The growth of high speed Internet connections has fueled an increase in the demand for high quality streaming video. In order to satisfy timing constraints, streaming video typically uses UDP as the default network transport protocol. Unfortunately, UDP does not have any end-to-end congestion control mechanisms, and so in the absence of higher layer congestion control can lead to unfairness and possibly congestion collapse. While there has been research done in video measurement and characterization using custom tools, to the best of our knowledge, there have been no measurement studies where the researchers had control over a commercial streaming media server and client, and control of the network conditions and content. A goal of this research is to characterize the bitrate response of Windows Streaming Media in response to network-level metrics such as capacity, loss rate, and round-trip time. We build a streaming media test bed that allows us to systematically vary network and content encoding characteristics. We analyze responsiveness by comparing streaming media flows to TCP-friendly flows under various streaming configurations and network conditions. We find Windows Streaming Media has a prominent buffering phase in which it sends data at a bitrate significantly higher than the steady-state rate. Overall, Windows Streaming Media is responsive to available capacity, but is often unfair to TCP. Knowledge of streaming media's response to congestion encountered in the network is important in building networks that better accommodate their turbulence. The additional characteristics we measure can be combined to guide emulation or simulation configurations and network traffic generators for use in further research.