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Re: Connection Header

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Tue, 20 Dec 94 16:42:52 PST
Message-Id: <9412210042.AA25593@acetes.pa.dec.com>
To: Rob McCool <robm@neon.mcom.com>
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
    I agree... for instance, I'm not sure how I would implement something
    to keep track of how idle multiple server processes are without using
    shared memory or writable mmap()ed files, which I already have found
    are not available on certain platforms we support...
    
Well, I have some suggestions.  Have Netscape send a check to Digital,
and I'll share them with you :-).

    I'm not sure where the demand for this is either... The generality of
    a session seems to me to be not that great a win if the session is
    still a batch request-response cycle. I'd rather have real sessions
    similar to what Simon proposes in HTTP-NG, where we can have
    interactive stock quotes streaming in through one window while at the
    same time the user is browsing the same server's other HTML documents,
    all in one connection.
    
This is the kind of situation where I could imagine it would be
better to use two TCP connections, instead of trying to multiplex
one.  That is, if you have enough data flow to amortize the costs
of two connections, then it's probably worth following that relatively
simple approach, instead of going through all the work of implementing
HTTP-NG.

    Yes, and to that end we have to keep in mind that while <img width=N
    height=M> is useful, it means that in order to see that performance
    win, everyone has to edit their HTML. That will take time, and
    Netscape's perceived performance works everywhere without having to
    edit (or parse) every single HTML doc on a server...

This is only true if one believes that Netscape's perceived performance
is independent of network dynamics.  Which is, I believe, an open question.
My own intuition is that we can follow two paths:
	(1) Stick with the parallel connection approach, which gives
	reasonably good performance today but which might turn into
	a global performance disaster in the future.
	(2) Encourage people to shift ASAP to an alternative (besides
	the WIDTH and HEIGHT tags, several HTTP-level mechanisms have
	been proposed).  This might avert future global problems, but
	in the short term it might be a while before enough servers
	support it to make it highly beneficial.  I would also expect
	that in the long run (i.e., with widespread support), it would
	improve UPP because you wouldn't have to wait even for the initial
	bits of the images to arrive.

This dilemma is similar to the global warming issue: do we reduce CO2
emissions now, or do we wait and see if the icecaps really will melt?
And are there other benefits to reducing emissions, beyond averting
global warming?

-Jeff
Received on Tuesday, 20 December 1994 16:52:07 EST

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