Telecommunications & Networking Glossary

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# (Names beginning with numbers)

1Base-5 - Twisted pair cable with maximum segment lengths of 500 meters and transmission speeds of up to 1 Mbit/sec.

10Base-2 - 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 - a transmission medium specified by IEEE 802.3 that carries information at rates up to 10Mbps in baseband form using 50 ohm coaxial cable 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 - 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 or better UTP wiring, 100 meters (328 ft.) of point-to-point link segments are possible. Uses RJ45 connectors and sometimes 50-pin AMP connectors to a patch panel.

100Base-X - 100 Mbits/sec throughput over hierarchical twisted-pair wiring configurations using the existing CSMA/CD access method.

100Base-T4 - 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 UTP3, UTP4, or UTP5. *

100Base-TX - 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 UTP5. *

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. *

A

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 - 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.

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 RJ45 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.

B

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 or more 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.

Brouter - a network device that can perform the functions of both a bridge and a router.

Buffer - a block of storage 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 - the structure used in LANs whereby connection between devices is accomplished by connecting all devices to a single transmission medium such as fiber or wire.

Byte - a sequence of eight adjacent bits representing one character or digit.

C

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.

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 types, 10BASE2 (thinnet) and 10BASE5 (thicknet).

Collision - an unwanted condition in which two packets 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.

D

Data Communication Equipment (DCE) - In the RS232 specification a module, such as a modem, which is used to connect a DTE to other equipment. A repeater connected to a terminal or workstation for OMEGA LOCAL management use is wired as a DCE.

Data Terminal Equipment (DTE) - In the RS232 specification a module which is typically at the end of the segment. The DTE could be an Ethernet workstation, repeater, or bridge that attaches to a network.

Defense Data Network (DDN) - 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.

Directory Access Protocol (DAP) - the protocol used between a Directory User Agent (DUA) and a Directory System Agent (DSA) in an X.500 directoru system.

Distributed Computing Environment - a framework for distributed computing by the Open Software Foundation.

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 an operating system.

E

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.

F

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 RJ45 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.

H

Harmonic Adapter - a simple way to convert the 50-pin Telco connection to RJ45 connections.

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").

I

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 - a physical layer standard that uses the CSMA/ CD access method on a bus topology LAN.

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.

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.

J

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.

K

Kernel- the software that interfaces directly with the hardware (when referring to operating system software).

L

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.

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.

M

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.

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 - a repeater that collects signals from one transmission channel and, after performing the standard repeater functions, retransmits the signals to more than one new transmission channel.

Multiport transceiver - a transceiver that allows a number of devices to be attached to one LAN transceiver attachment on the backbone network.

N

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.

Network - a communications system made up of various stations.

Network Driver Interface Specification (NDIS) 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.

Network management - a set of procedures, software and operations designed to keepa 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 and 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.

O

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.

P

Packet - the basic unit of data transfer in LANs. A chain of one or more buffers that compose a network message.

Packet Internet Groper (Ping) - 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.

Physical Medium Attachment (PMA) - the portion of the MAU that contains the functional circuitry.

Physical Signaling (PLS) - 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.

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.

R

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.

Remote network monitoring probe (Rmon) - 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. *

RJ45 - this connector is a 10BASE-T 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.

S

Session layer - the layer of the OSI model responsible for establishing and maintaining communications between two applications or software modules in different nodes.

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.

T

T-connectors - connectors used to join thin Ethernet cable section. The connectors also have a connector that is attached directly to a station.

Tap - a device in the feeder cable that connects a device to a network.

TCP (Transmission Control Protocol) - the transport protocol offering a connection-oriented 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 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. *

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 message delivery services to higher level protocols.

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).

U

Unshielded twisted pair (UTP) - see 10BASE-T

W

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.

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* Some definitions used in this document are from the hypertext product, LexiCAT, and are the copyrighted property of TRA, with all rights reserved. For additional information on LexiCAT or to obtain additional copies, please contact TRA at 505 W. Bertrand Ave., St. Marys, KS, USA 66536. Telephone 1-913-437-2000. LexiCAT is a registered trademark of TRA.

  This page is maintained by:   Michael P. Harris

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