This paper focuses on the application of the NBS Network Measurement Instrument (NMI) to synchronous data communication. The suitability of the underlying Stimulus - Acknowledgement - Response (SAR) model to support the implementation of this methodology permitting quantitative evaluation of interactive teleprocessing service delivered to the user is described. The logic necessary to interpret SAR components and boundaries depends on character time sequence for asynchronous data communications traffic but entails protocol decomposition and content analysis for character synchronous data traffic. The decomposition and analysis rules necessary to evaluate synchronous communications are discussed and the level of protocol violation detection which results as a byproduct is cited. Extensions to the utility of the Network Measurement Instrument (NMI), deriving from additional workload profiling measures desirable for character synchronous communications, are also presented.