Telecommunications & Networking Glossary
1Base-5 (StarLAN) - Twisted pair cable
with maximum segment lengths of 500 meters and transmission speeds of up to 1
Mbit/sec.
10Base-2 (Ethernet) - a transmission medium
specified by IEEE 802.3 that carries information at rates up
to 10Mbps in baseband form using low-cost coaxial cable over distances up to 185
meters (607 ft). Also called "thin Ethernet" or "thinnet" or
"thin coax" or "cheapernet".
10Base-5 (Ethernet) - a transmission medium
specified by IEEE 802.3 that carries information at rates up
to 10Mbps in baseband form using 50 ohm coaxial cable (RG8) over distances up to 500
meters (1,640 ft). Also called "thick Ethernet" or "thicknet" or
"thick coax", the cable is commonly referred to as yellow cable. Thick
Ethernet cable is typically used as a trunk or backbone path of the network.
10Base-FL - IEEE 802.3 Fiber Optic Ethernet.
A fiber optic standard that allows up to 2,000 meters (6,560 ft.) of multimode duplex
fiber optic cable in a point-to-point link.
10Base-T (Ethernet) - a transmission medium
specified by IEEE 802.3 that carries information at rates up to
10Mbps in baseband form using twisted pair conductors. Also called unshielded twisted
pair (UTP) wire. Using low cost Level 3 (CAT3) or better UTP wiring, 100 meters (328
ft.) of point-to-point link segments are possible. Uses RJ-45 connectors for cable
termination and to the patch panel.
100Base-X (Ethernet) - 100 Mbits/sec throughput
over hierarchical twisted-pair wiring configurations using the existing
CSMA/CD access method.
100Base-T4 (Ethernet) - A particular alternative
within the 100Base-TX CSMA/CD proposals before the IEEE 802.3 for a 100 Mb/s
Ethernet that specifies four pair of CAT3 or CAT4 cable. *
100Base-TX (Ethernet) - A particular alternative
within the 100Base-TX CSMA/CD proposals before the IEEE 802.3 for a 100 Mb/s
Ethernet that specifies two pair of a CAT5 cable. *
100Base-T - A generic name for 100 Mb/s twisted
pair CSMA/CD proposals before the IEEE 802.3. Specific proposals include 100Base-Tx
and 100Base-T4. *
Access method - the way in
which a node is permitted to send data over the media. With Ethernet,
the node listens to the line to determine if it is available before
transmitting.
Adapter card (NIC) - circuit board or
other hardware that provides the physical interface from a PC, workstation or
other equipment to the communications network.
Address - a number uniquely identifying
each node in a network. See Physical Address or MAC address.
ANSI (American National Standards Institute) -
a voluntary, U.S. based standards-setting organization for the information
processing industry. A member of the ISO.
ASCII (American Standard Code for Information
Interchange) - a widely used 7-bit code-set established by ANSI to achieve
compatibility between products manufactured by different companies.
Application layer - the seventh layer in
the OSI model which is ultimately responsible for managing communication between
application processes.
ARP (Address Resolution Protocol) - an
Internet Protocol that dynamically maps Internet addresses to
physical (hardware) addresses on a LAN.
AT-ADAPT-2 - a harmonic-style adapter
that allows direct conversion from a 50-pin Telco connector to
RJ-45 receptacles.
ATM (Asynchronous Transfer Mode) - a new
type of cell switching technology which uses fixed-length packets to transmit
data from source to destination. ATM uses fixed-length 53-byte cell-switching
to transmit data, voice and video over both LANs and WANs. Also referred to as
BISDN and Cell Relay.
AUI (Attachment Unit Interface) - the branch
cable interface located between a MAU (transceiver) and a DTE (typically a workstation). Includes a 15-pin D-sub connector and
sometimes a 15-conductor twisted pair cable. Maximum length is 50 meters (164 ft.).
AWG (American Wire Gauge) - a system that
specifies wire size. The gauge varies inversely with the wire diameter size.
