We present the architecture for data collection for the T3 NSFNET backbone service, and difficulties with using the collected statistics for long-term network forecasting of certain traffic aspects. We describe relevant aspects of the T3 backbone architecture, describe the instrumentation for the statistics collection process, and how it differs from that on the T1 backbone. We then present longterm NSFNET data to elucidate long term trends in both the reachability of Internet components via the NSFNET as well as the growing cross-section of traffic. We focus on the difficulties of forecasting and planning for these two traffic aspects in an infrastructure whose protocol architecture and instrumentation for data collection was not designed to support such objectives. I. Introduction NSFNET, the National Science Foundation Network, is a general purpose packet-switching network supporting access to scientific computing resources, data, and interpersonal electronic communications. 2 Cl...