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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
align=left border=0> 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 150300m.
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 lengthstheoretically 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 1331062Mbps. 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
align=left border=0> 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.
NOTE
align=left border=0> 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 .
Check with the hardware manufacturer or at target="_blank">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-dsll ,
but these drivers are an unsupported modification of existing Ethernet drivers
and may not work on 2.4.
x or later kernels.
TIP
align=left border=0> 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
target="_blank">http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Toolsl
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 (
for further details, including wiring for the necessary cable, if you can't
find a Turbo Laplink cable.
