EVALUATION OF THE HUB NODE IN A STAR NETWORK: A CASE STUDY.

A network design is presented which provides teleconference services in a star topology via voice grade dialup links. The hub of the star network considered is a packet switching microprocessor node called the Databridge. It provides subnet services for routing graphics information to multiple teleconference participants. The architecture implements seven layers of the Open Systems Interconnection Reference Model. Three analytic queueing models of the Databridge are presented. Each concurrent process is modeled in a separate job class using Decomposition Approximation method. The results are compared against empirical data to choose the best model. Model limitations are defined and a refined model is presented that yields very accurate performance predictions for packet interdeparture times. Performance predictions are made for a broad range of packet arrival rates and context swap times. Guidelines for generalization of the model for a Databridge supporting more than three participants are given.