Performance Models of an Experimental Computer Communication Network

An experimental computer communication network is currently being designed and built. The function of this network is to provide a flexible communication medium between computers, users, and peripheral devices. The network can accommodate sources with varying input-output rates and varying activity. Many of the components of the system employ techniques that are new. In order to gain insight into the operation of these components and thereby aid in design decisions, mathematical models were developed. The study of these models involved both analysis and simulation. The results are presented in the form of sets of curves. The system under study consists of several T1 carrier lines,* configured as loops, connected to a Central Switch (see Fig. 1). The system is accessed through Terminal Interface Units (TIU) connected between User Terminals and the T1 line. In addition to forming an interface between the user and the T1 line, the TIU also does signaling. This signaling plays a role in switching calls and controlling the traffic flow. There may be a wide variation of users accessing the system, ranging from Teletypes1 to high-speed computer systems. The switch receives messages from all terminals and delivers messages to all addressed terminals so that any terminal in the system may communicate with * The T1 carrier line is a digital synchronous short-haul transmission system operating at 1.544-Mb/s rate. 1 Registered trademark of the Teletype Corporation. 226 THE BELL SYSTEM TECHNICAL JOURNAL, FEBRUARY 1974