Re: 0-RTT Design for HTTP/2

[Cory Benfield <[e-mail]>]

On Wed, 16 Dec 2020 at 07:15, Martin Thomson <[e-mail]> wrote:
>
> As part of our adoption call for HTTP/2 (reprise), I opened https://github.com/httpwg/http2-spec/issues/781 regarding the use of TLS early data.
>
> I thought that it might be worth the time to go through the exercise of defining an extension to h2 that enabled saving of settings across connections.  Here it is:
>
>    https://martinthomson.github.io/h2-0rtt/draft-thomson-httpbis-h2-0rtt.html
>
> For those who prefer text: https://tools.ietf.org/html/draft-thomson-httpbis-h2-0rtt-00
>
> Though this is conceptually simple (indicate 1 if you are prepared to remember settings), there are enough fiddly details here that I'm now unsure whether it is worthwhile trying to roll into our revision of HTTP/2.

I am somewhat nervous here about how many servers will implement this.

Typical OSS server implementations have a somewhat arms-length
relationship with their TLS stack. This tends to mean they don't
actually know exactly when new session ticket messages were sent.
While this is not a hard limitation (OpenSSL has the requisite
functions) it's the kind of barrier to entry that could be quite
awkward. This may also lead to limitations in how many HTTP/2 stacks
go through the effort of implementing the extension.

With that said, I'm sure that CDNs and browsers would, and that may be enough.

>
> I'm interested in what people think about this.  One of the major criticisms of the current arrangement is the time it takes to learn that an extension is available and this could help with that.
>
> Cheers,
> Martin
>