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A glossory of networking & telecommunications term
GLOSSARY OF NETWORKING & TELECOM - PART 1
ONLINE LIBRARIES AND MICROCOMPUTERS
APRIL 1989
Msg. G0069 Category: NEWS & TRENDS
BRIEF GLOSSARY OF NETWORKING & TELECOMMUNICATIONS, PART 1
Telecommunications and networking of library computer systems has become a
major trend. It is virtually impossible to read about any library
automation project without being bombarded with a plethora of specialized
terminology, technical terms and acronyms. The scope of telecommunications
technology is immense and it is impossible to provide a complete list of
terms.However, this brief glossary is intended to offer non-technical
definitions to some commonly used terms.Even this brief listing is too
lengthy to fit in one issue of Online Libraries and Microcomputers, so
that the definitions will be finished in the May 1989 issue.
Combining Parts 1 and 2 of this series will provide the information
manager with a very useful list of terms which may be useful to keep as a
reference tool.
FILE SERVER - A device on a LAN that provides central storage for data
files.
FREQUENCY DIVISION MULTIPLEXING - Divides the bandwidth of a data channel
into two or more subchannels. See multiplexing.
FTAM - File Transfer, Access, and Management. An application utility in
OSI that offers access to files on the network no matter what file format
or host operating system.
FTP - File Transfer Protocol. An application utility in TCP/IP.
FULL DUPLEX - Simultaneous independent transmission in two directions.
GATEWAY - A device connecting between two dissimilar networks that adds
security, flow control, and protocol conversion.It requires software
ACCESS CHANNELS - Used to connect a local subscribers equipment to a long
distance network (often phone lines).
ACCUMASTER INTEGRATOR - AT&T's UNIX-based system capable of automatically
uploading information from other element management systems via the NMP
interface.
ACCUMASTER CONSOLIDATED WORKSTATION (ACW) - An MS-DOS based system that
displays a consolidated network view by providing separate windowing
sessions to various AT&T EMSs.
ACOUSTIC COUPLER - A device into which one puts a telephone headset to
receive and transmit data.These are outmoded devices and are now rarely
sold although many are still in use with microcomputers and terminals in
homes.
ASYNCHRONOUS TRANSMISSION - Bytes (characters) of information are sent
with special starting bits and stop bits which are identifiable by the
sending and receiving devices. Since characters can be sent one at a time
itrequires aless sophisticatedinterfacethana synchronous
transmission. Contrast with synchronous transmission.
AIX - a form of UNIX that operates on an IBM RT PC workstation.
ANALOG SIGNALS - Signals that vary continuously by amplitude or frequency.
Historically older transmission systems have been analog (e.g. the phone
service) although most newer systems are digital in nature. Compare with
digital signals.
ANSI - American National Standards Institute.
API - Application Program Interface.This is a program which allows
applications programs to talk to communications software, thus allowing
particular applications to be developed separately from communications.
APPC - Advanced Program-to-Program Communication. This API was developed
by IBM to allow its SNA networks to communicate without the need of a
mainframe (also called LU6.2).
APPLICATION LAYER - In the OSI model this is the 7th layer (highest) and
is responsible for providing application programs for the end user.
ARCNET - Datapoint has developed this low-cost LAN which operates at 2.5
Mbps per second.
ARPANET - The Defense Advanced Research Projects Agency developed this
packet-switching network to connect computing facilities between the
federal government and academia.TCP/IP was originally developed as a
part of the ARPANET project.
ATTENUATION - The amount by which an electrical signal (including
microwave, radio, infrared, and light waves) weakens over distance as it
moves through the transmission media.
AUTO-DIAL - The ability of a computer to automatically dial a telephone
number through a modem.
BACKBONE NETWORK - a high speed network that links smaller or lower-speed
networks.
BANDWIDTH - The range of frequencies that can be transmitted in a
communications medium (cable, fiber, radio, etc.).The higher the
bandwidth, the more data that can be transmitted.
BASEBAND - A single channel network that transmits digital signals (see
broadband). An example is an Ethernet data link channel.
