Networking Hardware and Common Terminologies
CABLES
Cat-5
Short for Category 5, network cabling that consists of four twisted pairs of copper wire
terminated by RJ45 connectors. Cat-5 cabling supports frequencies up to 100 MHz and
speeds up to 1000 Mbps. It can be used for ATM, token ring, 1000Base-T, 100Base-T,
and 10Base-T networking.
Computers hooked up to LANs are connected using Cat-5 cables, so if you're on a LAN,
most likely the cable running out of the back of your PC is Category 5.
Cat-5 is based on the EIA/TIA 568 Commercial Building Telecommunications Wiring
Standard developed by the Electronics Industries Association as requested by the
Computer Communications Industry Association in 1985.
RJ-45
Short for Registered Jack-45, an eight-wire connector used commonly to connect
computers onto a local-area networks (LAN), especially Ethernets. RJ-45 connectors look
similar to the ubiquitous RJ-11 connectors used for connecting telephone equipment, but
they are somewhat wider.
Dark fiber
Dark fiber refers to unused fiber-optic cable. Often times companies lay more lines than
what's needed in order to curb costs of having to do it again and again. The dark strands
can be leased to individuals or other companies who want to establish optical connections
among their own locations.
In this case, the fiber is neither controlled by nor connected to the phone company.
Instead, the company or individual provides the necessary components to make it
functional.
FTTC
Short for fiber-to-the-curb, the installation of optical fiber from a telephone switch to
within 1,000 feet of a home or enterprise. Typically, coaxial cable is used to establish the
connection from curb to building.
IDF
Short for intermediate distribution frame, a cable rack that interconnects and manages the
telecommunications wiring between an MDF and workstation devices. Cables entering a
building run through a centralized MDF, then each individual IDF and then on to specific
workstations. For example, an enterprise that encompasses a building with several floors
may have one MDF on the first floor and one IDF on each of the floors that is connected
to the MDF.
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Null-modem cable
A specially designed cable that allows you to connect two computers directly to each
other via their communications ports (RS-232 ports). Null modems are particularly useful
with portable computers because they enable the portable computer to exchange data with
a larger system.
Patch cord
Also known as a patch cable, a patch cord is a piece of copper wire or fiber optic cable
that connects circuits on a patch panel.
Plenum cable
Cable that is run in the plenum spaces of buildings. In building construction, the plenum
(pronounced PLEH-nuhm) is the space that is used for air circulation in heating and air
conditioning systems, typically between the structural ceiling and the suspended ceiling
or under a raised floor. The plenum space is typically used to house the communication
cables for the buildings computer and telephone network(s). However, use of plenum
areas for cable storage poses a serious hazard in the event of a fire as once the fire
reaches the plenum space there are few barriers to contain the smoke and flames. Plenum
cable is coated with a fire-retardant coating (usually Teflon) so that in case of a fire it
does not give off toxic gasses and smoke as it burns. Twisted-pair and coaxial versions of
cable are made in plenum versions.
Ribbon cable
A flat, thin cable containing many parallel wires. Because of their shape, ribbon cables
are ideal for situations where space needs to be conserved. They're used, for example,
within a computer chassis to connect disk drives to the disk drive controllers.
Twisted-pair cable
A type of cable that consists of two independently insulated wires twisted around one
another. One wire carries the signal while the other wire is grounded and absorbs signal
interference.
While twisted-pair cable is used by older telephone networks and is the least expensive
type of local-area network (LAN) cable, most networks contain some twisted-pair cabling
at some point along the network. Other types of cables used for LANs include coaxial
cables and fiber optic cables.
Coaxial cable
A type of wire that consists of a center wire surrounded by insulation and then a
grounded shield of braided wire. The shield minimizes electrical and radio frequency
interference.
Coaxial cabling is the primary type of cabling used by the cable television industry and is
also widely used for computer networks. Although more expensive than standard
telephone wire, it is much less susceptible to interference and can carry much more data.
Because the cable television industry has already connected millions of homes with
coaxial cable, many analysts believe that they are the best positioned to capitalize on the
much-heralded information highway.
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Information highway
A popular buzzword to describe the Internet, bulletin board services, online services, and
other services that enable people to obtain information from telecommunications
networks. In the U.S., there is currently a national debate about how to shape and control
these avenues of information. Many people believe that the information highway should
be designed and regulated by government, just like conventional highway systems.
