Re: [tor-dev] Revising Proposal 140

[Nick Mathewson <nickm@xxxxxxxxxxxx>]

On Thu, May 1, 2014 at 4:17 AM, Roger Dingledine <arma@xxxxxxx> wrote:
> On Thu, May 01, 2014 at 10:02:30AM +0200, Daniel Martà wrote:
>> * Regarding their size, #140 suggests that they are not useful past 16
>>   hours. I thought we could compare the compressed size of the diffs
>>   when creating them, since they may be of use for a longer time. We
>>   could do this relative size limit first as well as the time limit
>>   mentioned above.
>>
>> That is all that we came up with for now, what do you think? Ideas about
>> what might be missing or needing an update are welcome, of course :)
>
> Hypothesis: a good chunk of the new lines are lines that you've already
> seen in some recent consensus. That is, they're relays that lost the
> Running flag but now they have it again.
>
> Step zero, see to what extent this theory is true in practice.
>
> If it's true a lot, is there something clients can do to take advantage
> of this fact? Like, keep several recent consensuses so they already have
> the lines they're told to add back in? Or do the numbers work out poorly
> here, since the bytes we spend saying "yes, those lines from back then,
> the ones that hash to H" eat too much into our savings to warrant the
> extra complexity?

One alternative in this case would be to include non-running relays in
the consensus.  This would make each individual consensus longer, but
(if your guess is right) might make compressed diffs shorter.

-- 
Nick
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