Re: HTTP/3 Preface (PRI method)

[[e-mail]]

I understand. It would be only useful when having HTTP/3 on TCP without 
SSL/TLS. I should read more to find out if that is even possible, but if 
it is, I think you need a preface. HTTP/3 over unsecured TCP would not 
be useful except for debugging/test purposes, so there is no need for 
adding preface to the spec, unless this feature will be covered too.

Piers O'Hanlon schreef op 2021-07-08 11:38:

> Hi Ben,
> 
> It is also being proposed (and implemented by a number of organisations 
> including Apple see: 
> https://github.com/MikeBishop/dns-alt-svc/blob/master/svcb-implementations.md) 
> that the ALPN (and IP address(es)) may be obtained via the new proposed 
> "HTTPS"  DNS resource record request:
> https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-svcb-https
> 
> Using this approach one can in principle pre-empt a "preface", though 
> clients would need to handle a potential discrepancy.
> 
> Best,
> 
> Piers O'Hanlon
> 
>> On 29 Jun 2021, at 20:10, ben=[e-mail] wrote:
>> 
>> Hello all,
>> 
>> When reading about QUIC, it comes to me as a better alternative of 
>> TCP, build upon UDP.
>> In this case, servers that run on TCP could easily also run on 
>> UDP/QUIC; think about DNS, SMTP, FTP.
>> 
>> Now there is also a new version of HTTP. HTTP/3. This version will be 
>> transfered over QUIC by default.
>> However, as I mentioned above, it could be possible to have "TCP 
>> protocols" that use QUIC too.
>> That makes me think about also transfering some old HTTP versions, for 
>> example HTTP/0.9 (I came across a library that transfered HTTP/0.9 
>> over QUIC).
>> But also HTTP/1.0, HTTP/1.1 and HTTP/2 are possible.
>> 
>> All older HTTP versions send the following request line: <METHOD> 
>> <PATH> [VERSION] \n
>> If an endpoint is directly accessed (without some negotiation), it 
>> will find out the version directly by reading the first line.
>> For 0.9 the version will be absent. For 2.0 this will be a preface 
>> with a PRI method and * as path.
>> 
>> When I think about running a HTTP server, I think about this:
>> 
>> TCP (80) or TCP/SSL (443):
>> - HTTP/0.9
>> - HTTP/1.0
>> - HTTP/1.1
>> - HTTP/2.0
>> - HTTP/3.0 (I think this is possible too)
>> 
>> UDP/QUIC:
>> - HTTP/0.9 (HTTP/0.9 but over QUIC)
>> - HTTP/1.0 (HTTP/1.0 but over QUIC)
>> - HTTP/1.1 (HTTP/1.1 but over QUIC)
>> - HTTP/2.0 (HTTP/2.0 but over QUIC)
>> - HTTP/3.0 (Default)
>> 
>> However, if I listen for all versions on my HTTP-QUIC server, how am I 
>> supposed to know that it is HTTP/3? Does HTTP/3 has a preface? And if 
>> not, why not?
>> I think the preface of HTTP/2 is great and I think it would be great 
>> in HTTP/3 too: PRI * HTTP/3.0
>> 
>> I would like to see a preface added to HTTP/3.0. It is only 18 extra 
>> bytes at the beginning of the request. It could be ignored by some 
>> servers if they want, but for servers that want to have backwards 
>> compatibility it would be a great feature. (Luckily HTTP/3 is not a 
>> released standard yet.)
>> 
>> Ben