BAUD RATE - One signal element transmission per second. A baud and Bps are
not necessarily the same although they may be.With various modulation
techniques it is possible to encode more than one bit of data into a
single signal element. Compare with Bps.
BITNET - An electronic mail system that has been established between
academic institutions through the auspices of EDUCOM.
Bps - Bit Per Second.Transmission at one bit per second. Compare with
baud rate.
BRIDGE - A device similar to a gateway except it connects similar networks
to one another and is normally self-programmed. Bridges function at the
data link layer of the OSI model.
BROADBAND - A multiple channel network that carries information by carrier
waves rather than directly as digital signals providing greater capacity.
Such backbones can carry data, radio, video and voice signals.
BSD - Berkeley Software Distribution. A version of UNIX developed by the
University of California at Berkeley.
BUS - In LANs this is a topology in which devices are attached to a single
strand of cable running between two points.
CARRIER - A signal on a communications media that does not carry data
until it is modified in some way (frequency modulation, amplitude
modulation).
CCITT-ComiteConsultatifInternationaledeTelegraphique et
Telephonique. An international body that develops standards.
CENTRAL SUPPORT UNIT - a department that has the staff and technical
expertise to provide high-levelsupport for agiven computer or
communications system.
CHANNEL CAPACITY - The volume of data that can be transmitted over a
particular circuit or line.
CHEAPERNET - A name variation for Thin Ethernet.
CMIP - Common Management Information Protocol.An OSI standard for
network management.
CMIS - Common Management Information Services. An OSI standard for network
management. CMIS services are provided by CMIP.
COAX - Coaxial cable is a type of electrical cable which has high
bandwidth, low cost, and low susceptibility to interference. However, it
is often difficult and expensive to install.
COMMON CARRIER - A government regulated private company that furnishes the
public with telecommunications services (e.g. phone companies).
CONCENTRATOR - A device used to divide a data channel into two or more at
a lower speed. Also called an asynchronous time division multiplexor.
CONNECTIVITY - The ability of computer devices to send and receive data
with one another. However, this does not mean that two devices
necessarily interoperate.
CORPORATION FOR OPEN SYSTEMS - A group of computer companies which are
developing support for OSI-based products with a special emphasis on
conformance testing.
CROSSTALK - A leakage of a transmitted signal whena signal on one path
escapes onto another transmission path causing distortion.
CSMA/CD - Carrier Sense Multiple Access with Collision Detection. A LAN
access method in which if data is being sent by one node and it detects a
collision with other data, it waits and then retransmits. This method is
used in Ethernet.
DAA - Data Access Arrangement. Data communications equipment approved or
furnished by a common carrier that permits the attachment of a computer to
the common carrier network (usually phone line).
DARPA - Defense Advanced Research Projects Agency. A U.S. federal agency
which was responsible for the development of the ARPANET network and the
development of the TCP/IP protocols.
DATA CLOCK - The signal timing element which is necessary for the
detection and decoding of a received signal. This can be derived from the
incoming signals.
DATAGRAM - Data which is transmitted as an isolated entity across a
network.This data does not need to be transmitted in order and in this
type of service any error checking must be accomplished by higher-layer
protocols or by the end user.
DATA LINK LAYER - In the OSI model this is layer 2 which represents the
physical medium.The IEEE splits this layer into two sections: LLC and
MAC.
DCNA - Data Communication Network Architecture. A communications network
developed by IBM/Japan and Nippon Telegraph and Telephone Corporation
(NTT).
DECNET - Digital Equipment Corporation's proprietary networking protocol.
Phase V which will be available in late 1989 will be OSI compliant.
DE FACTO STANDARD - An unofficial standard that is widely used in the
industry because manufacturers choose to use it.
DE JURE STANDARD - An official standard developed and adopted by a formal
standards making body such as IEEE, ANSI, CCITT, ISO, etc.
DEDICATED LINE - A dedicated or leased line is a communication line used
exclusively by one customer.In a telephone leased line the line often
does not pass through inter-exchange switching equipment and the line is
leased on a flat monthly fee regardless of how much data is transmitted.
DIGITAL SIGNALS - Signals which consist of a series of discrete elements
that have only one value at a time.Digital transmission systemsare
the heart of most modern communication systems. Contrast with analog
signals.