Backbone - any network considered to
provide interconnection among subnetworks.
Backup Module - a repeater that behaves
as the management module when the Master fails in a department concentrator.
Bandwidth - the difference between the
two limiting frequencies of a band, expressed in Hz (hertz).
Baseband - a transmission technique
that allows only one signal at time to travel on a cable.
Binding - a process during which a protocol
driver and a MAC driver exchange information, via the NDIS interface library, about identities, capabilities, function
addresses, and binding context.
Bit - a contraction of Binary digIT. The
smallest unit of digital information.
Bit Rate (BR) - The rate of data throughput on the
medium in bits per second. Ethernet specifies 10 million bits per second.
Bit Time - The duration of one bit
symbol (1/BR). Ethernet specifies a bit time of 100 ns.
Bps (bits per second) - a unit of measure
for the transmission of signals that represent characters of data.
BNC connector - a specific type of
connector used for coaxial RG58 cable connection.
BOOTP (Boot Protocol) - a TCP/IP network
protocol that lets network nodes request configuration
information from a BOOTP "server" node.
Branch Cable - the AUI cable interconnecting
the DTE and MAU system components also known as
a Drop cable.
Bridge - a LAN interconnection device used to link
two local or remote LANs. Bridges are used extensively in LAN systems to extend their
physical dimensions or modify their performance.
Bridge MIB - a specification that defines an
experimental portion of the Management Information Base for use with network managing
protocols in TCP/IP based internets. In particular, it defines objects for managing
bridges based on the IEEE 802.1d draft standard between LAN segments.
Broadband - a method of transmission in which
data flows from source to destination in a different form that existed at the source.
Also indicates multiple channels on a transmission medium.
Brouter - a network device that can perform the
functions of both a bridge and a router.
Buffer - a block of storage (memory) used to hold
a portion of an information packet.
Buffer descriptor - a data structure containing
information about a buffer, such as a pointer to the buffer's physical location, number
of bytes, and size. It does not include the actual data in the buffer.
Bus topology - a (physical or logical) structure
used in LANs whereby connection between devices is accomplished by connecting all
devices to a single transmission medium such as fiber or UTP.
Byte - a sequence of eight adjacent
bits representing one character or digit.
CATNIP (Common Architechture for Next
Generation Internet Protocol) - One of the three IPng
candidates.
CHAP (Challenge Handshake Authentification Protocol) -
Authentification scheme for PPP where the password not only is required to begin
connection but is also required during the connection - failure to provide a correct
password during either the login or challenge mode will result in disconnect.
Client - in the ISO/OSI specifications,
the client is referred to as the service requester. See Host.
CLR (Cell Loss Ratio) - ATM performance parameter which
specifies the ratio of lost (non-delivered) cells to the total cells transmitted
over a given virtual circuit.
CLNP (Connectionless Network Protocol) - the OSI
equivalent to Internet IP, sometimes called ISO IP. The OSI protocol for providing
the OSI Connectionless Network Service (datagram service).
CLTP (Connectionless Transport Protocol) - the OSI
equivalent to UDP. Provides for end-to-end Transport data addressing and error control,
but cannot guarantee delivery or provide flow control.
CMIP (Common Management Information Protocol) - the
network management protocol defined by OSI specifications. Used to convey CMIS defined
operations over an OSI network.
CMIS (Common Management Information Services) -
the portion of the OSI network management specification which defines the management
services available to a network management system (works with CMIP).
CMOT (CMIP Over TCP) - an historical effort to use
the OSI network management protocol to manage TCP/IP networks.
Coaxial cable - a form of cable that has an
inner conductor and an outer grounded shield positioned around a common axis. There
are two primary LAN types, 10BASE2 (thinnet) and 10BASE5 (thicknet).
Collision - an unwanted condition in which two
packets (frames) are being transmitted over a medium at the same time, resulting in
destruction of the data.
