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02 Lesson 2 Purchasing the Right Hardware

LESSON 2 - Purchasing the Right Hardware

Greetings! Take a seat, sit back and enjoy todays fully illustrated foray
into the copper enriched world of networking hardware. Illustrated? You bet!
There are some things in life that just should not be attempted by the
written word.

Because sending graphics or indeed any large attachment to a mailing list is
a hanging offence, this document uses URLs as place holders for where the
graphic should be. If supported by your mailer, you can just click on the
link to view it. Otherwise copy and paste the link into your browser.
Alternatively, this whole lesson including pictures exists as a HTML
document at
http://linux.invisiblepixels.org/writings/networkcourse/2.hardware.html

This lesson is aimed at people who aren't that interested in networking, but
just want to know enough to be able to purchase what they need to get their
home network up and the lights flashing. In order to keep this lesson
simple, I've had to make one assumption: your computer and any networking
equipment you already own was bought recently (within the last two years or
so).

Section one is a basic introduction to what you need to know before you make
any purchases. Section looks at putting it all together and what to try when
it doesn't work. Section three describes a special case scenario where all
you want to do is network two computers. Not three or four, but two and only
two.

For those wanting a more in depth look at the world of networking and its
equipment and technologies, that's coming in lesson three. It was originally
written as a part of this lesson, but the whole thing became as large as Mr
Creosote from Monty Python's Meaning of Life, so I split it into separate
lessons.


#########################################
## Section One - Just the Facts Ma'am ##
#########################################

The type of network we're building is represented in the following diagram.

http://linux.invisiblepixels.org/writings/networkcourse/img/starinternet.jpg

The first decision you need to make before you begin purchasing equipment is
what speed you want your network to be. You have three choices - 10Mbps
(Megabits per second), 100Mbps (also called Fast Ethernet) or 1000Mbps (also
called gigabit). As with everything in the computing world, the difference
is a simple trade-off between speed and price. The faster you want to go,
the more you'll have to pay. Vroom vroom.

So which one should you choose? Your decision needs to based on the
following points:

* Availability of components.

1000Mbps networks are still "up and coming" and equipment rated at this
speed is not readily available (that might not be true where you live, but
I'm talking in general). 10 and 100Mbps hardware is as common in computer
shops as bread is in a supermarket, so I can't imagine any problems with
getting either. 100Mbps equipment is perhaps the most prevalent of all, as
it's slowly taking over from the older 10Mbps gear.

* Your budget.

1000Mbps networking equipment is expensive. Gear rated at 10Mbps is usually
only fractionally cheaper than that rated at 100Mbps. My personal advice on
this is to go for 100Mbps unless you're on an excruciatingly tight budget or
your local shops make a liar out of me.

* What you want to do with your network.

The concept of "average use" is as vague as the length of a piece of string.
A 10Mbps network should be perfectly adequate for "average use" where this
means a shared internet connection, file sharing between the computers and
printing to a common printer. All things considered though, such as the
(largely) insignificant cost difference, and gradual decreasing availability
of 10Mbps equipment, deciding to go with a 100Mbps network is perhaps the
wiser choice. Not only does it give you a faster network from the word go,
but also room to grow. Who can predict what we might want do on our home
networks in a few years?

What you must be aware of is that a network can only run as fast as its
slowest component. If you want your network to operate at 100Mbps, then
*everything* needs to be rated at a minimum of 100Mbps. A single 10Mbps
component will restrict the whole network to 10Mbps. The story changes
slightly if you use a 100Mbps switch rather than a hub. More on hubs and
switches in lesson three. Realise though that these speeds refer only to the
rate at which computers on your network communicate with each other, and
have no bearing what so ever on your internet connection.

Whatever your choice, you need three hardware components - network cards,
cables and hub - each of which I'll discuss in turn.

# Cable #

No matter which speed network you've chosen, the one cable used by them all
goes by the full name of category 5 UTP, however most sales staff understand
what you mean if you simply ask for "cat 5" or "UTP". UTP stands for
Unshielded Twisted Pair (for reasons that should become apparent in the next
photo) and is actually the name for a family of similar looking cables.

http://linux.invisiblepixels.org/writings/networkcourse/img/utpstripped.jpg

You may get asked two things in the shop:

* if you want "straight through" or "crossover".

The correct answer is "straight-through". To make sure you've been given a
straight-through, hold the plug at each end in either hand, with the clips
facing away from you. Look at the order in which the individual coloured
wires are arranged in the plug. If the sequence is the same in each plug,
you've got a straight-through. If the order of the colours is different,
it's either a crossover or a faulty cable. What crossover cable is and what
it's used for is discussed in lesson three.

* if you would prefer cat5e.

The "e" stands for enhanced, and guarantees the cable will work at speeds up
to 1000Mbps. Technically normal cat5 is also rated at 1000Mbps, but poorer
quality cat5 can't achieve that speed. Cat5e is more expensive and not
necessary for our 100Mbps network, but if the price difference is small or
the computer shop doesn't sell plain old cat5 anymore, then there is no
problem whatsoever with using cat5e.

You need to purchase one length of cable for every computer you wish to
network.

Important Tip: Common telephone wire is also part of the UTP family but you
can't use it for networking. It's easy to tell the difference though, cat5
has an 8 pin plug on the end (telephone has 4) and cat5 often has one of
"FIVE", "CATEGORY FIVE", "4PR" or similar printed on the outer sheath. Any
attempts to use telephone wire will end in tears (and a net"work" that
doesn't).