DIALNET - DIALOG Information Service'sproprietary packet switching
network.
DNA - Digital Network Architecture.The network architecture of Digital
Equipment Corporation of which DECnet is one implementation.
DNS - Domain Name Server.A system that provides for the translation of
computer names to individual TCP/IP addresses.
DS1 - An AT&T standard for the transmission of high speed data over T1
facilities.
DSU/CSU - The DSU is a synchronous data line driver for short-distances
and a CSU is an access arrangement that offers local-loop equalization,
protectionfrom electricaltransients,self-testing,and circuit
isolation.Thus a DSU/CSU is used to connect digital data devices to a
digital network. These devices are commonly bundled.
ELEMENT MANAGEMENT SYSTEM (EMS) - A system that manages network elements.
This encompasses a host of devices such as modems, multiplexers and DSUs.
EMA - Enterprise Management Architecture. Digital Equipment Corporations
OSI-based network management strategy.Like UNMA, EMA provides for
multivendor network management using interfaces based on OSI standards.
END-TO-END - Communication between the source and destination nodes on a
network.The transport layer handles end-to-end communications (contrast
with point-to-point).
ETHERNET - A comprehensive baseband CSMA/CD data communications standard
that interconnects computers and local area networks.The standard
version of Ethernet is defined by IEEE in 802.3, 10BASE5. A broadband
version is defined in 10BASE36; Thin Ethernet using RG-58 coax cable is
defined in 10BASE2 and a version using twisted pair cable is specified in
10BASET.
FCC - Federal Communications Commission.A U.S. Government agency which
regulates many aspects of communications.
FDDI - Fiber Distributed Data Interface. This is ANSI standard X3T9.5 and
was developed to allow a cluster of large computers to communicate with
each other and peripheral devices with 100-Mbps bandwidth for up to 500
station connections over an optical fiber. Dual rings can support up to
1000 nodes.
FIBER OPTIC CABLE - A transmission medium that uses light waves to
transmit data over glass fibers. This medium offers higher transmission
rates and better security than electromagnetic signals but is more
expensive.
programming and central management.
GOSIP - Government OSI Profile.An OSI based standard that the U.S.
federal government has specified as an information processing standard for
government contracts.
HALF DUPLEX - A circuit that permits data communications in two directions
but not at the same time.
HANDSHAKING - The exchange of predetermined signals for the purposes of
control between two devices.
HIGH LEVEL DATA LINK CONTROL (HDLC) - A bit oriented data link control
developed by ISO.
HUB - A central server in a star-configured network.
IBM CABLING SYSTEM - The specifications for the types of cables to be used
in connecting IBM products.
IBM LAN SERVER - An IBM network operating system built around the LAN
Manager.
IBM PC LAN - An IBM network operating system built around MS-NET.
IBM TOKEN RING NETWORK - A 2 Mbps LAN from IBM which uses token-passing
techniques in a ring technology.Higher speed versions at 4 Mbps and 16
Mbps are also available (IEEE 802.5 is the standard).
IEE - Institution of Electrical Engineers.A British-based society of
professional engineers.
IEEE - The Institute of Electrical and Electronic Engineers. A U.S.-based
society of professional engineers.
IETF - Internet Engineering Task Force. An organization which updates the
TCP/IP standards.
AN INTERNET - A set of interconnected, logically independent networks.
INTERNET - The collection of networks that connect government, university
and commercial agencies (e.g. NSFNET, WestNet, etc.).
INTEROPERABILITY - The ability of devices from different companies to
exchange information and to understand and operate on the data that are
exchanged.
INTEROPERATOR - A hardware device or software package which implements
part of OSI standards and can work with hardware or software using other
parts of the OSI model.
IP ADDRESS - The address used to define the computer node number according
to the TCP/IP protocol.
ISDN- IntegratedServices Digital Network. Adigitized
telecommunications network in which data and voice would be carried over
the same line using OSI standards.
ISO - The International Standards Organization.An international group
which promotes the development of computer (and other) standards. The OSI
standards have been developed by this organization.
JABBER - Noise on a network caused by the random transmission of data due
to a malfunction.
