Re: Holding connections open: an immodest proposal

Chris Lilley, Computer Graphics Unit (
Wed, 14 Sep 1994 21:07:33 +0200

In message <> Phil HB wrote:

> There are two ways of doing this :
> 1) The server sends back everything as a unit
> 2) The client requests the inline images separately.
> The Server is actually in the best position to know whether an image
> is specific to one html or shared by many. ...

That last sentence seems to carry an implicit assumption that images are
*always* on the same server that references them, which is clearly not true.
Unless you mean for the server to use a citation index such as the Webcrawler

In general, sending a package of text+images requires that there is also a
separate file of just text, for text mode browsers, or that textmode browsers
are forced to download all the images then discard them. The former solution
imposes a load on the server maintainer - many servers are all maintained by
hand, so thre is a risk that the html in the text+images file and the text only
file diverges. The latter solution uis rather a waste of bandwidth.

One possibility, if an all-in-one text+images file is deemed desirable, is to
have the server construct the all-in-one file on the fly and cache it for future
requests. It would need to check the last modified date of all the components
though, each time it sent the all-in-one file.

Phil, your suggestion did not address the case I outlined yesterday about images
cached in the client and in intervening cacheing proxies. Could you outline how
your proposed solution deals with this?

Chris Lilley
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