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Appendix D: Abbreviations
AAL ATM Adaptation Layer. A function performed during ATM cell processing to adapt
traditional IP or Ethernet traffic for transmission through an ATM network.
ADSL Asymmetric Digital Subscriber Line. A method for modulating data to achieve high
bit rates over common twisted-pair copper wire.
ATM Asynchronous Transfer Mode. A method of networking the uses a fixed length cell
to transmit data (versus a variable length packet). The fixed length cell improved
cell switch performance, hence improves end-to- end data transfer performance.
CBR Constant Bit Rate. This class of service delivers ATM traffic at a consistent rate.
The rate is specified during virtual circuit construction and cannot exceed the
specified value.
CSA Control and Status Application. Basis for this whole document.
GUI Graphical User Interface. The Windows-based interface a user interacts with to
manage and monitor the ADSL modem activity.
LEC Local Exchange Carrier. The business party responsible for delivery of telephone
service to a geographic region.
PDU Protocol Data Unit. Similar to a data packet, a protocol data unit is simply a data
packet that has some protocol processing applied to it.
PVC Permanent Virtual Circuit. A virtual circuit that is defined and exists until explicitly
destroyed.
SAR Segmentation and Reassembly. The process of segmenting AAL PDUs into cells
and reassembling received cells as AAL PDUs.
SVC Switched Virtual Circuit. A virtual circuit that is dynamically created and destroyed
using UNI signaling.
UBR Unspecified Bit Rate. This class of service attempts to deliver ATM traffic in a ‘best
effort’ mode, as long as the amount of bandwidth consumed by the effort does not
exceed a specified peak rate.
UNI User-To-Network Interface. The interface between the user endpoint equipment
and the first ATM switch encountered in the network. The UNI specification suite
(versions 3.0, 3.1, and 4.0) is maintained by the ATM Forum.
VBR Variable Bit Rate. Service class attempts to deliver ATM traffic.
VC Virtual Circuit. A data path setup across an ATM link.