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RE: current HTTP/2 spec prevents gzip of response to "Range" request

From: <K.Morgan@iaea.org>
Date: Thu, 27 Mar 2014 20:55:27 +0000
To: <matthew@kerwin.net.au>
CC: <fielding@gbiv.com>, <derhoermi@gmx.net>, <roland@zinks.de>, <C.Brunhuber@iaea.org>, <ietf-http-wg@w3.org>
Message-ID: <0356EBBE092D394F9291DA01E8D28EC20100F4015E@sem002pd.sg.iaea.org>
Hi Matthew-

On 27 March 2014 05:45, Matthew Kerwin wrote:
> ... It's entirely up to my server configuration to decide whether to
> serve up the contents of index.html, or index.html_gz, or index.txt,
> or any other random *representation* of that resource.  Importantly,
> each of these representations is a distinct entity, with its own
> entity-specific metadata (Content-Type, Content-Encoding,
> Content-Length, Last-Modified, ETag, etc.)...

What if a client requests directly /index.html_gz, do you still send that as "Content-Encoding: gzip\r\nContent-Type: text/html" or just "Content-Type: application/x-gzip"?

What about a resource e.g. /search.php that has dynamic results and the response body is gzip compressed to save bandwidth? Are you saying each unique result is a distinct entity and so that too should be "Content-Encoding: gzip\r\nContent-Type: text/html" or is this a case where it really should be called "Transport-Encoding: gzip\r\nContent-Type: text/html"?

> It also allows entity-specific operations like range requests.

What if user directly requests a range of /huge.resource (e.g a huge non-compressed entity), but you want to save bandwidth on the transfer with compression? Based on the requirements of RFC2616, I assert you can't compress without using "Transport-Encoding: gzip".

> -p2 <http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-26>
> doesn't even have a section 14.  You seem to be referencing RFC 2616,
> which AFAIK isn't split into parts.

Got it. Thanks. I'll fix that.

> I propose not confusing hop-by-hop transport with end-to-end content.
> We already have an end-to-end compression mechanism, which works for
> the most part. I just don't like it because people have gotten
> confused by it. That doesn't mean that it *can't* be used correctly,
> or that it doesn't have any value.

Can you give some examples of what you consider the confusion?

> Even were gzip transport a MUST-level requirement for HTTP/2, there
> would still be 2->1.1 gateways that are forced to strip the transport
> compression because the machinery on the 1.1 side doesn't send TE
> headers. Therefore I argue that we should definitely NOT get rid of
> Content-Encoding: gzip. What I propose is that we recommend support
> for TE:gzip, and hope that the 1.X parts of the web fade away enough
> that nobody cares about them not having compressed data everywhere.
> Hence "best practice guideline, not an interoperability requirement."

In our original proposal we had guidelines for what intermediaries have to do for the 2->1.1 gateways if the 1.1 side doesn't send a "TE: gzip" header. I'm not sure why that wouldn't work with a MUST-level requirement for HTTP/2.

I'm also not sure exactly what part of our proposal you are referring to that should be a best practice guideline (also not exactly sure how you put a "best practice" guideline in an RFC - is there a guideline on how to write such a guideline).
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Received on Thursday, 27 March 2014 20:56:43 UTC

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