Concentrator - any communications device that
allows a shared transmission medium to accommodate more data sources than there are
channels currently available within the transmission medium. See Department Concentrator.
Configuration management - the process of
obtaining information from network devices and using it to manage their setups.
CSMA (Carrier Sense Multiple Access) - a medium access
control technique for multiple-access transmission media. A station wishing to transmit
first senses the medium and transmits only if the medium is idle.
CSMA/CD (Carrier Sense Multiple Access with Collision
Detection) - a refinement of CSMA in which a station ceases transmission if it detects
a collision.
DAP (Directory Access Protocol) - the protocol used
between a Directory User Agent (DUA) and a Directory System Agent (DSA) in an X.500
directoru system.
DCE (Data Communication Equipment) - In the RS232
specification a module, such as a modem, which is used to connect a DTE to other
equipment. Also a repeater, hub, or switch connected to a terminal or workstation is
wired as a DCE.
DTE (Data Terminal Equipment) - In the RS232
specification a module which is typically at the end of the segment. The DTE could
be an Ethernet workstation or router that is attached to a network.
DDN (Defense Data Network) - the
MILENET and several other Department of Defense networks.
Department Concentrator - a hub which provides
a large number of workstation connections. The term, department concentrator, refers
to multiple repeaters housed in an AT-36C8 chassis. See Hub/Repeater,
Repeater.
Distributed Computing Environment - a
framework for distributed computing by the Open Software Foundation.
DME (Distributed Management Environment) - a
framework for distributed management proposed by the Open Software Foundation.
Driver - a set of software routines used
to control input and output from a hardware device for an operating system.
Ethernet - the LAN technology that uses
CSMA/CD physical access method and 10 Mbps digital transmission. The forerunner
of the IEEE 802.3 CSMA/CD standard.
Fiber optics- light transmission
through optical fibers for communication and signaling.
Finger - an Internet utility that
provides information about the users who are logged in to a
server, in an attempt to provide directory services.
FOIRL (Fiber Optic Inter Repeater Link) -
A fiber optic signaling method based on the IEEE
802.3 standard governing fiber optics. Allows up to 1,000 meters
(3,280 ft.) of multimode duplex fiber optic cable in a
point-to-point link.
50-Pin Telco (RJ21) - This connector
is very common in 10BASE-T wiring. As opposed to the RJ-45
connector, the 50-pin Telco connector concentrates up to 12 UTP
connections onto one connection. This concentration of UTP ports is then broken out
for connection to a punch-down block inside a building's wiring closet. 50-pin Telco
connections provide a very clean, uncluttered interface to the building's wiring.
FTP (File Transfer Protocol) - a TCP/IP protocol for file transfer.
Harmonica Adapter - a simple way to
convert the 50-pin Telco connection to RJ-45 connections.
Host - a terminal station, usually connected to a
LAN, providing some local processing capability and storage as
well as access to other workstations and shared resources.
Also called a Workstation.
Hot Swapping - the process of replacing
a hub module without bringing down the network. This process
occurs by sliding an active module into a fully powered up
concentrator, replacing a failed module.
Hub/Repeater - the central signal
distributor, used in a wiring topology consisting of several
point-to-point segments originating from a central point. The
term hub is often used interchangeably with the term repeater.
Multiport 10BASE-T, 10BASE2, and fiber optic (10BASE-FL, FOIRL)
repeaters are considered hubs. See Repeater.
Hub MIB - a specification that defines
an experimental portion of the Management Information Base for use
with network managing protocols in TCP/IP based internets. In
particular, it defines objects for managing IEEE 802.3 10
Mbpsecond baseband repeaters (also referred to as "hubs").
IEEE (Institute of Electrical and
Electronics Engineers) - a U.S. professional organization active
in the creation, promotion, and support of communications
specifications and standards.
