A Simulation Model for Assessing Network Capacity

NASA has procured a large scale software development facility, known as the Ground Systems Development Environment (GSDE), to support the development of the ground systems software for Space Station Freedom. The GSDE is geographically distributed and includes Local Area Networks (LANs) and T1 lines connecting users at multiple contractor facilities to a mainframe complex at the Johnson Space Center (JSC). In order to assess the adequacy of the planned GSDE network, a discrete event simulation model was developed using Network II.5. In addition to models of each Ethernet segment and each communication link, the network model included detailed models of the architecture of key components, such as routers. A utilization model was developed to estimate the traffic that would be generated by the network users. The simulation model of the GSDE network yielded component utilization, queue lengths, and other performance data. A nominal scenario was simulated, as well as five other potential scenarios that can result in higher network traffic.