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Chapter 7.
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 ex-
ceed 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.
VCI Virtual Circuit Identifier. A 16-bit value that is included in an ATM cell
header to identify the destination virtual circuit.
VPI Virtual Path Identifier. An 8-bit value that is included in an ATM cell header
to identify the destination virtual path.
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