Authentication
Authentication is the act of verifying a claimed identity, in the form of a pre-existing label from a mutually known namespace, as the originator of the message or as the channel end point.

Authorization
Authorization is the act of determining whether a particular right can be granted to the presenter of a particular credential. This particular right can be, for example, an access to a resource.

Accounting
Accounting is the act of collecting resource consumption data for the purposes of trend analysis, and capacity planning, billing, auditing, and cost allocation.

AAL
ATM Adaptation Layer
Fully independent of the physical layer, this ATM layer converts higher-layer information, such as data packets, into ATM cells for transmission across the ATM network. At the receiving end, the AAL converts the cells back into the higher-layer information.

AAL3/4
Used only for SMDS-to-ATM internetworking, and supported only over ATM data exchange interface - ATMDX.

AAL5
Used for connectionless data traffic, such as LAN protocols.

AAL-SDU
ATM adaptation layer service data unit. Packet of data containing information about the ATM adaptation layer, such as AAL5. dir

AAR
Automatic Alternative Routing
Automatic switching of a call to other routes when first choice routes are unavailable.
A system for providing continued telecommunications service in the event that a primary transmission route fails catastrophically

ABM
Asynchronous Balanced Mode - Link Layer
An HDLC and derivative protocol, communication mode supporting peer-oriented point-to-point communications between two stations, where either station can initiate transmission. A service of the SNA data link level in IBM ¨ 's token-passing ring that allows devices to send data link commands at any time.

ABR
Available Bit Rate
ABR is an ATM layer service category for which the limiting ATM layer transfer characteristics provided by the network may change subsequent to connection establishment because of changes in network conditions - addition/deletion of other ABR traffic, changes in characteristics of VBR connections etc. A closed loop flow control mechanism is specified which supports different types of feedback to the traffic generating sources about the changing ATM layer transfer characteristics. One of the mechanisms is by the use of Resource Management cells. A source generates forward RM-cells which are turned around by the destination and sent back to the source as backward RM-cells. These backward RM-cells carry feedback information provided by the network elements and/or the destination back to the source. In addition to the RM cells generated by the sources, the network elements may also generate backward RM cells. The source, on receipt of the backward RM cell, will adjust the rate of data put by it into the network - the amount of adjustment depending on the feedback obtained from the network.

ACD
Automatic Call Distribution
The ACD portion of the system ensures that incoming calls are distributed evenly, so agent productivity is maintained at a high level, and inbound callers are handled efficiently.

ACK
Acknowledge

ACL
Access Control List
The usual means by which access to and denial of network services is controlled by network security systems. It is a list of the available services and the hosts permitted to use each service.


ACR
Allowed Cell Rate - ATM
Current permitted rate at which the source router can send, based on dynamic feedback from the network.

ACR
Attenuation Crosstalk Ratio
Attenuation crosstalk ratio is the difference between attenuation and crosstalk at a given frequency along a cable. Measured in decibels, ACR is a calculation used in networking transmission to assure that a signal transmitted across a twisted-pair cable is stronger at the receiving end than any interference signals imposed on that same pair by crosstalk from adjacent pairs.


Active Hub
The central connecting device in a network that regenerates or amplifies transmission signals. An active hub can be used to add workstations to a network or to increase the distance between workstations and a file server.

Active Monitor
A single station on a token ring network that performs tasks such as token monitoring and resolving certain error conditions.

Active Open
The operation that a client performs to establish a TCP connection with a server at a known address.

ACTLU
Activate Logical Unit - SNAª command sent by the SSCP to an LU to activate a session and establish session parameters.

ACTPU
Activate Physical Unit - SNAª command sent by the SSCP to activate a PU, so that any logical units controlled by this PU are available to the SNA network.

AD
Administrative Domain
A collection of hosts and routers and interconnecting network(s) managed by a single administrative authority.


ADCCP
Advanced Data Communications Control Protocol - ANSI
An ANSI standard bit-oriented data-link-control protocol.

ADM
Add Drop Multiplexer

ADMD
Administration Management Domain - X.400
ADMD in all countries worldwide together provide the X.400 backbone

ADPCM
Adaptive Differential Pulse Code Modulation - Voice compression
Process by which the high statistical correlation between consecutive voice samples is used to create a variable quantizing scale. ADPCM can encode analog voice samples into high - toll - quality digital signals.

Used to optimize the cost. The difference of amplitude is analyzed and compared to the former sample Silence are detected. ITU-T Norm from G.720 to G.730

ADR
Advanced Digital Recording
An all-new, variable speed, digital tape storage solution.ADR is based on revolutionary 8-channel array technology that allows the solid-state design to read and write eight tracks of data simultaneously.