Kbps - Kilobits per second.
LAN - Local Area Network. A cluster of PCs and other computer peripherals
inarelatively smallarea interconnected forthepurpose of
communications, file transfer and sharing of peripheral hardware.
LAN MANAGER - A network operating system developed by 3Com and Microsoft
that takes advantage of the OS/2 operating system. This term is also used
to refer to a person who is responsible in an organization for the daily
operations and maintenance of a LAN.
LAN SERVER - A proprietary version of IBM's LAN Manager.
LAT - Digital Equipment Corporation has developed this proprietary
protocol for terminal services which provides communication for terminals
across an Ethernet LAN.
LAYER - The conceptual level of network processing functions. For
example, in OSI Reference Model the network processing takes place in 7
different layers from the physical transmission of data up to the
applications layer.
LAYER INTERFACE - A means of communication between the different adjacent
layers of the OSI model.
LEASED LINE - See Dedicated Line.
LINE DRIVERS - A device which boosts a signal between its place of origin
and its destination.
LLC - Logical Link Control. The upper sublayer of the data link layer as
defined by IEEE 802.2.The LLC is common to all IEEE 802 LAN standards
thus allowing different LANs to communicate in the upper layers. Compare
with MAC.
LOCAL AREA DATA TRANSPORT (LADT) - LADT is based on the x.25 packet
switching protocol and allows data to be sent over voice lines at higher
frequencies than voice at speeds ranging from 1200 to 9600 bps.
LOCALTALK - Apple Computer's local area network using the AppleTalk
network architecture and the network operating system called AppleShare.
LOCKING - The ability to restrict or control access to files so that data
are not destroyed when more than one person tries to simultaneously modify
them.
LSP - Linked Systems Project. This is a development project by the Library
of Congress, the Research Libraries Information Network, OCLC, and the
Western Library Network to link their computer systems to exchange MARC
authority records and MARC bibliographic records.
LSP -Linked SystemsProtocol. A draftnational standard for
bibliographic information retrieval being developed by the National
Information Standards Organization (NISO), Committee D. (Z39.50).
LU 6.2 - See APPC.
[GSM]
-----------------------------------------------------------------------------
GLOSSARY OF NETWORKING & TELECOM - PART 2
ONLINE LIBRARIES AND MICROCOMPUTERS
MAY 1989
Msg. G0079 Category: NEWS & TRENDS
BRIEF GLOSSARY OF NETWORKING & TELECOMMUNICATIONS, PART 2
This is part 2 of a telecommunications and networking glossary for the
librarian or informationprofessional.Definitionsare brief and
non-technical although it may be necessary to refer to last month's part 1
when acronyms or jargon from last month's list are used. The combination
of parts 1 and 2 of this series may provide a useful list of terms as a
reference tool.
MAC - Media Access Control. The lower sublayer of the data link layer as
defined by IEEE 802 LAN standards (see LLC).
routers, or gateways.
more follows -- press <RETURN> (Q to quit)
SYNCHRONOUS TRANSMISSION - A transmitting device sends pecial characters
(synch characters) at the beginning of an entire message and the message
must be sent in sequence. Contrast with asynchronous transmission.
T1 - A digital communications facility developed by AT&T that operates at
a speed of 1.544 Mbps.
TCP/IP - Transmission Control Protocol/Internet Protocol is a set of
computer programs that enable communication between similar or dissimilar
computers on a network.Internet Protocol (IP) is the standard for
sending basic units of data through an internet. TCP/IP enjoys wide vendor
MAP/TOP - Manufacturing Automation Protocol/Technical Office Protocol.
MAP is the, OSI protocols and application utilities for the manufacturing
environment which was originally developed by General Motors.TOP was
developed by Boeing Corporation but applies to the office environment.
MARC - MAchine Readable Cataloging.
Mbps - Megabits per second.
MICROWAVE RADIO - Microwave data links can easily carry up to 6,000
telephone circuits per channel but must have line-of-sight between towers
(every 25-30 miles).
MODEM - A modulation/demodulation device which allows a digital device to
be connected to an analog transmission network and vice-versa.
