Network Hardware Options


The Network Device Support kernel menu contains options related to network hardware. The most important of these options are drivers for specific network cards. The most common types of network cards today are Ethernet devices, but others include traditional local network hardware, long-distance devices, and wireless devices. PC Card devices (for notebook computers) have their own submenu off of the Network Device Support menu. You also select dial-up devices (used to establish connections over telephone modems and some other types of hardware) here.

Most of these devices require that you select the Network Device Support option at the top of the Network Device Support menu. If you fail to do this, other options won't be available.

Ethernet Devices

Ethernet is the most common type of local network hardware in 2002, and it seems likely to retain that status for some time. (Wireless technologies, discussed shortly, are becoming popular in some environments, but they lag behind Ethernet and several other wired technologies in terms of speed.) From the point of view of an OS, the problem with Ethernet's popularity is that it's spawned literally hundreds, if not thousands, of specific Ethernet cards.

Fortunately, most Ethernet cards use one of just a few chipsets, so Linux can support the vast majority of Ethernet cards with about 60 drivers. These drivers are split across two submenus: the Ethernet (10 or 100 Mbit) and Ethernet (1000 Mbit) menus . By far the most drivers appear in the first menu, which as the name implies covers 10 and 100Mbps devices. (The most popular type of Ethernet in 2002 is 100Mbps, although 1000Mbps, or gigabit Ethernet, is gaining in popularity, and 10 gigabit Ethernet is being developed.)

NOTE

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In addition to three common Ethernet speeds, there are several different types of Ethernet cabling: coaxial (used only with some forms of 10Mbps Ethernet), twisted-pair (used by some types of 10Mbps, all types of 100Mbps, and some forms of gigabit Ethernet), and fiber- optic (used by some forms of gigabit Ethernet). Twisted-pair cabling supports distances of up to 100 meters (m) between devices (one of which is normally a central hub or switch), and fiber-optic cabling permits distances of up to 5 kilometers (km) between devices.


The organization of the 10 or 100Mbps driver menu is less than perfect. The menu begins with listings for several popular or once-popular devices from 3Com, SMC, Racal-Interlan, and a few other companies; proceeds with a grouping of Industry Standard Architecture (ISA) bus cards; continues with a grouping of Extended ISA (EISA), VESA Local Bus (VLB), and Peripheral Component Interconnect (PCI) cards; and concludes with a grouping of parallel-to-Ethernet adapters. You may need to search for your card in two or three places because of this organization.

A few Ethernet devices aren't activated through drivers in the Network Device Support menu or its submenus. Specifically, PC Card devices have their own drivers, as described shortly, and USB-to-Ethernet adapters are activated in the USB Support menu. To use a USB device, you must activate Support for USB; either UHCI Support or OHCI Support, depending upon which type of controller your motherboard uses; and an appropriate USB network driver option, such as USB ADMtek Pegasus-Based Ethernet Device Support.

Alternative Local Network Devices

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 x 86 boards for interfacing x 86 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.

NOTE

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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.


Broadband and WAN Devices

Broadband is a term that's commonly applied in a couple of different ways. First, it may refer to a networking technology that allows for the simultaneous transmission of multiple types of information, such as video, audio, and digital data. Second, it may refer to a substitute for ordinary dial-up telephone network connections that permits substantially higher speeds (typically 200Kbps or greater). Although 200Kbps doesn't sound like much compared to technologies like Ethernet, it's a substantial improvement over 56Kbps telephone dial-up speeds.

Residential and small business customers frequently use broadband technologies to link to the Internet through an Internet Service Provider (ISP), or occasionally to link multiple sites without running dedicated cables. Typically, broadband connections link a computer that you own to the Internet as a whole. This contrasts with the other network technologies described here, which normally link together a group of computers that you own or administer. Therefore, broadband connections frequently require that you conform to some requirements of the ISP that provides the connection. Many low-end broadband ISPs require that you not run servers, for instance.

In 2002, the most popular forms of broadband are Digital Subscriber Line (DSL) and cable modems. DSL comes in several varieties, such as Asymmetric DSL (ADSL) and Single-Line (or Symmetric) DSL (SDSL), and operates using high-frequency signals over ordinary telephone lines. Cable modems operate over cable TV networks by occupying the bandwidth of one TV channel (often with some additional bandwidth reserved, as well). Broadband through satellite systems, local radio-frequency transmissions, and fiber-optic cabling are also available in at least some areas.