# Network Card #

Now you've got some cable, you need something to plug it into. A large
number of of motherboards manufactured in the last two years have network
cards built-in. Don't confuse a modem jack with that of a network card. A
modem jack only has 4 pins (to go with the 4 pin telephone wire) whereas a
networking jack has 8. If your machine has a built-in network card then you
don't need to purchase one separately. If a purchase is necessary, simply
asking for a "network card" and remembering to specify which speed is
probably all you need to do. If you see cards labelled "10/100", that's just
the manufacturer's way of saying "this card can do either 10 or 100Mbps".

Many cards are emblazoned with pretty stickers announcing to the world
"Works with XP" or "NetWare certified". Don't let this alarm you too much -
many network cards either come with linux drivers or provide a website you
can download them from. If this doesn't appear to be true for your card, all
is not lost 'cause linux itself comes with many drivers. You'd have to be
really, very, extremely unlucky if none of these sources yielded a driver
for you card.

You often come across a huge price difference between various brands of
cards rated at the same speed. I've never had any problems using the cheap
brands on a home network, but its not something I'd recommend for a busy,
high load, corporate network. The more expensive brands provide a lot of
extra features that are of no relevance to a home network, such as remote
monitoring and management and buffers large enough to cope with a huge
network operating at full capacity.

# The Hub #

The is the central point of the network that each computer connects into. A
hub works by taking the network traffic it receives on one port, and copying
it to the rest.

Hubs are commonly sold (here at least) with either 5, 8 or 16 ports. 16 is
perhaps overkill for our home network, unless of course you have a really
big family! Whichever configuration you choose, make sure you have enough
ports for all the computers you want to network now, and a few ports over
for unforeseen circumstances - new computers, visitors, the one port that
becomes defective a day after the warranty expires...

There is an alternative to a hub, called a switch. Usually more expensive
(but the price gap is growing smaller every day), it performs the same
function as a hub, but in a different way. This makes it more efficient and
reduces network traffic, but once again, switches aren't necessary in a home
network, just "nice" to have. Base your decision on cost. A more detailed
look at the differences is presented in lesson three.

Hubs, like network cards, are available in two speeds - 10Mbps or 100Mbps
(switches are all 100Mbps). If you're building a 100Mbps network, you'll
need a 100Mbps hub (or switch).

Someone once asked why they couldn't find their hub on the Hardware
Compatibility List of their distro. The reason is: the list only contains
equipment that the computer communicates with directly. Items such as hubs,
switches or speakers aren't included because the computer couldn't care less
what brand they are or even if they're installed at all.


###########################################
## Section Two - Putting it all together ##
###########################################

Installing the network card requires opening up your computer, finding a
spare slot and inserting the card. Close the case and switch on! Most linux
distros come with a programme that runs on boot and is designed to detect
and install new hardware. If you want instructions on how to install a
network card without relying on these tools, or are having trouble with
drivers, ASK!

Installing the hub is a simple matter of finding a power point and plugging
it in. Neither hub nor switch requires configuration - they just work.

The last stage is to grab your network cables. Plug one end of the cable
into the computer, and the other end into the hub. Do this for each
machine on your network.

Now we do a preliminary test on everything by switching your computer on. It
doesn't have to boot into any particular operating system, it doesn't matter
if you leave it at the lilo/grub menu screen; as long as the machine is
switched on. You should now see the hub light up. These lights are called
"link lights" and are also present on most network cards. Each port on the
hub has its own link light, and their purpose is to tell you if there is a
connection between that particular port and the network card that's plugged
into it. Link lights often flash or change colour according to what's
happening on your network. You'll have to refer to the manual to see exactly
what the different codes mean for your particular hub. If nothing is plugged
into a particular port, there will be no link light.

# Troubleshooting #

If there are no lights on your hub at all, check it's plugged into a power
supply.

If you switch a computer on, but no link light appears on either the hub or
the network card, the problem could be one of the following:

* Incorrect or damaged cable.
* The cable isn't plugged in properly. It should click when you plug it
in.
* The network card hasn't been inserted properly into the computer. You'll
need to try reinserting the card. Don't forget to screw it down - if you
don't do this sometimes the act of plugging the cable in can cause the
card to unseat itself.
* That particular port on the hub is faulty. It's not all that unusual for
a port on a hub to die while the others keep working. Try plugging the
cable in to another port and see if it works there.
* The port you've plugged it into is set on "uplink". On some hubs, a
button or switch can be used to toggle one port between two modes. The
mode you don't want is called "uplink", "crossover", "cascade" or similar,
and is used when connecting a second hub to the first. Check your manual
to make sure the port is on the correct mode for normal use.

When all else fails, post the details of your problem to the courses mailing
list (don't forget to put [Networking] in the subject).


##########################################
## Section Three - Two Computer Network ##
##########################################

If you only have two computers that you want to network, there is a way of
networking them that doesn't require the purchase of a hub. It's very
important to realise though that this method works *only* for
*two* computers. As soon as you want to network three or more you'll
have to purchase a hub and enough cables.

What you will need is:

* Two network cards - one for each machine. Once again, if your motherboard
has an on-board network card, you don't need to buy an additional one.

* One cat5 crossover cable. The crossover part is important. This
*won't* work with a straight-through cable. A before, it doesn't matter
if it's true cat5 or cat5e.

Setup simply requires the installation of the two network cards, and
plugging one end of the crossover cable into each computer. Voila.

Due to the absence of the hub, you will need to rely on the link lights on
the cards themselves to test if you've got a connection once the computers
are switched on.

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ACKNOWLEDGEMENTS: Many thanks to Dana for the drawings!