The ANR research was supported by a grant on ``Analysis and Modeling Tools for High-Speed Networks'' from the National Science Foundation (NCR-9119473), an NSF augmentation of the SDSC base award for work on NREN Engineering issues, and a NSF grant for an ``Interagency ATM Connection at the San Diego Supercomputer Center'' (NCR-9214104). The CASA component was supported by National Science Foundation and the Advanced Research Projects Agency under Cooperative Agreement NCR-8919038 with the Corporation for National Research Initiatives.