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Re: Content-MD5 and partial responses

From: Yves Lafon <ylafon@w3.org>
Date: Tue, 30 Jun 2009 04:37:10 -0400 (EDT)
To: Mark Nottingham <mnot@mnot.net>
cc: HTTP Working Group <ietf-http-wg@w3.org>, Larry Masinter <LMM@acm.org>
Message-ID: <alpine.DEB.1.10.0906300432450.4210@wnl.j3.bet>
On Mon, 29 Jun 2009, Mark Nottingham wrote:

> a) C-MD5 applies to the bytes in the entity-body (as above), and therefore we 
> need to specify what a cache does with it when it combines partial responses 
> (throw it away?).
> b) C-MD5 applies to the *full* response body, avoiding the combination 
> issues, and allowing clients to do a MIC of the full response (assuming they 
> have it), but removing the ability to do a MIC on a partial response on its 
> own.
> Anybody aware of C-MD5 being used with partial responses in the wild (I'm 
> looking at you, Adobe)?

A while back, I implemented option a) as it seemed to be the most logical 
interpretation of the spec.

HEAD /Distrib/jigsaw_2.2.6.zip HTTP/1.1
Host: jigsaw.w3.org

HTTP/1.1 200 OK
Content-Length: 9331520
Content-Md5: fBhlh9ttr14YAqe45Yi+xg==


GET /Distrib/jigsaw_2.2.6.zip HTTP/1.1
Host: jigsaw.w3.org
Range: bytes=0-1

HTTP/1.1 206 Partial Content
Content-Length: 2
Content-Md5: 1xvdIsi7k7jSh9zm9GrtJQ==
Content-Range: bytes 0-1/9331520

Caches should "throw away" the md5 (after verification of the partial body 
received, and it is up to the cache to recompute the md5 sum of the bytes 

Baroula que barouleras, au tiéu toujou t'entourneras.

Received on Tuesday, 30 June 2009 08:37:20 UTC

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