- AppleTalk
-
A communications
protocol developed by Apple Computer to allow networking between
Macintoshes. All Macintosh computers have a LocalTalk port, running
AppleTalk over a 230K bps serial line. AppleTalk also runs over
Ethernet (EtherTalk) and Token Ring (TokenTalk) network media.
-
Auto-Negotiate
-
Clause 28 of the IEEE
802.3u standard specifies a MAC sublayer for the identification of
the speed and duplex mode of connection being supported by a device.
Support of this feature is optional for individual vendors.
- Auto-sense
-
Ability of a 10/100
Ethernet device to interpret the speed or duplex mode of the
attached device and to adjust to that rate. Official term is
Auto-Negotiation in Clause 28 of the IEEE 802.3u standard.
- AUI
-
Attachment Unit
Interface. A 15-pin shielded, twisted pair Ethernet cable used
(optionally) to connect between network devices and a MAU.
- Autobaud
-
Automatic determination
and matching of transmission speed.
- AWG
-
American Wire Gauge. A
system that specifies wire size. The gauge varies inversely with the
wire diameter size.
- Backbone
-
The main cable in a
network.
- Bandwidth on
Demand
-
Feature that allows a
remote access device to initiate a second connection to a particular
site to increase the amount of data transferred to that site to
increase the desired threshold. The network manager configuring the
remote access server will specify a number of bits or a percentage
of connection bandwidth threshold which will trigger the secondary
connection. Multilink PPP is an emerging standard to allow this
feature to be interoperable, but right now the only way to ensure
correct operation is to use devices on both end from the same
vendor.
- Baseband LAN
-
A LAN that uses a
single carrier frequency over a single channel. Ethernet, Token Ring
and Arcnet LANs use baseband transmission.
- Baud
-
Unit of signal
frequency in signals per second. Not synonymous with bits per second
since signals can represent more than one bit. Baud equals bits per
second only when the signal represents a single bit.
- Binaries
-
Binary, machine
readable forms of programs that have been compiled or assembled. As
opposed to Source language forms of programs.
- Binary
-
Characteristic of
having only two states, such as current on and current off. The
binary number system uses only ones and zeros.
- Bitronics
-
-
Specification for
parallel printing which allows bidirectional communication on a
Centronics-type interface. Pioneered by Hewlett-Packard, mainly used
for postscript printers.
- Bit
-
The smallest unit of
data processing information. A bit (or binary digit) assumes the
value of either 1 or 0.
- BNC
-
-
A standardized
connector used with Thinnet and coaxial cable.
- BOOTP
-
A TCP/IP network
protocol that lets network nodes request configuration information
from a BOOTP "server" node.
- bps
-
Bits per second, units
of transmission speed.
- Bridge
-
A networking device
that connects two LANs and forwards or filters data packets between
them, based on their destination addresses. Bridges operate at the
data link level (or MAC-layer) of the OSI reference model, and are
transparent to protocols and to higher level devices like routers.
- Broadband
-
A data transmission
technique allowing multiple high-speed signals to share the
bandwidth of a single cable via frequency division multiplexing.
- Broadband
Network
-
A network that uses
multiple carrier frequencies to transmit multiplexed signals on a
single cable. Several networks may coexist on a single cable without
interfering with one another.
-
- Brouter
-
A device that routes
specific protocols, such as TCP/IP and IPX, and bridges other
protocols, thereby combining the functions of both routers and
bridges.
- Bus
-
A LAN topology in which
all the nodes are connected to a single cable. All nodes are
considered equal and receive all transmissions on the medium.
-
- Byte
-
A data unit of eight
bits.
- Channel
-
-
The data path between
two nodes.
-
- CHAP
-
(Challenge Handshake
Authentication Protocol) Authentication scheme for PPP where the
password not only is required to begin connection but also is
required during the connection - failure to provide correct password
during either login or challenge mode will result in disconnect.
- Coaxial Cable
-
An electrical cable
with a solid wire conductor at its center surrounded by insulating
materials and an outer metal screen conductor with an axis of
curvature coinciding with the inner conductor - hence "coaxial."
