Choosing and Buying Components - Network adapters
(Page 17 of 22 )
A network adapter—also called a LAN (Local Area Network) adapter, or NIC (Network Interface Card)—is used to connect a PC to a home or business network. A network adapter provides a relatively fast communication link—from 10 to 1,000 megabits per second (Mb/s)—between the PC and other devices connected to the network. Network adapters are available in wired and wireless versions. A network may use all wired network adapters, all wireless network adapters, or some combination of the two.
Wired network adapters
In a typical wired network, the network adapters in each PC connect to a central hub or switch that allows any connected device to communicate with any other connected device. In a home or SOHO setting, a wired network adapter may also be used to connect an individual PC directly to a cable modem or xDSL modem.
Nearly all wired network adapters support one or more of a family of networking standards that are collectively referred to as Ethernet. Current Ethernet adapters use unshielded twisted pair (UTP) cable, which resembles standard telephone cable, and communicate at 10 Mb/s (10BaseT), 100 Mb/s (100BaseT or “Fast Ethernet”), or 1,000 Mb/s (1000BaseT or “Gigabit”). Wired Ethernet adapters use an 8-position, 8-connector (8P8C) jack that resembles an oversized telephone jack, and is usually (although incorrectly) called an “RJ-45” connector.
(Not Always) Backward Compatible
Most Ethernet adapters are backward compatible with slower Ethernet versions. For example, most 100BaseT adapters can also communicate with 10BaseT devices, and most 1000BaseT adapters can also communicate with 100BaseT and 10BaseT devices. This is not invariably true, however. Some Ethernet devices support only one or two standards. That can cause problems if, for example, you connect a 10BaseT adapter to a hub or switch that supports only 100BaseT or 100BaseT and 1000BaseT. Although the devices can be physically connected, they do not communicate. Components that support multiple speeds, called hybrid components, are usually labeled in the form 10/100BaseT, 100/1000BaseT, or 10/100/1000BaseT.
Many motherboards include embedded wired Ethernet adapters, which are typically 10/100 or 10/100/1000 hybrid devices. You can add wired Ethernet to a system that lacks an embedded NIC by installing an inexpensive PCI expansion card. Embedded network adapters are reliable and add little or nothing to the cost of a motherboard, but they do extract a small performance penalty because they use the main system CPU for processing. Standalone desktop PCI network adapters typically cost from $15 to $40, depending on manufacturer and speed. PCI network adapters place little or no load on the main system CPU, and are often more efficient and fully featured than embedded adapters.
The best rule of thumb for most desktop systems is to use an embedded network adapter, if your chosen motherboard offers that option and if you do not require the additional management and other features available only with standalone adapters. For servers, use a standalone 100BaseT PCI network adapter unless you are using a special server motherboard that incorporates one or more server-class 100BaseT or 1000BaseT network adapters. For 1000BaseT on a server, use only an embedded adapter. A PCI 1000BaseT adapter simply consumes too much of the available PCI bandwidth to be usable in such an environment.
 | If you've enjoyed what you've seen here, or to get more information, click on the "Buy the book!" graphic. Pick up a copy today!
Visit the O'Reilly Network http://www.oreillynet.com for more online content. |
Next: Wireless Network Adapters >>
More Computer Systems Articles
More By O'Reilly Media
