Agilent Technologies J3919A Installation & User Manual page 155

Agent
A node (or software/hardware on a node) that supplies network management
information.
Alarm Indication Signal (AIS)
An Alarm Indication Signal (AIS) is transmitted downstream when a major alarm
condition such as LOS, LOF, or LOP is detected. Different AIS signals are sent
depending on the level of the maintenance hierarchy.
ANSI (American National Standards Institute)
The United States coordinating organization for voluntary standards.
ASCII (American Standard Code for Information Interchange)
Seven bit code providing a total of 128 upper and lower case letters, numerals,
punctuation marks, and control characters. Also referred to as CCITT Alphabet
Number 5.
Asynchronous
A transmission process such that there is always an integer number of units
between any two significant instances in the same signal but there is not always an
integer number of units between significant instances in two independent signals.
Asynchronous Transfer Mode (ATM)
Asynchronous Transfer Mode (ATM) is a fast packet-switched technology based
on fixed length cells. Data is divided into individual units and routed across an
ATM network in a constant stream. Unused packets are filled with idle cells.
Flexible bandwidth is possible with ATM - a service can use as many ATM cells
as it needs. Voice, video, and data can be sent in a consistent manner over an ATM
network, making ATM a valuable solution for many different services.
ATM Adaptation Layer (AAL)
The ATM Adaptation Layer isolates the higher layers from the specific
characteristics of the ATM Layer and provides a way to map data from variable
length frames into the fixed size of ATM cells. Different Adaptation layers are
used (AAL-1, AAL-3/4, and AAL-5) to implement different types of service.
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