Cisco ESR10008 Hardware Installation Guide - Page 152

Glossary A 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 10008 router 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 See ASIC. integrated circuit 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 10008 router 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. GL-2 Cisco 10008 Router Hardware Installation Guide OL-0659-13