Others argue that government should adopt a more laissez faire attitude. Nearly everyone
agrees that accessing the information highway is going to be a normal part of everyday
life in the near future.
Fiber optics
A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic
cable consists of a bundle of glass threads, each of which is capable of transmitting
messages modulated onto light waves.
Fiber optics has several advantages over traditional metal communications lines:
- Fiber optic cables have a much greater bandwidth than metal cables. This means that
they can carry more data.
Fiber optic cables are less susceptible than metal cables to interference.
- Fiber optic cables are much thinner and lighter than metal wires.
Data can be transmitted digitally (the natural form for computer data) rather than
analogically.
The main disadvantage of fiber optics is that the cables are expensive to install. In
addition, they are more fragile than wire and are difficult to split.
Fiber optics is a particularly popular technology for local-area networks. In addition,
telephone companies are steadily replacing traditional telephone lines with fiber optic
cables. In the future, almost all communications will employ fiber optics.
FTTH
Short for fiber-to-the-home, the installation of optical fiber from a telephone switch
directly into the subscriber’s home. Fiber optic cable is an alternative to coaxial cable.
FTTH is also referred to as fiber-to-the-building (FTTB), which includes optical fiber
that is installed directly into a home or enterprise.
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MDF
Short for main distribution frame, a cable rack that interconnects and manages the
telecommunications wiring between itself and any number of IDFs. Unlike an IDF, which
connects internal lines to the MDF, the MDF connects private or public lines coming into
a building with the internal network. For example, an enterprise that encompasses a
building with several floors may have one centralized MDF on the first floor and one IDF
on each of the floors that is connected to the MDF.
OTDR
Short for Optical Time Domain Reflectometer, an instrument that analyzes the light loss
in an optical fiber in optical network trouble shooting. An OTDR injects a short, intense
laser pulse into the optical fiber and measures the backscatter and reflection of light as a
function of time. The reflected light characteristics are analyzed to determine the location
of any fiber optic breaks or splice losses.
NIC
BNC connector
Short for British Naval Connector or Bayonet Nut Connector or Bayonet Neill
Concelman, a type of connector used with coaxial cables such as the RG-58 A/U cable
used with the 10Base-2 Ethernet system. The basic BNC connector is a male type
mounted at each end of a cable. This connector has a center pin connected to the center
cable conductor and a metal tube connected to the outer cable shield. A rotating ring
outside the tube locks the cable to any female connector.
BNC T-connectors (used with the 10Base-2 system) are female devices for connecting
two cables to a network interface card (NIC). A BNC barrel connector allows connecting
two cables together.
BNC connectors can also be used to connect some monitors, which increases the
accuracy of the signals sent from the video adapter.
IRMA board
A popular expansion board for PCs and Macintoshes that enables these personal
computers to emulate IBM 3278 and 3279 mainframe terminals. In other words, personal
computers with IRMA boards can function as both stand-alone computers and as
terminals connected to a mainframe computer. IRMA boards are made by a company
called DCA.
MAC address
Short for Media Access Control address, a hardware address that uniquely identifies each
node of a network. In IEEE 802 networks, the Data Link Control (DLC) layer of the OSI
Reference Model is divided into two sublayers: the Logical Link Control (LLC) layer and
the Media Access Control (MAC) layer. The MAC layer interfaces directly with the
network media. Consequently, each different type of network media requires a different
MAC layer.
On networks that do not conform to the IEEE 802 standards but do conform to the OSI
Reference Model, the node address is called the Data Link Control (DLC) address.
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NDIS
Short for Network Driver Interface Specification, a Windows device driver interface that
enables a single network interface card (NIC) to support multiple network protocols. For
example, with NDIS a single NIC can support both TCP/IP and IPX connections. NDIS
can also be used by some ISDN adapters.
NDIS includes a protocol manager that accepts requests from the network driver (at the
transport layer) and passes these requests to the NIC (at the data link layer). So multiple
NDIS-conforming network drivers can co-exist. Also, if a computer contains multiple
NICs because it is connected to more than one network, NDIS can route traffic to the
correct card.
NDIS was developed by Microsoft and 3COM. Novell offers a similar device driver for
NetWare called Open Data-Link Interface (ODI).
