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Re: fast rendering of text, containing images (Was: Persistent ...)

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Fri, 22 Sep 95 14:11:19 MDT
Message-Id: <9509222111.AA21083@acetes.pa.dec.com>
To: Balint Nagy Endre <bne@bne.ind.eunet.hu>
Cc: http WG <http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com>
    > Note that, unlike the Netscape model, which breaks down if you
    > need more than 4 images to decide how to render the text, this
    > mechanism scales to arbitrary numbers of images.  It doesn't
    > allow the browser to render several images simultaneously, but
    > I think that is a much less useful feature if the alternative
    > is faster completion for all images!
    
    Under Linux, I use normally 16 connections! Four is the default!

Many BSD-based TCP implementations cannot have more than a small
number of connections in the SYN_RCVD state for any given TCP
server port.  The default limit is often 8, and many server
programs make it even worse (by using something like "5" as the
second argument to the listen() system call).

If the network is fast enough to deliver your 16 SYN packets in a
burst, many of those will be delayed by your TCP's initial RTT
timeout (probably 1 second) because they won't get any response.

So 16 is not necessarily a good number.  4 usually works, because it is
less than 5, which is about the smallest SYN_RCVD quota I've seen.

By the way, this is a design flaw in BSD, but BSD is what many
people have.  I don't know if other TCP implementations have this
flaw; I know that some BSD-based systems have fixed it.

-Jeff
Received on Friday, 22 September 1995 14:38:48 EDT

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