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Re: content-encoding and range headers

From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Tue, 10 Dec 2002 08:59:26 -0700 (MST)
To: Stefan Eissing <stefan.eissing@greenbytes.de>
cc: ietf-http-wg@w3.org
Message-ID: <Pine.BSF.4.44.0212100851390.8496-100000@measurement-factory.com>

Stefan,

	The following paper, written by one of the RFC 2616 authors,
may help you to navigate through the ranges, transfer, and content
encoding mess (see Figure 4-1b on page 8 if you do not want to read
the entire paper).

	"Clarifying the Fundamentals of HTTP"
	Jeffrey C. Mogul
	WWW Conference, 2002
	http://research.compaq.com/wrl/people/mogul/www2002/mogulwww2002preprint.pdf

HTH,

Alex.

On Tue, 10 Dec 2002, Stefan Eissing wrote:

> I have unsuccessfully tried to google an answer to this, maybe someone
> on this list has an answer.
>
> My understanding of 2616 is that range is applied to the
> content-encoded entity. So if an entity is gzipped, the
> byte selection is applied on the gzipped representation.
> Given that:
>
> What is a server to do when a client sends a request with
> Accept-Encoding: gzip
> Range: bytes=0-499
>
> Is the server free to chose the content-encoding to its liking
> (identity or gzip)?
>
> Assuming there is a second request later
> Accept-Encoding: gzip
> Range: bytes=500-1000
>
> Is the server allowed to use another content-encoding in the response?
>
> If yes, that would mean it is purely the client's responsibility
> to detect varying content-encodings in partial responses and
> act accordingly?
>
> Or did I misunderstand the order of range and content-encoding
> and the byte range is selected on the unencoded entity and
> content-encoding is applied *after* the range selection process?
>
> In that case, a server storing gzipped entities has some work to do
> answering range request. It would then need to "uncompress"
> (ungzip?) the entity before it can select the correct range.
>
>   Thanks for any help.
>
> //Stefan
>
>
>

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Received on Tuesday, 10 December 2002 10:59:42 GMT

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