Picking an Appropriate Network Card

If you're adding a computer to a network or if you need to replace a NIC, your first task is to pick one. Most network cards sold today are Ethernet models, which work only on Ethernet networks. For this reason, I focus on this type of hardware. If your network uses another type of network hardware, such as Token Ring, you must instead purchase a card for that type of hardware.

Note Wireless networking technologies are becoming popular, particularly in homes and small offices where the cost or hassle of laying network wires is prohibitive. Wireless networking hardware works much like Ethernet or other wired network tools, but without the wires. Warning When using wireless hardware, be particularly cautious about security.

Someone parked in a car outside your building could easily snoop on your network traffic if you use a wireless protocol. Wireless protocols do include encryption tools, but these tools often slow down network accesses, and they may not be enabled by default. You might want to put a firewall between your wireless devices and your wired computers as a precaution in case an interloper abuses your wireless network.

Most Ethernet cards on store shelves today are 10/100 devices, meaning that they work at both 10 megabits per second (Mbps) and 100Mbps. Not coincidentally, most twisted-pair Ethernet networks today run at one or both of these two speeds. Earlier Ethernet standards used either thin or thick coaxial cabling and ran at 10Mbps. The up-and-coming standard is for gigabit Ethernet, which runs at 1,000Mbps (1 gigabit per second, or Gbps). Gigabit Ethernet variants that use twisted-pair and optical cabling are available. In early 2003, Gigabit Ethernet is starting to become affordable—gigabit Peripheral Component Interconnect (PCI) NICs sell for $50 to $200, as compared to $10 to $50 for most 10/100 PCI NICs. Therefore, you may want to at least consider gigabit hardware if you're upgrading an entire network or a large part of one. Gigabit hardware is also worthwhile for systems that transfer a lot of data, such as busy servers. (Such systems may need special support switches or routers to feed several 100Mbps connections into a single 1Gbps NIC, though.)

Fortunately, Linux includes drivers for the vast majority of network cards, especially in the 10/100 Ethernet realm. You're more likely to have problems with non-Ethernet hardware, including some wireless devices. Support for PC Card and USB adapters is also spottier than for PCI cards and Ethernet chipsets built into motherboards. For advice on specific models, perform a web search, including a search on Google Groups (http://groups.google.com). Be sure to click the link to sort responses by date so that you can spot the most recent responses. Chances are that somebody's asked about the compatibility of specific models or chipsets recently. You can also check your distribution's hardware compatibility page. Remember that Linux drivers are written for chipsets, and any given chipset may appear on dozens of manufacturers' cards. This fact is particularly true of Ethernet chipsets and Ethernet NICs sold under store brands or lesser-known labels. Chapter 1, "Optimizing System Architecture Usage," includes information on identifying the chipset that a board uses. Many of these techniques, though, work only after you've installed the board, or at least can examine it visually—you may not learn much by looking at the box in a store.

For use on a workstation or a light-duty server, you won't find much performance difference between NICs; these machines don't move enough data to make a noticeable difference. For use on heavily loaded servers, you may want to stick to well-known brand names, such as Intel and 3Com. Such products have mature Linux drivers, and the hardware is usually capable of sustaining heavy data transfer rates. Some other brands, and even many generic boards, also use good hardware. In particular, many NICs, including some models from Linksys and NetGear, use the original Digital Equipment Corporation (DEC) "Tulip" chipset or its clones. These chipsets perform well, and boards based on them are less expensive than many competing name-brand devices. Tulip-based boards have a drawback, though: Because there are so many Tulip clones, and because manufacturers change their hardware frequently, the driver authors have a hard time keeping up with new devices. There have been periods where a popular new Tulip-based board hasn't worked reliably until the Linux drivers have been updated. Boards based on some other low-end chipsets don't always perform very well on heavily loaded systems. NICs based on the RealTek 8139, for instance, sometimes yield worse speed than is possible with Intel, 3Com, or Tulip hardware, and may impose higher CPU loads, to boot. These deficiencies most likely won't be noticeable on a workstation or lightly loaded server, though.

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