A bit about networks
This unit is not really concerned to much with the hardware that make up networks, but I don't think you can understand what is happening within a network unless you have some grasp of the physical bits a network is made up of So I will start by looking at these.
Things (concepts you need) to understand before you get the hang of networks.
WAN (wide area network)
The best example of this is the internet . Lots, (billions) of computers connected together through ISP's (internet service providers).
Most of what you see and use when you are browsing online is the World Wide Web or Just Web. There is other stuff out there in the ether. Email uses the internet, Chatrooms (IRC) and PIM (messenger) services also use the internet, as do downloading services like Itunes and other content provides.
LAN (Local Area Network)
A smaller network of computers connected together to share files or services like printers or a connection to the internet.
Lots of LAN's will also have an Intranet this is web content (pages) that are only available to computers on the LAN. Most oganisations will also make use of internal email for communication on their LAN and may also have messaging systems running which may also make use of telephone networks as well.
To protect the LAN computers from virus and malware attacks from the internet
it is usual to use a firewall to connect the LAN to the
A firewall can be a piece of software in windows xp for example or it can be a hardware device.
Most Broadband routers have a harware firewall built in to them these days.
Now a few terms you might not know
How fast you can move data think of it as the size of the pipe you connect with if you want.
Big pipe, big bandwith.
You can't make a network out of computers unless you join them together. You can do this in a few ways and you need a few pieces of hardware.
Ethernet/ CAT5 cable
There have been all sorts of ways of connecting computers together perhaps the most common and most successful is Ethernet. The computers in school are connected Uising Ethernet . These are often just called "network cables". The cable itself is more often than not Category 5 or just Cat 5.
Its made up of eight individual copper wires in 4 pairs which are twisted together so you sometimes hea it called UTP or Unsheilded Twisted Pair.
Its cheap but you can't have single length length over 90m so its only really useful for LAN's
It can support very fast data transmission speeds typically up to 1000MB/s or 1,000,000000 bits of information a second (1Gb/s). Most networks at the moment can't run at this speed as the computers can't yet move the data that fast.
Fibre Optic Cable
About as good as it gets at the moment from a speed point of view but not as easy to use as Cat 5. needs special convertors at either end to work with cat 5 cable.
Good for high bandwith and long distances so often used for LAN "backbones". Starting to be used in place of copper wire for "broadband" networks.
Existing Telephone Network.
When the GPO built up our phone network after the second world war they built it to do a good job for voice telephone calls. The fact that we can get a broadband connection of up to 8MB/s over it and have a telephone call at he same time is a bit of a minor miracle.
To do this a technology called ADSL is used. This stands for Asymetric Digital Subscriber Line.
The Asymetric bit comes from the fact that upload and download speeds are not equal. In fact downloading web pages from the internet is twice as fast as the speed you get when you are sending email for example.
In the other "half"of the upload bandwith your voice telephone calls live.
There are some limits to this technology you have to live less than 1500m from the exchange for example but until we put cat 5 cable or fibre all over the country (which is what Australia have done) it will have to do.
Wireless or WiFi
This connects computers without cables. Sounds great no need to take up the floorboards and run miles of spaghetti to all your computers.
Downsides at the moment are speed and instability
The 802.11G standard which is the fasted one that is available at the moment only gives 54MB/s. This will just about do dvd quality video. There are lots of bleeding edge technologies promising speeds of more than 100MB/s but manufactures are arguing about who's should be the standard as I write (June 2006).
On the upside surfing the internet from the sofa is cool if a bit antisocial
and you can sometimes get on your neighbours network and use their bandwith
if they have not secured their wifi network properly.
Hardware you need for a network
People still talk about network cards even though almost all computers made in the last 5 years have them built onto their motherboard. A few years ago when networks weren't so common they where an optional extra. What I call a "bolt on goodie" and they were a card that you dropped in your computer.
Network cards pretty much come in 3 speeds.
- 10MB/s or 10BASE-T obsolete now and to slow for streaming video for example.
- 100MB/s or 100BASE-Tstill sometimes confusingly called fast ethernet as it is faster than 10MB/s. Most LANs are using this at the moment
- 1000MB/s or 1000-BASE-T or Gigabit Ethernet. Most computers you can buy today support this but just because you have a gigabit Ethernet card it doesn't mean you will get a blistering network connection you will need a Gigabit card in your server at the other end.
With all these technologies connection speeds are "negotiated" down to the fasted speed both cards can support.
A very simple network
The simplest network you can make is two computers joined together. We could make it a little more complicated by having one of the computers have a printer attached to it.
Provided both computers have Network cards in you can just connect them together with a length of Cat 5 cable and you should have a simple network.
What can I do with my simple network?
- The first thing is share files between computers.
- If you have Itunes set up on both computers you can share music. If you use Word or any other software on both machines you can work on files on both machines.
- If only one of the computers has a printer on it you can print files from either machine.
This sort of network is called a peer to peer network neither computer is in charge of the network and to get it running successfully you might have to set a few things up on each computer.
- You need to tell both computers to use the protocol TCP/IP so they send the data to each other in an agreed way.
- You need to set the IP Adressses of both computers manually.
- You need to give the computers a name on the network
- You need to share some folders and or drives on each computer so they can be seen from the other computer and vice versa
- You would need to set up the computer that does not have a printer on it to "see"the other computers printer.
The basics of computer networking