Traffic Service Position System No. 1B: Capacity and Reliability Evaluation

One of the development objectives of the Traffic Service Position System No. IB (TSPS No. IB) was to improve the call-handling capacity of the TSPS No. 1 by replacing the Stored Program Control No. 1A (SPC 1A) with the Stored Program Control No. IB (SPC IB).1 The SPC IB consists of the 3B20 Duplex (3B20D) Processor together with the Peripheral System Interface (PSI) unit, which adapts the 3B20D to existing TSPS peripherals. The 3B20D is microprogrammed to execute the SPC 1A instructions, thus allowing TSPS call-processing software developed for the SPC 1A to be ported to the SPC IB with minimal changes. This emulated TSPS software executes as a kernel process under the DMERT operating system. References 2 and 3 contain further details on the SPC IB architecture. 1.1 Call-processing capacity analysis The increased speed of the SPC IB in executing the emulated SPC 1A instructions provides the increase in call-processing capacity. The 919 initial objective for capacity increase established for TSPS No. IB was that the SPC IB call-processing capacity should be at least 160 percent that of the SPC 1A. Early in TSPS No. IB development, a capacity prediction and evaluation plan was established for monitoring the progress in meeting the capacity improvement objective. This plan involved formulating a mathematical model of the SPC IB real-time usage, where the parameters of this model represent the various call-processing and overhead activities performed by the processor. Laboratory and test-site measurements of these parameters during development provided, through use of the real-time model, estimates of the call-processing capacity.