The objective of the present study was the development of a methodology to be used as an aid in decision making for the attainment of optimum operational efficiency in large-scale computer communications networks. The above methodology is realized in two stages. In the first stage, a queueing model (M/M/1/K) of a typical network is developed, and analytical results for the main performance indicators are obtained. The results are used, in the second stage, as a starting point for the application of a data envelopment analysis (DEA) procedure to obtain characteristics of network operational efficiency. Emphasis is placed on suggestions for improving the efficiency level of (relatively) inefficient nodes; numerical examples are also provided to illustrate the applicability of various options. Finally, possible routes for achieving a higher level of overall network efficiency are discussed, within the context of a performance tuning procedure, which are aimed at reducing the effects of performance bottlenecks.