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Processor Architecture Patterns II

We have already seen processor architecture patterns that are helpful in architecture design. In this article we will compare the requirements for different types of processors that are used in developing a system.

Comparison Matrix

Different Processor Patterns are compared for different attributes in the following matrix:

  Operations and Maintenance Processor Central Manager Module Manager Terminal Manager Device Controller
Software Complexity Medium

Complexity depends upon the following factors:

  • Overall system complexity
  • Total number of processors that need to be maintained
  • Skill level of operators using the O&M Processor
High

Complexity depends upon the following factors:

  • Total number and type of Module Managers controlled
  • Degree of involvement in every transaction
  • Redundancy and Availability Requirements
  • Global resources that need to be managed
High

Complexity depends upon the following factors:

  • Total number and type of nested Module Managers controlled
  • Total number and type of Terminal Managers controlled
  • Module resources that need to be managed
  • Redundancy and Availability Requirements
Medium

Complexity depends upon the following factors:

  • Number and type of Terminals managed
  • Number of terminals that share the same hardware
  • Degree of transparency needed from future hardware changes
  • Impact of Terminal Manager cost on the cost of the complete system
Medium/Low

Complexity depends upon the following factors:

  • Programming model of the hardware device
  • Degree of transparency needed from future hardware changes
  • Impact of Device Controller cost on the cost of the complete system
Performance Requirement Medium

Use of HTTP, Java and SNMP increases the performance requirements for a O&M Processor.

High

A high performance platform should be used as the Central Manager so that its performance doesn't become a bottleneck when the system is expanded.

High

In most cases the top level Module Managers will handle most of the transaction processing load on the system. A high performance platform should be used. 

Medium

Overall performance requirements for the Terminal Manager might not be very high. However, the Terminal Manager might be executing a lot of time critical code, thus needing a reasonably good performance platform.

High/Medium/Low

Device controller performance requirement varies a lot from one device to another. For example, a controller involved in digital signal processing might need a very high MIPS CPU. A device handling protocols might work well with a medium performance CPU. Most devices however would work very well even with low performance CPUs. 

Redundancy Cold Standby

Failure of the O&M processor has no impact on system performance. A replacement can be brought in service manually. (This assumes that both O&M processors communicate to an off-the-shelf database server machine.)

Hot Standby

Central Manager's failure can result in the complete system going out of control. Thus a hot standby should be maintained for quick recovery from the fault condition.

e.g. CAS card in Xenon Switching System.

N + X Redundancy

All transactions handled by a failed Module Manager will be released abnormally by the Central Manager. Central Manager would then configure a spare Module Manager to replace the failed module. 

e.g. XEN card in Xenon Switching System.

N + X Redundancy

All transactions handled by a failed Terminal Manager will be released abnormally by the controlling Module Manager. Controlling Module Manager would then configure a spare Terminal Manager to replace the failed board.

e.g. Digital trunk card in Xenon Switching System.

None

Device controllers are not redundant within a Terminal Manager.

Hardware Cost Sensitivity Low

Only two machines are required for the O&M Processor. The cost of these machines is not a significant portion of the overall hardware cost.

Low

Only two machines are required for the Central Manager. The cost of these machines is not a significant portion of the overall hardware cost.

Medium

Typically a system will need many Module Managers. Their aggregate cost may be a significant portion of the system cost.

High

A large number of Terminal Managers might be needed. Aggregate cost of Terminal Managers may be a large percentage of the total system cost. This might mean that the software developers have to optimize their code to work within the cost limitations.

High

A very large number of Device Controllers might be needed. Aggregate cost of Device Controllers may be a very large percentage of the total system cost. This might mean that the software developers have to optimize their code to work within the cost limitations.

Suitable Platform
  • Unix Servers and Work Stations
  • Linux PC Servers
  • Windows PC Server
  • Unix Servers and Work Stations
  • Linux PC Servers
  • Windows PC Server

If the Module Manager does not perform time critical operations:

  • Unix Servers and Work Stations
  • Linux PC Servers
  • Windows PC Server

If the Module Manager performs time critical operations, use PCs running:

  • VxWorks
  • P-SOS
  • RT-Linux
  • etc.

PCs or proprietary hardware running:

  • VxWorks
  • P-SOS
  • RT-Linux
  • etc.
 

Micro-controller OS or proprietary.

Operator Interface Support High

O&M Processor completely handles the operator interface.

High

Central Manager has a large operator interface component.  It supports system wide statistics, status and alarm reporting.

Medium

Module Manager has a considerable operator interface component.  It supports module wide statistics, status and alarm reporting.

Low

Terminal Manager does not have a direct operator interface. It reports statistics and alarm conditions to the Module Manager. Module Manager would then directly interact with the O&M processor.

None/Low

Device Controller might report error conditions which result in alarms being generated. It might report some statistics to the Terminal Manager.

Developer Skill Set
  • Graphical user interfaces
  • Relational databases
  • SNMP
  • HTTP/HTML
  • Java
  • State machine design
  • Message interaction design
  • System level design experience
  • Object oriented design
  • C/C++
  • State machine design
  • Message interaction design
  • Real-time software development
  • Object oriented design
  • C/C++
 
  • Real-time software development
  • State machine design
  • C/C++
  • Software and hardware interfacing
 
  • Device programming
  • Hardware interfacing and hardware design knowledge
  • C/C++
  • Assembly programming
  • Signal processing knowledge
  • DSP programming
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