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From Brian Behlendorf <>
Subject Re: WWW Form Bug Report: "Netscape & Mosaic cache files inappropriately when received from Apache/NCSA server" on Linux
Date Tue, 24 Oct 1995 16:25:08 GMT
On Tue, 24 Oct 1995, wrote:
> >Note that I have not tested this problem on latest version of Apache or
> NCSA.  Also, note that I think that this is a bug with Netscape 2.0b and
> latest version of Mosaic but I thought I better report it to you just in
> case.  Put a file, such as test123.pdf in a directory on the Apache server.
> Now download that file using Netscape 2.0b (for Unix or Windows) by entering
> the URL then save the file to disk.  Now, copy a new file over test123.pdf
> (but name it test123.pdf).  Make sure they are different sizes.  

WAIT - first make sure the second file has a later *modification* time 
than the former.  If test123.pdf(1) has a later modification date than 
test123.pdf(2), when the client does an If-Modified-Since request, the 
server will say "Nope, test123.pdf hasn't been changed since you last got 
it".  This would perfectly describe the situation you were seeing.  If 
you "touch" the file its modification time will be pushed to the current 

The different responses from different servers may be due to either an 
incapacity to deal with if-modified-since requests (AIX server?) or a 
problem with the date string in the IMS request header (CERN?).  

This came up on the workgroup mailing lists a couple of weeks ago, when 
Netscape wanted to add a file size parameter to the IMS request line, on 
the assumption that one can check file size *or* modification time to 
discern between whether a copy in a cache is current.


> Now,
> download the file using Netscape as above. Save to disk as a different file
> name.  You will notice that the original test123.pdf and the new test123.pdf
> that you saved are the SAME size.  This is because Netscape cached the first
> test123.pdf and didn't reload from the server the next time you went to
> download it.  On versions of Netscape prior to 2.0b this behavior doesn't
> happen.  That made me think that this is a bug with Netscape.  However, I
> then tried this same s!
> > cenario using Netscape 2.0b but using different http servers.  Both Apache
> (0.6.5) and NCSA exhibited the problem.  However, IBM's AIX Server (which is
> based on CERN) did NOT exhibit the problem with Netscape 2.0b.  Very
> strange.  So, I then started looking at the HTTP headers output by Cern and
> NCSA/Apache and noticed some differences. I modified my Apache source to try
> to get the headers as close as possible to the CERN version but it made no
> difference.  So, this is probably a bug in Netscape 2.0b and Mosaic.
> However, it concerns me that it doesn't happen on CERN based servers.  That
> makes me think that Netscape & Mosaic have tightened up on their HTTP
> compliance and that somehow it's not fully compatible with NCSA-based
> servers thus resulting in the cache problem.  Note that the Last-modified
> time was sent by all three servers I tested.

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