Cache servers and Date: header

John Franks (
Fri, 16 Sep 1994 22:20:35 +0200

According to Karl Auerbach:
> > > for cache management.
> > Can you explain this? If the Date: is just the current time doesn't the
> > client/proxy server know it as well as the server.
> The Date: line should indicate when the document was peeled from the
> original content provider. If a cache intervenes, it should not
> change the Date: line. Thus there may be a substantial difference
> between the Date: as published and the time of document reception.

Do caching servers add there own headers before passing along the document?
I hope so. As with mail it should be possible from the header to learn
through whose hands a document has passed on the way to the client. Also
each caching server should add a Date-cached: header similar to the mail
Received: header.

If this is done there really isn't much reason for having a Date:
header from the original server (the Last-Modified-Date: is analogous
to the Date: in mail). On the other hand it isn't very expensive

John Franks Dept of Math. Northwestern University