A network, for purposes here, is a collection of computers and related equipment (printers, webcams, game consoles, etc.) connected so that data can move between them. Even if you have a single computer, it looks to the Internet as part of a network. The Internet, then, is a network of networks.

If you have two or more computers in your small business or at home, it generally makes good sense to network these computers. By networking your computers, you can share files, printers, and other resources between them. If you are using broadband access to the Internet, networked computers can share a single Internet access account. Even with a single computer, if you use broadband Internet access, you normally connect to the Internet through the computer's networking port - which means when you install your broadband you also install your networking software on the single computer.

Moreover, when using Windows (98/ME/2000/XP), the software for networking is already a part of Windows. Hardware and cabling is not very expensive; and many computers today come with the necessary network adapter (NIC) for an Ethernet network already installed. All you need is a hub and some cable to have a wired network.

Types of Networks

Micrososft Windows supports two basic types of networks: server/client and peer-to-peer. In a server/client network, one system is the big cheese and the others systems are work stations. The server system has files, printers, and other resources shared by everyone. It also is the Internet gateway and others reach the Internet through the server. The server manages security and related issues. Servers are useful in a corporate environment where top-down control is needed.

Windows also can support a peer-to-peer network in which no computer is more important than any other computer. Printers, files, and other resources are shared across the network. As with the server/client network, generally one system has access to the Internet with others sharing that single access at the same time. This is generally the best approach for a home or small business. It is also easier to manage and generally less cost, as no server is needed. If some type of mini-server is used, it generally is used to back up all the systems on the network and that's about it.

What Do I Need to Network?

The majority of networking, particularly at the corporate level, is done using the Ethernet standard. At the center of the basic diagram of a wired network is either a hub or a switcher (they aren't the same - keep reading), and computers are connected to the hub, much like spokes of a wheel or star. Each connection at the hub is called a port. Hubs are inexpensive devices sold at most computer and office supply stores, and come in varying port sizes. Always get a hub with a few more ports that you need.

You may think that if you have only two computers in your network, you can omit the hub and simply connect them. Trust me - you still need that hub. Connecting two computers won't work unless you use a special cable, and using a hub is a better idea.

At each computer, you will need an internal Ethernet adapter (wired or wireless). If you already have the Ethernet adapter in your desktop computer as a card, you'll see a card's plug with a single telephone-like jack on the back of the computer. For a laptop, there is either a card for your network or a jack on the back of the laptop.

• Don't confuse the network connector and cable with your telephone cable and its connector. The Ethernet cable is slightly larger (called CAT 5) and, like the telephone cable, twisted pair.
• Don't confuse the network interface card (NIC) with a modem card, which has two jacks that are similar. The modem card on a desktop computer has two jacks - one for the input telephone line, another for the line going out for a phone or another computer. The Ethernet card has only one jack, as the computer needs only a single line that runs to the hub or switcher.

If you don't have this Ethernet card, you will need to purchase this adapter at a local computer store for each computer. They are inexpensive. For most desktop computers in a wired network, you need a PCI version of the Ethernet adapter card. The Ethernet card should support 100 Mbps. over the network. If you plan a wireless connection to the network, you need a wireless Network Ethernet adapter card instead. You need the main computer as a wired connection to configure the rest of the wireless network.

If you are networking a laptop computer, the Ethernet adapter is a small card that plugs into the card slot of the laptop. Some newer laptops have the adapter built-in, but for most laptops you need the Ethernet adapter laptop card. Like the desktop adapters, it should support 100 Mbps. over the network. If you are purchasing a Wireless Ethernet adapter card, it will have a small antenna that sticks out.

Finally, you need the cable. For most systems you can simply measure the distance from each computer to the hub or switcher and purchase cables for that distance already made with the connectors on each end. Pre-made cables are generally available at computer stores up to fifty feet. You want Ethernet cables, Category 5. (Don't try to use ordinary telephone cable, although the connectors appear the same.) If you are going wireless, the switcher is generally near the main computer and you only need a short cable for that main computer.

Hubs can be active or passive. A passive hub uses no power and simply supports the relevant wire connections inside the box. An active hub requires power and provides some amplification for the signals as they pass through. A cable can be a maximum of about 300 feet. An active hub can be a maximum of 300 feet from each computer, which enables computers to be up to 600 feet apart. Don't rush to the store to get that hub just yet. There is more to the story.

Here is a simple system in which the hub has four RJ-45 jacks on the back for each computer. Each of these jacks is called a port. Any computer can be plugged into any port on the hub.

The Switch

The hub has a serious problem if there are more than even a few users on the network.

The information travels between the computers in packets, little chunks of information that also contain overhead information about the information, its destination, and to provide error checking. If Computer 1 wishes to send information to Computer 4, it must broadcast it to whole network. If a lot of users are using the network at the same time, those packets of information will collide and won't make it to their destination. Computer 1 never gets an acknowledgment that Computer 4 got what was sent and sends the information again. In addition, each computer must process every packet that is transmitted on the network to see if it is addressed to it. The network slows down dramatically.

To solve this problem, the hub is usually replaced by a switcher.

Now if Computer 2 wishes to send information to Computer 4, the switcher momentarily connects Computer 2 directly with Computer 4 for the packet transfer. Then the switcher releases the connection. This prevents collisions and dramatically improves the speed of the network. The switcher, to do this, has to have intelligence about the network and the physical addresses of the network components. Each component on the network has its own physical, or MAC, address. For example, the MAC address of a client adapter card or other component is generally on a tag somewhere on the component. You can also find the physical address of a component by using software programs (more on this later).

You can also combine switches and hubs in a network.

For most small wired home networks, the switcher is the best alternative. The cost difference over the hub isn't much. Don't rush out and buy that switcher yet if your network interfaces with the Internet. There is still more to the story.

When using a switch, you need to remember that the switch has a learning curve. When you first turn it on, it acts as no more than a hub and broadcasts to all computers. As you use it, it builds an internal table in memory that identifies the MAC address at each port. This takes a few minutes. It is generally a good decision to put the switches on a UPS (Uninterruptable Power Supply) so that if you lose power the switch with its table stays up. Otherwise, the switch has to rebuild its table if the power is interrupted.

Do I Need a Switcher or Hub?

Hubs were the only cost-effective solution for networks until the late nineties; but by now the switches have come down in price. Their only disadvantages of the switch are cost (lower prices now) and the slight time delay they need to connect for a packet transmission. The hub never looks at the information in the packets, broadcasting all of them to all systems on the network. The switcher looks at the packets and broadcasts only to the appropriate output port.

For a small network, a hub is generally quite adequate unless you are mixing wired Ethernet speeds (10 and 100 Mbps). Even at the small network size, however, a switcher gives room for expansion and provides a more intelligent network.

The Basic Rule

The basic rule for network design is known as the 5-4-3 rule. It states that in a 10 Mbps. Ethernet network:

• You can have a maximum of five cable segments between any two computers
• You can have a maximum of four repeatesrs (hubs, switches, wireless access points, etc.) between any two computers
• Of the five cable segments (maximum) between any computers, only three of these can terminate in computers.

For example, in the previous example you have a three-segment cable path that terminates in three computers. Another laptop here from this hub gets somewhat iffy.

Network Bridges

A network bridge is a switch with a single port. When used in a wireless network, it enables an Ethernet device to connect wirelessly to a wireless internet access point. Probably game consoles are the primary use of bridges in a home network; but bridges can also be used to connect a printer or webcam with an Ethernet port to a wireless network.

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8/19/2004