Cisco Cisco Packet Data Interworking Function (PDIF) Guía Para Resolver Problemas
System Software Task and Subsystem Descriptions
▀ Primary Task Subsystems
▄ Cisco ASR 5000 Series System Administration Guide
OL-22969-02
Primary Task Subsystems
The individual tasks that run on the CPUs are divided into subsystems. Following is a list of the primary subsystems
responsible for call session processing:
responsible for call session processing:
System Initiation Task (SIT): This subsystem starts tasks and initializes the system. This includes starting a set
of initial tasks at system startup time (static tasks), and starting individual tasks on demand at arbitrary times
(dynamic tasks).
(dynamic tasks).
High Availability Task (HAT): With the Recovery Control Task (RCT) subsystem, the HAT subsystem
maintains the operational state of the system. HAT monitors the various software and hardware components of
the system. If there are unusual activities, such as the unexpected termination of another task, the HAT
subsystem takes a suitable course of action, such as triggering an event to the RCT subsystem to take corrective
action or to report the status. The end result is that there is minimal or no impact to the service.
the system. If there are unusual activities, such as the unexpected termination of another task, the HAT
subsystem takes a suitable course of action, such as triggering an event to the RCT subsystem to take corrective
action or to report the status. The end result is that there is minimal or no impact to the service.
Recovery Control Task (RCT): This subsystem executes a recovery action for any failure that occurs in the
system. The RCT subsystem receives signals from the HAT subsystem (and in some cases from the NPU
subsystem) and determines what recovery actions are needed.
subsystem) and determines what recovery actions are needed.
The RCT subsystem runs on the active SPC/SMC and synchronizes the information it contains with the RCT
subsystem on the standby SPC/SMC.
subsystem on the standby SPC/SMC.
Shared Configuration Task (SCT): This subsystem provides a facility to set, retrieve, and receive notification
of system configuration parameters. The SCT is mainly responsible for storing configuration data for the
applications that run on the system.
applications that run on the system.
The SCT subsystem runs only on the active SPC/SMC and synchronizes the information it contains with the
SCT subsystem on the standby SPC/SMC.
SCT subsystem on the standby SPC/SMC.
Resource Management (RM): This subsystem assigns resources, such as CPU loading and memory, for every
system task upon start-up. The RM subsystem monitors resource use to verify that allocations are as specified.
RM also monitors all sessions and communicates with the Session Controller to enforce capacity licensing
limits.
RM also monitors all sessions and communicates with the Session Controller to enforce capacity licensing
limits.
Virtual Private Network (VPN): This subsystem manages the administrative and operational aspects of all
VPN-related entities in the system. The functions performed by the VPN subsystem include:
Creating separate VPN contexts
Starting the IP services within a VPN context
Managing IP pools and subscriber IP addresses, and distributing the IP flow information within a VPN
context.
All IP operations within the system are done within specific VPN contexts. In general, packets are not
forwarded across different VPN contexts. The only exception currently is the Session subsystem.
forwarded across different VPN contexts. The only exception currently is the Session subsystem.
Network Processing Unit (NPU): This subsystem is responsible for the following:
Using the database to match address and port numbers to destination tasks for fast-path forwarding of
dataframes
Receiving and transmitting user data frames to/from various physical interfaces
IPv4 forwarding decisions (both unicast and multicast)
Per-interface packet filtering