AARNet: Australian Academic and Research Network
Australian Academic and Research Network (AARNet) offers Internet services to the Australian education and research communities and their partners. AARNet is a non-profit company with 37 Australian universities and the CSIRO Australia as its share holders.

AARP probe packets
AARP probe packets are those packets transmitted by AARP that determine whether a randomly selected node ID is being used by another node in a nonextended AppleTalk network. If the node ID is not being used, the sending node uses that node ID. If the node ID is being used, the sending node chooses a different ID and sends more AARP probe packets.

ABR Compliance / Conformance
ABR (Available Bit Rate ) conformance or compliance refers to the behavior specified for ATM Available Bit Rate (ABR) destination and switches, but allows for delays between the source and the UNI (Unser to Network Interface), which may perturb the traffic flow. The cells on an ABR connection applies to CLP=0 cells, which are tested upon arrival. At the arrival point, each cell is identified as conforming or non-conforming.

ABC Compliance / Conformance
ABR connection conformance or compliance refers to the behavior specified for ATM Available Bit Rate (ABR) destination and switches, but allows for delays between the source and the UNI [UNI3.1, UNI4.0], which may perturb the traffic flow. The cells on an ABR connection applies to CLP=0 cells, which are tested upon arrival. At the arrival point, each cell is identified as conforming or non-conforming. The minimal conformance definition for ABR is GCRA((1/PCR),t1), where PCR is defined for CLP=0 flow.

Abilene Network
Abilene Network is the U.S. backbone network created by the Internet2 community. Over 220 member institutions participate in Abilene, mostly universities with some corporate and affiliate institutions, in all of the US states as well as the District of Columbia and Puerto Rico.

ABM: Asynchronous Balanced Mode
Asynchronous Balanced Mode (ABM) is a communication mode of HDLC and derivative protocols supporting peer-oriented, point-to-point communications between two stations, where either station can initiate the transmission.

Abort
In a computer or data transmission system, abort means to terminate, usually in a controlled manner, a processing activity for many reasons. Abort may also mean that a program or process is terminated abnormally and suddenly, with or without diagonstic information.

ABR: Area Border Router
Area Border Router (ABR) is a router located on the border of one or more OSPF areas that connect those areas to the backbone network. ABRs are considered members of both the OSPF backbone and the attached areas. They therefore maintain routing tables describing both the backbone topology and the topology of the other areas.

ABR: Available Bit Rate
Available Bit Rate (ABR) is a type of service or a QOS class defined by the ATM Forum for ATM networks. ABR is used for connections that do not require timing relationships between source and destination. ABR provides no guarantees in terms of cell loss or delays, providing only best-effort service. Traffic sources adjust their transmission rates in response to information they receive describing the statue of the network and its capability to successfully deliver data. Compare with CBR, UBR, and VBR.

ABRD: Automatic Baud Rate Detection
Automatic baud rate detection (ABRD) is a scheme which a receiving device (such as a modem) determines the speed, code level, and stop bits of incoming data by examining the first character, usually a preselected sign-on character. ABRD allows the receiving device to accept data from a variety of transmitting devices operating at different speeds without needing to establish data rates in advance.

ABS: Application Bridge Server
Application Bridge Server (ABS) is a software module that allows the ICM to share the application bridge interface from an Aspect ACD with other applications.

Absolute Address
Absolute Address refers to an address scheme in communications, computer, and data processing systems. This address directly identifies a storage location without the use of an intermediate reference, e.g., a base address or a relative address.

Access Device
Access Device is the hardware component used to gain access to network resources from a remote location, and vice versa. Common access devices are routers, MUX and modem pools. Integrated Access Device (IAD) is a type of access devices that can simultaneously deliver traditional PSTN voice services, packet voice services, and data services (via LAN ports) over a single WAN link. An access device aggregates multiple channels of information including voice and data across a single shared access link to a carrier or service provider PoP (Point of Presence).

Access List
Access list in networking refers to a list kept by routers to control access to or from the router for a number of services. For example, the list can prevent packets with a certain IP address from leaving a particular interface on the router.

Access Method
Generally, access method means the way in which network devices access the network medium. When talking about IBM SNA, access method refers to the software within an SNA processor that controls the flow of information through a network.

Access Server
Access Server, also called network access server, is a computer server that connects asynchronous devices to a LAN or WAN through network and terminal emulation software. An access server (NAS) enables an internet service provider (ISP) to provide connected customers with Internet access. An access server has interfaces to both the local telecommunication service provider such as the phone company and to the Internet backbone. The server authenticates users requesting login, usually by verifying a user name and password, and then allows requests to begin to flow between the user host and hosts (computers) elsewhere on the Internet.

ACCESS.bus (A.b)
ACCESS.bus (or A.b) is a peripheral-interconnect computer bus developed by Philips in the early 1990s. It is similar in purpose to USB, in that it allows low-speed devices to be added or removed from a computer on the fly. While it was in use earlier than USB, it never became popular, largely due to considerably less corporate backing in the industry.A.b is a physical layer definition that describes the physical cabling and connectors used in the network. The higher layers, namely the signaling and protocol issues, are already defined to be the same as Philips' I2C bus.

Accounting
Accounting in networking refers to network resource usage and billing management. The goal is to gather network usage statistics for users. Using the statistics the users can be billed and usage quota can be allocated and enforced.

ACF/NCP: Advanced Communications Function/Network Control Program
Advanced Communications Function/Network Control Program (ACF/NCP), often referred as ACF or NCP, is the primary SNA network control program. ACF/NCP resides in the communications controller and interfaces with the SNA access method in the host processor to control network communications. ACF/NCP can also communicate with multiple hosts using local channel or remote links (PU type 5 or PU type 4) thus enabling cross-domain application communication. In a multiple mainframe SNA environment, any terminal or application can access any other application on any host using cross-domain logon.

ACF: Admissions ConFirmation
Admissions ConFirmation (ACF) is an RAS (Registration, Admission, and Status) message sent as an admissions confirmation for the gatekeeper to control the admission of the endpoints into the H.323 network.

ACF: Advanced Communications Function
Advanced communication function (ACF), also known as Advanced Communications Function/Network Control Program (ACF/NCP) and often referred to as NCP, is the primary SNA network control program. ACF/NCP resides in the communications controller and interfaces with the SNA access method in the host processor to control network communications. ACF/NCP can also communicate with multiple hosts using local channel or remote links (PU type 5 or PU type 4) thus enabling cross-domain application communications. In a multiple mainframe SNA environment, any terminal or application can access any other application on any host using cross domain logon.

ACK: Acknowledgment
ACK, the abbreviated form of Acknowledgment, refers to the notifications sent from one network device to another to acknowledge that some event (for example, receipt of a message) has occurred.

ACO: Alarm Cut-Off
Alarm Cutoff (ACO) is a feature in many network devices that allows the manual silencing of the alarm in the system. (Subsequent new alarm conditions might reactivate the audible alarm.)

