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Re: HTTP/1.2 stuff: try it out!

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Wed, 23 Aug 95 13:56:07 MDT
Message-Id: <9508232056.AA27684@acetes.pa.dec.com>
To: Dave Kristol <dmk@allegra.att.com>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
DMK wrote:
    Jeffrey Mogul <mogul@pa.dec.com> wrote (Fri Aug 18 21:11:10 1995):
      >   [dmk wrote:]
      >   1) If there's a Connection: keepalive request header, the server will
      >   hold the connection open for 10 seconds.
      > 
      > This might be a bit short.  My trace-based curves show a fairly
      > sharp "knee" in mean requests/connection at somewhat higher timeouts,
      > around 1-2 minutes.
    As you mentioned in your paper there are two sources of such
    requests:  requests for inlined images and subsequent hits on links
    by a user.  I'm shooting for the first batch, I admit.  In the
    future, with authentication and payment additions to HTTP, the
    short keepalive will address a larger proportion of the same-server
    traffic.  Do you have any measurements for which of the two sources
    produces more of the same-server hits?
    
I did not break down the traces by file name, so I don't have explicit
results for inlined images vs. subsequent clicks.

But in the paper I plot "requests arriving for already-open connections"
vs. idle timeout.  Generally, a large fraction of the gain (almost
half) comes with timeouts greater than 10 seconds.  This implies
either of two things:
	(1) Many clients were delaying ca. 10 seconds before retrieving
	inlined images.
	(2) there were a lot of subsequent hits in the 10-100 second
	range.
Hypothesis #1 seems rather unlikely, so I'd bet on #2.

-Jeff
Received on Wednesday, 23 August 1995 14:08:59 EDT

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