Universal Broadband Router Hardware Installation Guide

Glossary
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Cisco uBR10012 Universal Broadband Router Hardware Installation Guide
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AAL
ATM adaptation layer. Service-dependent sublayer of the data link layer. The AAL accepts data from
different applications and presents it to the ATM layer in the form of 48-byte ATM payload segments.
AALs consist of two sublayers:the convergence sublayer and the segmentation and reassembly
sublayer. Four types of AAL recommended by the ITU-T are AAL1, AAL2, AAL3/4, and AAL5; the
Cisco uBR10012 uses AAL5.
Access list
List kept by routers to control access to or from the router for a number of services. For example, access
lists can be used to prevent packets with a certain IP address from leaving a particular interface on the
router.
Add drop
Multiplexer
See ADM.
ADM
Add Drop Multiplexer. A multiplexer that allows a signal to be added into or dropped out of a SONET
span. See also
SONET.
Alarm
A status condition that shows that a module or port is experiencing an abnormal operating condition.
See also
Critical alarm, Major alarm, and Minor alarm.
Application-specific
integrated circuit
See ASIC.
APS
Automatic Protection Switching. A SONET switching mechanism that achieves network resiliency by
automatically switching from a primary circuit to a secondary circuit. This switching process occurs if
the primary circuit fails or if the error rate on the primary line exceeds a set threshold. The Cisco 10000
ESR supports 1+1 APS, which provides permanent electrical bridging to the service and protection
equipment, placed at both ends of the circuit.
ASIC
Application-specific integrated circuit. A chip that is built for a specific application.
Asynchronous
Transfer Mode
See ATM.
ATM
Asynchronous Transfer Mode. International standard for cell relay in which multiple service types
(such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow
cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take
advantage of high-speed transmission media such as E3, SONET, and T3.
Authentication
In security, the verification of the identity of a person or process.
Automatic
protection
switching
See APS.
Alarm
A status condition that shows that a module or port is experiencing an abnormal operating condition.
See also
Critical alarm, Major alarm, and Minor alarm.