Cisco Systems 78-11450-03 See also Critical alarm, Major alarm, and Minor alarm, GL-2

Glossary

A

AAL

Access list

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.

Add drop

Multiplexer

ADM

Alarm

Application-specific integrated circuit

APS

See ADM.

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

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.

See ASIC.

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	See ATM.
Transfer Mode
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	See APS.
protection
switching
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.

	Cisco uBR10012 Universal Broadband Router Hardware Installation Guide
GL-2	78-11450-03 Rev.B0