RTP Circuit Breakers: Updated IETF draft (-01)

We've just submitted an updated version of the RTP circuit breakers draft. This is a minor update, to address the comments from our presentations at IETF 83 in Paris earlier this year. The main change in this version is to use the simple TCP throughput model of Mathis et al in place of the more complex model used in the earlier version of the draft. There have also been various minor editorial clarifications and corrections.