IEEE 802.3 (Ethernet) - the IEEE physical
layer standard that defined a LAN protocol that uses the CSMA/CD access method
on a (logical) bus topology LAN. See Ethernet
IEEE 802.5 (Token Ring) - the IEEE
committee and its specification that defined a LAN protocol suite. Originated by
IBM, now an IEEE standard for a token-passing, ring network that can be configured
in a star topology. Token Ring cards are available in 4 Mb/s and 16 Mb/s versions.
Subsequent upgrades for fiber are specified in ANSI X3T9. *
IESG (Internet Engineering Steering Group) - the
executive committee of the IETF.
Impedance - an electrical characteristic of a
circuit dealing with the combination of the AC and DC resistance and the appearance
of that resistance to attached circuits.
Interface layer - the layer in the Internet
suite of protocols responsible for transmission on a single physical network.
Internet - a collection of networks that are
interconnected by linking devices such as bridges, routers, and gateways to operate
as a single large network.
Internet suite of protocols - a
collection of computer-communication protocols. Synonymous with TCP/IP.
Internetworking - communication
among devices across multiple networks (WAN).
Interoperability - the process whereby
computers can operate interactively with each other across a network without data
conversion or human intervention.
IP (Internet Protocol) - a connectionless protocol
which provides best-effort delivery of datagrams across an internet (the network
layer protocol of the TCP/IP protocol suite).
IPng (IP Next Generation) - Name for the efforts
of the Internet Engineering Task Force to define a new version of the Internet
Protocol (IP) to handle larger IP addresses. There were three candidates - CATNIP, TUBA, and SIPP.
IPX (Internetwork Packet Exchange) - a network layer
protocol developed by Novell, Inc. and used in NetWare implementations.
ISO (International Standards Organization) - an
organization that promotes the development of standards for computers. Developers
of the OSI model.
Jabber Lock-Up - the MAU's ability to
automatically inhibit the transmit data from reaching the medium
if the transmit data time exceeds a specified duration. This
duration is in the range of 20 ms to 150 ms. Jabber lock-up
protects the medium from being overrun with data packets from a
possibly defective device.
Jam - this term describes the collision
reinforcement signal output by the repeater to all ports. The jam
signal consists of 96 bits of alternating 1s and 0s. The purpose is to
extend a collision sufficiently so that all devices cease transmitting.
JANET (Joint Academic Network) - A
university network in the U.K. With the increase in network speed
in recent years, it has been renamed to "Super-JANET."
Jitter - the fluctuation of the data packet in
respect to a standard clock cycle. Jitter is undesirable and must be minimized.
JUNET - Japan UNIX Network.
Kernel- the software that interfaces
directly with the hardware (when referring to operating system software).
LAN (Local Area Network) - a network system
that provides a relatively small area with high-speed data transmission at a
low error rate. May include PCs, printers, minicomputers, and mainframes linked
by a transmission medium such as a coaxial cable or twisted pair wiring.
Also calleda Subnet, Atonomous System, and Broadcast Domain.
Layer - a conceptual level of network
processing functions defined by OSI model. Processing takes place
in layers starting from the physical transmission of data up
through to the commands of an end-user.
Learning bridge - a bridge which
automatically "learns" the topology of the LAN addresses of each node
as it receives packets. Requires little or no setup at time of installation.
LED (Light Emitting Diode) - a solid state
device that radiates light at a single frequency through plastic or glass.
MAC (Medium Access Control) - the control circuitry
in a LAN that converts the protocols of the DTE to those required by the LAN.
MAN (Metropolitan Area Network) - a network
whose facilities are restricted to individual populated areas.
Distances of up to 50 miles are possible.
Managed Module - an intelligent repeater
in a department concentrator chassis that makes management data available to
the Master. See SNMP.
Management Agent - software that is used
to view hub activity and set hub variables.
Master - a repeater in the top-most
position in a department concentrator chassis that contains and
downloads the management agent software to Backup and Slaves. The
Master contains the only active image of the management agent and
controls the management functions of the Backup and Slaves.