MS-NET - A network operating systems developed by Microsoft which operates
with MS-DOS 3.1 or later.
MULTIDROP LINE - A single communications line with several interconnecting
stations. Using this type of line often requires a polling mechanism.
MULTIPATH DISTORTION - When signals arrive at slightly different times at
a receiver due to different data paths.
MULTIPLEXING - A method for transmitting two or more separate channels of
data on a singlefacility. Three techniques are commonly used:
frequency-division multiplexing (FDM); time-division multiplexing (TDM);
and statistical multiplexing.
MULTITASKING - The ability to run more than one program at a time on a
computer.
NACO - Name Authority Cooperative.Name authority records are being
transmitted via the Linked Systems Project.
NAMED PIPES - An API for LAN Manager which allows the transfer of data
from one application to another.
NCCF - Network Communication Control Facility.IBM's host-based network
management software that provides the operator interface and network
logging facilities.
NETBIOS - An API developed for IBM networks and is widely used as a
standard interface to communications protocols.
NETVIEW - The network management product from IBM for its SNA networks.
Data from non-SNA environments can be obtained through NetView/PC.
NETWARE - Novell, Inc.'s network operating system.
NETWORK FILE SYSTEM (NFS) - Sun Microsystems, Inc. has developed this
network service that allows transparent access to files located anywhere
on the system.
NETWORK LAYER - In the OSI Reference Model this is layer 3 which is
responsible for routing data across the network.
NETWORK MANAGEMENT PROTOCOL (NMP) - The protocol used in UNMA to
communicate information from various vendors' element management systems
to the Accumaster Integrating System. NMP is full compliant with OSI.
NETWORK OPERATING SYSTEM (NOS) - The software that manages file sharing,
security, electronic mail, methods for interfacing with different computer
networks and any other resources of a network.
NETWORK SERVER - a central computing device on the LAN that provides for
file storage, printing operations, modem connection, etc.
NODE - a computer or single PC on a network.
NPDA -Network Problem Determination Application- IBM's network
management product that uses a series of panels to provide operators with
information needed to perform problem determination and resolution.
OCLC - Online Computer Library Center.
OPEN SOFTWARE FOUNDATION - A group of computer firms which is working on
developing a standardized UNIX operating system.
OPEN SYSTEM - A computing system that uses publicly available standards
for its architecture.This allows easy development of third party
products as well as easier networking with this type of system.
OPERATING SYSTEM - Software which interfaces the physical resources of a
computer and an applications program.
OPTICAL FIBERS - see FIBER OPTIC CABLE.
OSAK - OSI Applications Kernel. A full implementation of the OSI Session
Layer in DECnet phase V that provides an API that manages the dialog
between an applications program on an OSI network.
OS/2 - An operating system developed by Microsoft for IBM and its PS/2
line of computers.
OSI - Open Systems Interconnection.The general name used for ISO's
effort to standardize computer-to-computer communications.The standard
has a seven layer model for communications and sections of the protocol
are still in development.The OSI model defines an open system as one
that obeys OSI standards in it communications with other systems. This
contrasts with proprietary architectures (such as IBM's SNA) which are
designed to support one vendor's equipment.
OSI/NETWORK MANAGEMENT FORUM - A group of companies which is focused on
supporting network management standards for the OSI model.
PACKET - A unit of data which is transmitted at the network layer. It is
also commonly used to denote an envelope of data bundled with addressing
information for transmission through a network.
PACKET RADIO - A communications technique in which packets of data are
sent via radio waves.
PACKET-SWITCHING - A method in data communications in which data are
divided into packets and are routed to the final destination via the
fastest route. The final destination node is responsible for reassembling
the packets into the proper order.
PARALLEL TRANSMISSION - The sending of several bits (making up a byte) at
a time from a computer to an external device.Contrast with serial
transmission.
PBX - Private Branch Exchange. A private switching system often located on
a customer's premises.
PHYSICAL LAYER - In the OSI model this is layer one and is responsible for
the actual sending of the data on the transmission medium.
POINT-TO-POINT - Data communications that occurs between two nodes on a
network without passing through any intermediate nodes. The network layer
handles this type of communications.
