Re: [secdir] Secdir last call review of draft-ietf-httpbis-early-hints-03

[Willy Tarreau <[e-mail]>]

On Fri, Jul 07, 2017 at 05:54:41AM +0000, Melinda Shore wrote:
> On 7/6/17 8:40 PM, Kazuho Oku wrote:
> > Regarding the wording, I think it would be better to keep the tone
> > as-is, rather than suggesting implementers not to send an Early Hints
> > response over HTTP/1.1 depending on the client.
> 
> Yeah, you don't want to discourage implementation.  I think
> the goal is to find some balance between not putting off
> implementers on the one hand, and having to deal with an
> embarrassing incident on the other.  I'd be more comfortable
> with language that's a bit stronger but it's not a huge
> issue, certainly not one that's an impediment to moving the
> document forward (particularly given that it's intended for
> publication as an experimental standard).

I'm just thinking about the fact that we're not even sure that any 
HTTP/1.1 client doesn't support these informational responses,
because such clients can already make use of Expect: 100-continue
(so they know about 100), and if I remember well when designing the
101 upgrade for WebSocket, which was reused for HTTP/2, some of
the difficulties we faced was that some clients/intermediaries
were consuming 101 as 1xx and waiting for a final response after
it.

Maybe the stronger wording should be oriented differently, such as
"Servers MUST not send 103 to HTTP/1.0 clients nor to any client
known not to support 1xx informational responses" ? This way it
leaves the possibility opened (ie rely on version and/or user-agent
or anything else once an exception is known).

Just my two cents,
Willy