Re: New Version Notification for draft-kuhn-quic-0rtt-bdp-07.txt

[Ian Swett <[e-mail]>]

I agree with most of the points made by Kazuho and Christian.

In particular, I think relying on information the client repeats back to
the server which is not encrypted by the server is potentially quite
dangerous.  Even with that, there's real potential for abuse, particularly
when combined with 0-RTT, so if we're going to document something, I
believe we need a lot of MUST NOTs to prevent that abuse.  Using the same
token across many connections seems particularly concerning.

On Mon, Oct 26, 2020 at 10:30 PM Kazuho Oku <[e-mail]> wrote:

>
>
> 2020年10月27日(火) 11:14 Christian Huitema <[e-mail]>:
>
>>
>> On 10/26/2020 6:20 PM, Lucas Pardue wrote:
>>
>>
>>
>> On Tue, 27 Oct 2020, 01:12 Matt Joras, <[e-mail]> wrote:
>>
>>> Indeed, but as much as I love HTTP it's not the only protocol we have on
>>> top of QUIC. A consistency argument can also be made for having a
>>> connection-level metric tied to a connection-level semantic (i.e. a QUIC
>>> frame) rather than the transactional-level semantic (HTTP header).
>>>
>>
>> I agree! A QUIC-level frame could be the most appropriate thing in this
>> case. I think this will be an interesting space for innovation. And let's
>> not forget all the other datagram-oriented protocols that have preceeded -
>> so perhaps there will be some re-innovation.
>>
>>
>> I am glad that we agree. Now, we have an issue regarding security.
>> Nicolas Kuhn and his coauthors have pursued a design in which the server
>> sends an encrypted blob to the client, and then client echoes it in the new
>> connection. This is largely based on concerns about potential attacks.
>> Suppose the client said "I received at 1Gbps last time", when in fact it
>> can only absorb 10 Mbps. Some bad stuff might well be happening along the
>> way. But then, Matt is looking at passing statistics from server to client,
>> so the client can debug issues, display statistics in the app, and
>> potentially also reuse the statistics to inform server that the last
>> connection had an RTT of 600 ms and a data-rate of 100 Mbps, and maybe we
>> should shortcut initial congestion control in order to gain lots of time.
>> How do we reconcile these multiple goals?
>>
>
> I think that the answer is simple.
>
> Loss recovery and CC states are properties maintained by an endpoint. The
> peer should not be given the right to change them (e.g., CWND, RTT).
> Servers might offload the state to the client, but that state has to be
> encrypted and integrity-protected. NEW_TOKEN tokens cover this purpose.
>
> OTOH, servers can expose any information to the client regarding the
> quality of the connection. It is totally reasonable to give the client the
> bandwidth information that the server retains, so that the client could
> choose a good bandwidth. There are no security concerns providing such
> information, regardless of the medium being a QUIC frame or a HTTP header.
> And that's because it does not affect loss recovery or CC.
>
> -- Christian Huitema
>>
>
>
> --
> Kazuho Oku
>