Goals
- We want to know about how many Tor users there are, and which
+ We want to know approximately how many Tor users there are, and which
countries they're in, even in the presence of a hypothetical
"directory guard" feature. Some uncertainty is okay, but we'd like
to be able to put a bound on the uncertainty.
[In both of the above cases, clients choose a running
directory cache at random with odds roughly proportional to
- its bandwidth.]
+ its bandwidth. If they're just starting, they know a ]
- In some future version, clients will choose directory caches
to serve as their "directory guards" to avoid profiling
Notes:
- [Over H hours, the N for V2 clients is 2*H, and the N for V3
- clients is currently around N/2 or N/3. [***FIGURE THIS
- OUT***XXXX]]
+ clients is currently around N/2 or N/3.]
- (We should only count requests that we actually intend to answer;
503 requests shouldn't count.)
- - These measurements *shouldn't* be taken at directory
- authorities: their picture of the network is too skewed by the
- special cases in which clients fetch from them directly.
+ - These measurements should also be be taken at a directory
+ authority if possible: their picture of the network is skewed
+ by clients that fetch from them directly. These clients,
+ however, are all the clients that are just bootstrapping
+ (assuming that the fallback-consensus feature isn't yet used
+ much).
+
+ - These measurements also overestimate the V2 download rate if
+ some downloads fail and clients retry them later after backing
+ off.
Methods for directory guards: