Glossary Section "A" ( Definitions )
abstract syntax A description of a data structure that is (Adaptation Layer). Protocol used on top of ATM to support higher layer service requirements. For data communications services, the AAL defines a segmentation reassembly protocol for mapping large data packets into the 48 octet information field of the ATM cell.
AAR Automatic Alternate Routing; failure recovery
AB signaling A technique for carrying telephony signaling information across T1 spans. In A & B signaling, the least significant bit from each channel in the 6th and 12 frames is robbed to pass signaling information. Bits from the 6th frame are the A bits, while the B bits are in the 12th frame.
ABR Available Bit Rate. An ATM service type in which the ATM network makes a "best effort" to meet the transmitters bandwidth requirements. ABR differs from other "best effort" service types by employing a congestion feedback mechanism that the ATM network uses to notify the transmitters that they should reduce their rate of data transmission until the congestion situation ceases. Thus, ABR does offer qualitative guarantee that the transmitters data should get to the intended receivers without experiencing unwanted cell loss.
A-bis GSM term for an interface linking between the BTS (base transceiver station) and the BSC (bas stattion controller).
AC Alternating Current
ACAMI Alternat Channel Alternate Mark Inversion. A method of enable Clear Channel capability while running Fractional T1 in areas where B8ZS is not available. ACAMI does this by filling even numbered time slots with a special fill pattern that contains seven ones. Customer data is transmitted in the odd numbered slots. therefore, the average Ones Density is sufficient to ensure that the T1 line staYs in sync.
ACCTS Aviation Coordinating Committee for Telecommunications Services, part of ARINC.
ACF Access Coordination Function; tariffed service where AT&T obtains local loops between customer premises and AT&T serving office.
ACL Access Control List; Most network security systems operate by allowing selective use of services. An Access Control List is the usual means by which access to, and denial of, services is controlled. It is simply a list of the services available, each with a list of the hosts permitted to use the service.
ACM – Association for Computer Machinery
ActiveX Microsofts Windows-specific non-Java technique for writing applets. ActiveX applets take considerably longer to download than the equivalent Java applets, however, they more fully exploit the features of Windows 95. ActiveX is sometimes said to be a "superset of Java."
address A coded representation of the origin or destination of data.
address mask A bit mask used to select bits from an Internet address for subnet addressing. The mask is 32 bits long and selects the network portion of the Internet address and one or more bits of the local portion. Sometimes called sub-net mask.
ADMD Administration Management Domain. An X.400 Message Handling System public carrier. Examples: MCImail and ATTmail in the U.S., British Telecom's Gold400mail in the U.K. The AIMDs in all countries worldwide together provide the X.400 backbone. See PRMD.
ADSL Asymmetrical Digital Subscriber Line
agent In the client-server model, the part of the system that performs information preparation and exchange on behalf of a client or server application. In SNMP, the word agent refers to the managed system.
AIS Alarm Indicating signal. another name for a Blue Alarm.
ALG Application Layer Gateway
AMI Alternate Mark Inversion A bipolar coding which uses successive ones (marks) must alternate in polarity.
Analog A continuous wave or signal (such as a human voice)
Analog Transmission The transmission of a continuous variable signal
Anonymous FTP Allows a user to retrieve documents, files, programs, and other archived data from anywhere in the Internet without having to establish a user id and password. By using the special user id of "anonymous" the network user will bypass local security checks and will have access to publicly accessible files on the remote system. See FTP.
Answer Supervision A signaling on telephone lines generally used for the billing purposes. Basically, a signal is sent back to the originating central office (CO) that tells that office that the call has been answered.
ANSI American National Standards Institute
AP Access Point. A device which allows for a wireless to a network.
APC Angled Polished Connector
applet A small program, often used in the context of a Java-based program, that is compiled and embedded in an HTML page.
AppleTalk A networking protocol developed by Apple Computer for communication between Apple Computer products and other computers. This protocol is independent of what network it is layered on. Current implementations exist for LocalTalk (235Kbps) and EtherTalk (10Mbps).
Application Layer The top layer of the network protocol stack. The Application Layer is concerned with the semantics of work (e.g., formatting electronic mail messages). How to represent that data and how to reach the foreign node are issues for lower layers of the network.
APS Automatic Protection Switching
ARD Automatic Ring Down: lifting your phone rings the far end without dialing.
ARIN American Registry for Internet Numbers. A non-profit organization established for the purpose of administration and registration of Internet Protocol (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.
ARP Address Resolution Protocol. The Internet protocol used to dynamically map Internet addresses to physical (hardware) addresses on local area networks. Limited to networks that support hardware broadcast.
ARQ Automatic Request for Retransmission
ASDS Accunet Spectrum of Digital Services.
Assigned Numbers The RFC ISTD2] which documents the currently assigned values from several series of numbers used in network protocol implementations. This RFC is updated periodically and, in any case, current information can be obtained from the Internet Assigned Numbers Authority (LANA). If you are developing a protocol or application that will require the use of a link, socket, port, protocol, etc., please contact the LANA to receive a number assignment.
Asynchronous A mode where characters travel individually down the line as they are keyed.
Asynchronous Transmission A transmission method that sends units of data on character at a time. Characters are proceeded by start bits and followed by stop bits, which provide synchronization at the receiving device
Attenuation Signal power loss through equipment, lines or other devices.
attribute The form of information items provided by the X.500 Directory Service. The directory information base consists of entries, each containing one or more attributes. Each attribute consists of a type identifier together with one or more values.
AUP Acceptable Use Policy. Many transit networks have policies which restrict the use to which the network may be put. A well known example is NSFNET's AUP which did not allow for commercial use. Enforcement of AUPs varies with the network.
authentication In security, the verification of the identity of a person or process.
Autonomous System (AS) Internet (TCP/IP) terminology for a collection of gateways (routers) that fall under one administrative entity and cooperate using a common Interior Gateway Protocol (IGP). See subnetwork.
AWG The American Wire
System, which specifies wire width.