POLLING - A means of controlling terminals on a multidrop line. Thus each
terminal is sequentially queried to determine if any data is ready to
send.
POSIX - A type of UNIX using IEEE standards.
PRESENTATION LAYER - In the OSI model this is layer six and is responsible
for sending data in proper format between the application program and the
lower layers.
PROPRIETARY STANDARD - A standard developed or owned by one company or
group. Some companies license their proprietary products to third party
developers.
PROTOCOL - A collection of rules that control the exchange of information
between the same layers in different nodes on a network.
PROTOCOL STACK (PROTOCOL SUITE) - A set of related protocols. This phrase
is often used when referring to the protocols as implementing the layers
of the OSI model.
PULSE CODE MODULATION (PCM) - Transmission of information by modulation of
an intermittent carrier.Pulse width, count, phase or amplitude may be
varied.
REDIRECTOR - Software that reroutes network commands away from MS-DOS and
onto the network in MS-NET.
REPEATER - A device which boosts an electrical signal thus increasing the
transmission distance possible.
RING - A network topology in which each node is connected in series to
form a loop (contrast with BUS and STAR).
RLIN - Research Library Information Network.
ROUTER - A device which interconnects two networks. These function at the
network layer of OSI and can determine the most efficient route by which
to send data.
RS-232C - A standard developed by EIA (Electronics Industries Association)
which specifies a low-speed interface between computer equipment such as
modems or printers and computers.
SAA -SystemsApplicationArchitecture. IBM products use this
architecture to provide a common a programming interface, a common means
of user access and common communications support for IBM operating
systems.
SDLC - Synchronous Data Link Control. Used by IBM under the SNA with IBM
3270 family of terminals.
SERIAL TRANSMISSION - The sending of data sequentially one bit at a time
over a single channel.Modems for microcomputers usually operate in this
mode.
SERVER - See File Server.
SESSION LAYER - In the OSI model this is layer five and is responsible for
directing user commands to a local operating system or to the network.
SHORT HAUL TRANSMISSION DEVICES - This transmission medium is commonly 2
or 4 strand twisted pair wire which allows transmission from a few
thousand feet to a few miles. The range depends on transmission rate, the
transmission mode, and the transmitting and receiving devices.
SIGNAL TO NOISE RATIO - The amount by which a signal exceeds its
underlying noise.
SMFA - Specific Management Functional Area.In the OSI model this will
define individual network management services.
SMTP - Simple Mail Transfer Protocol. An application utility in TCP/IP.
SNA -SystemsNetworkArchitecture. IBM'sproprietary network
architecture for communicating with IBM and non-IBM computers.
SNI - Standard Network Interconnection.The mechanism that supports the
intersystem communication for the Linked Systems Project.It follows OSI
standards.
SNMP - Simple Network Management Protocol.A TCP/IP network management
protocol.
SOCKETS - A program which interfaces TCP/IP with Berkeley's version of
UNIX.
STAR - A network topology in which a central device (Hub) has all other
devices in the network directly linked to it. It is also possible to have
several hubs linked forming a hierarchy.
STARLAN - A local area network operating in a star or daisy chain topology
and was originally developed by AT&T.It is now part of the IEEE 802.3
standard.
STATISTICAL MULTIPLEXING (STAT MUX) - A multiplexing technique in which
channel capacity is allocated based on the transmission of productive
traffic.
STORE AND FORWARD NETWORKS - A network in which messages are collected,
packaged, transmitted, unpackaged and delivered by a network processor.
STREAMS - UNIX v.3's framework for network communications.
SUBNET - A network that is connected to a larger network via bridges,
support particularly among universities and the federal government.
However, TCP/IP is not compliant with the emerging OSI standard which is
universally expected to be the standard of the future.Thus migration
paths will need to be developed to move from one protocol to the other.
TELNET - An software application utility for TCP/IP that provides terminal
emulation.
TELENET - A commercial packet switching network.
TERMINAL EMULATION PROGRAM - Software which allows microcomputers to
emulate different terminal types. Different terminal emulations are often
incorporated into popular communications packages.
TERMINAL SERVER - A device that connects terminals (or other equipment) to
a local area network.A server lets users of terminals connect to more
than one computer.
