Today, many people have more than one computer in their home. These computers can be connected together to form a small network, allowing both data and other computer resources to be shared. These could include printers, CD-writers, Internet connectivity and so forth.

I am going to assume you are familiar with basic PC terminology. To start with, I shall consider networking just 2 PCs. Later I shall present a SOHO (Small Office Home Office) solution. There are also security matters to address. For now, let's get started:

The simplest network involves connecting 2 computers together. To do this, you will require the following:

• Two PCs running Windows 95 or later.
  These can be two desktops, a laptop and a desktop, or whatever. You don't need the same version of Windows software on both PCs.
  
  
• An ethernet connection port on each PC.
  Some of the newer integrated motherboards come with an ethernet port fitted. Otherwise, the port is provided by adding a card to the computer. You may see this card referred to as a 10/100 NIC (Network Interface Card). The 10/100 numbers indicate that the card will transfer data at either 10 Megabits per second or 100Mbps. These days 100Mbps is the norm, while 10Mbps is provided for compatibility with legacy networking equipment. Aim to standardize on 100Mbps.
  
  
  
  For a desktop, the ethernet card plugs into a spare slot on the PCI bus inside the computer. For a laptop, a different card is used - one that plugs into a PCMCIA slot. Check that you have the necessary spare slots before spending any money.
  
  
• An inter-connecting cable to join the ethernet ports on the two PCs.
  Specifically, a Cat5 cross-over cable is required that has an RJ45 male connector on each end. Category 5 network cable will allow 100Mbps data transfer between two devices at distances of up to 100 metres.

Ensure your PC is powered off and disconnected from the mains supply. Open-up the system unit and plug the ethernet card into a spare PCI slot. The card will usually be provided with drivers on an accompanying diskette or CD.

When Windows boots up, it should discover the new network card and prompt you for the media containing the drivers. Have your Windows Operating System CD to hand because the PC may require additional files from this.

Once the ethernet ports are installed on each PC, you may connect the two PCs using the Cat5 cross-over cable.

The networking protocol we are going to use for our private network is called TCP/IP (Transmission Control Protocol / Internet Protocol). This is provided as standard with Windows, and is also the protocol used World-wide over the Internet.

Each PC on our private network needs to have a unique IP address. It looks like this:

192.168.1.87

This address uniquely identifies a machine, and allows data to be routed to it - much like your postal address. For private networks in homes and offices, an International Standard RFC1918 defines blocks of IP addresses available for use. The aim is to ensure that these addresses are different from those deployed by machines on the Internet.

We shall adhere to the Standard and pick the following private IP addresses for our two PCs:

Machine name	IP Address	Subnet mask
Machine 1	192.168.1.100	255.255.255.0
Machine 2	192.168.1.101	255.255.255.0

The subnet mask is used to split the IP address into two parts. One part is the network ID, the other part is the host ID of the computer. Think of the network ID as being your street and town, while the host ID is your house number. In our case, the network ID is 192.168.1 while Machine 1 has a host ID of 100, and Machine 2 a host ID of 101.

These addresses will be permanently assigned to your two PCs for use on the private network. They are known as static IP addresses.

In addition, a PC may have a dial-up connection to the Internet. When you use your dial-up connection, your ISP (Internet Service Provider) will temporarily assign the machine a public IP address for use during the dial-up session on the Internet. This public address is different every time you dial-up and is known as a dynamic IP address.

A PC is quite capable of handling both private network traffic and dial-up Internet traffic simultaneously. In this configuration, it is said to be running two separate IP Protocol Stacks. Of course, working with different networks raises security issues. We shall come back these later.