[tor-dev] Reporting Relay Bandwidth Less Often

[teor]

Here's an update on this change:

> On 26 Oct 2017, at 08:46, teor <teor2345 at gmail.com> wrote:
> 
>> On 26 Oct 2017, at 06:36, nusenu <nusenu-lists at riseup.net> wrote:
>> 
>> teor:
>>> We would like to make Tor relays report their bandwidth statistics
>>> every 24 hours, rather than every 4 hours.
>> 
>> How has the new time period been decided on?
>> Is one day the upper bound for some use-case?
>> If longer periods (2, 3 or 7 days...) are safer: why not increase it
>> even more?
> 
> We decided to make the bandwidth statistics interval 24 hours

We will change the bandwidth statistics interval to 24 hours, and
remember and report 5 periods in each extra-info.

(It used to be 4 hours and report 6 periods in each extra-info.)

> because relays already report observed bandwidth every 24 hours
> in their descriptors. (More precisely, they re-post their descriptors
> approximately every 24 hours

We will leave the regular bandwidth reporting in descriptors as it
is.

> or when the bandwidth changes by
> more than 2x

Bandwidth changes could trigger a descriptor re-post every 20 minutes,
we will change this to 3 hours.

We chose 3 hours because it takes about that much time for updated
relay bandwidths to get to most clients:
* 10 minutes to 70 minutes for descriptor upload to be included in a
  consensus
* 0 minutes to 30 minutes for a mirror to have the new consensus
* 0 minutes[1] to 110 minutes for a client to fetch the new consensus

[1] when bootstrapping, clients sometimes fetch directly from
    authorities. Otherwise, this would be 45 minutes.

https://gitweb.torproject.org/torspec.git/tree/dir-spec.txt#n3412

> To increase both these intervals beyond 24 hours, we would have
> to make major changes to the bandwidth authority subsystem as
> well.
> 
> So this is the simplest change that yields a significant improvement
> in client anonymity.

We have deferred any major changes to at least 0.3.3, and opened a new
ticket:

https://trac.torproject.org/projects/tor/ticket/24104

--
Tim / teor

PGP C855 6CED 5D90 A0C5 29F6 4D43 450C BA7F 968F 094B
ricochet:ekmygaiu4rzgsk6n
------------------------------------------------------------------------

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: Message signed with OpenPGP
URL: <http://lists.torproject.org/pipermail/tor-dev/attachments/20171101/447a0702/attachment.sig>