Re: Structuring the BKK spin bit discussion

[Martin Thomson <[e-mail]>]

On Tue, Oct 30, 2018 at 3:54 AM Christian Huitema <[e-mail]> wrote:
> I think the strongest objection to the spin bit was put up by Marten during the last interim: measuring the RTT with the spin bit discloses the use of hidden path segments like VPN. This issue was not discussed during the privacy analysis.

I had assumed that was part of the analysis and it was covered by the
assumption that spinning could be disabled

> One solution would be to remove the spin bit from the spec, trading off better privacy for worse management. I am considering another solution in which privacy sensitive clients hide the RTT by controlling the spin, for example spinning at fixed intervals. I plan testing that option in Picoquic.

I've done a little thinking about this one, and it might conflict with
the natural signals the transport emits, along the lines of what
Andrew McGregor has mentioned on a couple of occasions.  If the spin
bit is enabled, then privacy-sensitive endpoints will need to make a
hard call regarding standing out.

Note also that you probably can't hide the fact that you aren't at the
same network location as the address you are using.  Spoofing a
shorter RTT is impossible in general because you have to assume edges
that haven't arrived yet.  If there are no edges you expose the
charade.