Glossary Terms - A

abstract syntax (abstract syntax)
A description of a data structure that is independent of machine-oriented structures and encodings. [Source: RFC 1208]
ARPANET (Abstract Syntax Notation One)
A packet switched network developed in the early 1970s. The "grandfather" of today's Internet. ARPANET was decommissioned in June 1990. [Source: RFC 1208]
ACL (Access Control List)
A set of rules that determine which packets of information to pass and which to block depending on their source / destination address or port number.\r\n [Source: Internetwork Training]
(Access Layer)
Part of Cisco's hierarchical model, which consists of three layers. This is the lowest layer which provides users access to the network. [Source: Internetwork Training]
address mask (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 subnet mask. [Source: RFC 1208]
address resolution (address resolution)
A means for mapping Network Layer addresses onto media-specific addresses. See ARP. [Source: RFC 1208]
Application Layer (Address Resolution Protocol)
The top-most layer in the OSI Reference Model providing such communication services as electronic mail and file transfer. [Source: RFC 1208]
ADMD (Administration Management Domain)
An X.400 Message Handling System public service carrier. Examples: MCImail and ATTmail in the U.S., British Telecom Gold400mail in the U.K. The ADMDs in all countries worldwide together provide the X.400 backbone. See PRMD. [Source: RFC 1208]
ARPA (Advanced Research Projects Agency)
Now called DARPA, the U.S. government agency that funded the ARPANET. [Source: RFC 1208]
agent (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. See NMS, DUA, MTA. [Source: RFC 1208]
ANSI (American National Standards Institute)
The U.S. standardization body. ANSI is a member of the International Organization for Standardization (ISO) [Source: RFC 1208]
API (Application Program Interface)
A set of calling conventions defining how a service is invoked through a software package. [Source: RFC 1208]
The Internet protocol used to dynamically map Internet addresses to physical (hardware) addresses on local area networks. Limited to networks that support hardware broadcast. [Source: RFC 1208]
AOW (Asia and Oceania Workshop)
One of the three regional OSI Implementors Workshops, equivalent to OIW and EWOS. [Source: RFC 1208]
ASN.1 (ASN.1)
The OSI language for describing abstract syntax. See BER. [Source: RFC 1208]
ACSE (Association Control Service Element)
The method used in OSI for establishing a call between two applications. Checks the identities and contexts of the application entities, and could apply an authentication security check. [Source: RFC 1208]
attribute (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. Each directory Read operation can retrieve some or all attributes from a designated entry. [Source: RFC 1208]
Autonomous System (Autonomous System)
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. [Source: RFC 1208]

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