ODI
Short for Open Data-link Interface, an application programming interface (API)
developed by Novell for writing network drivers. ODI separates the physical network
layer (the Data-Link Layer in the OSI model) from the network protocol layer (the
Transport Layer). As a result, the same network interface card (NIC) can be used to carry
data for different protocols. For example, ODI allows a computer with just one NIC to be
simultaneously connected to both an IPX/SPX network and a TCP/IP network.
AUI
Short for Attachment Unit Interface, the portion of the Ethernet standard that specifies
how a cable is to be connected to an Ethernet card. AUI specifies a coaxial cable
connected to a transceiver that plugs into a 15-pin socket on the network interface card
(NIC).
DLC
Short for Data Link Control, the second lowest layer in the OSI Reference Model. Every
network interface card (NIC) has a DLC address or DLC identifier (DLCI) that uniquely
identifies the node on the network. Some network protocols, such as Ethernet and TokenRing use the DLC addresses exclusively. Other protocols, such as TCP/IP, use a logical
address at the Network Layer to identify nodes. Ultimately, however, all network
addresses must be translated to DLC addresses. In TCP/IP networks, this translation is
performed with the Address Resolution Protocol (ARP).
For networks that conform to the IEEE 802 standards (e.g., Ethernet), the DLC address is
usually called the Media Access Control (MAC) address.
Jabber
1) an error in which a faulty device (usually a NIC ) continuously transmits corrupted or
meaningless data onto a network. This may halt the entire network from transmitting data
beacuse other devices will perceive the network as busy.
2) a sent data packet greater than the maximum 1518 bytes specified in IEEE 802.3. To
prevent this, jabber control should be added to the hardware to make the circuitry
incapable of sending information for more than 150 milliseconds (approximately 1500
bytes).
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MAC Layer
The Media Access Control Layer is one of two sublayers that make up the Data Link
Layer of the OSI model. The MAC layer is responsible for moving data packets to and
from one Network Interface Card (NIC) to another across a shared channel.
The MAC sublayer uses MAC protocols to ensure that signals sent from different stations
across the same channel don't collide.
Different protocols are used for different shared networks, such as Ethernets, Token
Rings, Token Buses, and WANs.
Network Interface Card
Often abbreviated as NIC, an expansion board you insert into a computer so the computer
can be connected to a network. Most NICs are designed for a particular type of network,
protocol, and media, although some can serve multiple networks.
Protocol Stack
A set of network protocol layers that work together. The OSI Reference Model that
defines seven protocol layers is often called a stack, as is the set of TCP/IP protocols that
define communication over the internet.
The term stack also refers to the actual software that processes the protocols. So, for
example, programmers sometimes talk about loading a stack, which means to load the
software required to use a specific set of protocols. Another common phrase is binding a
stack, which refers to linking a set of network protocols to a network interface card
(NIC). Every NIC must have at least one stack bound to it. In Windows, the TCP/IP stack
is implemented by the Winsock DLL.
TERMINOLOGIES
Patch panel
A panel of network ports contained together, usually within a telecommunications closet,
that connects incoming and outgoing lines of a LAN or other communication, electronic
or electrical system. In a LAN, the patch panel connects the network's computers to each
other and to the outside lines that enable the LAN to connect to the Internet or another
WAN. Connections are made with patch cords. The patch panel allows circuits to be
arranged and rearranged by plugging and unplugging the patch cords.
TC
Short for Telecommunications Closet, an area, typically a room or closet, that houses all
the equipment associated with telecommunications wiring systems. The TC also serves as
a termination point for the horizontal cabling system of a network, the point of circuit
administration and contains the network's distribution panels, cross-connects and
backbone. All telecommunications wiring is channeled through the TC. The TC may also
house auxiliary power supplies for workstation equipment. The larger the network, the
more TCs are needed since the end workstations can only be a certain distance away from
the TC because of constraints in the type of wiring used. Networks that span multi-level
buildings, such as hospitals, typically have a TC on each floor.
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UTP
Short for Unshielded Twisted Pair, a popular type of cable that consists of two unshielded
wires twisted around each other. Due to its low cost, UTP cabling is used extensively for
local-area networks (LANs) and telephone connections. UTP cabling does not offer as
high bandwidth or as good protection from interference as coaxial or fiber optic cables,
but it is less expensive and easier to work with.
Loopback plug
Also referred to as a loopback adapter. A connection device that is plugged into a
computer's port in order to perform a loopback test.