Examples are standard Ethernet cable and Thinwire Ethernet cable.
-
- Collision
-
The result of two
network nodes transmitting on the same channel at the same time. The
transmitted data is not usable.
- Collision
Detect
-
A signal indicating
that one or more stations are contending with the local station's
transmission. The signal is sent by the Physical layer to the Data
Link layer on an Ethernet/IEEE 802.3 node.
- Communication
Server
-
A dedicated, standalone
system that manages communications activities for other computers.
- Console
-
The terminal used to
configure network devices at boot (start-up) time.
- Crosstalk
-
Noise passed between
communications cables or device elements.
-
- Cut-through
-
Technique for examining
incoming packets whereby an Ethernet switch looks only at the first
few bytes of a packet before forwarding or filtering it. This
process is faster than looking at the whole packet, but it also
allows some bad packets to be forwarded.
- CSMA/CD
-
Carrier Sense Multiple
Access with Collision Detection is the Ethernet media access method.
All network devices contend equally for access to transmit. If a
device detects another device's signal while it is transmitting, it
aborts transmission and retries after a brief pause.
- Data Link
-
A logical connection
between two nodes on the same circuit.
-
- Data Link
Layer
-
Layer 2 of the
seven-layer OSI reference model for communication between computers
on networks. This layer defines protocols for data packets and how
they are transmitted to and from each network device. It is a
medium-independent, link-level communications facility on top of the
Physical layer, and is divided into two sublayers: medium-access
control (MAC) and logical-link control (LLC).
- DECnetTM
-
Digital Equipment
Corporation (DEC) proprietary network architecture, a system for
networking computers. It runs on point-to-point, X.25 and Ethernet
networks.
-
- Dial on
Demand
-
When a router detects
the need to initiate a dial-up connection to a remote network, it
does so automatically according to pre-defined parameters set by the
network manager.
- Dialback
-
A security feature that
ensures people do not log into modems that they shouldn't have
access to. When a connection is requested, the system checks the
user name for validity, then "dials back" the number associated with
that user name.
- Distributed
Processing
-
A system in which each
computer or node in the network performs its own processing and
manages some of its data while the network facilitates
communications between the nodes.
- Domain Name
-
A domain name is a text
name appended to a host name to form a unique host name across
internets.
- Download
-
The transfer of a file
or information from one network node to another. Generally refers to
transferring a file from a "big" node, such as a computer, to a
"small" node, such as a terminal server or printer.
- End Node
-
-
A node such as a PC
that can only send and receive information for its own use. It
cannot route and forward information to another node.
- Ethernet
-
The most popular LAN
technology in use today. The IEEE standard 802.3 defines the rules
for configuring an Ethernet network. It is a 10 Mbps, CSMA/CD
baseband network that runs over thin coax, thick coax, twisted pair
or fiber optic cable.
-
- EtherTalk
-
Apple Computer's
protocol for Ethernet transmissions.
- FDDI
-
-
Fiberoptic Data
Distribution Interface. A cable interface capable of transmitting
data at 100 Mbps. Originally specified for fiber lines, FDDI can
also operate over twisted-pair cable for short distances.
- Fiber-Optic
Cable
-
-
A transmission medium
composed of a central glass optical fiber cable surrounded by
cladding and an outer protective sheath. It transmits digital
signals in the form of modulated light from a laser or LED
(light-emitting diode).
- File Server
-
A computer that stores
data for network users and provides network access to that data.
- Filtering
-
Process whereby an
Ethernet switch or bridge reads the contents of a packet and then
finds that the packet does not need to be forwarded, drops it. a
filtering rate is the rate at which a device can receive packets and
drop them without any loss of incoming packets or delay in
processing.
- Firmware
-
Alterable programs in
semipermanent storage, e.g., some type of read-only or flash
reprogrammable memory.
- Forwarding
-
Process whereby an
Ethernet switch or bridge reads the contents of a packet and then
passes that packet on to the appropriate attached segment. A
forwarding rate is the time that it takes the device to execute all
of the steps.
- Flash ROM
-
See ROM.
- Framing
-
Dividing data for
transmission into groups of bits, and adding a header and a check
sequence to form a frame.