ACOM: Acombined
Acombined (ACOM) refers to the combined loss achieved by the echo canceller, which is the sum of the echo return loss, echo return loss enhancement, and nonlinear processing loss for the call. Acombined is defined in G.165, "General Characteristics of International Telephone Connections and International Telephone Circuits: Echo Cancellers."

ACR: Allowed Cell Rate
Allowed Cell Rate (ACR) is an ABR service parameter, defined by the ATM Forum for ATM traffic management. ACR is the current rate (cells/second) at which a source is allowed to be sent. ACR varies between the MCR (minimum cell rate) and the PCR (Peak Cell Rate ), and is dynamically controlled using congestion control mechanisms.

ACS: Asynchronous Communications Server
Asynchronous Communications Servers (ACS) enables a user to dial out of the local area network and into the public switched telephone network (PSTN), or to access nailed-up lines for asynchronous communications. An asynchronous communications server is also called a dial-in/dial-out server or a modem server. ACS also allows Local Area Network users to share modems, fax boards, serial ports, or other asynchronous devices across the Network.

ACSE: Association Control Service Element
Association Control Service Element (ACSE) is the OSI protocol at the application layer (layer 7) used to establish, maintain, or terminate a connection between two applications.

Activation
Activation in networking refers to the process of enabling a subscriber device for network access and privileges on behalf of a registered account. In computer software, activation may refer to the process of enabling a user with a valid license key the privilege to use a particular software.

Active Discovery Packet
Active Discovery Packet refers to the type of packet used by PPPoE (Point-to-Point Protocol over Ethernet) during the discovery stage. The value of the Active Discovery packet of PPPoE is 0x8863 in the EtherType field, which deals with the search for a PoP (point of presence) using ethernet broadcast, the creation of a connection to it, and the interruption of this connection.

Active FTP
Active FTP is an alternative FTP mode which was designed before firewalls. In active mode FTP, the client connects from a random unprivileged port (N > 1023) to the FTP server's command port, port 21. Then, the client starts listening to port N+1 and sends the FTP command PORT N+1 to the FTP server. The server will then connect back to the client's specified data port from its local data port, which is port 20.

Active Hub
Active Hub, also known as a repeater, is a multiported network device that amplifies LAN transmission signals, in addition to forwarding the signals. Contrast with a passive hub, which only forwards the signals to all ports.

Active Monitor
Active Monitor is the device in a token ring that performs network-management duties, such as keeping track of tokens and weeding out frames that would otherwise circulate indefinitely. A network node is selected to be the active monitor if it has the highest MAC address on the ring. The active monitor is responsible for management tasks such as ensuring that tokens are not lost or that frames do not circulate indefinitely.

Active Directory
Active Directory is an implementation of LDAP directory services by Microsoft for use in Windows environments. Active Directory allows administrators to assign enterprise-wide policies, deploy programs to many computers, and apply critical updates to an entire organization. An Active Directory stores information and settings relating to an organization in a central, organized, accessible database. Active Directory networks can vary from a small installation with a few hundred objects, to a large installation with millions of objects.

Active2
Active2, codenamed "CNNSlayer", is a free, open-source codebase project for the Indymedia network and its allies that would provide 'next-generation' trusted multi-language open publishing including enhanced security and privacy, customization, syndication, and distributed (peer-to-peer) media storage, searching and streaming.

ACUTA: Association of College and University Telecomm Administrators
Association of College and University Telecomm Administrators (ACUTA) is is a member-driven organization dedicated to the enhancement of teaching, learning, research, and public (community) service by providing leadership in the application of telecommunications technology for higher education.

ACX: Asynchronous Cross-Connect
Asynchronous Cross-connect (ACX) is an ATM specific switch that can connect different ATM-compatible services together.

AD: Administrative Domain
Administrative Domain (AD) is a group of computers, routers, and networks operated and managed by a single organization. The devices that operate in a singular administrative domain share common security features that are administered across the network and the entities that are associated with it.

Adaptive routing
Adaptive routing, commonly used in data networking, refers to the ability of a network to select a new communications path to get around heavy traffic or a node or circuit failure. The adaptation is intended to allow as many routes as possible to remain valid (that is, to have destinations that can be reached) in response to the change. There are several routing protocols used to achieve this: RIP, OSPF, IS-IS, IGRP/EIGRP etc.

Adaptive switching mode
Adaptive switching mode is a user-defined facility to maximize the efficiency of the switch. Adaptive switching starts in the default switch forwarding mode you have selected (cut-through if you selected adaptive mode as the default switching mode). Depending on the number of runts and CRC errors at that port, the mode changes to the "best" of the other two switching modes. As the numbers of runts and CRC errors change, so does the forwarding mode.

Add Pass Request
Add Pass Request is a request made by the network to add a path, which establishes a multi-hop path between two network nodes. Although the two nodes are usually the source and destination nodes of a Virtual Wavelength Path (VWP), there are cases in which other nodes might want to establish a path between them. Unlike the Restore Path Request, the Add Path Request is never flooded; it is instead forwarded using information carried in the path itself (source routing).

Address
In networking, address is a data structure or logical convention used to identify a unique entity, such as a particular process or a network device. Important addresses include IP address for network routing and MAC address for a hardware device.

Address Aging Period
The Address Aging Period is the maximum time during which the forwarding database entries are considered valid. This value should be set low if your network has regularly heavy traffic. Each new device that sends a packet to the Matrox iSwitch has their MAC address added to the System Forwarding Database. The Database can store up to a maximum of 8192 MAC addresses at any one time. After the maximum number of MAC addresses has been reached, the earliest stored addresses are overwritten with new, incoming, information. To avoid this overwriting from happening, you set the address aging period so that the System Forwarding Database discards MAC addresses fast enough to keep up with the influx of new information.

Address bus
An address bus is part of a computer bus, used by CPUs or DMA-capable units for communicating the physical addresses of computer memory elements/locations that the requesting unit wants to access (read/write). The address bus is the set of lines that carry information about where in memory the data is to be transferred to or from. No actual data is carried on this bus, rather memory addresses, which control the location that data is either read from or written to, are sent here. The speed of the address bus is the same as the data bus it is matched to.

Address Mapping
Address Mapping refers to a technique that allows different protocols to interoperate by translating addresses from one format to another. For example, when routing IP over X.25, the IP addresses must be mapped to the X.25 addresses so that the IP packets can be transmitted by the X.25 network.

Address Mask
Address Mask, also known as subnet mask or mask, is a bit combination in an IP adddress used to describe which portion of an address refers to the network or subnet and which part refers to the host.

Address Resolution
Address Resolution refers to the process of translating or expressing the address of an entity on one system to the equivalent address of the same entity in the second system, when two addressing systems refer to the same entity. For instance, translating an IP address to its given DNS name, or translating an IP address to its MAC address.

Addressed Call Mode
Addressed Call Mode permits control signals and commands to establish and terminate calls in V.25bis.

ADF: Adapter Description File
Adapter Description File (ADF) is a type of data format with an extension .adf.

Adjacency
Adjacency in networking means the relationship formed between selected neighboring routers and end nodes for the propose of exchanging routing information. Adjacency is based upon the use of a common media segment.

