A network interface card, or NIC, is the hardware component that enables a computer to communicate on a network. NICs act as a computer’s physical interface and hardware address within a network. Without a NIC installed, it is impossible for a computer to communicate on a local area network or the internet.
All NICs have a unique physical address assigned to them called a MAC address. This address consists of 6 pairs of hexadecimal characters separated by dashes or colons (i.e. 01:23:45:67:89:ab.) This address is used to identify the card on the local network and assist in the efficient delivery of data from one location to the next. Generally, a MAC address is burned into the card on ROM and cannot be changed.
Network interface cards are designed to use a standardized interface to the transition media. In other words, they only work with specific connectors or wireless standards. Some common examples of these technologies include the ISDN, DSL, Ethernet, Bluetooth and Wi-Fi standards. In order for a local network to function properly, the NIC must utilize the same technology as the other devices on the network.
The two most common network standards are Ethernet (via RJ45 connector) and Wi-Fi (via 802.11 wireless standards.) An Ethernet NIC will generally have one RJ45 input that can be used to connect a computer to a router or modem with a Cat-5 cable. A Wi-Fi NIC will generally use a small antenna to transmit and receive the 802.11g or n wireless standard signal. There are many less common variations and alternatives to these technologies, but Ethernet and Wi-Fi are by far the most broadly available.
NICs can interface with a computer in several different ways. Internal NICs can be built directly on the motherboard or installed in a PCI slot. External NICs will often use a USB or Firewire interface. Some are built specifically for use with laptops and can fit in a free PCMCIA card slot.
When choosing a NIC the most important factor to consider is the technology utilized by the network it will be interfacing with. If the NIC operates using incompatible cabling or technology it will be unable to communicate on a network. If the network in question is wireless, it is important to make sure the standard of the wireless router is the same as the wireless standard used by the NIC. Other factors that influence the performance of a Wi-Fi NIC are distance from router, radio interference and matching channels of all devices on the network.