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For more information on broadband Internet connections, consult my Broadband Internet Connections: A User 's Guide to DSL and Cable (Addison-Wesley, 2001).


Most broadband connections use an external modem that sports a broadband connector for linking to the broadband network and an Ethernet port for connecting to your computer. You therefore need a supported Ethernet adapter, and you configure that adapter with the standard Linux drivers. The broadband modem itself needs no special drivers, although some ISPs require you to use the Point-to-Point Protocol over Ethernet (PPPoE), which is implemented in Linux via the experimental PPP over Ethernet driver in the Network Device Support menu. (This option requires that you first enable the PPP Support option, discussed shortly in "Dial-Up Devices.") Another PPPoE option is to use the Roaring Penguin PPPoE package, available from http://www.roaringpenguin.com/pppoe/.

Some broadband modems come with USB interfaces rather than Ethernet interfaces. The 2.4.17 Linux kernel supports none of these devices, although Alcatel provides Linux drivers for its Speed Touch USB DSL modem at http://www.alcatel.com/consumer/dsl/supuser.htm. Check with the hardware manufacturer or at http://www.linux-usb.org for updated information on drivers for other USB products.

Some broadband modems, particularly for low-end ADSL accounts, come as internal PCI cards. As with USB devices, support for these is rare. The 2.4.17 kernel includes support for the General Instruments Surfboard 1000, an old one-way cable modem. ( One-way means that it only receives data; you must use a conventional telephone modem to send data. One-way broadband services are undesirable and are becoming rare.) Drivers for the Diamond 1MM DSL modem are available from http://www.rodsbooks.com/network/network-dsl.html, but these drivers are an unsupported modification of existing Ethernet drivers and may not work on 2.4. x or later kernels .

TIP

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If your broadband provider doesn't give you the option of an Ethernet- interfaced modem, buy one yourself and sell the modem your ISP provides on an auction site like eBay (http://www.ebay.com). Be sure you buy a compatible modem, though, and only sell the one your ISP provides if it's given to you or if you must buy it; don't sell a modem your ISP rents to you!


Another type of long-distance connection is a Wide-Area Network (WAN). This type of technology allows connections over dedicated long-distance circuits, often called leased lines because they may be ordinary telephone lines leased from the telephone company. (The phone company doesn't provide a signal on the other end, though; you do.) Such connections often use external devices, known as WAN routers, which link to a Linux computer or local network much as do broadband modems. Another option is to use a dedicated WAN interface card. Linux includes support for a range of such devices in the WAN Interfaces submenu of the Network Device Support menu. As with many other submenus, you must select the first option (WAN Interfaces Support), then select the option corresponding to the device you intend to use.

Wireless Devices

Beginning in the late 1990s, wireless networking technologies rose rapidly in popularity. These technologies allow computers to network even without physical cabling connecting them. Such an arrangement is particularly helpful in existing homes and offices in which running conventional wired network cables would be troublesome , and for users of notebook computers and other portable devices, who might want or need to roam about without plugging the computer into a physical network.

Unfortunately, in 2001 the wireless world still suffers from some drawbacks compared to conventional Ethernet networks. Wireless networks are more expensive than are Ethernet networks, they're slower, and they aren't as well standardized. The most important standards for wireless in 2001 are 802.11 and 802.11b. The former supports speeds of 2Mbps, with a fallback to 1Mbps. ( Fallback refers to a renegotiation of the connection when signal strength falls , as when there's interference or the computers are far apart from one another.) 802.11b supports speeds of 11Mbps, with fallback speeds of 5.5Mbps, 2Mbps, and 1Mbps. Another wireless technology that's received a lot of press is Bluetooth, which supports speeds of up to 1Mbps. Bluetooth-enabled printers, cell phones, and the like will probably begin shipping in volume in 2002. Future developments are likely to increase available speeds. For instance, plans are underway to develop a wireless version of ATM with speeds of up to 155Mbps.

Wireless LANs are typically implemented through wireless PC Cards in notebook computers. These cards may either communicate directly with one another or may require the use of a base station, which may also serve as an interface to a conventional wired network or to a broadband or conventional telephone modem connection to the Internet. There are also wireless ISA and PCI cards, so that desktop systems can participate in wireless networks, or serve as base stations for roaming devices. PC Cards, ISA cards, and PCI cards all require Linux drivers, but base stations require no special support.

