JUNOS Enterprise Routing

Glossary

AAL

Asynchronous Transfer Mode (ATM) adaptation layer. A series of protocols enabling various types of traffic, including voice, data, image, and video, to run over an ATM network.

AAL5 mode

Asynchronous Transfer Mode (ATM) adaptation Layer 5. One of four ATM adaptation layers (AALs) recommended by the ITU-T. AAL5 is used predominantly for the transfer of classical IP over ATM. AAL5 is the least complex of the current AAL recommdations. It offers low-bandwidth overhead and simpler processing requirements in exchange for reduced bandwidth capacity and error-recovery capability. It is a Layer 2 circuit transport mode that allows you to send ATM cells between ATM2 intelligent queuing (IQ) interfaces across a Layer 2 circuit-enabled network. You use Layer 2 circuit AAL5 transport mode to tunnel a stream of AAL5-encoded ATM segmentation and reassembly protocol data units (SAR-PDUs) over a Multiprotocol Label Switching (MPLS) or IP backbone. See also cell-relay mode, Layer 2 circuits, standard AAL5 mode, trunk mode.

ABR

Area border router. Router that belongs to more than one area. Used in Open Shortest Path First (OSPF). See also OSPF.

access concentrator

Router that acts as a server in a Point-to-Point Protocol over Ethernet (PPPoE) session—for example, an E-series router.

accounting services

Method of collecting network data related to resource usage.

ACFC

Address and Control Field Compression. Enables routers to transmit packets without the two 1-byte address and control fields (0xff ...