of a Fast Ethernet collision domain is

limited to 205 meters; in contrast, the maximum 10BASE-T

Ethernet collision domain diameter can be up to 2500 meters.

Hubs

Unlike 10BASE-T hubs which are all functionally identical, Fast

Ethernet hubs are divided into two distinct types:  Class I and

Class II.  A Class I hub repeats all incoming signals on one port to

the other ports by first translating them to digital signals and

then retranslating them back to line signals.  These translations

are necessary when connecting various network media to the

same collision domain, such as when combining two wire-pair

100BASE-TX media with four wire-pair 100BASE-T4 media.  Only

one Class I hub can exist within the same collision domain, thus

this type of hub cannot be cascaded.  A Class II repeater, on the

other hand, immediately repeats all incoming line signals on one

port to the other ports; no translations are performed.  This type of

hub connects identical media to the same collision domain; for

example, TX to TX.  At most, two Class II hubs can exist within

the same collision domain.  The cable used to cascade these hubs is

called an inter-repeater link (IRL).

As mentioned earlier, stackable hubs can be used to increase the

number of available nodes in a collision domain.  An entire hub

stack counts as a single repeater.