Cisco Systems 78-11450-03 Manual De Usuario

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.

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.

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Add Drop Multiplexer. A multiplexer that allows a signal to be added into or dropped out of a SONET 
span. See also 

A status condition that shows that a module or port is experiencing an abnormal operating condition. 
See also 

, 

.

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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.

Application-specific integrated circuit. A chip that is built for a specific application.

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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.

In security, the verification of the identity of a person or process.

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A status condition that shows that a module or port is experiencing an abnormal operating condition. 
See also 

, 

.