We have already seen processorarchitecture patterns that are helpful in architecturedesign. In this article we will compare the requirements for different typesof processors that are used in developing a system.
Different Processor Patterns are compared for different attributes in thefollowing matrix:
| Operations and Maintenance Processor | Central Manager | Module Manager | Terminal Manager | Device Controller | |
| Software Complexity | Medium Complexity depends upon the following factors:
| High Complexity depends upon the following factors:
| High Complexity depends upon the following factors:
| Medium Complexity depends upon the following factors:
| Medium/Low Complexity depends upon the following factors:
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| 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 |
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| If the Module Manager does not perform time critical operations:
If the Module Manager performs time critical operations, use PCs running:
| PCs or proprietary hardware running:
| 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. |
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