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Re: Header compression: header set diff

From: Roberto Peon <grmocg@gmail.com>
Date: Thu, 21 Mar 2013 17:09:53 -0400
Message-ID: <CAP+FsNdvWxMuxMvw3zqfRG_gWf8tMUhahejp_nGkqB-VOvjboA@mail.gmail.com>
To: James M Snell <jasnell@gmail.com>
Cc: Patrick McManus <pmcmanus@mozilla.com>, HTTP Working Group <ietf-http-wg@w3.org>, RUELLAN Herve <Herve.Ruellan@crf.canon.fr>
To clarify-- when we do server push, often many resources with extremely
similar headers are being pushed.

Herve-- have you checked in the changes to HeaderDiff for this so I can

On Thu, Mar 21, 2013 at 4:47 PM, Roberto Peon <grmocg@gmail.com> wrote:

> Unless, of course, you ever intend to do server push :)
> -=R
> On Thu, Mar 21, 2013 at 3:53 PM, James M Snell <jasnell@gmail.com> wrote:
>> +1.. In addition to this,  response headers tend to be significantly more
>> variable than request headers...  Which,  of course means much lower
>> compression ratios anyway if we're talking about delta based mechanisms.
>> It makes very little sense to optimize for the response side.
>>  On Mar 21, 2013 6:14 AM, "Patrick McManus" <pmcmanus@mozilla.com> wrote:
>>> On Thu, Mar 21, 2013 at 8:50 AM, RUELLAN Herve
>>> <Herve.Ruellan@crf.canon.fr> wrote:
>>> > To better understand the impact of this choice of persisting the
>>> header set, we tested it inside HeaderDiff and saw a slight improvement of
>>> compaction for requests but also a slight(er) decrease of compaction for
>>> responses.
>>> All else being equal (which is of course never true), compression
>>> ratio of requests is more important than responses because the MUX
>>> allows multiple requests to fit inside the cwnd (and thus avoid
>>> scaling by rtt). The better the ratio, the greater the number of
>>> transactions in 1-flight-mux. On the response side the headers are
>>> mixed in with data frames which in many (but not all) scenarios
>>> overhwelm the headers on a byte count basis - so the effect of header
>>> compression is less likely to impact congestion control.
Received on Thursday, 21 March 2013 21:10:21 UTC

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