[tor-dev] Proposal 275: Stop including meaningful "published" time in microdescriptor consensus

[Nick Mathewson]

On Sun, Feb 26, 2017 at 6:17 AM, teor <teor2345 at gmail.com> wrote:
>
>> On 25 Feb 2017, at 03:25, Nick Mathewson <nickm at torproject.org> wrote:
>>
>> Filename: 275-md-published-time-is-silly.txt
>> Title: Stop including meaningful "published" time in microdescriptor consensus
>> Author: Nick Mathewson
>> Created: 20-Feb-2017
>> Status: Open
>> Target: 0.3.1.x-alpha
>>
>> ...
>>
>> 4. Proposal
>>
>> ...
>>
>>   As an interim solution: We should add a new consensus method number
>>   that changes the process by which Published fields in consensuses are
>>   generated.  It should set all all Published fields in the consensus
>>   should be the same value.  These fields should be taken to rotate
>>   every 15 hours, by taking consensus valid-after time, and rounding
>>   down to the nearest multiple of 15 hours since the epoch.
>
> I wonder what this does to relays that have a broken clock.
> Is there any particular reason you chose 15 hours, rather than, say,
> 18 hours (the interval at which relays re-post descriptors), or 12 hours
> (the re-post interval - the consensus lifetime - 3 hours skew allowance)

I chose 15 because it was approximately in the middle of 12 and 18.
But 12 might be more conservative.

>> 5. Analysis
>>
>>   ...
>>
>>   With the longer-term solution in place, and all published times held
>>   constant permanently, the compressed diff sizes were uniformly at
>>   least 56% smaller.
>>
>>   With this in mind, I think we might want to only plan to support the
>>   longer-term solution.
>
> Do you mean "only implement" the longer-term solution?

Yes.