ADSL
Asymmetrical Digital Subscriber Line

High level transmission using the copper telephone line.
limit is 2 Mbits for downloading and 640 KB for uploading.
A New modem technology, converts existing twisted-pair telephone lines into access paths for multimedia and high speed data communications. ADSL transmits more than 6 Mbps - optionally up to 8 Mbps - to a subscriber, and as much as 640 Kbps - optionally up to 1 Mbps - more in both directions.
Such rates expand existing access capacity by a factor of 50 or more without new cabling. ADSL can literally transform the existing public information network from one limited to voice, text and low resolution graphics to a powerful, ubiquitous system capable of bringing multimedia, including full motion video, to everyone's home.
An ADSL circuit connects an ADSL modem on each end of a twisted-pair telephone line,
creating three information channels - a high speed downstream channel, a medium speed duplex channel , depending on the implementation of the ADSL architecture, and a POTS (Plain Old Telephone Service) - or an ISDN channel. The POTS/ISDN channel is split off from the digital modem by filters, thus guaranteeing uninterrupted POTS/ISDN, even if ADSL fails. The high speed channel ranges from 1.5 to 6.1 Mbps, while duplex rates range from 16 to 640 Kbps. Each channel can be submultiplexed to form multiple, lower rate channels, depending on the system.
-ADSL is called asymmetrical because most of its bandwidth is devoted to the downstream direction, sending data to the user.
-ADSL was originally designed by telephone companies to provide video-on-demand to compete with the cable industry.

• HDSL
  High bit-rate DSL is symmetrical: an equal amount of bandwidth is available in both directions.
  High bit rate DSL (HDSL2) is a symmetrical technology intended to replace T1/E1 lines and the older generation HDSL technology, by transporting data at rates of up to 1.5 Mbps over a single pair of copper wires over distances of up to 3,650m.
  
• vIDSL
  Integrated Digital Subscriber Line.
  Disc. - An ISDN based version of DSL, closer to ISDN data rates and service at 128 Kbps
  
• RADSL
  Rate-Adaptive DSL is an ADSL technology from Westell in which software is able to determine the rate at which signals can be transmitted on a given customer phone line and adjust the delivery rate accordingly.
  
• SDSL
  Symmetric DSL works on a single twisted-pair line, at 1.544 Mbps T1 or 2.048 Mbps E1
  Called symmetric as it offers the same data rate in both directions.
  
• VDSL
  Very high data rate DSL
  Offers between 51 and 55 Mbps over lines up to 300 meters
  The bandwidth will allow high definition TV
  
• G.Lite
  Is a DSL-Lite, is offering lower speeds but without the need for POTS splitters at the customer premises. This is limited to 1.5 Mbps downstream and 384 kbps upstream
  
• SHDSL
  Single Pair High-speed Digital Subscriber Line provides symmetrical high speed data transmission over a single copper wire pair. Transmission speed is 64 kbps to 2,312 Mbps.
  
  

ATM Data Service Unit
ADSU used to access an ATM network via High-Speed Serial Interface - HSSI.

ADWARE
Advertising Supported Software - Shareware and freeware paid by commercials.

 


ADSUAES
Advanced Encryption Standard
Will be a cryptographic algorithm for use by U.S. Government organizations to protect sensitive information.

AF
Alternate Frequencies - RDS

AFI
A authorityF frame I identifier
Specifies the format of the initial domain identifier - IDI - in the initial domain par - IDP - of an OSI

Agent
Intelligent software that monitors a managed SNMP network device, such as a network management module - NMM - and gathers statistical data in management information base - MIB - format. A central network management entity regularly polls the agents and downloads the contents of their MIBs.

AH
Authentication Header
Used to provide connectionless integrity and data origin authentication for IP datagrams, and to provide protection against replays. This latter, optional service may be selected, by the receiver, when a Security Association is established. AH provides authentication for as much of the IP header as possible, as well as for upper level protocol data. AH may be applied alone, in combination with the IP Encapsulating Security Payload, or in a nested fashion through the use of tunnel mode.

AHIP
Authentication Header IP

AI
Artificial Intelligence

AIFF
Audio Interchange File Format
The sound format originally used on Apple and Silicon Graphics (SGI) computers. AIFF stores waveform files in an 8-bit monaural format.

AIN
Advanced Intelligent Network - Telephony
The AIN replaces the service-specific software in the original intelligent network architecture with generic triggers for each function involved in processing a call.
The AIN also replaces service-specific code in the SCPs with a generic Service Logic Execution Environment.
The AIN also added a new intelligent peripheral with interactive voice response capability. Under instructions from the SCP, the intelligent peripheral communicates with the caller through DTMF tones, digitized speech, and speech recognition. The GR-1129-CORE protocol, which utilizes ISDN signaling, was specified for intelligent peripheral/SCP communication. SR-3511, a variation of GR-1129-CORE, provides similar capabilities over TCP/IP.

