- From: Jon Butler <jkbutler@google.com>
- Date: Wed, 10 Sep 2008 13:31:37 -0400
- To: "Yves Lafon" <ylafon@w3.org>
- Cc: "Wei-Hsin Lee" <weihsinl@google.com>, ietf-http-wg@w3.org
I should have perhaps used zlib or some other compression format rather than gzip in my example below. My intent was to address Mark's point that a variety of compressors could underly a dictionary-based protocol like SDCH. Jonathan On Wed, Sep 10, 2008 at 1:17 PM, Jon Butler <jkbutler@google.com> wrote: > An interesting difference between content and transfer codings is that > transfer codings are allowed to have attributes. Were sdch to use the > Transfer-Encoding header, this might allow more flexibility in the > actual compression scheme used, e.g., Transfer-Encoding: sdch;c=vcdiff > vs Transfer-Encoding: sdch;c=gzip. The client would indicate what > compression schemes were allowed in the TE header, e.g. TE: > sdch;c="vcdiff,gzip". In that scenario, I expect we would need to > specify some default compression scheme to be used if none is > specified. > > Jonathan > > On Wed, Sep 10, 2008 at 12:31 PM, Jon Butler <jkbutler@google.com> wrote: >> Yves-- >> >> You raise an interesting point. SDCH was designed to be applied to >> the message body before gzip (since cross-payload redundancy is much >> harder to detect after gzipping the payloads). One of the differences >> between the two sets of headers is that transfer encodings must be >> applied after and removed before content encodings, since transfer >> encodings are properties of the message and content encodings are a >> property of the entity inside the message. So, we have a choice: >> either we indicate both SDCH and gzip in the Content-Encodings, or >> both in the Transfer-Encoding header. Since the prior art for gzip is >> to indicate it in the Content-Encoding header (a holdover from the >> HTTP/1.0 standard as I understand), we proposed putting sdch there as >> well. >> >> From my reading of the standard, it would be more in keeping with the >> HTTP/1.1 standard to put both encodings (gzip and sdch) in the >> TE/Transfer-Encoding headers, but it is not clear that it would be >> more practical. >> >> We'd be happy to hear others' opinions on this. >> >> Jonathan >> >> >> On Wed, Sep 10, 2008 at 4:17 AM, Yves Lafon <ylafon@w3.org> wrote: >>> >>> On Mon, 8 Sep 2008, Wei-Hsin Lee wrote: >>> >>>> Hi, >>>> >>>> Over the last few weeks we've been experimenting with a way to get better >>>> compression for HTTP streams using a dictionary-based compression scheme, >>>> where a user agent obtains a site-specific dictionary that then allows >>>> pages >>>> on the site that have many common elements to be transmitted much more >>>> quickly. >>> >>> One question, why using Accept-Encoding/Content-Encoding instead of >>> TE/Transfer-Encoding ? >>> Cheers, >>> >>> >>> -- >>> Baroula que barouleras, au tiéu toujou t'entourneras. >>> >>> ~~Yves >>> >>> >>> >> >
Received on Wednesday, 10 September 2008 17:32:38 UTC