Loopback test
A diagnostic procedure in which a signal is transmitted and returned to the sending
device after passing through all or a portion of a network or circuit. The returned signal is
compared with the transmitted signal in order to evaluate the integrity of the equipment
or transmission path. A computer needs a loopback plug that is inserted into a port in
order to perform a loopback test.
ASPI
Short for Advanced SCSI Programming Interface, an interface specification developed by
Adaptec, Inc. for sending commands to a SCSI host adapter. ASPI has become a de facto
standard that enables programmers to develop applications and drivers that work with all
ASPI-compatible SCSI adapters.
De facto standard
A format, language, or protocol that has become a standard not because it has been
approved by a standards organization but because it is widely used and recognized by the
industry as being standard. Some examples of de facto standards include:
- Hayes command set for controlling modems
Kermit Communications Protocol
- Xmodem Communications Protocol
Hewlett-Packard Printer Control Language (PCL) for laser printers.
- PostScript page description language for laser printers
DIP switch
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A series of tiny switches built into circuit boards. The housing for the switches, which
has the same shape as a chip, is the DIP.
DIP switches enable you to configure a circuit board for a particular type of computer or
application. The installation instructions should tell you how to set the switches. DIP
switches are always toggle switches, which means they have two possible positions -- on
or off. (Instead of on and off, you may see the numbers 1 and 0.)
One of the historic advantages of the Macintosh over the PC was that it allowed you to
configure circuit boards by entering software commands instead of setting DIP switches.
However, the new Plug & Play standard developed by Microsoft makes DIP switches
obsolete for PC expansion cards too.
Jumper
A metal bridge that closes an electrical circuit. Typically, a jumper consists of a plastic
plug that fits over a pair of protruding pins. Jumpers are sometimes used to configure
expansion boards. By placing a jumper plug over a different set of pins, you can change a
board's parameters.
Hot plugging
The ability to add and remove devices to a computer while the computer is running and
have the operating system automatically recognize the change. Two external bus
standards -- Universal Serial Bus (USB) and IEEE 1394 -- support hot plugging. This is
also a feature of PCMCIA. Hot plugging is also called hot swapping.
3COM
One of the largest networking companies in the world. The name is derived from the
prefixes of three terms -- computer, communication, and compatibility. The company was
founded in 1979 by Dr. Robert Metcalfe, one of the co-inventors of Ethernet.
3COM offers a wide array of products, with special emphasis on hubs, switches, routers,
modems, and NICs.
Bridge
A device that connects two local-area networks (LANs), or two segments of the same
LAN that use the same protocol, such as Ethernet or Token-Ring.
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Concentrator
A type of multiplexor that combines multiple channels onto a single transmission
medium in such a way that all the individual channels can be simultaneously active. For
example, ISPs use concentrators to combine their dial-up modem connections onto faster
T-1 lines that connect to the Internet.
Concentrators are also used in local-area networks (LANs) to combine transmissions
from a cluster of nodes. In this case, the concentrator is often called a hub or MAU.
DSLAM
Short for Digital Subscriber Line Access Multiplexer, a mechanism at a phone company's
central location that links many customer DSL connections to a single high-speed ATM
line.
When the phone company receives a DSL signal, an ADSL modem with a POTS splitter
detects voice calls and data. Voice calls are sent to the PSTN, and data are sent to the
DSLAM, where it passes through the ATM to the Internet, then back through the
DSLAM and ADSL modem before returning to the customer's PC.
More DSLAMs a phone company has, the more customers it can support.
Hub
A common connection point for devices in a network. Hubs are commonly used to
connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one
port, it is copied to the other ports so that all segments of the LAN can see all packets.
A passive hub serves simply as a conduit for the data, enabling it to go from one device
(or segment) to another. So-called intelligent hubs include additional features that enable
an administrator to monitor the traffic passing through the hub and to configure each port
in the hub. Intelligent hubs are also called manageable hubs.
A third type of hub, called a switching hub, actually reads the destination address of each
packet and then forwards the packet to the correct port.
JavaStation
A network computer from Sun Microsystems that uses a Java application platform and a
100-MHZ CPU. JavaStation is a thin client -- a product relying on a network server for
much of its processing -- and Sun promotes it as low-cost alternative for high volume,
fixed-function needs, like processing reservations and transactions. The computer began
shipping in March, 1998.
