Hi tor devs, Steven, Rob, and I wrote a tech report on evaluating Steven's libutp Tor implementation in the public Tor network and using Chutney and Shadow: https://research.torproject.org/techreports/libutp-2013-10-30.pdf

From the introduction:

""" Datagram designs are a promising approach to overcome Tor's performance-related problems. Advantages of datagram designs over stream designs are that they allow better end-to-end congestion management, reduce queue lengths on nodes, and prevent cell loss on one circuit delaying cells on other circuits. In earlier reports we compared possible Tor datagram designs and outlined a testing plan. In this report we evaluate our implementation of a libutp-based Tor datagram design. However, this evaluation does not focus on performance improvements over the current stream-based Tor implementation, because we found that our datagram-based Tor implementation is not mature enough for such a comparison. The focus is rather on our approach to integrate a datagram design into the Tor source code and on setting up test environments to evaluate the new design. We hope that our findings will be useful when further tweaking our libutp-based design or implementing other datagram designs. In the next section we describe our libutp-based Tor implementation in sufficient detail for others to understand our source code and to act as blueprint for implementing other datagram designs. Sections 3 to 5 outline the experimental setup that we used to evaluate our implementation and point out roadblocks that kept us busy longer than necessary. Section 6 concludes the report by sketching out possible next steps. """ As the introduction says, this report doesn't contain shiny performance comparisons, because we kept hitting bugs and then ran out of time. But the report contains detailed instructions for experimenting with libutp and Tor, and it has plenty of footnotes containing starting points and a conclusion with suggested next steps. In short, we had to stop when things started to be fun. Unfortunately, neither of us can work on this topic in the next two months at the very least. If anybody here wants to pick up this work and comes up with bug fixes or even a performance comparison to current Tor, please post your findings here! All the best, Karsten