.: Advanced Linux Networking :.

Although it's extremely popular, Ethernet isn't the only choice for local network hardware. The Linux kernel includes support for several other types of network, although there aren't as many drivers available for any of these as there are for Ethernet. (There are also fewer models of non-Ethernet network hardware available, so this restricted range of drivers doesn't necessarily mean poor support for the hardware that is available.) Options available in the 2.4.17 kernel's Network Device Support menu include the following:

• Token Ring— Historically, Ethernet's most important competitor has been IBM's Token Ring. Ethernet gained momentum in the 1990s, in part at the expense of Token Ring. Most Token Ring cards support a top speed of 16Mbps, although 100Mbps models have now become available. Maximum distances between Token Ring stations vary from 150–300m. Linux includes support for several Token Ring cards, in the Token Ring Devices submenu of the Network Device Support menu.

• LocalTalk— Apple developed its own networking technologies, including both hardware (LocalTalk) and software protocols (AppleTalk), for its Macintosh line of computers. A few x86 boards for interfacing x86 systems to LocalTalk networks were produced, and Linux supports some of these, from the AppleTalk Devices submenu. (Ironically, Linux on Macintosh hardware doesn't support that hardware's own LocalTalk interfaces.) LocalTalk is slow by the standards of 2002, reaching a maximum speed of 2Mbps.

• ARCnet— ARCnet is a network technology that's often used for specialized purposes like security cameras and scientific data acquisition systems. These devices support speeds ranging from 19Kbps to 10Mbps over coaxial, twisted-pair, or fiber-optic cabling. Linux's ARC net support is activated from items in the ARCnet Devices submenu. In addition to drivers for your specific chipset, you'll need to enable a driver for a specific ARCnet packet format (RFC 1051 or RFC 1201).

• FDDI and CDDI— Fiber Distributed Data Interface (FDDI) and Copper Distributed Data Interface (CDDI) are closely related 100Mbps local network technologies that use fiber-optic and copper wiring, respectively. FDDI's primary advantage over 100Mbps Ethernet is that it supports greater cable lengths—theoretically up to 2km, vs. 100m for twisted-pair Ethernet. Gigabit Ethernet with fiber-optic cabling supports distances of up to 5km, though. The 2.4.17 kernel includes support for two lines of FDDI/CDDI products, both selectable from the Network Device Support menu after selecting FDDI Driver Support.

• HIPPI— High-Performance Parallel Interface (HIPPI) supports speeds of 800Kbps or 1600Kbps, with distances of up to 25m over twisted-pair copper wiring, 300m on multi-mode fiber-optic cabling, or 10km on single-mode fiber-optic cabling. The 2.4.17 kernel supports one HIPPI card, the Essential RoadRunner, but the driver is considered experimental.

• Fibre Channel— This type of network interface supports both copper and fiber-optic network media, and provides speeds of 133–1062Mbps. When used over fiber-optic cables, Fibre Channel can be used over a 10km range. The 2.4.17 kernel includes support for one Fibre Channel chipset, the Interphase 5526 Tachyon.

Some of these network media, such as Token Ring, are most often used on local networks, typically contained within a single building or a small cluster of buildings. Others, like FDDI and HIPPI, are more often used to link clusters of computers across greater distances, such as between buildings on corporate or university campuses. Linux's support for these technologies means that Linux can function as a router, linking a local network with Ethernet to a broader network that uses a wider-ranging (and higher-speed) standard.

Throughout this book, the assumption is that a computer uses Ethernet. The main feature that changes if one or more interfaces use some other networking technology is the name for the network interface. For Ethernet, this is eth0 for the first device, eth1 for the second, and so on. Other devices use other names, such as tr0 for the first Token Ring device or fddi1 for the second FDDI device.