Adjacent Nodes
Adjacent Nodes may refer to a few things in different environment: 1. In SNA, adjacent nodes are connected to a given node with no intervening nodes. 2. In DECnet and OSI, adjacent nodes share a common network segment (in Ethernet, FDDI, or Token Ring networks).

ADM: Add/Drop Multiplexer
Add/Drop Multiplexer (ADM), the main building blocks of SONET/SDH networks, combines, or multiplexes, several lower-speed streams of data into a single beam of light. ADMs, upon receipt of an optical signal (OC-n/STM-n), are configured to drop off the whole incoming signal or drop-off only certain lower rate optical signals and/or lower rate PDH signals (T1,T3). The remaining signal passes through. At the same time, optical or PDH signals could be added to replace the dropped-off signal and complete the outgoing optical signal. ADMs can be used both in long-haul core networks and in shorter-distance metro networks. A recent shift in ADM technology has introduced so called multi-service SONET/SDH (also known as a multi-service provisioning platform, or MSPP) equipment which has all the capabilities of legacy ADMs, but can also include cross-connect functionality to manage multiple fiber rings in a single chassis. These new devices can replace multiple legacy ADMs and also allow connections directly from Ethernet LANs to a service provider's optical backbone.

ADMD: Administration Management Domain
Administration Management Domain (ADMD) is the X.400 Message Handling System public carrier. The ADMDs in all countries worldwide together provide the X.400 backbone. For example, MCImail and ATTmail in the U.S., British Telecom Gold400mail in the U.K.

Administrative Distance
Administrative distance is the feature used by routers to select the best path when there are two or more different routes to the same destination from two different routing protocols. Administrative distance defines the reliability of a routing protocol. Each routing protocol is prioritized in order of the most to the least reliable (believable) using an administrative distance value. Administrative distance often is expressed as a numerical value between 0 and 255. The higher the value, the lower the trustworthiness rating.

Administrator
Administrator, or network administrator, is the person who manages a local area communications network (LAN) within an organization. Responsibilities include network security, installing new applications, distributing software upgrades, monitoring daily activity, enforcing licensing agreements, developing a storage management program and providing for routine backups.

ADP: Automatic Data Processing
Automatic Data Processing (ADP) refers to computer aided storing, manipulating or processing of information in the data format, requiring minimal or no human interaction.

ADPCM: Adaptive Differential Pulse Code Modulation
Adaptive Differential Pulse Code Modulation(ADPCM) is the process by which analog voice samples are encoded into high-quality digital signals. The first ADPCM standardized by the CCITT is G.721 for 32 kbps. Later came the standards G.726 and G.727 for 40, 32, 24 and 16 kbps. ADPCM is used to send sound on fiber-optic long-distance lines as well as to store sound along with text, images, and code on a CD-ROM.

ADSL modem
An ADSL modem, also known as a DSL modem, is a device used to connect one or more computers to a phone line, in order to use an ADSL service. Some ADSL modems also manage the connection and sharing of the ADSL service with a group of machines, making an ADSL router or ADSL modem/router a more accurate name for the device.

ADSL: Asymmetric Digital Subscriber Line
Asymmetric Digital Subscriber Line (ADSL), a variation of DSL technology, allows data to be sent over existing copper telephone lines. ADSL supports data rates of from 1.5 to 9 Mbps when receiving data (known as the downstream rate) and of from 16 to 640 Kbps when sending data (known as the upstream rate). ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair.

ADSU: ATM DSU
ATM DSU (ADSU), often used together with Channel Service Unit (CSU), is a communications device that connects an in-house line to an external digital circuit (e.g. T1) to an ATM network. The ADSU converts data into the required format, while the CSU terminates the line, and provides signal regeneration and remote testing.

ADTF: ACR Decrease Time Factor
ACR Decrease Time Factor (ADTF) is the time permitted between sending RM-cells before the rate is decreased to ICR (Initial Cell Rate). The time units are .01 to 10.23 seconds with a granularity of 10 ms. For ABR traffic, ADTF constitutes the time rate of the ACR. This value effects TCP round trip time calculations, which in turn effects TCP throughput.

Advertising
Advertizing in networking refers to the router process in which routing or service updates are sent at specified intervals so that other routers on the network can maintain lists of usable routes.

AE: Application Entity
Application Entity(AE) is the system-independent application activities that are made available as application services to the application agent, e.g., a set of application service elements that together perform all or part of the communication aspects of an application process.

AERM: Alignment Error Rate Monitor
Alignment Error Rate Monitor (AERM) is SS7 MTP 2 function that provides monitoring of link alignment errors.

AES47
AES47 (IEC 62365) is an open standard that specifies a method for packing AES3 professional digital audio streams over Asynchronous Transfer Mode networks. The change in thinking from traditional ATM network design is not to necessarily use ATM to pass IP traffic (apart from management traffic) but to use it in parallel with standard Ethernet structures to deal with extremely high performance secure media streams.

AFCEA: Armed Forces Communications and Electronics Association
Armed Forces Communications and Electronics Association (AFCEA), a non-profit international association, is dedicated to supporting global security by providing an ethical environment that encourages a close cooperative relationship among civil government agencies, the military and industry.

Affinity bits
Affinity bits in MPLS networking refers to the requirements of an MPLS traffic engineering tunnel on the attributes of the links it will cross. The tunnel's affinity bits and affinity mask bits of the tunnel must match the attribute bits of the various links carrying the tunnel.

AFI: Authority and Format Identifier
Authority and Format Identifier (AFI) is the part of an NSAP-format ATM address that identifies the type and the format of the IDI portion of an ATM address.

AFNOR: Association Francaise de Normalisation
Association Francaise de Normalisation (AFNOR) is France's standardization body and the French member of the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC). It is a private, state-approved, non-profit organization. AFNOR is the SCC's counterpart in France, promoting standardization through cooperation with interested national and international stakeholders.

AFS: Andrew File System
The Andrew File System (AFS) is a distributed network file system that enables files from any AFS machine across the country to be accessed as easily as files stored locally. AFS is composed of cells, with each cell representing an independently administered portion of file space. Cells connect to form one enormous UNIX file system under the root /afs directory.

Agent
Generally in computer networking, an agent is an active process in a computer that is responsible for a certain type of activity when demanded by an outside entity. For example, in a SNMP system, an agent is responsible for determining the parameters defined in the MIB (Management Information Base) and reporting them on demand to a Console.

AI: Artificial Intelligence
Artificial intelligence (also known as machine intelligence and often abbreviated as AI) is intelligence exhibited by any manufactured (i.e. ) system. The term is often applied to general purpose computers and also in the field of scientific investigation into the theory and practical application of AI.

AIM: AOL Instant Messaging
AOL Instant Messaging (AIM) is a peer-to-peer instant messaging (IM) application and service supplied by America Online (AOL). The AIM client application is a free download that runs on Windows, Linux, Macintosh, other computers, and cell phones. AIM supports basic "chat" based instant messaging as well as file sharing. Local folders can be shared in AIM and a "Get File" option allows others to reach those folders.

