Network Interface Cards

Every computer on a network, both clients and servers, requires a network interface card (or NIC) in order to access the network. A NIC is usually a separate adapter card that slides into one of the server's motherboard expansion slots. However, most newer computers have the NIC built into the motherboard, so a separate card isn't needed.

For client computers, you can usually get away with using the inexpensive built-in NIC because client computers are used only to connect one user to the network. However, the NIC in a server computer connects many network users to the server. As a result, it makes sense to spend more money on a higher quality NIC for a heavily used server. Most network administrators prefer to use name-brand cards from manufacturers such as Intel, SMC, or 3Com.

The network interface cards that you use must have a connector that matches the type of cable that you use. If you plan on wiring your network with thinnet cable, make sure that the network cards have a BNC connector. For twistedpair wiring, make sure that the cards have an RJ-45 connector.

Some network cards provide two or three connectors. I see them in every combination: BNC and AUI, RJ-45 and AUI, BNC and RJ-45, and all three. Selecting a card that has both BNC and RJ-45 connectors isn't a bad idea. This way, you can switch from thinnet cable to twisted-pair cable or vice versa without buying new network cards. You can get both types of connectors for a cost of only $5 to $10 more per card. Don't worry about the AUI connector, though. You'll probably never need it.

Most NICs made today work with both 10Mbps and 100Mbps UTP networks (that is, 10BaseT and 100BaseT) and are called 10/100 cards. These cards automatically adjust their speed to match the speed of the network. So you can use a 10/100 card on a network that has older 10Mbps cards without trouble. You can find inexpensive 10/100 cards for as little as $15 each. Name-brand cards cost three or four times that much.

1000BaseT cards are more expensive than 10/100 cards, though the price has come down dramatically in recent years. You can find inexpensive 1000BaseT cards for less than $50, but the price can go up to $100 or more for cards with advanced features such as larger on-board buffers and embedded network I/O processors.

Here are a few other points to ponder concerning network interface cards:

• A NIC is a Physical layer and Data Link layer device. Because a NIC establishes a network node, it must have a physical network address, also known as a MAC address. The MAC address is burned into the NIC at the factory, so you can't change it. Every NIC ever manufactured has a unique MAC address.
• For server computers, it makes sense to use more than one NIC. That way, the server can handle more network traffic. Some server NICs have two or more network interfaces built into a single card.
• Fiber-optic networks also require NICs. Fiber-optic NICs are still too expensive for desktop use in most networks. Instead, they're used for high-speed backbones. If a server connects to a high-speed fiber backbone, it will need a fiber-optic NIC that matches the fiber-optic cable being used.