Automatic protection switching (APS) refers to the mechanism of using a protect POS interface in the SONET network as the backup for a working POS interface. When the working interface fails, the protect interface quickly assumes its traffic load. Based on the configuration, the two circuits can be terminated in the same router, or in different routers.
Far End Alarm Control (FEAC). C-bits are used to send alarm or status information from far-end terminals to near-end terminals and to initiate DS-3 and DS-1 remote loops. This is a repeating 16-bit word consisting of 0xxxxxx0 11111111. When no code is being transmitted, all 1's are transmitted. The code is transmitted for 10 times or the alarm state length, which ever is longer.
Internet Service Engine (ISE) is a programmable hardware-based forwarding engine 3. It provides 4-Mpps performance with traffic shaping and advanced QoS support.
Maintenance bus (Mbus) is a communication channel that interconnects to each of the line cards on the router. It is a 1 Mbps - 2 wire serial interface that provides logging details, online insertion and removal (OIR) of line card and console access to the line card using attach command.
Online insertion and removal (OIR) is a feature supported by line cards, allowing removal of the cards while the router and the cards are activated, without affecting the operation of other cards or the router.
Performance route processor (PRP) is the newer version of the gigabit route processor (GRP). The main function of the PRP is to boot and manage line cards, to provide and coordinate routing services, to build and distribute FIB tables across line cards, to provide intelligence and console and auxiliary ports; and to enable system monitoring and access.
Performance route processor-3 (PRP-3) is the next-generation route processor and addresses increased scale requirements for Cisco IOS XR Software Release 3.8.0 or a later release. PRP-3 has a new ROMMON, and boot flash memory is removed. PRP-3 contains an external CompactFlash that replaces the PCMCIA slots of PRP-2. PRP-3 has more speed, specifically the CPU speed; DDR2; and more hard disk space (80 GB) than PRP-2.