AIM: Asynchronous Interface Module
Asynchronous Interface Modules (AIM) are the network modules in routers/switches for asynchronous connections.

AIO: Asynchronous Input/Output
Asynchronous Input/Output is one of the two basic operating modes for any particular input/output stream (synchronous and asynchronous input/output). In the asynchronous mode, the physical input/output transactions are not necessarily synchronized or interlocked with the execution of a program's input/output statements. For example, a user at a typewriter would be allowed to type messages into the system prior to the execution of the read statement which would use them; every execution of a read statement merely plucks the next waiting message out of an input buffer. This example of asynchronous input is analogous to buffered read-ahead schemes which have been used with discs, tapes, etc. An example of asynchronous output is the collecting of output in a core buffer until some physical record size is reached.

AIP: ATM Interface Processor
ATM Interface Processor (AIP) is the ATM network interface for Cisco 7000 series routers designed to minimize performance bottlenecks at the UNI. The AIP supports AAL3/4 and AAL5.

AIR: Additive Increase Rate
Additive Increase Rate (AIR) is an ABR service parameter, AIR controls the rate at which the cell transmission rate increases. For ABR traffic, AIR effects the time rate of change of the ACR. This value effects TCP round trip time calculations, which in turn effects TCP throughput.

AIRF: Additive Increase Rate Factor
Additive Increase Rate Factor (AIRF) is a relative measure of Additive Increase Rate (AIR) with the following relationship: AIRF = AIR*Nrm/PCR. Nrm is an ABR service parameter that is the maximum number of cells a source may send for each forward RM-cell. PRC is the Peak Cell Rate in ATM network.

Alarm
Generally speaking, an alarm gives an audible or visual warning of a problem or condition. In networking, alarm refers to notification sent by an network monitoring system to tell network administrators or other people about possible problems in the network.

Alberta Supernet
Alberta Supernet is a high-speed backbone conecting several hubs in the Canadian province of Alberta. Government institutions such as schools, libraries, and hospitals are supposed to get free access; however, private companies can set up services to provide access to the backbone to the general public. The most popular method of doing this is wireless high-speed Internet which provides accesses over a large area without the need to trench cables.

ALG: Application Level Gateway
Application Level Gateway (ALG), also known as Application Layer Gateway, is a type of gateway that consists of a security component that augments a firewall or NAT employed in a computer network. It allows legitimate application data to pass through the security checks of the firewall that would have otherwise restricted the traffic for not meeting its limited filter criteria.

Algorithm
Algorithm, basically, is the well-defined rule or process for arriving at a solution to a problem. In networking, algorithms commonly are used to determine the best route for traffic from a particular source to a particular destination. The queuing algorithms of routers and switches are critical to determine the speed of packet processing.

Alien Port Adapter
Alien Port Adapter is a dual-wide port adapter for the Cisco 7200 router. The Alien Port Adapter is ABR-ready and supports traffic shaping.

Alignment Error
Alignment Error happens in IEEE 802.3(Ethernet) networks. It is an error that occurs when the total number of bits of a received frame is not divisible by eight. Alignment errors are usually caused by frame damage due to collisions and by misaligned reads and writes. For example, a two-byte read where the memory address is not an even multiple of two bytes is an alignment error. Alignment errors are caused by a software bug.

All-rings Explorer packet
All-rings Explorer packet, also called All-routes Explorer Explorer Packet, is the packet that traverses an entire SRB network, following all possible paths to a specific destination.

All-routes Explorer Explorer Packet
All-routes Explorer Explorer Packet, sometimes called all-rings explorer packet, is the packet that traverses an entire SRB network, following all possible paths to a specific destination.

ALO transaction
At-Least-Once (ALO) transaction refers to one of the two types of the AppleTalk Transaction Protocol (ATP) transaction services in which the request is repeated until a response is received by the requester or until a maximum retry count is reached. This recovery mechanism ensures that the transaction request is executed at least once. The other type of ATP transaction mechanism is Exactly-Once (XO) transaction.

Alphanumeric
Alphanumeric refers to a group of printable characters that include the letters of the alphabet in both upper and lower case, the numerals plus a limited group of additional symbols and punctuation marks.

ALPS circuit
Airline Product Set (ALPS) circuit is a communication path across a TCP connection between a host reservation system and an agent set control unit (ASCU). When MATIP (Mapping of Airline Traffic over Internet Protocol) encapsulation is used on an ALPS circuit, it is equivalent to a MATIP session.

ALPS: Airline Product Set
Airline Product Set (ALPS) is a tunneling mechanism that transports airline protocol data across a Cisco router-based TCP/IP network to an X.25-attached mainframe. This feature provides connectivity between agent set control units (ASCUs) and a mainframe host that runs the airline reservation system database.

Altivore
Altivore is an open-source network sniffer developed by Network ICE. This is a sample program containing some of the features of the features of the FBI's "Carnivore" program. Network ICE created Altivore to educate the public on the inner workings of Carnivore and the privacy and security issues involved with such systems. Altivore snoops a network to monitor email traffic (both headers and content), requests to Web and FTP servers, and IP address discovery and packet sniffing of that address.

AMBA: Advanced Microcontroller Bus Architecture
Advanced Microcontroller Bus Architecture (AMBA) was introduced in 1996 and is widely used as the on-chip bus for ARM processors. The first AMBA buses were ASB and APB. In its 2nd version, ARM introduced AHB that is a single clock-edge protocol. This protocol is today a de-facto standard for 32-bit embedded platforms cause it is well documented and can be used without royalties.

Ambient network
Ambient network is a network integration solution to the modern-day problems of switching from one network to another in order to keep in contact with the outside world. This project aims to develop a network software-driven infrastructure that will run on top of all current or future network physical infrastructures to provide a way for devices to connect to each other, and through each other to the outside world.

AMIX: American Information Exchange
The American Information Exchange (AMIX), started in 1984 by Salin, is an international network for the exchange of information, consulting contracts, computer code and research. Salin envisaged a world in which the ready exchange of expertise would reduce transaction costs, with wide-ranging beneficial effects. In particular, he predicted that information markets would reduce the need for redundant employees at different organizations, so that companies would become smaller and more efficient, relying on each other as external sources of expertise.

ANN: Artificial neural network
An artificial neural network (ANN), also called a simulated neural network (SNN) or just a neural network (NN), is an interconnected group of artificial neurons that use a mathematical or computational model for information processing based on a connectionist approach to computation. There is no precisely agreed definition amongst researchers as to what a neural network is, but most would agree that it involves a network of relatively simple processing elements, where the global behaviour is determined by the connections between the processing elements and element parameters.

Anonymous P2P
An anonymous P2P refers to a particular type of computer network in which the users and their nodes are pseudonymous by default. The primary difference between regular and anonymous networks is in the routing method of their respective network architectures. These networks allow for unfettered free flow of information, legal or otherwise.