MAU
(1) Short for Media Access Unit, an Ethernet transceiver.
(2) Short for Multistation Access Unit (also abbreviated as MSAU), a token-ring network
device that physically connects network computers in a star topology while retaining the
logical ring structure. One of the problems with the token-ring topology is that a single
non-operating node can break the ring. The MAU solves this problem because it has the
ability to short out non-operating nodes and maintain the ring structure. A MAU is a
special type of hub.
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MTU
Short for Maximum Transmission Unit, the largest physical packet size, measured in
bytes that a network can transmit. Any messages larger than the MTU are divided into
smaller packets before being sent.
Every network has a different MTU, which is set by the network administrator. On
Windows 95, you can also set the MTU of your machine. This defines the maximum size
of the packets sent from your computer onto the network. Ideally, you want the MTU to
be the same as the smallest MTU of all the networks between your machine and a
message's final destination. Otherwise, if your messages are larger than one of the
intervening MTUs, they will get broken up (fragmented), which slows down transmission
speeds.
Trial and error is the only sure way of finding the optimal MTU, but there are some
guidelines that can help. For example, the MTU of many PPP connections is 576, so if
you connect to the Internet via PPP, you might want to set your machine's MTU to 576
too. Most Ethernet networks, on the other hand, have an MTU of 1500, which is the
default MTU setting for Windows 95.
Router
A device that connects any number of LANs.
Routers use headers and a forwarding table to determine where packets go, and they use
ICMP to communicate with each other and configure the best route between any two
hosts. Very little filtering of data is done through routers. Routers do not care about the
type of data they handle.
RTU
Short for remote terminal unit. In SCADA systems, an RTU is a device installed at a
remote location that collects data, codes the data into a format that is transmittable and
transmits the data back to a central station, or master. An RTU also collects information
from the master device and implements processes that are directed by the master. RTUs
are equipped with input channels for sensing or metering, output channels for control,
indication or alarms and a communications port.
Switching hub
Short for port-switching hub, a special type of hub that forwards packets to the
appropriate port based on the packet's address. Conventional hubs simply rebroadcast
every packet to every port. Since switching hubs forward each packet only to the required
port, they provide much better performance. Most switching hubs also support load
balancing, so that ports are dynamically reassigned to different LAN segments based on
traffic patterns.
Some newer switching hubs support both traditional Ethernet (10 Mbps) and Fast
Ethernet (100 Mbps) ports. This enables the administrator to establish a dedicated, Fast
Ethernet channel for high-traffic devices such as servers.
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Terminator
A device attached to the end-points of a bus network or daisy-chain. The purpose of the
terminator is to absorb signals so that they do not reflect back down the line. Ethernet
networks require a terminator at both ends of the bus, and SCSI chains require a single
terminator at the end of the chain.
Transceiver
Short for transmitter-receiver, a device that both transmits and receives analog or digital
signals. The term is used most frequently to describe the component in local-area
networks (LANs) that actually applies signals onto the network wire and detects signals
passing through the wire. For many LANs, the transceiver is built into the network
interface card (NIC). Some types of networks, however, require an external transceiver.
In Ethernet networks, a transceiver is also called a Medium Access Unit (MAU).
In radio communications, a transceiver is a two-way radio that combines both a radio
transmitter and a receiver that exchanges information in half-duplex mode.
Backbone
Another term for bus, the main wire that connects nodes. The term is often used to
describe the main network connections composing the Internet.
Brouter
Short for bridge router, and pronounced brau-ter, a device that functions as both a router
and a bridge. A brouter understands how to route specific types of packets, such as
TCP/IP packets. Any other packets it receives are simply forwarded to other network(s)
connected to the device (this is the bridge function).
Digital access and cross-connect system (DACS)
A digital switching device in telecommunications for routing T1 lines. The DACS can
cross-connect any T1 line in the system with any other T1 line also in the system. DACS
can also connect any DS-0 channel or group of channels on a T1 line to any DS-0 time
slots of any other line.
FRAD
Short for Frame Relay Assembler/Disassembler, a communications device that breaks a
data stream into frames for transmission over a Frame Relay network and recreates a data
stream from incoming frames. A Frame Relay router serves the same purpose but
provides more intelligence in avoiding congestion.
