SV: Structuring the BKK spin bit discussion

[Marcus Ihlar <[e-mail]>]

Hi Kazuho,

I believe the biggest difference is the size of the hidden network segment.

In the NAT case the client and NAT are still in the same country or continent.

A quick glacne at distancecalculator.net shows that the city farthest from Tokyo in Japan is Naha-Shi, at 1554 km.

That translates to roughly 5ms at the speed of light, so the kinds of measurements to determine distance from Tokyo based on RTT will be extremely sensitive and error prone.

Please note that the distance analyis can be performed on handshake RTT as well, for connections where the initial handshake is visible at the measurement point.


________________________________
Från: QUIC <[e-mail]> för Kazuho Oku <[e-mail]>
Skickat: den 31 oktober 2018 11:20
Till: Christian Huitema
Kopia: Lars Eggert; IETF QUIC WG; Dmitri Tikhonov
Ämne: Re: Structuring the BKK spin bit discussion

2018年10月30日(火) 1:54 Christian Huitema <[e-mail]>:
>
>
>
> > On Oct 29, 2018, at 9:08 AM, Dmitri Tikhonov <[e-mail]> wrote:
> >
> >> On Mon, Oct 29, 2018 at 05:26:34PM +0200, Lars Eggert wrote:
> >> We'd specifically like to ask client and server implementors with
> >> projected sizable deployments to indicate whether they intent to
> >> implement and deploy, if the WG decided to include the spin-bit in
> >> the spec.
> >
> > LiteSpeed Technologies will support the spin bit -- both in our
> > server and client QUIC implementations -- if it make it into the
> > draft.
>
> My implementation is not used in any large scale deployment, but it does support the spin bit. In fact, it has configuration options to support spin bit variants: node, just spin, spin + vec, spin + QR.
>
> 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.

May I ask if the VPN users are the only ones that lose some privacy
with spin bits?

I ask this because I live in a country where IIUC the mobile carriers
place their nation-wide carrier-grade NAT near the capital city (i.e.,
Tokyo). That means that for people living in the country, having spin
bits turned on could reveal their distance from Tokyo.

So the question is: if VPN users need special care, do some NAT users
as well? Or if the answer is no, what is the difference from between
the two groups?

Generally speaking, I am not against giving users the freedom to
expose spin bits, however I am wondering how the endpoints should
provide the freedom of choice (UI question) as well as what the
default should be.

>
> The privacy issue could be mitigated by turning off the spin bit at privacy sensitive clients, but this would make these clients "stick out".
>
> 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.
>
> -- Christian Huitema
>
>


--
Kazuho Oku