Re: I-D Action: draft-nottingham-http-browser-hints-00.txt

[Mark Nottingham <[e-mail]>]

[ sending replies to apps-discuss ]

Hi Willy, 


On 17/05/2011, at 3:34 PM, Willy Tarreau wrote:

> Hi Mark,
> 
> On Tue, May 17, 2011 at 02:23:29PM +1000, Mark Nottingham wrote:
>> A URL for this Internet-Draft is:
>> http://www.ietf.org/internet-drafts/draft-nottingham-http-browser-hints-00.txt
> 
> While I have still not replied to your previous mail about the pipelining
> draft, I must say that I like this new proposal a lot more than the old one.

Thanks, but they're orthogonal.

> I think that default values should be indicated for all values there.

The defaults are the current behaviours of implementations; anything else would make this mechanism non-optional, and introduce lots of problems.

> For
> instance, if a site complies with this draft and delivers a browser-hints
> file, it means that it's likely to comply with many of the server
> requirements, so pipelining should be supported for instance.

Pipelining already has to be supported, if it's a HTTP/1.1 server. As has been discussed ad nauseum, a "I support pipelining" or even a "I really support pipelining" flag doesn't do anyone any good.

> Thus, we
> could reasonably suggest that max-pipeline-depth is non-zero when not
> specified.
> 
> For "small-hdrs", we should explicitly indicate what Accept* header values
> will be used by the server when they are not sent by the browser.

It'll work just like it does when you don't send the Accept-Headers values in HTTP today. Anything else would be introducing incompatible changes to HTTP.

> Concerning the no-referer, we're risking that people always ask for a
> referer header to be sent because they want to see how they're indexed.
> My suggestion would be that we provide the ability not to send a referer
> header for requests coming from the same site (eg: fetching images from
> a site's page enlarges all requests for nothing). That could probably be
> combined with the new Ref header you're proposing with various options :
> 
>   - no referer from the same site
>   - relative referer only without query string
>   - relative referer only with query string
>   - full referer

I suspect that the referer-related mechanisms are going to be refined, based on feedback I've already received. Also, see Adam Barth's related work on Origin. 

> I'm seeing a minor issue though : we're mixing there two distinct pieces of
> information. We have infrastructure-related information (pipelining, concurrent
> persistent connections, etc...) and application informationn (referer, ...).
> 
> Some large hosting infrastructures I know will like the connection related
> informations to be directly delivered from outer shared reverse proxies for all
> hosted sites, while the application-specific information will be delivered from
> hosted applications. Eg: one app will want the referer while another won't care,
> however neither knows what to announce for pipelining or persistent conns.

IME more complex deployments like this tend to develop back-end practices and tools to manage those issues.

> Thus we should probably have two distinct well known files. In order to
> reduce the number of requests, we could suggest that if the browser-hints
> file does not contain any connection information, then the browser is
> invited to get /.well-known/connection-hints too as a complement.

I have a pretty strong suspicion that this will end up being too complex, but let's see what others think.

> Anyway I don't think that fetching two files is an issue, considering that
> the connection-specific one would be cached much longer.
> 
> While we're at it, the same file could be used to announce the configured
> keep-alive timeout so that browsers don't try to send requests over
> supposedly dead connections.


Possibly, but I'm not sure what that achieves, vs. the Keep-Alive header that's already implemented. Some servers also want this to be dynamic. See also Martin Thompson et al's work on timeouts.

Cheers,

--
Mark Nottingham   http://www.mnot.net/