• System Initiation Task (SIT) Subsystem: This subsystem is responsible for starting a set of initial tasks at system startup and individual tasks as needed.
• High Availability Task (HAT) Subsystem: Working in conjunction with the Recovery Control Task (RCT) subsystem, HAT is responsible for maintaining the operational state of the system. HAT maintains the system by monitoring the various software and hardware aspects of the system. On finding any unusual activities, such as the unexpected termination of a task, the HAT would take a suitable action like triggering an event prompting the RCT to take some corrective action or report the status.
• Recovery Control Task (RCT) Subsystem: Responsible for executing a defined recovery action for any failure that occurs in the system. The RCT subsystem receives recovery actions from the HAT subsystem.
• Shared Configuration Task (SCT) Subsystem: Provides the system with a facility to set, retrieve, and be notified of system configuration parameter changes. This subsystem is primarily responsible for storing configuration data for the applications running within the system.
• Resource Management (RM) Subsystem: The RM subsystem is responsible for assigning resources to every system task upon their start-up. Resources are items such as CPU loading and memory. RM also monitors these items to verify the allocations are being followed. This subsystem is also responsible for monitoring all sessions and communicating with the Session Controller, a subordinate task of the Session subsystem, to enforce capacity licensing limits.
• Virtual Private Network (VPN) Subsystem: Manages the administrative and operational aspects of all VPN-related entities in the system. The types of entities managed by the VPN subsystem include:
• Network Processing Unit (NPU) Subsystem: The NPU subsystem is responsible for the following:
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• Card/Slot/Port (CSP) Subsystem: Responsible for coordinating the events that occur when any card is inserted, locked, unlocked, removed, shut down, or migrated, the CSP subsystem is responsible for all card activity for each of the 48 slots in the chassis. It is also responsible for performing auto-discovery and configuration of ports on a newly inserted line card, and determining how line cards map to processing cards (including through an RCC in failover situations).
• Session Subsystem: The Session subsystem is responsible for performing and monitoring the processing of a mobile subscriber's data flows. Session processing tasks for mobile data calls include: A10/A11 termination for CDMA2000 networks, GSM Tunneling Protocol (GTP) termination for GPRS and/or UMTS networks, asynchronous PPP processing, packet filtering, packet scheduling, Diffserv codepoint marking, statistics gathering, IP forwarding, and AAA services. Responsibility for each of these items is distributed across subordinate tasks (called Managers) to provide for more efficient processing and greater redundancy. A separate Session Controller task serves as an integrated control node to regulate and monitor each of the Managers and to communicate with the other active subsystems.
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