- FTP
-
File Transfer Protocol,
a TCP/IP protocol for file transfer.
- Full-Duplex
-
Independent,
simultaneous two-way transmission in both directions, as opposed to
half-duplex transmission.
-
- Gateway
-
A device for
interconnecting two or more dissimilar networks. It can translate
all protocol levels from the Physical layer up through the
Applications layer of the OSI model, and can therefore interconnect
entities that differ in all details.
-
- Hardware
Address
-
See Network Address.
-
- Header
-
-
The initial part of a
data packet or frame containing identifying information such as the
source of the data, its destination, and length.
-
- Heartbeat
-
Ethernet defined SQE
signal quality test function.
- Hertz (Hz)
-
A frequency unit equal
to one cycle per second.
- Host
-
Generally a node on a
network that can be used interactively, i.e., logged into, like a
computer.
- Host Table
-
A list of TCP/IP hosts
on the network along with their IP addresses.
- IEEE 802.3
-
The IEEE (Institute of
Electrical and Electronic Engineers) standard that defines the CSMA/CD
media-access method and the physical and data link layer
specifications of a local area network. Among others, it includes
10BASE2, 10BASE5, 10BASE-FL and 10BASE-T Ethernet implementations.
- Internet
-
A series of
interconnected local, regional, national and international networks,
linked using TCP/IP. Internet links many government, university and
research sites. It provides E-mail, remote login and file transfer
services.
-
Internetworking
-
General term used to
describe the industry composed of products and technologies used to
link networks together.
- IP Address
-
See Network Address.
-
- IPX
-
Internetwork Packet
eXchange, a NetWare protocol similar to IP (Internet Protocol).
- ISDN
-
(Integrated Services
Digital Network): All digital service provided by telephone
companies. Provides 144K bps over a single phone line (divided in
two 64K bps "B" channels and one 16K bps "D" channel).
- ISO Layered
Model
-
The International
Standards Organization (ISO) sets standards for computers and
communications. Its Open Systems Interconnection (OSI) reference
model specifies how dissimilar computing devices such as Network
Interface Cards (NICs), bridges and routers exchange data over a
network. The model consists of seven layers. From lowest to highest,
they are: Physical, Data Link, Network, Transport, Session,
Presentation and Application. Each layer performs services for the
layer above it.
- Jabber
-
Network error caused by
an interface card placing corrupted data on the network. Or, an
error condition due to an Ethernet node transmitting longer packets
than allowed.
- Kbps
-
Kilobits per second.
-
- Kermit
-
A popular file transfer
and terminal emulation program.
- LAN
-
Local Area Network, a
data communications system consisting of a group of interconnected
computers, sharing applications, data and peripherals. The
geographical area is usually a building or group of buildings.
- LAT
-
Local Area Transport, a
Digital Equipment Corporation proprietary network communication
protocol. The protocol is based on the idea of a relatively small,
known number of hosts on a local network sending small network
packets at regular intervals. LAT will not work on a wide area
network scale, as TCP/IP does.
- Latency
-
The delay incurred by a
switching or bridging device between receiving the frame and
forwarding the frame.
- Layer
-
In networks, layers
refer to software protocol levels comprising the architecture, with
each layer performing functions for the layers above it.
- Line Speed
-
Expressed in bps, the
maximum rate at which data can reliably be transmitted over a line
using given hardware.
- Load
Balancing
-
Shifting a user job
from a more heavily loaded resource to a less loaded resource.
- Local Network
Interconnect (LNI)
-
A Port Multiplier, or
concentrator supporting multiple active devices or communications
controllers, either used standalone or attached to standard Ethernet
cable.
- LocalTalk
-
Apple Computer's
proprietary 230 Kbps baseband network protocol. It uses the CSMA/CD
access method over unshielded twisted pair wire.
- Logical Link
-
A temporary connection
between source and destination nodes, or between two processes on
the same node.
-
- LPD
-
Line Printer Daemon, a
process on Berkeley spooler implementations that provides LPR
support.
- LPR
-
The LPR command is used
to queue print jobs on Berkeley queuing systems.
