Implement microdescriptors
Microdescriptors are a feature designed to greatly reduce the amount of data that needs to be transmitted to implement the Tor directory protocol. See proposal 158 "Microdescriptors" and proposal 162 "Publish the consensus in multiple flavors" for design details.
There's an initial implementation at the server level (authorities generate microdescriptors and the appropriately flavored consensus).
We need to implement the remaining server and client components for May 1 2011.