Anycast
Anycast means a one-to-many association between network addresses and network endpoints: each destination address identifies a set of receiver endpoints, but only one of them is chosen at any given time to receive information from any given sender. In anycast, data is routed to the "nearest" or "best" destination as viewed by the routing topology. The term is introduced in IPv6 and is intended to echo the terms unicast, broadcast and multicast.

Apache
Apache is the most popular web server on the Internet with more than 70% of the web sites on the Internet using Apache. The Apache HTTP Server is a project of the Apache Software Foundation and the software is free. Originally designed for Unix servers, Apache has been ported to Windows and other network operating systems (NOS). The name "Apache" was derived from the word "patchy" that the Apache developers used to describe early versions of their software. Apache provides a full range of Web server features, including CGI, SSL, and virtual domains. Apache also supports plug-in modules for extensibility.

APaRT: Automated Packet Recognition/Translation
Automated Packet Recognition/Translation(APaRT) is a technology that allows a server to be attached to CDDI or FDDI without requiring the reconfiguration of applications or network protocols. APaRT recognizes specific data link layer encapsulation packet types and, when these packet types are transferred from one medium to another, translates them into the native format of the destination device.

APIPA: Automatic Private IP Addressing
Automatic Private IP Addressing (APIPA), a feature of Windows OS, is a DHCP failover mechanism. APIPA allows DHCP clients to obtain IP addresses when DHCP servers are nonfunctional. When a DHCP server fails, APIPA allocates addresses in the private range from 169.254.0.1 to 169.254.255.254. Clients verify that their address is unique on the LAN using ARP. When the DHCP server is again able to serve requests, clients update their addresses automatically.

APP Server
The APP Server is a utility which lets users respond to token password challenges received from a remote network access server (NAS). Network access servers offer a complex security algorithm that forces a user to have possession of a security card that can generate a password. When a user on the LAN starts an application that requires a connection to a host on a secure network, the Pipeline initiates the call, and after the initial session negotiation, the remote NAS returns a password challenge. The user has 60 seconds to obtain and enter the current dynamic password from the security card.

APPC: Advanced Program-to-Program Communication
Advanced Program-to-Program Communications (APPC), a protocol roughly in the OSI presentation and session layers, is a programming interface standard in the IBM SNA system that allows interconnected systems to communicate and share the processing of programs. Originally developed by IBM as a remote transaction processing tool between Logic Units (LUs), APPC is now used to provide distributed services within a heterogeneous computing environment. APPC establishes and tears down connections between communicating programs, and consists of two interfaces, a programming interface and a data-exchange interface. The former replies to requests from programs requiring communication; the latter establishes sessions between programs.

Applejuice
Applejuice is a centralized peer-to-peer file sharing network similar to the original EDonkey network. Users of the Applejuice client connect to an Applejuice server, search for and find files and then download them directly from another client (or "peer").

Appletalk call filter
An Appletalk call filter can instruct the Pipeline to place a call and reset the Idle Timer based on Appletalk activity on the LAN, and can prevent inbound packets or Appletalk Echo (AEP) packets from resetting the idle timer or initiating a call.

Application Layer
Application Layer is the layer 7 of the OSI reference model, which provides services to application processes (such as electronic mail, file transfer, and terminal emulation). The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and agreement on procedures for error recovery and control of data integrity.

Application Layer Firewall
Application layer firewall is a firewall operating at the application layer of the networking communication. Generally it is a host using various forms of proxy servers to proxy traffic instead of routing it. As it works on the application layer, it may inspect the contents of the traffic, blocking what the firewall administrator views as inappropriate content, such as certain websites, viruses, attempts to exploit known logical flaws in client software, and so forth.

Application Level Gateway
Application level gateways, also known as application layer firewalls or application proxy firewalls, are often described as third generation firewalls. When a user on the trusted networks wishes to connect to a service on the untrusted network such as the Internet, the application is directed to the proxy server on the firewall. The proxy server effectively pretends to be the real server on the Internet. It evaluates the request and decides to permit or deny the request based on a set of rules that are managed for the individual network service.

APPN: Advanced Peer-to-Peer Networking
Advanced Peer-to-Peer Networking (APPN) is an enhancement to the original IBM SNA system. APPN handles session establishment between peer nodes, dynamic transparent route calculation, and traffic prioritization for APPC traffic.

APPN+
APPN+, renamed as HPR (High Performance Routing) or APPN-HPR, is the next-generation APPN (Advanced Peer-to-Peer Networking) that replaces the label-swapping routing algorithm with source routing. IBM designed the protocol to provide the same internetworking functionality as TCP/IP. HPR was designed as a transport for legacy data over frame- and cell-based networks.

APR: Automated Packet Recognition
Automated Packet Recognition (APR), also known as Automated Packet Recognition/Translation(APaRT), is a technology that allows a server to be attached to CDDI or FDDI without requiring the reconfiguration of applications or network protocols. APaRT recognizes specific data link layer encapsulation packet types and, when these packet types are transferred from one medium to another, translates them into the native format of the destination device.

APS: Automatic Protection Switching
Automatic Protection Switching(APS) is method that allows transmission equipment to recover automatically from failures. APS is the capability of a transmission system to detect a failure on a "working" facility and switch to a "protection" facility to recover the traffic, thus increasing overall system availability. Protection switching may be initiated as a result of signal failure (hard failures such as Loss of Frame), signal degradation (soft failures such as an error rate exceeding a configured threshold), or user command (via local craft port or remote management).

AR: Access Registrar
Access Registrar (AR) provides RADIUS services to DOCSIS cable modems for the deployment of high-speed data services in a one-way cable plant requiring telco-return for upstream data.

ARA: AppleTalk Remote Access
AppleTalk Remote Access (ARA) is a protocol in the AppleTalk protocol suite that provides Macintosh users direct access to information and resources at a remote site using AppletTalk.

Arbitrated Loop
Arbitrated Loop, also known as FC-AL, is a Fibre Channel topology that requires no fibre channel switches. Arbitrated Loop is a serial data architecture that is compatible with SCSI, handling up to 126 devices per port (NL_port). It handles 127 devices if counting the 1 port connected to an optional fabric switch port. Only one connection may be a switch port. Devices are connected in a one-way loop fashion.

ARC: ATM Research Consortium
ATM Research Consortium (ARC) is a team of Universities proposed to perform application experiments over Pacific Bell's CalREN ATM Network.

Archie
Archie is a search engine designed to index FTP archives, allowing people to find specific files. Archie servers could be accessed in multiple ways: using a local client (such as archie or xarchie); telneting to a server directly; sending queries by electronic mail; and later via World Wide Web interfaces. The name is derived from the word "archive".

Architecture
Architecture, in networking, refers to the overall structure, topology, protocols and framework of a network. The architecture of the network influences the capabilities and limitations of the network.

ARCNET: Attached Resource Computer NETwork
Attached Resource Computer NETwork (ARCNET or ARCnet) is a local area network (LAN) protocol, similar in purpose to Ethernet or Token Ring. ARCNET was the first widely available networking system for microcomputers and became popular in the 1980s for office automation tasks. It has since gained a following in the embedded systems market, where certain features of the protocol are especially useful. ARCNET was eventually standardized as ANSI ARCNET 878.1.

