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Cajun P550/P880 ATM Uplink User Guide, Version 1.1
G-1
Glossary
ACM - ATM
Connection
Manager
A software entity within each device that is responsible for setting
up and maintaining ATM virtual channel connections.
Address
Resolution
Protocol (ARP)
A protocol used to map 32-bit IP addresses into 48-bit Ethernet
addresses. Conforms to RFC 826.
Asynchronous
Transfer Mode
(ATM)
A high-speed, connection-oriented switching and multiplexing
technology that uses 53-byte cells (5-byte header, 48-byte payload)
to transmit different types of traffic simultaneously, including
voice, video, and data. It is asynchronous in that information
streams can be sent independently without a common clock.
ATM Adaptation
Layer (AAL)
A set of four standard protocols that translate user traffic from the
higher layers of the protocol stack into a size and format that can
be contained in the payload of an ATM cell and return it to its
original form at the destination. Each AAL consists of two
sublayers: the Segmentation And Reassembly (SAR) sublayer and
the convergence sublayer. Each is geared to a particular class of
traffic, with specific characteristics concerning delay and cell loss.
All AAL functions occur at the ATM endstation rather than at the
switch.
AAL 1 addresses CBR (Constant Bit Rate) traffic, such as digital
voice and video and is used for applications that are sensitive to
both cell loss and delay and to emulate conventional leased lines. It
requires an additional byte of header information for sequence
numbering, leaving 47 bytes for payload.
AAL 2 is used with time-sensitive VBR (Variable Bit Rate) traffic,
such as packetized voice. It allows ATM cells to be transmitted
before the payload is full to accommodate an application’s timing
requirements. The AAL 2 specification has not been completed by
the ATM Forum.