IDF
Short for intermediate distribution frame, a cable rack that interconnects and manages the
telecommunications wiring between an MDF and workstation devices. Cables entering a
building run through a centralized MDF, then each individual IDF and then on to specific
workstations. For example, an enterprise that encompasses a building with several floors
may have one MDF on the first floor and one IDF on each of the floors that is connected
to the MDF.
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Jukebox
A device that stores numerous CD-ROMs and uses a mechanical arm, carousel or other
device to bring the disk to an optical station for reading and writing. A jukebox can reside
in a PC or be an external device. Some of the larger jukeboxes hold as many as 500 disks
and have multiple readers and drives to allow a network of users to simultaneously access
data.
Repeater
A network device used to regenerate or replicate a signal. Repeaters are used in
transmission systems to regenerate analog or digital signals distorted by transmission
loss. Analog repeaters frequently can only amplify the signal while digital repeaters can
reconstruct a signal to near its original quality.
In a data network, a repeater can relay messages between subnetworks that use different
protocols or cable types. Hubs can operate as repeaters by relaying messages to all
connected computers. A repeater cannot do the intelligent routing performed by bridges
and routers.
Routing switch
A switch that also performs routing operations. Usually a switch operates at layer 2 (the
Data Link layer) of the OSI Reference Model while routers operate at layer 3 (the
Network layer). Routing switches, however, perform many of the layer 3 functions
usually reserved for routers. And because the routing is implemented in hardware rather
than software, it is faster. The downside of routing switches is that they are not as
powerful or as flexible as full-fledged routers.
Because they perform some layer 3 functions, routing switches are sometimes called
layer-3 switches.
Switch
(1) In networks, a device that filters and forwards packets between LAN segments.
Switches operate at the data link layer (layer 2) and sometimes the network layer (layer
3) of the OSI Reference Model and therefore support any packet protocol. LANs that use
switches to join segments are called switched LANs or, in the case of Ethernet networks,
switched Ethernet LANs.
(2) A small lever or button. The switches on the back of printers and on expansion boards
are called DIP switches. A switch that has just two positions is called a toggle switch.
(3) Another word for option or parameter -- a symbol that you add to a command to
modify the command's behavior.
TPS
Short for transactions per second, a measurement used to determine how many
transactions have been processed in one second in transaction-oriented systems.
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SCSI
Acronym for small computer system interface. Pronounced "scuzzy," SCSI is a parallel
interface standard used by Apple Macintosh computers, PCs, and many UNIX systems
for attaching peripheral devices to computers. Nearly all Apple Macintosh computers,
excluding only the earliest Macs and the recent iMac, come with a SCSI port for
attaching devices such as disk drives and printers.
SCSI interfaces provide for faster data transmission rates (up to 80 megabytes per
second) than standard serial and parallel ports. In addition, you can attach many devices
to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.
Although SCSI is an ANSI standard, there are many variations of it, so two SCSI
interfaces may be incompatible. For example, SCSI supports several types of connectors.
While SCSI has been the standard interface for Macintoshes, the iMac comes with IDE, a
less expensive interface, in which the controller is integrated into the disk or CD-ROM
drive. Other interfaces supported by PCs include enhanced IDE and ESDI for mass
storage devices, and Centronics for printers. You can, however, attach SCSI devices to a
PC by inserting a SCSI board in one of the expansion slots. Many high-end new PCs
come with SCSI built in. Note, however, that the lack of a single SCSI standard means
that some devices may not work with some SCSI boards.
The following varieties of SCSI are currently implemented:
- SCSI-1: Uses an 8-bit bus, and supports data rates of 4 MBps
- SCSI-2: Same as SCSI-1, but uses a 50-pin connector instead of a 25-pin connector,
and supports multiple devices. This is what most people mean when they refer to plain
SCSI.
- Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit transfers.
- Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data rates of 10
MBps.
- Fast Wide SCSI: Uses a 16-bit bus and supports data rates of 20 MBps.
- Ultra SCSI: Uses an 8-bit bus, and supports data rates of 20 MBps.
- SCSI-3: Uses a 16-bit bus and supports data rates of 40 MBps. Also called Ultra Wide
SCSI.
- Ultra2 SCSI: Uses an 8-bit bus and supports data rates of 40 MBps.
- Wide Ultra2 SCSI: Uses a 16-bit bus and supports data rates of 80 MBps.
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