Linux support for wireless devices appears under the Wireless LAN (Non-Hamradio) submenu. This menu lists specific drivers by the chipsets or cards for which they're written, not for the technology (such as 802.11b or Bluetooth) those cards use. In addition to kernel drivers, there are two packages known as the Wireless Extensions and Wireless Tools that help you manage a wireless network under Linux. Check http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html for information on these packages, and for additional links to information on wireless networking in Linux.

PC Card Devices

Most notebook computers come with at least one PC Card slot. (Much Linux documentation refers to PC Card technology by its old name, PCMCIA, which stands for the developer of the standards, the Personal Computer Memory Card International Association. ) PC Card devices can be installed and removed from a computer while it's still running, and the OS has no say over this matter. Because Linux was designed with the assumption that network interfaces would not disappear without warning, a separate package, Card Services, helps manage these matters, cleanly starting and stopping kernel features related to PC Card devices when they're inserted or removed. You can find more information on Card Services at http:// pcmcia-cs . sourceforge .net.

The 2.4.17 kernel includes support for many PC Card network devices in the PCMCIA Network Device Support submenu. Some wireless cards' drivers appear in the Wireless LAN (Non-Hamradio) submenu. When you select such a card and configure it, it functions much like a standard ISA or PCI card. For instance, an Ethernet PC Card appears as eth0 and is configured with the standard tools, as described in Chapter 2.

Kernels prior to the 2.4. x series required a separate package of drivers to use PC Card devices, and in fact many PC Card devices are still not supported in the standard kernel. You may therefore need to check out this package, which is part of the Card Services collection. You're unlikely to need to use special drivers for a PC Card network device if you use a 2.4. x or later kernel, but you might need this for a modem, SCSI host adapter, or something else.

Dial-Up Devices

The final class of network devices is the dial-up device. Most typically, this is a conventional telephone modem used in conjunction with the Point-to-Point Protocol (PPP) to establish a connection to the Internet via an ISP. Such connections are established via command-line or GUI tools, as described in Chapter 2. In addition to these tools, though, the Linux kernel requires support for the dial-up connection.

To activate this support, you must select the PPP (Point-to-Point Protocol) Support option in the Network Device Support menu. When you select this option, several suboptions will become available, such as PPP Support for Async Serial Ports and PPP Deflate Compression. These options aren't usually strictly necessary, but sometimes they can improve a connection, such as by automatically compressing highly compressible data like text for higher net throughput. The experimental PPP over Ethernet option is required if you intend to use the kernel's PPPoE features for some DSL connections, but this option is not required with some add-on PPPoE packages, like Roaring Penguin.

PPP is sometimes used on connections that don't involve modems. For instance, you can use it to network two computers via their serial ports. Such configurations are seldom worthwhile with desktop systems, because Ethernet cards are inexpensive and provide much faster connections. You might want to use this type of link when connecting a desktop system to a palmtop computer, though, or for a temporary connection if you don't want to bother installing network cards.

PPP isn't the only type of dial-up connection that Linux supports. The kernel includes support for the older Serial Line Internet Protocol (SLIP), which serves much the same function as PPP. SLIP has been largely abandoned by ISPs, so it's unlikely you'll need to use it over a modem. A few Linux tools use it locally, though; for instance, some types of dial-on-demand utilities (which dial a PPP connection whenever network activity is detected ) use SLIP to detect outgoing connection attempts.

Another protocol that's akin to PPP and SLIP is the Parallel Line Internet Protocol (PLIP). As you might guess by the name, this protocol lets you connect two Linux computers via their parallel (printer) ports. Because these ports are much faster than are RS-232 serial ports, PLIP offers a speed advantage over PPP or SLIP for two-computer local networks. Ethernet is still faster, though. To use PLIP, you must select the PLIP (Parallel Port) Support option in the Network Device Support menu. To do this, you must first activate the Parallel Port Support option in the menu of the same name, including the PC-Style Hardware option (if you're using an x 86 computer). If you need to use PLIP networking, you should consult the PLIP Mini-HOWTO (http://www.linuxdoc.org/HOWTO/mini/PLIP.html) for further details, including wiring for the necessary cable, if you can't find a Turbo Laplink cable.



Advanced Linux Networking
Advanced Linux Networking
ISBN: 0201774232
EAN: 2147483647
Year: 2002
Pages: 203

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