[tor-project] Cor Tor Team sponsor4 February work report

[isabela]

Core Tor Team February 2017 Report

We started to work on collecting measurements[1] of our consensus diff
proposal (prop140) to analyze how much data Tor downloads today, how
much data it would download after the consensus diff implementation is
complete, and what we could do in order to reduce the downloaded volume
further.

We created the following tools[2] to help us collect and analyze our data:

The populate.py and analyze.py scripts are for looking at the amount and
causes ofmicrodescriptor change over time.
The populate-consenus and analyze-consensus.py scripts look at the
amount and causesof routerstatus change over time in the consensus.
The diff-size tool determines the mean size for ed-based consensus
diffs, after various consensus transformations and diff compression
algorithms.

With these tools, we were able to improve[3]  Proposal 140 [4] "Provide
diffs between consensuses", which is an important part for us to do to
achieve our objective. They also lead to the creation of proposals 274
through 276, each of which will reduce the required bandwidth for
directory operations (see below).

We also created tools[5] to analyze different compression schemes
related to Proposal 278 [6] "Directory Compression Scheme Negotiation",
which is one of the design proposals we plan to implement in order to
achieve our goals under this objective. We have the results of the first
collection/analyses[7].

The other proposals related to directory bandwidth savings are:
Proposal 274 [8] - Rotate onion keys less frequently
Proposal 275 [9] - Stop including meaningful "published" time in
microdescriptor consensus
Proposal 276 [10] - Report bandwidth with lower granularity in consensus
documents


[1] https://trac.torproject.org/projects/tor/ticket/21205
[2] https://github.com/nmathewson/consensus-diff-analysis
[3] https://trac.torproject.org/projects/tor/ticket/21209
[4]
https://github.com/torproject/torspec/blob/master/proposals/140-consensus-diffs.txt
[5] https://gitlab.com/ahf/tor-sponsor4-compression
[6]
https://github.com/torproject/torspec/blob/master/proposals/278-directory-compression-scheme-negotiation.txt
[7]
https://docs.google.com/spreadsheets/d/1devQlUOzMPStqUl9mPawFWP99xSsRM8xWv7DNcqjFdo/edit#gid=0
[8]
https://github.com/torproject/torspec/blob/master/proposals/274-rotate-onion-keys-less.txt
[9]
https://github.com/torproject/torspec/blob/master/proposals/275-md-published-time-is-silly.txt
[10]
https://github.com/torproject/torspec/blob/master/proposals/276-lower-bw-granularity.txt
[11]
https://github.com/torproject/torspec/blob/master/proposals/277-detect-id-sharing.txt