ARDRT: ABR Rate Decrease Response Time
ABR Rate Decrease Response Time (ARDRT), a term in the ATM networking, is the amount of time required by the SUT to adjust its transmission rate based on an ABR rate decrease request. During the ARDRT, cells transmitted by the SUT may be dropped by the network due to traffic policing. These dropped cells may contain a portion of an IP datagram. This may cause IP and TCP packet loss.

Area
An Area, in networking, refers to a logical set of network segments and their attached devices. Areas usually are connected to other areas via routers, making up a single autonomous system. There are local area, metro areas, wide areas, etc.

ARIN: American Registry for Internet Numbers
American Registry for Internet Numbers (ARIN) is a nonprofit organization established for the purpose of administrating and registrating IP numbers to the geographical areas currently managed by Network Solutions (InterNIC). Those areas include, but are not limited to, North America, South America, South Africa, and the Caribbean.

ARIRT: ABR Rate Increase Response Time
ABR Rate Increase Response Time (ARIRT), a term in ATM networking, is the amount of time required by the SUT to adjust its transmission rate based on an ABR rate increase request. During the ARIRT, the SUT will not fully utilize the available bandwidth. This will negatively impact IP and TCP throughput.

ARJ: Admission ReJection
Admission ReJection (ARJ) is an RAS (Registration, Admission, and Status) message sent as an admissions rejection for the gatekeeper to control the admission of the endpoints into the H.323 network.

ARM: Asynchronous Response Mode
Asynchronous Response Mode (ARM) is an HDLC communication mode involving one primary station and at least one secondary station, where either the primary or one of the secondary stations can initiate transmissions.

ARNES: Academic and Research Network of Slovenia
Academic and Research Network of Slovenia (ARNES), established as an independent public institution in 1992, is an organization of developing, operating and managing the communication and information network for education and research.

ARPA: Advanced Research Projects Agency
Advanced Research Projects Agency (ARPA), now called DARPA (Defense Advanced Research Projects Agency), is a research and development organization under DoD (Department of Defence of USA). ARPA is responsible for numerous technological advances in communications and networking.

ARPANET: Advanced Research Projects Agency Network
Advanced Research Projects Agency Network(ARPANET) is a landmark packet-switching network established in 1969. ARPANET was developed in the 1970s by BBN and funded by ARPA (and later DARPA). It eventually evolved into the Internet. The term ARPANET was officially retired in 1990.

ARQ: Admission ReQuest
Admission Request (ARQ) is an RAS (Registration, Admission, and Status) message sent as an admission request for the gatekeeper to control the admission of the endpoints into the H.323 network.

ARQ: Automatic Repeat reQuest
Automatic Repeat-reQuest (ARQ) is an error control method for data transmission in which the receiver detects transmission errors in a message and automatically requests a retransmission from the transmitter. Usually, when the transmitter receives the ARQ, the transmitter retransmits the message until it is either correctly received or the error persists beyond a predetermined number of retransmissions. A few types of ARQ protocols are Stop-and-wait ARQ, Go-Back-N ARQ and Selective Repeat ARQ.

ARU: Alarm Relay Unit
Alarm Relay Unit (ARU) is a module on some network devices which supports physical office alarming functions required by many telephone companies.

AS: Autonomous System
Autonomous System (AS) is a collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the IANA. Sometimes abbreviated as AS.

ASAM: ATM Subscriber Access Multiplexer
ATM Subscriber Access Multiplexer (ASAM) is a telephone central office multiplexer that supports SDL ports over a wide range of network interfaces. An ASAM sends and receives subscriber data (often Internet services) over existing copper telephone lines, concentrating all traffic onto a single high-speed trunk for transport to the Internet or the enterprise intranet. This device is similar to a DSLAM (different manufacturers use different terms for similar devices).

ASBR: Autonomous System Boundary Router
Autonomous System Boundary Router (ASBR) is a router located between an OSPF autonomous system and a non-OSPF network (such as RIP). ASBRs run both OSPF and another routing protocol, such as RIP. ASBRs must reside on a non-stub OSPF area.

ASCII Armor
ASCII Armor is a term used to describe an encoding process, in which data in a binary format is transformed into a textual format, to allow the data to be successfully transmitted through channels designed only for text messages, such as e-mail or usenet.

ASCU: Agent-Set Control Unit
Agent-Set Control Unit (ASCU) is a concentrator or multiplexer which groups of terminals and printers at a remote location. ASCU routes data back and forth between the Host computer and the location’s terminals and printers over a telephone line.

ASI: ATM Service Interface
ATM Service Interface (ASI) is a line card for use in the BPX switch to interface an ATM user device, such as, Customer Premise Equipment (CPE). The ASI provides an industry-standard ATM User-to-Network Interface (UNI) or ATM Network-to-Network Interface (NNI) to the BPX switching fabric.

ASIST: Application Software Integration Support Tools
Application Software Integration Support Tools (ASIST) is a set of C-language application development tools designed to facilitate the creation of host-controlled applications by Cisco VCO/4K customers.

ASP: Auxiliary Signal Path
Auxiliary Signal Path (ASP) is the link between TransPaths that allows them to exchange signaling information that is incompatible with the PSTN backbone network. ASP is used to provide feature transparency.

ASPI: Advanced SCSI Programming Interface
Advanced SCSI Programming Interface (ASPI) is a standard SCSI (Small Computer System Interface) software interface that acts as a communication link between a host adapter board and SCSI device drivers. ASPI enables host adapters and device drivers to share a single SCSI hardware interface.

Assigned Numbers
In the Internetworking world, there are many special names and numbers required for the communication, such numbers include IP addresses, DNS domain names, Protocol parameters, TCP/UDP port numbers etc. The organization that performs these duties is the Internet Assigned Numbers Authority (IANA). IANA is presently operated by ICANN (Internet Corporation for Assigned Names and Numbers).

AST: Automatic Spanning Tree
Automatic Spanning Tree (AST) is a function that supports the automatic resolution of spanning trees in source-route bridging (SRB) networks, providing a single path for spanning explorer frames to traverse from a given node in the network to another. AST is based on the IEEE 802.1 standard.

ASTA: Advanced Software Technology and Algorithms
Advanced Software Technology and Algorithms (ASTA) is a component of the High Performance Computing and Communications (HPCC) program. The purpose of the ASTA component is to develop the scalable parallel algorithms and software needed to realize the potential of the new high performance computing systems in solving Grand Challenge problems in science and engineering.

Asymmetry
In networking, asymmetry refers to a system in which the relationship between two entities is inherently unequal, with each entity restricted to a set of operations and prerogatives defined by its role in the relationship.

Asynchronous
Asynchronous means not synchronized. In data communication, it describes the type of communication that are transmitted without precise clocking. Asynchronous data transmissions usually encapsulate individual messages in control bits (called start-and-stop bits) that designate the beginning and end of each message. Other types of communications include Isochronous, plesiochronous, and synchronous communications.