AIP
ATM Interface Processor - Cisco ¨


AIS
Alarm Indication Signal - ATM
In T1, an all-ones signal transmitted in lieu of a normal signal to maintain transmission continuity and to indicate to the receiving terminal that there is a transmission fault that is located either at, or upstream from, the transmitting terminal.

AIX
Advanced Interactive eXecutive - IBM ¨

ALAP
AppleTalk ª L ink Access Protocol

AMI
Alternate Mark Inversion - ATM
Address mark inversion or alternate mark inversion - T1 lines. A signal-encoding scheme in which a "1" is represented alternately as positive and negative voltage. It does not use translation coding but can detect noise-induced errors at the hardware level.

Amplitude
The maximum value of an analog or digital waveform.

AMP
Active Monitor Present - Token-Ring

AMPS
Advanced Mobile Phone Service/System
An analog mobile standard widely used throughout the Americas, as well as the Asia Pacific region
and Eastern Europe. Operates in the 800 MHz frequency band.

Analog Transmission
Signal Transmission over wires or through the air in which information is conveyed through variation of some combination of signal amplitude, frequency, and phase.

ANI
Automatic Number Identification
A call association type service that tells the recipient of a telephone call the telephone number of the person making the call. This number can be passed to computer equipment to automatically retrieve associated information about the caller - that is, account status, billing records .

ANR
Automatic Network Routing
An APPN high-performance routing - HPR - option that provides connectionless end-to-end routing. It reduces storage and processing requirements for routing packets through intermediate nodes.

ANSI
American National Standard Institute
The coordinating body for voluntary standards groups within the United States. ANSI is a member of the International Organization for Standardization - ISO.

AO/DI
Always On / Dynamic - ISDN
BellSouth Business¨ provides continuous low-cost network connectivity. This connectivity helps teleworkers avoid problems associated with repeatedly opening connections to a corporate network AODI automatically switches network traffic to the channel that best supports it. The D-channel link, which is used whenever B channels are not required. When traffic increases one or both B channels are used for .

APE
All-Paths Explorer
Frame generated by an end station configured for all-paths broadcast routing that traverses all paths between source and destination end stations.

APIPA
Automatic Private IP Addressing
With APIPA, DHCP clients can automatically self-configure an IP address and subnet mask when a DHCP server isn't available.
When a DHCP client boots up, it looks for a DHCP server to obtain an IP address, subnet mask, and other possible DHCP options configured on the server. If the client is unable to obtain a lease from a DHCP server, the client uses APIPA and automatically configures itself with an IP address from the Microsoft-reserved IP address range of 169.254.0.1 through 169.254.255.254. The Internet Assigned Numbers Authority has reserved this range for private IP addressing, so no one can use it on the Internet. The client also configures itself with a default class B subnet mask of 255.255.0.0. A client uses the self-configured IP address until a DHCP server becomes available. Obviously, APIPA is meant for non routed small business environments.



APPC
Advanced Program-to-Program Communications - IBM ¨
A standard unit of information transmitted over an SNA network. A BTU consists of the TH - transmission header, the RH - request/response header and the RU - request/response unit. The maximum size of the BTU is controlled in VTAM by the MAXDATA=parameter and in SNA Server by the MAX BTU Length parameter.

APPI
Advanced Peer-to-Peer Internetworking

APPN
Advanced Peer-to-Peer Networking - IBM ¨ based on PU type 2.1 and LU 6.2
Network architecture defined within IBM ¨'s Systems Applications Architecture ª - SAA - environment that allows peer-to-peer communication between computers on a network without a mainframe host computer.
It supports distributed processing among multiple peer systems.
APPN includes distributed network services to communicate routing, connection, topology, and directory information among network nodes throughout an APPN network. APPN Network Nodes provide these services in support of Low Entry Networking Nodes and End Nodes, such as AS/400. Bay Networks APPN interacts with other NNs such as ES/9000 VTAM, AS/400, 3174, and 6611. APS
Advanced Photo System

APS
Advanced Planning and Scheduling
This feature allows switchover of packet-over-SONET - POS - circuits in the event of circuit failure and is often required when connecting SONET equipment to telco equipment. APS refers to the mechanism of using a "protect" POS interface in the SONET network as the backup for "working" POS interface. When the working interface fails, the protect interface quickly assumes its traffic load.

APS
Automatic Protection Switching - Sonet

ARB
Adapter Request Block
This is a reactive control where the source rate adapts to the state of the network based on the feedback it receives from the network.

