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AAL
ATM Adaptation Layer. A collection of standardized protocols that adapts user traffic to a cell format. Specifically, the ATM adaptation layer (AAL) receives packets from upper-level protocols and breaks them into the 48-byte segments that form the payload field of an ATM cell. Memotec currently supports two types of ATM adaptation layers: AAL0 and AAL5.

AAL0
ATM Adaptation Layer type0. Typically used by Memotec to transport voice.

AAL5
ATM Adaptation Layer Type 5. Protocol used for the transport of all types of traffic over ATM. Applications over AAL5 include Frame Relay, LAN, ATM-DXI, Voice, as well as legacy protocols. There are no limitations for new applications to be added over AAL5.

ABR
Available Bit Rate. One of the two "best effort" service types (orservice categories) in ATM (the other one is UBR), where the network makes no absolute guarantee of cell delivery; however, it guarantees a minimum bit rate for user transmission. The objective of ABR service is to provide rapid access to network bandwidth that is not being used.

access channel
In a public network, the amount of bandwidth on a dedicated link that is dedicated to Frame Relay orATM traffic.

access line
A communications line interconnecting a Frame Relay-compatible end-device (DTE) to a Frame Relay switch (DCE).

access rate
The data rate of the user access channel. The speed of the access channel determines how much data (maximum rate) the end user can inject into a Frame Relay network.

access switch
See Frame Relay access switch

ACELP II
AlgebraicCode-Excited Linear Prediction. A voice compression algorithm used in Memotec’s Frame Relay equipment which provides 5.8 and 8 Kbps compression rates.

ADPCM
Adaptive Differential Pulse Code Modulation. A speech coding method which uses fewer bits than the traditional PCM (Pulse Code Modulation). ADPCM, which many voice processing makers use, allows encoding of voice signals at 16, 24, 32 and 40 Kbps.alternate routing
A routing algorithm feature that finds an alternate route for a connection that has been interrupted due to a fault or other cause.

ANI
Automatic Number Identification. A feature used by ISDN and Signaling System 7 to provide the calling party number.

ANSI
American National Standards Institute. A non-profit, non-governmental organization that defines standards,including telecommunications standards, for use in the United States. ANSI is a member of the International Organization for Standardization (ISO).ARP Address Resolution Protocol. Internet Protocol utility used to dynamically map IP addresses to Ethernet MAC address on local area networks.

ASCII
American Standard Code for Information Interchange. An 8 bit coding method used by computers forrepresenting letters, numbers, punctuation, and control codes into digital form.

Async
Short form for asynchronous. Also a term used to designate Async protocol. See also asynchronous and Async protocol.

Asynchronous
A mode of data transmission in which data can be sent at any time (no synchronization of data transfer). In asynchronous transmission, the information unit does not always have thesame number of bits, which causes variable time delay between data messages.

Async protocol
A transmission protocol in which data is transmitted one character at a time, each character being preceded by a start bit and followed by a stop bit in order to ensure correct receipt.

AT&T
American Telephone and Telegraph Company.

ATM
Asynchronous Transfer Mode. Very high-speed transmissiontechnology that allows multiple types of traffic (voice, video, data) to be transmitted in fixed-size cells of 53 bytes. It can support transmission speeds up to several gigabits per second. Also known as cell relay.

ATM Forum
A consortium of organizations representing vendors, manufacturers, carriers, service providers, research groups, consultants and users which recommends and defines...
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