Asynchronous PPP
Asynchronous PPP is one of the modes used in the point-to-point protocol. Asynchronous PPP is commonly used in lower-speed transmission and less-expensive transmission systems such as dialup modems. Asynchronous PPP replaces earlier non-standard SLIP (Serial Line IP) protocol

Asynchronous transmission
Asynchronous transmission is a procedure or protocol in which each information character (or byte) is individually synchronized or framed by the use of Start-and-Stop Elements (also referred to as START BITS and STOP BITS). A start bit indicates the beginning of a new character; it is always 0 (zero). A stop bit marks the end of the character. It appears after the parity bit, if one is in use. The Asynchronous Transmission Format is also known as START-STOP mode or CHARACTER mode.

ATG: Address Translation Gateway
Address Translation Gateway (ATG) is Network Address Translation (NAT) gateway for the DECnet PhaseIV. ATG is also the DECnet routing software function in many Cisco products that allows a router to route multiple, independent DECnet networks and to establish a user-specified address translation for selected nodes between networks.

ATM Access Switch
ATM Access Switch is a specialized ATM switch located at the customer premise providing access into a carrier ATM network. Typically, the ATM Access Switch can provide both data and voice services and aggregate lower speed links at the customer site into a single high speed link to the carrier network.

ATM Address
Asynchronous Transfer Mode (ATM) uses addresses to identify and locate ATM devices. There are three types of ATM addresses: 1) Data Country Code (DCC) AESA - The AFI is 39. These addresses are to be used in public networks. For example, the initial domain identifier (IDI) value 0x84.0f identifies the United States. 2) International Code Designator (ICD) AESA - The AFI is 47. These addresses are used in private organizations, and the ICD field indicates the code set or organization. 3) NSAP encoding format for E.164 addresses - The authority and format identifier (AFI) is 45. These addresses are used in establishing ISDN calls by public networks, and they are normally used in public telephony.

ATM ARP server
ATM ARP server is a device that provides address-resolution services to Logical IP Subnet (LIS) when running classical IP (CLIP) over ATM.

ATM Backbone Switch
ATM Backbone Switch is a type of high speed ATM switch used to form the backbone of an enterprise ATM network or carrier's ATM network. ATM Backbone Switch can support multiple services such as data and voice.

ATM Cell
The ATM cell is the basic unit of information transfer in the ATM communication. The cell is comprised of 53 bytes. Five of the bytes make up the header field and the remaining 48 bytes form the user information field.

ATM Edge LSR
ATM Edge LSR (Label Switch Router) is a router that is connected to the core ATM-LSR network through LSC-ATM interfaces. The ATM edge LSR adds labels to unlabeled packets and strips labels from labeled packets.

ATM Edge Switch
ATM Edge Switch is a specialized ATM switch located at the edge of carrier's network to aggregate ATM traffic from multiple customers. The ATM Edge Switch can provide both data and voice services and aggregate lower speed links from customer's network into high speed backbone of the carrier, and vise versa.

ATM ELSU: ATM Ethernet LAN Service Unit
ATMToken Ring LAN Service Unit (TLSU) provides 12 independent virtual Token Ring bridges for running over ATM networks. TLSUs are designed for Token Ring LAN interworking with ATM network.

ATM Endpoint
ATM Endpoint is the point in an ATM network where an ATM connection is initiated or terminated. ATM endpoints include ATM-attached workstations, ATM-attached servers, ATM-to-LAN switches, and ATM routers. ATM is connection-oriented. An ATM endpoint establishes a defined path known as a virtual channel (VC), also called virtual circuit, to the destination endpoint prior to sending any data on the network. It then sends a series of same-size frames, called cells, along the virtual channel towards the destination.

ATM Forum
The ATM Forum was an international, industry-wide, nonprofit association of telecommunications, networking, and other companies focused on advancing the deployment of multi-vendor, multi-service packet-based networks, associated applications, and interworking solutions. The ATM Forum was originally formed with the objective of accelerating the use of ATM products and services. Now ATM Forum has become part of the MFA Forum.

ATM Forum UNI
ATM Forum UNI, also known as ATM UNI, is the ATM Signaling of User-to-Network Interface. ATM UNI is part of the ATM protocols by which ATM users and the network exchange the control of information, request the use of network resources, or negotiate for the use of circuit parameters.

ATM Inverse Multiplexing
Inverse Multiplexing (IMA) over ATM, also known as ATM Inverse Multiplexing, is a standard protocol defined by the ATM Forum. IMA provides a way to combine an ATM cell stream over two or more circuits (i.e., T1 lines), thus allowing an organization to lease just the bandwidth it needs. When more than T1 and less than T3 is required, IMA provides a solution. It lets an organization purchase just the bandwidth it needs to transmit ATM cells across a carrier's network to its remote sites.

ATM Link
An ATM Link is the virtual path link (VPL) or virtual channel link (VCL) between two ATM end points.

ATM LSR
ATM LSR is a label switch router with several LSC-ATM interfaces. The router forwards the cells among these interfaces using labels carried in the VPI/VCI field of the cells.

ATM NIC (Network Interface Card)
ATM NIC is a type of Network Interface Card (NIC) that transmits and receives Asynchronous Transfer Mode (ATM) traffic. ATM NIC is plugged into the bus of a client station or server.

ATM Peer-to-Peer Connection
ATM Peer-to-Peer Connection is a virtual channel connection (VCC) or a virtual path connection (VPC) directly established, such as workstation-to-workstation. This setup is not commonly used in ATM networks.

ATM Reference Model
ATM Reference Model, defined by ITU-T, is a logical model to describe the ATM architecture and functionality that it supports. The ATM reference model is composed of the following planes, which span all layers: 1) ControlThis plane is responsible for generating and managing signaling requests. 2) UserThis plane is responsible for managing the transfer of data. 3) ManagementThis plane contains layer management and plane management components. The ATM reference model is composed of three ATM layers: physical layer, ATM Layer and ATM adaptation layer.

ATM Switch
ATM Switch is a network device that can forward 53-byte ATM cells betweem network devices that have implemented ATM technologies. ATM switch can be used as both the LAN and WAN switches that support multiple types of services such as data and voice.

ATM Token Ring LAN Service Unit (TLSU)
ATM Ethernet LAN Service Unit (TLSU) provides up to 64 Token Ring ports for running over ATM networks. TLSUs are designed for Token Ring LAN interworking with ATM network.

ATM Traffic Descriptor
ATM Traffic Descriptor is a generic list of parameters that can be used to capture the intrinsic traffic characteristics of a requested ATM connection.

ATM user-user connection
ATM user-user connection is a connection created by the ATM layer to provide communication between two or more ATM service users, such as ATM Management (ATMM) processes. Such communication can be unidirectional, using one VCC, or bidirectional, using two VCCs.

ATM25 or ATM-25
ATM25 or ATM-25 refers to ATM running at 25 Mbps. ATM25 is mainly used for some corporate local area network.

ATMM: ATM Management
ATM Management (ATMM) is a process that runs on an ATM switch to control Virtual Channel Identifier (VCI) translation and rate enforcement.

