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
either.
John Franks Dept of Math. Northwestern University
john@math.nwu.edu