D. Scott Alexander, "Active Bridging" (work with M. Shaw, S. Nettles and J. Smith) The SwitchWare project is building an active network infrastructure based on programming language features to provide security. As a prototype, we have built an active bridge. The simplicity of the operation of a bridge makes it easy to implement and measure. Our active bridge is capable of loading a series of "switchlets," our active programs, to implement a (mostly) 802.1D compliant bridge. We have also built an additional set of switchlets which allows a controlled, coordinated transition of the network between two incompatible spanning tree algorithms. These switchlets also provide verification and fallback to a stable state if that verification should fail.