Chapter 6.4

Network Adapter

Considering how complicated networking can be, network adapters are rather simple.

Network Adapter Overview

A network interface card, more commonly referred to as a NIC, is a device that allows computers to be joined together in a LAN, or local area network. Networked computers communicate with each other using a given protocol or agreed-upon language for transmitting data packets between the different machines, known as nodes. The network interface card acts as the liaison for the machine to both send and receive data on the LAN.

The most common language or protocol for LANs is Ethernet, sometimes referred to as IEEE 802.3. A lesser-used protocol is Token Ring. When building a LAN, a network interface card must be installed in each computer on the network and all NICs in the network must be of the same architecture. For example, all must either be Ethernet cards, Token Ring cards, or an alternate technology.

An Ethernet network interface card is installed in an available slot inside the computer. The NIC assigns a unique address called a MAC (media access control) to the machine. The MACs on the network are used to direct traffic between the computers. The back plate of the network interface card features a port that looks similar to a phone jack, but is slightly larger. This port accommodates an Ethernet cable, which resembles a thicker version of a standard telephone line. Ethernet cable must run from each network interface card to a central hub or switch. The hub or switch acts like a relay, passing information between computers using the MAC addresses and allowing resources like printers and scanners to be shared along with data.

A network interface card does not have to be hard wired with physical cable. Wireless Ethernet cards are installed like their wired counterparts, but rather than a port for an Ethernet cable, the card features a small antenna. The card communicates with the central wireless switch or hub via radio waves. Wireless LANs may have some restrictions depending on the material the building is made from. For example, lead in walls can block signals between the network interface card and hub or switch.

When buying components for a LAN, make sure the NICs and hub or switch have the same capabilities. The entire network must be either wired or wireless, so a wireless network interface card cannot talk to a wired switch or hub. In addition, newer versions of hardware will likely support more features and/or greater speeds than older versions. Make sure your central switch or hub can utilize the highest capabilities of the network interface card under consideration.

How to Choose a Network Adapter

Older network adapters came in myriad types, but today's cards are mostly Ethernet cards. Ethernet is a network standard that almost exclusively uses Cat 5/Cat 5e UTP (unshielded twisted pair) cables with RJ-45 connectors. RJ-45 connectors are very similar to standard RJ14 modular telephone plugs, but are twice as wide and have eight wires. Many of today's motherboards come with built-in Ethernet adapters. Ethernet transmission speeds have increased from 10 to 100 to 1000 Mbps.

Older cards worked at a fixed speed, preventing their connection with any network device running at a different speed. Newer cards, however, can automatically switch to a lower-than-maximum speed to match the device they are directly connected to, be it a router, switch, hub, or other Ethernet adapter. The vast majority of Ethernet network adapters on the market will work fine for most users with home or small business networks, or high-speed Internet service that requires network adapters.