Cisco 10008 Hardware Installation Manual page 152

Glossary
A
ATM adaptation layer. Service-dependent sublayer of the data link layer. The AAL accepts data from
AAL
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 10008 router
uses AAL5.
List kept by routers to control access to or from the router for a number of services. For example, access
Access list
lists can be used to prevent packets with a certain IP address from leaving a particular interface on the
router.
See ADM.
Add drop
Multiplexer
Add Drop Multiplexer. A multiplexer that allows a signal to be added into or dropped out of a SONET
ADM
span. See also SONET.
A status condition that shows that a module or port is experiencing an abnormal operating condition.
Alarm
See also
See ASIC.
Application-specific
integrated circuit
Automatic Protection Switching. A SONET switching mechanism that achieves network resiliency by
APS
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 10008
router 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.
ASIC
See ATM.
Asynchronous
Transfer Mode
Asynchronous Transfer Mode. International standard for cell relay in which multiple service types
ATM
(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.
Authentication
See APS.
Automatic
protection
switching
A status condition that shows that a module or port is experiencing an abnormal operating condition.
Alarm
See also
Cisco 10008 Router Hardware Installation Guide
GL-2
Critical alarm, Major alarm, and
Critical alarm, Major alarm, and
Minor alarm.
Minor alarm.
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