Re: Call for Adoption: HTTP/2 Bis

> Am 11.12.2020 um 05:41 schrieb Willy Tarreau <>:
> Hi Mike,
> On Thu, Dec 10, 2020 at 10:05:22PM +0000, Mike Bishop wrote:
>> And to me, that's the real question over a new ALPN.  If we can keep the
>> token "h2" and add GREASE successfully, let's do that.  If we can't add
>> GREASE without changing the ALPN token, we should consider changing the ALPN
>> token.
> But why would GREASE require a new ALPN ? Bence is already doing some
> greasing and managed to find bugs in several of our implementations. I'd
> rather push stronger in this direction after some code points can be
> reserved for various purposes.


>> Of course, that means we're effectively minting "h2.1" or
>> "h2-nobugs", at which point we need not necessarily be limited to
>> non-breaking changes.
> What I hate with changing ALPN is that it's a user-visible change. Asking
> users to change their ALPN string from "h2,http/1.1" to "h2.1,h2,http/1.1"
> just because a working group decided to slightly change the protocol for
> the sake of better interoperability is hard to justify, especially after
> it was claimed that the protocol is called "HTTP/2" because it will not
> have a sub-version.

As a revised h2 would need to be h4, this seems like a silly way to go. I am doubtful that fixing the situation of broken implementations by new protocol versions can be applied very often.

I think servers would rather publish special resources to make capabilities known. A client could check the resource /.well-known/h2/capabilities, for example. Not everything is page load time sensitive.

> If we'd change the ALPN we should then think about all the on-wire changes
> that were discussed in the past, like the poor hpack encoding, changing
> initial settings etc. It doesn't seem worth doing with H3 knocking at the
> door in my opinion.

I was only half-joking when I said it would be "h4".

> Cheers,
> Willy

Cheers, Stefan

Received on Friday, 11 December 2020 08:48:53 UTC