THIN ETHERNET - A version of Ethernet that operates on an RG-58 coax
cable.
3+ - 3Com's popular network operating system.
TIME DIVISION MULTIPLEXING - Divides a data channel by time to support
several subchannels. See multiplexing.
TLI - Transport Layer Interface. UNIX System 5 Release 3 incorporates this
application program interface.
TOKEN - A method of passing data bits in a network.
TOKEN BUS - A local area network that uses the token passing method with a
bus topology.The IEEE 802.4 is the standard for this topology and MAP
specifies token bus as the LAN portion of its protocol stack.
TOKEN PASSING - A method in which a token is passed around the network and
is available to each station in the network.Only the station that has
the token can transmit on the network (contrast with CSMA/CD)
TOKEN RING - A local area network that uses the token passing method as a
ring topology.
TOP - See MAP/TOP.
TOPOLOGY - The physical layout of a network.It refers to the way in
which the transmission media are interconnected to form a complete system.
In LANs the major methods are star, bus and ring.
TP4 - The transport layer protocol in OSI.
TRANSCEIVER - A device that both transmits and receives.In an Ethernet
system this unit provides a physical and electrical interface to the
network cable and monitors the cable for activity toavoid data
collisions. This device is also called a media access unit.
TRANSPORT LAYER - In OSI this is layer four and is responsible for keeping
end-to-end communications.
TWISTED PAIR - Cabling which has two wires wrapped around each other. It
is most commonly used in phone systems but is a low-cost medium for LAN
connections or directly connecting workstations to a host computer.
TYMNET - A commercial packet switching network.
ULTRIX - A version of UNIX developed by Digital Equipment Corporation.
UNIX - One of the most popular multiuser and multitasking operating
systems which was originally developed by AT&T.There are many different
versions of this operating system and it is easily ported to different
kinds of computers.
UNMA - Unified Network Management Architecture.A proprietary three
tiered architecture for network management developed by AT&T. It is an
open architecture which employs interfaces based on OSI standards.
VALUE ADDED NETWORKS (VAN) - These are usually developed by companies
which lease common carrier phone lines and develop different tariff
structures. Examples in the United States would be Telenet and Tymnet.
VAX FTAM - In DECnet Phase V, this file transfer, access and management
protocol allows file management and transfers to OSI compliant systems.
VINES - VIrtual NEtworking System. A proprietary network operating system
developed by Banyan Systems, Inc.
VIRTUAL CIRCUIT - A communications link that gives the user the impression
that a dedicated line exists between the remote device and the host. This
impression is due to the fact that data are processed in the order in
which it was sent (just as with a real circuit). Contrast datagram.
VIRTUAL TERMINAL - A remote terminal emulation utility program for OSI.
VOTS - VAX OSI Transport Service. Provides OSI transport layer functions
in DECnet phase V and supports interworking among different subnetworks by
using the Internet Protocol,which provides Connectionless Network
Services over local area networks and X.25 wide area networks.
WAN - Wide Area Network. A communications network that spans large areas
(hundreds or thousands of miles) by using telecommunications lines
provided by a common carrier (e.g. the phone company).
WATS - Wide Area Telecommunications Service.Allows phone customers to
make long-distance calls and have them billed on a bulk basis rather than
one-by-one.
WAVE DIVISION MULTIPLEXING - Transmitting two or more separate channels of
data over an optical fiber using different wavelengths of light.
WAVEGUIDES - These microwave pipes can be used to transmit microwave
signals and are often used to transmit microwave signals up and down
microwave antenna towers.
WLN - Western Library Network.
WORKSTATION - A device, often a microcomputer, which serves as an
interface between a user and a file server or host computer.
X.25 - A CCITT standard that defines a protocol for gaining access to
public packet switching networks.
X.400 - A CCITT standard for electronic mail. In OSI this would be an
application utility.
XENIX -A version of UNIX developed forthe IBM ATclass of
microcomputers.
XNS - Xerox Network Systems. A local area network architecture developed
by Xerox Corporation but never became popular as a communications
standard. However, proprietary variations of this architecture are widely
used.
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