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AA	Auto-attendant (or automated attendant). Software application that provides automated operator-assistance messages and prompts based on input of voice or DTMF tones, guiding callers to appropriate extensions.
AAA	Authentication, Authorization, and Accounting. Suite of network-security services that provides the framework for setting up access control on a router or gateway. See also RADIUS.
AAL	ATM adaptation layer. Service-dependent sublayer of the data link layer. The AAL accepts data from different applications and presents it to the ATM layer in the form of 48-byte ATM payload segments. AALs consist of two sublayers: the convergence sublayer (CS) and the segmentation and reassembly sublayer (SAR). AALs differ on the basis of the source-destination timing used, whether they use constant bit rate (CBR) or variable bit rate (VBR), and whether they are used for connection-oriented or connectionless mode data transfer. The four types of AAL are AAL1, AAL2, AAL3/4, and AAL5.
access server	Communications processor that connects asynchronous devices to a LAN or WAN through network and terminal emulation software. Performs both synchronous and asynchronous routing of supported protocols. Sometimes called a network access server or or universal access server.
ACD	Automatic call distributor (or distribution). Device or service that routes incoming calls to targets within a call center or geographically distributed locations served by a CO.
ACF message	Admission confirmation RAS message.
ACK message	Acknowledgment message. Message sent by one network device to another to acknowledge that some event occurred (for example, the receipt of a message).
ACOM	Loose abbreviation for "a combined loss." Combined loss achieved by an echo canceller, equal to the sum of the echo return loss, echo return loss enhancement, and nonlinear processing loss for a call.
ADSL	Asymmetric digital subscriber line. One of four DSL technologies. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream. Downstream rates range from 1.5 to 9 Mbps, whereas upstream bandwidth ranges from 16 to 640 kbps. ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair.
aggregation interval	Interval during which call statistics are collected.
aggregation level	Voice-signaling interface level—for example, gateway, IP, PSTN, trunk group, and voice ports (DS1 only).
AIS	Alarm-indication signal. In a T1 transmission, an all-ones signal transmitted in lieu of the normal signal to maintain transmission continuity and to indicate to the receiving terminal that a transmission fault is located either at or upstream from the transmitting terminal.
Allow header	Message header that lists the set of methods supported by the user agent that generates the message.
AM	Amplitude modulation. Technique to modulate digital data onto high-frequency carrier tones by varying the amplitude of the signal.
AMA	Automatic message accounting. Automatic collection, recording, and processing of information relating to calls for billing purposes.
ANI	Automatic Number Identification (or Indication). Feature that records and sends the calling party's phone number over the network to the called party, typically for accounting and billing purposes but also for services such as enhanced 911. At the receiving end, Caller ID reads the ANI to display the caller's phone number. Often used to mean the number of the calling party.
API	Application programming interface.
ARP	Address Resolution Protocol. Broadcast protocol used by TCP/IP LAN-based host computers and routers to match MAC addresses with IP addresses. Operates only across a single physical network and is limited to networks supporting hardware broadcasts.
ARQ message	Admission-Request RAS message.
ARS	Automatic route selection. Way to provide least-cost routing.
AS	Application (or access) server. Logical entity that serves a specific application instance. An example of an application server is an MGC that handles Q.931 signaling and call processing for D channels that are terminated by signaling gateways. See also access server.
ASCII	American Standard Code for Information Interchange. 8-bit code for character representation (7 bits plus parity).
ASN.1	Abstract Syntax Notation One. OSI language for describing data types independent of particular computer structures and representation techniques.
ASP	Application-server process. Process instance of an application server. Examples are primary or backup MGC instances. Application-service provider (or process). Service provider that offers a unique application or service, typically hosted on another provider's core network.
ASR	Automatic speech recognition. Capability of an external media server to recognize speech that is provided as input by the user of an IVR application.
ATA	Analog telephone adaptor. Device that allows an analog phone to connect to an IP phone system.
ATM	Asynchronous Transfer Mode. Standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.
au	File extension for an audio file. See also wav.
AUCX message	Audit-Connection message.
audio	What the user hears on the phone. Includes both voice and DTMF digits.
AUEP command	Audit Endpoint command. An MGCP or SGCP command that a call agent uses to determine the status of a given gateway endpoint.
AUEP message	Audit-Endpoint message.
authentication	Method for identifying users, including login and password dialog, challenge and response, messaging support, and, depending on the security protocol that you select, encryption.
AV-pair	Attribute-value pair used in authentication.

Source: www.cisco.com