| AAL | ATM Adaptation Layer. A collection of standardized protocols that provide services to
higher layers by adapting user traffic to a cell format. The AAL is divided into the
Convergence Sublayer ( CS) and the Segmentation and Reassembly (SAR) sublayer. AAL Type 1. Protocol standard used for the transport of Constant Bit Rate (CBR) traffic (i.e. audio and video) and for emulating TDM-based circuits (i.e. DS1, E1). AAL Type 2. Protocol standard for supporting time-dependent Variable Bit Rate (VBR-RT) of connection-oriented traffic (i.e. packetized video and audio). AAL Type 3 and 4. Protocol standard for supporting both connectionless and connection-oriented Variable Bit Rate (VBR) traffic. Used also to support SMDS AAL Type 5. Protocol standard for supporting the transport of Lightweight Variable Bit Rate (VBR) traffic and signaling messages. Also used to support Frame Relay services. |
| ABR | Available Bit Rate. One of the two best effort service types (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. An effort is also made to keep cell loss as low as possible. |
| ACK | Acknowledgement. A message that acknowledges the reception of a transmitted packet. ACKs can be separate packets or piggybacked on reverse traffic packets. |
| ACM | Address Complete Message |
| ACR | Allowed (or Available ) Cell Rate. The available bandwidth, in cells per second, for a given QoS class, which is dynamically controlled by the network. |
| ACT | Activity Bit |
| ADPCM | Adaptive Differential Pulse Code Modulation |
| Ai | Signaling ID assigned by Exchange A |
| AIM | ATM Inverse Multiplexer |
| AIR | Additive Increase Rate. The cell rate a source can transmit after increasing its rate by the RIF. |
| AIS | Alarm Indication Signal. One of the OAM function types used for fault management (see also CC , RDI). |
| AIS-E | Alarm Indication Signal - External |
| AMI | Alternate Mark Inversion |
| ANI | Automatic Number Identification |
| ANM | Answer Message |
| ANSI | American National Standards Institute. An US technology standards organization. |
| API | Application Programming Interface. A set of functions used by an application program as a means for providing access to a system's (i.e. operating, communications) capabilities. |
| APPN | Advanced Peer to Peer Network |
| ARE | All Routes Explorer |
| ARP | Address Resolution Protocol. A TCP/IP protocol used for resolving local network addresses by mapping a physical address (i.e. a MAC address) to an IP address. |
| ARQ | Automated Repeat reQuest |
| ASE | Application Service Element |
| ASIC | Application Specific Integrated Circuit |
| ASN | Abstract Syntax Notation |
| ASP | Abstract Service Primitive |
| ATDM | Asynchronous Time-Division Multiplexing. An asynchronous and intelligent TDM where time slots are allocated to the users on demand (dynamically). |
| ATM | Asynchronous Transfer Mode. A broadband switching and multiplexing, connection-oriented, high-performance and cost-effective integrated technology for supporting B-ISDN services (i.e. multimedia). Since no clock control is necessary it is called asynchronous (see also STM). Information is transmitted at very high rates (up to hundreds of Mbps) in fixed-size format packets called cells. Traffic streams are distinguished and supported according to different QoS classes. |
| ATMARP | ATM Address Resolution Protocol |
| ATM-SAP | ATM-Service Access Point. The physical interface at the boundary between the AAL and the ATM layer (see also SAP, PHY-SAP). |
| ATS | Abstract Test Suite |
| AUU | ATM User-to-User |
| B-ICI | Broadband Inter-Carrier Interface. An interface that supports service connections (such as CRS, CES, SMDS, FR ) across public ATM networks and/or carriers. |
| B-ICI SAAL | B-ICI signaling ATM Adaptation Layer |
| B-ISDN | Broadband Integrated Services Digital Network. An ITU-T-introduced protocol platform to support the integrated, high-speed transmission of data, audio and video in a seamless fashion. ATM emerged as a suitable transport standard. |
| B-ISUP | Broadband ISDN User's Part |
| B-LLI | Broadband Low Layer Information |
| B-NT | Broadband Network Termination |
| B-TE | Broadband Terminal Equipment |
| BBC | Braodband Bearer Capability |
| BCBDS | Broadband Connectionless Data Bearer Service |
| BCD | Binary Coded Decimal |
| BCOB | Broadband Class of Bearer |
| BEC | Backward Error Correction. An error-correction scheme where the sender retransmits any data to be found in error, based on the feedback from the receiver. |
| BECN | Backward Explicit Congestion Notification |
| BER | Bit Error Rate |
| BGP | Border Gateway Protocol |
| BGT | Broadcast and Group Translators |
| Bi | Signaling ID assigned by Exchange B |
| BIP | Bit Interleaved Parity |
| BISDN | Broadband - Integrated Services Digital Network |
| BISSI | Broadband Inter Switching System Interface |
| BN | Bridge Number |
| BOF | Birds of Feather |
| BOM | Beginning of Message. A PDU that constitutes the beginning of a message. |
| BOOTP | Bootstrap Protocol |
| BPDU | Bridge Protocol Data Unit |
| BPP | Bridge Port Pair |
| BPS | Bits per second |
| BSVC | Broadcast Switched Virtual Connections |
| BT | Burst Tolerance. Proportional to the MBS, burst tolerance is used as a measure ( leaky bucket parameter) for conformance checking of the SCR. |
| BTAG | Begin Tag |
| BUS | Broadcast and Unknown Server. A server that forwards multicast, broadcast and unknown-destination address traffic to the attached LECs. |
| BW | Bandwidth. Transmission capacity of a communications medium. |