ARB
Adaptive Rate Based -congestion control

ARCnet
Attached Resource Computer Network
Runs at 2.5 Mbits/s and is really low-cost. Was popular before Ethernet and while Ethernet was still expensive. A newer development (ARCnetPlus) runs at 20 Mbits/s and can share cable (and communicate) with ARCnet stations.

ARL
Adjusted Ring Lengths

ARM
Asynchronous Response Mode
An HDLC communication mode involving one primary and at least one secondary, where either the primary or one of the secondaries can initiate transmissions.

ARP
Address Resolution Protocol
ARP is used to obtain the physical address of a node when only the IP address is known.
An Internet protocol used to bind an IP address to Ethernet 802.2 addresses. Defined in RFC 826.

ARPANET
Advanced Research Project Agency Network

ARQ
Admission Repeat Request - Modem
Communication technique whereby the receiver detects error and request retransmission.

AS
Autonomous System
A group of IP networks operated by one or more network operator/s which has a single and clearly defined external routing policy. Exterior routing protocols are used to exchange routing information between ASes.
A collection of networks, under the same administrative control, that share the same routing information with each other

AS/400
IBM¨ mid-range computer - 1988. Support of 5250 and 3270 data flow.

ASBR
Autonomous System Boundary / Border Router

ASCII
American Standard Code for Information Interchange
A coding scheme that assigns 7 bit string of zeros and ones to letters, numbers, punctuation marks and certain
other characters. ASCII enables computers and programs to exchange information.
7 bits + 1 extra bit for extended characters.
7 bits + parity
ASCII-hex

ATM
Automatic Teller Machine

ATMDXI
ATM Data Exchange Interface
A low-cost interface between DTE and DCE devices specified by the ATM Forum. Supports V.35, RS-449, and HSSI DTE-DCE up to 50 Mb/s.

ATP
AppleTalk ª Transaction Protocol

AT&T
American Telephone and Telegraph Company ¨

AuthXML
Allows the exchange of data related to security between organizations, using XML.

AVD
Alternating Voice and Data

AVI
Audio Video Interleaved - Microsoft ¨
A Windows multimedia file format for sound and moving pictures that uses the Microsoft RIFF specification.

AVM
ATM Voice Multiplexer

AVVID
Architecture for Voice, Video, and Integrated Data - Cisco ¨
Used only for SMDS-to-ATM internetworking, and supported only over ATM data exchange interface - ATMDX.

ASF
Advanced Streaming Format
An extensible file format designed to store synchronized multimedia data. It supports data delivery over a wide variety of networks and protocols while still proving suitable for local playback. ASF supports advanced multimedia capabilities including extensible media types, component download, scaleable media types, author-specified stream prioritization, multiple language support, and extensive bibliographic capabilities, including document and content management.

ASK
Amplitude-Shift Keying
Transmits 1's and 0's by representing each one as a different amplitude at the same frequency. Therefore, the amplitude of a 1 is larger than the amplitude of the 0.

ASN
Abstract Syntax Notation - ISO 8824
Used to describe the structure of data to be transferred between the Application Layer and the Presentation Layer of the Open Systems Interconnection next generation networking protocol.

ASVD
Analog Simultaneous Voice and Data

ASYNCHRONE
Character transmission mode with no regular length. The transmission is controlled by Start or Stop bits.

ATAPI
Advanced Technology Attachment Packet Interface
In a PC, the driver/interface, to access the CD-ROM.

ATD
Asynchronous Time Division

ATDM
Asynchronous Time-Division Multiplexing
A method of sending information in which normal time-division multiplexing - TDM - is used, except that time slots are allocated as needed rather than preassigned to specific transmitters.

ATG
Address Translation Gateway - Cisco ¨

ATM
Asynchronous Transfer Mode
A high bandwidth, low-delay, connection oriented packet-like switching and multiplexing technique.

A network technology capable of transmitting data, voice, video, and frame relay traffic in real time. Data, including frame relay data, is broken into packets containing 53 bytes each, which are switched between any two nodes in the system at rates ranging from 1.5 Mbps to 622 Mbps. ATM is defined in the broadband ISDN protocol at the levels corresponding to levels 1 and 2 of the ISO/OSI model.
Class A/B/C/D Different types of ATM service:

• Class A requires end-to-end timing, requires a constant bit rate, and is connection oriented.
• Class B requires end-to-end timing, requires a variable bit rate, and is connection oriented.
• Class C does not require end-to-end timing, supports a variable bit rate, and is connection oriented.
• Class D does not require end-to-end timing, supports a variable bit rate, and is connectionless.