Master Station - a station or network
node that maintains direct control over other stations or nodes.
MAU (Medium Attachment Unit) - a device used
to attach a processing node to a network at the physical level.
An example is the transceiver used to attach devices to an
Ethernet cable.
Medium- a physical conduit for data
transmission, e.g., coaxial cable or radio waves.
MDI (Medium Dependent Interface) - the
mechanical and electrical interface between the trunk cable
medium and the MAU. MDI-X is another version of the interface
that enables like devices to connect, using different pin-outs,
avoiding conflicts that occur when receiving and transmitting
packets use the same pin-out.
MIB (Management Information Base) - a
collection of objects that can be accessed via a network
management protocol.
Module - a single repeater when it is
mounted with other repeaters in an AT-36Cx or AT-36Ex
department concentrator chassis.
MOP (Maintenance Operations Protocol) - a
DEC protocol used for remote communications between hosts and
servers.
Multicast address - a 48-bit
identifier (as transmitted over an Ethernet network) naming the
group of stations that should receive a packet on the network. A
multicast address contains a unique group number by which
receiving stations can request to receive packets, rather than
being a bit mask (as for a functional address).
Multiport repeater (Hub) -
a repeater that collects signals from one transmission channel (port) and,
after performing the standard repeater signal cleanup, retransmits the signals
to all the other transmission channels (ports).
Multiport transceiver -
a transceiver that allows a number of devices to be attached to one LAN
transceiver attachment on the backbone network.
NREN (National Research and Education Network) -
a network that was expected to become the state-of-the-art high-speed network for
US research and education. Now synonymous with the Information Superhighway.
NetWare - a network operating system
implementation and control approach developed by Novell, Inc. that defines
the network architecture and the software modules needed for network operation.
Also the name of the network software (NOS).
Network - a communications system made up of
various stations. Also called a LAN, Subnet, Atonomous System, Broadcast Domain.
NDIS (Network Driver Interface Specification)
interface library - an interface modeled as a set of abstract functions that
either cause a request to be submitted to the operating system or cause a local
action to be performed that does not require full communications with other
software functions. The main purpose of the interface library is to allow
protocol drivers to send and receive packets on a network.
Network layer - the layer in the
OSI model that is responsible for ensuring that data passed to it
from the transport layer is routed and delivered through the network.
(OSI Layer 3)
Network management - a set of procedures,
software and operations designed to keep a network operating near maximum efficiency.
Network redundancy - the state of
having more connecting links than the minimum required to provide a connecting path
between all nodes.
Network topology - the physical or logical
relationship of nodes in a network typically of either a star, ring, tree, or bus
topology, or some hybrid combination thereof.
Node - a point where one or more functional
units interconnect transmission lines.
OSI (Open System Interconnection) - a seven layer
model developed by ISO for standardizing data transmission functions so equipment
made by different manufacturers can be interconnected.
Packet (frame) - the basic unit of data transfer
in LANs. A chain of one or more buffers that compose a network message.
Ping (Packet Internet Groper) - A program used to
test reachability of destinations by sending them an ICMP echo request and waiting
for a reply.
Packet switching - a method of
transmitting messages through a communications network in which long messages are
subdivided into short packets.
PSN (Packet Switch Node) - The modern term used for
nodes in the ARPNET and MILNET, formerly called Interface Message Processors (IMPs).
Physical layer - the lowest level in the
OSI model, responsible for the transmission of bits across the medium.
(OSI Layer 1)
PMA (Physical Medium Attachment) - the portion
of the MAU that contains the functional circuitry.
PLS (Physical Signaling) - the portion of the
physical layer contained within the DTE that provides the logical
and functional coupling between MAU and data link layers.
Port - an interface of a computer or other
transmission device that acts as an input or output point, or both.
Presentation layer - the level in the OSI model
responsible for adding structure to the units of data that are exchanged.
(OSI Layer 6)
Proprietary - a protocol or communications
system developed by a company, as opposed to those emanating from a standards
organization.
