ATM Terms and Acronyms
The following are common ATM terms and acronyms for your reference:
AAL—ATM Adaptation Layer. An AAL defines the conversion of user information into cells. AAL1 and AAL2 handle isochronous traffic, such as voice and video; AAL3/4 and AAL5 pertain to data communications through the segmentation and reassembly of packets.
ATM—Asynchronous transfer mode. A cell-switching and multiplexing technology combining the benefits of circuit switching (constant transmission delay, guaranteed capacity) with those of packet switching (flexibility, efficiency for intermittent traffic). ATM is defined by ITU-T standards.
Average-rate—The average rate, in kbps, at which a given virtual circuit (VC) will transmit data.
BISDN—Broadband Integrated Services Digital Network. A set of standards under development by the ITU-T for services based on ATM switching and SONET/SDH transmission.
CCITT—Consultative Committee for International Telegraph and Telephone (Although commonly referred to as the CCITT, this international standards body recently adopted the name International Telecommunication Union/Telecommunication Standardization Sector (ITU-T).
CLP—Cell loss priority.
DXI—Data exchange interface.
ILMI—Interim Local Management Interface. Described in the ATM Forum’s UNI specification, ILMI allows end users to retrieve a basic set of information, such as status and configuration about virtual connections and addresses, for a particular UNI.
MIB—Management Information Base.
MIC—Media interface connector.
MID—Message identifier. In AAL3/4 encapsulation, the 2-byte MID field allows multiplexing of streams of cells on one virtual channel.
NSAP—Network Service Access Point.
OAM—Operation Administration and Maintenance (cells).
PDU—Protocol data unit. An OSI term for a packet.
Peak-rate—The maximum rate, in kbps, at which a given VC can transmit data.
PMD—Physical medium dependent. The lower half of BISDN Layer 1.
PLIM—Physical layer interface module. The PLIM contains the interface to the ATM cable. (See the section “ACIP Interface” on page 5.)
PVC—Permanent virtual circuit.
QOS—Quality of service.
Rate queues—Rate queues define the speed at which individual VCs will transmit data to the remote end. Every VC must be associated with one rate queue. After attachment to this rate queue, the VC is assumed to have its peak rate set to that of the rate queue. Each rate queue can be configured independently to a portion of the overall bandwidth available on the ATM link. The combined bandwidths of all rate queues should not exceed the total bandwidth available.
SAR—Segmentation and reassembly.
SDH—Synchronous Digital Hierarchy. International standard for optical digital transmission at hierarchical rates from 155 Mbps to 2.5 Gbps and greater.
SDU—Service data unit.
