[K12OSN] Understanding ethernet - terminology and cables

William J McCloskey williamm at timbercon.com
Thu Sep 2 17:26:10 UTC 2004

There is
	Cabling and switching technology that supports transmission speeds
of up to 20mb/sec. Most commonly wired using Category 3

	Cabling and switching technology that supports transmission speeds
of up to 100mb/sec. Requires Category 5 or better wiring and has some
restrictions on how switches are daisy chained. Be careful when configuring
your network because with a "Class 2" switch you can only daisy chain 2
switches out and with "Class 1" you can only daisy chain 1. At least that's
how it was explained by the Intel engineer I was working with while setting
up a lab with some earlier generation 100Base-T equipment. Also caution when
using 100Base-T switches as opposed to hubs, they function in very different
ways and a switch is far better then a hub (or repeater).

  1000Base-T (aka, Gigabit)
	Cabling and Switching technology that support transmission speeds of
up to 1000mb/sec. Cabling requires that all 4 pairs in a Category 5 or above
cable be properly terminated and connected. The standards recommend Category
6 though a good Category 5e cable will work just fine for *most*
applications, just be aware that distance quickly becomes a problem with

  1000Base-Fx (aka, Gigabit)
	Fiber optic Cabling and Switching technology that support
transmission speeds of up to 1000mb/sec. This is often used in applications
that require longer distance runs as fiber optic cabling has a much lower
level of loss over longer distances. The biggest downside to fiber optics is
that the cables are somewhat more fragile then copper cables, but are still
pretty rugged.

Category 5 Cables:
>From Wikipedia, the free encyclopedia.
Category 5 cable, commonly known as Cat 5, is an unshielded twisted pair
type cable designed for high signal integrity. The actual standard defines
specific electrical properties of the wire, but it is most commonly known as
being rated for its Ethernet capability of 100 Mbit/s. Its specific standard
designation is EIA/TIA-568. Cat 5 cable typically has three twists per inch
of each twisted pair of 24 gauge copper wires within the cable. Another
important characteristic is that the wires are insulated with a plastic
(FEP) that has low dispersion, that is, the dielectric constant of the
plastic does not depend greatly on frequency. Special attention also has to
be paid to minimizing impedance mismatches at connection points.

It is often used in structured cabling for computer networks such as fast
Ethernet, although it is often used to carry many other signals such as
basic voice services, token ring, and ATM (at up to 155 Mbits/s, over short

The other well known flavour of this type of cable is the 10 Mbit/s Category
3 cable. Less well known is the 20 Mbit/s Cat 4. Cat 4 offered only a small
advance in speed over Cat3, and was generally ignored in favour of Cat 5.
Cat 1 and Cat 2 are 1 Mbit/s systems for voice and low-speed data.

Patch leads created from Cat 5 are often terminated with RJ-45 electrical
connectors. Normal Cat 5 cables are wired "straight through" and connect a
computer to a hub. In other words, pin 1 is connected to pin 1, pin 2 to pin
2, etc. The RJ-45 pinout for a Cat 5 cable can either be TIA-568A or
TIA-568B. TIA-568A is used by some phone systems and Token Ring. Most
everything else, such as the Ethernet standards 10BASE-T and 100BASE-TX, use

In Ethernet, "crossover" Cat-5 cables are used to connect two hubs together,
in which pairs two and three are reversed. Crossover cables can also be used
to connect two PC's NICs directly (with no intervening hub). See the
TIA-568B article for a pinout diagram.

Cat 5e cable is an enhanced version of Cat 5 for use with 1000 Base-T
networks, or for long-distance 100 Base-T links (350 m, compared with 100 m
for Cat5). It must meet the EIA/TIA 568A-5 specification.

Cat 6 cable is defined by the ANSI TIA/EIA 568B-2.1. It is suitable for 1000
Base-T (gigabit) Ethernet up to 100 m.

Hope that helps you!


-----Original Message-----
From: k12osn-bounces at redhat.com [mailto:k12osn-bounces at redhat.com] On Behalf
Of Gary Frederick
Sent: Thursday, September 02, 2004 9:00 AM
To: k12osn at redhat.com
Subject: [K12OSN] Understanding ethernet - terminology and cables


The recent conversation helped me to finally understand why I want the 
faster ethernet speeds between my servers and the switches.

Now I'm trying to understand the different terminology and what works 
where when hooking it up.

There is

Is Gigabit just another name for 1000Base-T?

and I looked at cables and there were cables for
   Cat 5e
   FastCat 5e
   Cat 6
   Cat 6 UTP



I am able to handle a screw driver - on a realy good day and would 
prefer to get a cable that was already built over messing up. Should I 
consider learning how to make cables?



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