Protocol - the rules or conventions
used to govern the exchange of information between networked nodes.
Repeater - a hardware device that regenerates
LAN signals to extend the length, topology or interconnectivity of the network, or
converts signals between media at the same time.
RFC (Request for Comment) - the procedure used by the
Internet community to exchange ideas and establish standards and specifications.
RMON (Remote network MONitoring probe) - a device
that was designed to help perform network management on a network segment.
RJ-11 (Registered Jack 11) - A modular
4-wire jack and/or connector typically used with copper cable
having two twisted pairs,
usually unshielded twisted pair category 3 or category 5. Used
for telephony, 10Base-T and 100Base-Tx Ethernet LANs, and Token Ring LANs. *
RJ-45 - this connector is a 10BASE-T/100Base-TX
standard for connecting UTP cabling. They are inexpensive and easy to install onto
UTP cable.
Router - a hardware/software product
which receives network layer datagrams and forwards them to their
destination based on the network layer address in the packet.
Session layer - the layer of the OSI
model responsible for establishing and maintaining communications
between two applications or software modules in different nodes.
(OSI Layer 5)
SIPP (Simple Internet Protocol Plus) - One
of the three IPng candidates.
Slave station - a device that can
transmit only to a specific controlling node upon that node’s request.
SNMP (Simple Network Management Protocol) -
a set of rules for performing network management functions. Approved for
use with TCP/IP in UNIX environments. Created within the Internet community using
the RFC process.
Subnetwork - a network that has been
connected to a larger and more powerful network system by a bridge or router.
See also: Subnet, Broadcast Domain, LAN, Atonomous System.
T-connectors - connectors used to
join thin Ethernet coax cable sections. The connectors also have a
connector that is attached directly to a station (NIC).
Tap - a device in the feeder cable that
connects a device to a network.
TCP (Transmission Control Protocol) - the
transport protocol (OSI Layer 4) offering a connection-oriented (reliable)
transport service in the Internet suite of protocols.
TCP/IP - the internetworking protocols
developed by the U.S. government’s Advanced Research Project
Agency (ARPA). Widely adopted and supported by computer and
software manufacturers as a standard computer networking protocol.
Telnet - the standard interactive login
protocol in the Internet suite of protocols which operates over the TCP/IP
protocol. Allows a user to login to a remote computer over the network.
TFTP (Trivial File Transfer Protocol) - used on
computers running TCP/IP, TFTP quickly sends files across
the network with fewer security features than FTP.
Thicknet - see 10BASE5
Thinnet - see 10BASE2
Token Ring (IEEE 802.5) - the IEEE
committee and its specification that defined a LAN protocol suite. Originated
by IBM, now an IEEE standard for a (logical) token-passing, ring network that can be
configured in a physical) star topology. Token Ring cards are available in 4 Mb/s and
16 Mb/s versions and for fiber specified in ANSI X3T9. *
Topology - the physical arrangement of
devices in a network, regardless of their logical relationships.
Types include star, ring, and bus.
Transceiver - the attachment
hardware connecting the controller interface to the transmission
cable in IEEE 802.3 networks.
Transport layer - layer four of the
OSI model that provides reliable (TCP)(connection-oriented) or unreliable
(UDP)(connectionless) message delivery services to higher level protocols.
(OSI Layer 4)
TUBA (Tcp and Udp with Bigger Addresses) -
one of the three IPng candidates.
Twisted pair wiring - two insulated
wires twisted together and used for transmission (the twisting creates a low level
of noise elimination).
Unshielded twisted pair (UTP) - see 10BASE-T
WAN (wide area network) - a network that includes
nodes distributed over a larger geographic area than can be served by a LAN.
Wiring closet - a room containing the
individual network connections for all devices in a specific area.
Workstation - a terminal station,
perhaps connected to a LAN, providing some local processing
capability and storage as well as access to other workstations and shared resources.
Also called a Host.
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