Attenuation
Attenuation refers to decreasing in signal magnitude between two points. These points may be along a radio path, transmission line or other devices.

Attribute
In network management, an attribute is a property or a parameter of a managed object in a particular value. Initial values for attributes can be specified as part of the managed object class definition. Attributes may be either mandatory or conditional.

AU: Access Unit
Access Unit (AU) is a device that interfaces with the access device on one side and with a service provider system on the other side. It converts formats, service elements, and protocols. For example, X.400 AU can provide non-X.400 services bidirectional flow of messages. ISDN AU is the device that provides ISDN access to public-serviced networks.

AUI: Attachment Unit Interface
An Attachment Unit Interface (AUI) is a 15 pin connection that provides a path between a node's Ethernet interface and the Medium Attachment Unit, sometimes known as a transceiver. It is the part of the IEEE Ethernet standard located between the MAC, and the MAU. An AUI cable may be up to 50 metres long, although frequently the cable is omitted altogether and the MAU and MAC are directly attached to one another.

AUP: Acceptable Use Policy
Acceptable Use Policy (AUP) refers to the policies that restrict the use to which the network can be put. The enforcement of AUPs varies with the network. Many public network services have an AUP. The AUP is a formal or informal document that defines the intended uses of the network, unacceptable uses, and the consequences for non-compliance. One often encounters an AUP when registering for a Web-based service or when working on a corporate intranet. A good AUP will include provisions for network etiquette, limits on the use of network resources if any, and clear indications of the level of privacy a member on the network should expect. The best AUPs incorporate "what if" scenarios that illustrate the usefulness of the policy in real-world terms.

AURP Tunnel
AURP Tunnel, a concept in the AppleTalk Update-Based Routing Protocol (AURP), is a connection created in an AURP WAN that functions as a single, virtual data link between AppleTalk internetworks physically separated by a foreign network (a TCP/IP network, for example). Any number of physical nodes can exist in the path between exterior routers, but these nodes are transparent to the AppleTalk networks. Two kinds of AURP tunnels exist: point-to-point tunnels and multipoint tunnels. A point-to-point AURP tunnel connects only two exterior routers. A multipoint AURP tunnel connects three or more exterior routers.

AUSM: ATM UNI Service Module
ATM UNI Service Module (AUSM) is a product of Cisco Systems designed for use with the MGX 8220 Edge Concentrator, the MGX 8230 and MGX 8250 multiservice gateways and the MGX 8800 series wide-area edge switches.

AUSTPAC
AUSTPAC is an Australian public X.25 network operated by Telstra. Started in the early 1980s, AUSTPAC was Australia's first public packet-switched data network, supporting applications such as on-line betting, financial applications and remote terminal access to academic institutions, who maintained their connections to AUSTPAC up until the mid-late 1990s in some cases.

Authority Zone
Associated with DNS (Domain Name System), Authority Zone or DNS Zone is a section of the domain-name tree for which one name server is the authority. The Domain Name System (DNS) is a distributed database system that provides hostname-to-IP resource mapping (usually the IP address) and other information for computers on an internetwork. DNS is made up of two distinct components, the hierarchy and the name service. The DNS hierarchy specifies the structure, naming conventions, and delegation of authority in the DNS service. The DNS name service provides the actual name-to-address mapping mechanism.

AUTODIN: Automatic Digital Network
The Automatic Digital Network (AUTODIN) is a legacy data communications service in the United States Department of Defense. ARPANET has replaced AUTODIN for the Defense Data Network.

Automatic Routing Management
Automatic Routing Management, also known as AutoRoute, is the connection-oriented mechanism used in Cisco WAN switches to provide connectivity across the network. Switches perform a connection admission control (CAC) function on all types of connections in the network. Distributed network intelligence enables the CAC function to route and reroute connections automatically over optimal paths while guaranteeing the required QoS.

Auto-Negotiation
Auto-Negotiation is a protocol defined in the Ethernet standard that allows devices at either end of a link segment to advertise and negotiate modes of operation.

Autonomous Confederation
Autonomous Confederation refers to a group of autonomous systems that rely on their own network-reachability and routing information more than they rely on that received from other autonomous systems or confederations.

Autonomous Switching
Autonomous Switching refers to a type of switching in which an incoming packet matches an entry in the autonomous-switching cache located in the interface processor. Autonomous switching provides faster packet switching by allowing the Bus controller to switch packets independently without having to interrupt the system processor.

Autonomous System
Autonomous System (AS) refers to a collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number (sometimes called an Autonomous System Number (ASN)) by the IANA.

Autoreconfiguration
Autoreconfiguration is a process performed by nodes within the failure domain of a Token Ring network. Nodes automatically perform diagnostics in an attempt to reconfigure the network around the failed areas to fix the problem without disrupting the entire network. If autoreconfiguration proves unsuccessful, manual correction becomes necessary.

Availability
Availability in networking refers to the amount of time that a network or telephony system (or other device) is operational over a given period of time. Availability is calculated as the ratio, such as 99.99%, of the total time a network or device is operational during a given time interval to the length of that interval. For example, the switching system of the PSTN is claimed to have a 99.999% (5 9's) availability, which translates into a 4 minutes down time each year.

Avalanche
Avalanche is the name of a proposed peer-to-peer (P2P) network created by Microsoft, which claims to offer improved scalability and bandwidth efficiency compared to existing P2P systems. Avalanche works in a similar way to BitTorrent, but aims to improve some of the latter's shortfalls. Like BitTorrent, Avalanche splits the file to be distributed into small blocks. However, rather than peers simply transmitting the blocks, they transmit random linear combinations of the blocks along with the random coefficients of this linear combination.

Average Rate
Average rate is a measure of network bandwidth usage with a unit in kilobits per second (kbps) or megabit per second (mbps) or gigabit per second (gbps).

AVVID: Architecture for Voice, Video and Integrated Data
Architecture for Voice, Video and Integrated Data (AVVID) is a Cisco-defined architecture providing multiple services on a converged network for an enterprise. Cisco AVVID Network Infrastructure provides a documented roadmap for planning, building, and expanding enterprise networks with consideration for quality of service (QoS), high availability, and security. Cisco AVVID Network Infrastructure extends beyond a single-box approach, focusing on good design principles, interoperability between different network components, and the use of features and protocols needed to build a converged voice, video, and data network.

AW: Admin Workstation
Admin Workstation, or Administration Workstation (AW), is typically a personal computer used to monitor, change and configure a network software or hardware systems.

AW: Administrative Weight
Administrative Weight (AW), one of four link metrics exchanged by PTSPs to determine the available resources of an ATM network, is the value set by the network administrator to indicate the desirability of a network link.

AX.25
AX.25 is a data link layer protocol derived from the X.25 protocol suite and designed for use by amateur radio operators on amateur packet radio networks. AX.25 occupies the first and second layers of the OSI networking model, and is responsible for transferring data (encapsulated in packets) between nodes and detecting errors introduced by the communications channel. AX.25 supports both connected and connectionless modes of operation, the latter used to great effect by the Automatic Position Reporting System.