Cisco Cisco Packet Data Gateway (PDG)
StarOS Tasks
Primary Task Subsystems ▀
VPC-VSM System Administration Guide, StarOS Release 19 ▄
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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 primary function of the HAT task is to minimize service impacts.
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 primary function of the HAT task is to minimize service impacts.
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 management card and synchronizes the information it contains with the
RCT subsystem on the standby management card.
RCT subsystem on the standby management card.
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 management card and synchronizes the information it contains
with the SCT subsystem on the standby management card.
with the SCT subsystem on the standby management card.
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 StarOS are done within specific VPN contexts. In general, packets are not forwarded
across different VPN contexts. The only exception currently is the Session subsystem.
across different VPN contexts. The only exception currently is the Session subsystem.
Network Processing Unit (npuctrl/npumgr on ASR 5000; npusim on ASR 5500, and knpusim on VPC-DI and
VPC-SI): 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
IP forwarding decisions (both unicast and multicast)
Per-interface packet filtering
Traffic management and traffic engineering