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    Networks Explained

Networks are merely a means to allow computers to communicate with one and other.  That can be two computers in your home or a hundred computers in your office.  Since you are reading this, you are using the largest existing network in the world, the Internet.

In our discussions we will be connecting Personal Computers, PCs, into an environment where they utilize common data, common peripheral devices such as printers or modems, common software programs and sharing these resources.

These are examples of simple peer-to-peer networks, where only two computers are connected by a single cable.  In these types of networks only a network card in each computer and a connecting cable is required.  In these examples although you have two computers, they share the resources of data, modem access, printer and other components.

A peer-to-peer network requires a special cable, different from a normal network patch or connecting cable.  This cable is called a "cross-over" or "cross-pin" cable. 

If your network contains three or more computers, then you are required to add one more component, either a hub or a switch.

A network connected with either a hub can have two or more computers connected.  The hub allows for additional computers to be added to the network at any time.  All that is required is an additional cable connected from the hub or switching hub to a network card inside of the new computer.  Each computer, printer, or other peripheral device that is connected to the network is called a node. Networks can have tens, thousands, or even millions of nodes.

Like most things, networks are are assembled according to certain rules. Cabling, for example, has to be a certain length, each cabling strand can only support a certain amount of network traffic, etc. The rules that govern how a network is set up is called its topology.  The most popular topology in use today is called Ethernet, which consists of computers and peripherals cabled together in specific ways. Ethernet is relatively inexpensive, easy to set up and use, and very, very fast.

Ethernet networks are categorized by how fast they can move information. Speed is expressed in megabits per second (or Mbps), where one "bit" is equal to 1/8th of a character, letter, or number. There are currently two Ethernet speed categories. Standard Ethernet operates at a fast 10Mbps, which is quick enough for most networking tasks. Fast Ethernet, by contrast, races along at 100Mbps, making it ideal for desktop video, multimedia, and other speed-hungry applications. The new technology behind Fast Ethernet, which was introduced in the beginning of 1995, is not readily compatible with standard Ethernet. Making the two "talk" with each other requires special equipment (see switching hub below) and some knowledge of internetworking. If you're building your first network, decide whether to go with standard or Fast Ethernet before you begin shopping around for network hardware and software. Unless you plan on using video, multimedia, or heavy graphics software, plan on using standard Ethernet. For more information on standard and Fast Ethernet, see the Cabling & Hubs section.

Cabling Basics
The two most popular types of network cabling are twisted-pair (also known as 10BaseT) and thin coax (also known as 10Base2). 10BaseT cabling looks like ordinary telephone wire, except that it has 8 wires inside instead of 4. Thin coax looks like the copper coaxial cabling that's often used to connect a VCR to a TV set. 

Which type of cabling is best for you?
Thin coax and 10BaseT can both be used exclusively or together, depending on the type of network that you're putting together. Small networks, for example, may want to use 10BaseT cabling by itself, because it's inexpensive, flexible, and ideal for going short distances.  This is recommended for home networks as it is the easiest.

Larger networks (usually with 10 or more computers) may use a thin coax backbone with small clusters of 10BaseT cabling that branch off from it at regular intervals.

I will bet you have lots of questions already, here are a few quick answers:



Network Adapter Card
A network computer is connected to the network cabling with a network interface card, (also called a "NIC", "nick", or network adapter). Some NICs are installed inside of a computer: the PC is opened up and a network card is plugged directly into one of the computer's internal expansion slots. 286, 386, and many 486 computers have 16-bit slots, so a 16-bit NIC is needed.  Faster computers, like high-speed 486s,  Pentiums, PentiumII and PentiumIII, all have 32-bit, or PCI slots. These PCs require 32-bit NICs to achieve the fastest networking speeds possible for speed-critical applications like desktop video, multimedia, publishing, and databases.  And if a computer is going to be used with a Fast Ethernet network, it will need a network adapter that supports 100Mbps data speeds as well. These cards are often referred to as 10/100cards.

If a PC lacks expansion slots (which is true with portable PCs), special network adapters are used. A PCMCIA network adapter connects a PC to a network if the PC has a credit card-sized PCMCIA expansion slot, while a pocket adapter connects a PC to a network through the its printer port.


The central connecting device is called a hub. A hub is a box that is used to gather groups of PCs together at a central location with 10BaseT cabling. If you're networking a small group of computers together, you may be able to get by with a hub, some 10BaseT cables, and a handful of network adapters. Larger networks often use a thin coax "backbone" that connects a row of 10BaseT hubs together. Each hub, in turn, may connect a handful of computer together using 10BaseT cabling, which allows you to build networks of tens, hundreds, or thousands of computers. 

Like network cards, hubs are available in both standard (10Mbps) and Fast Ethernet (100Mbps) versions. 


The Switching hub, sometimes called a "Switch" is a more advanced unit over the basic hub.  In a basic hub, all the computers connect to it and the speed of the network is defined by the slowest computer network card connected.  If you have 10 100Mbps cards on the network and just on 10Mbps card, the system cannot run faster than that one 10Mbps card.  There in comes the Switching hub.  This hub treats each network card independently and in the matter of the 10 100Mbps network with the one 10Mbps network card, the Switching hub allows all of the faster connections to remain at the higher speed and still interact with the 10Mbps system.









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