Re: Caching Servers Considered Harmful (was: Re: Finger URL)

Sarr Blumson (
Mon, 22 Aug 1994 15:38:33 -0400

Brian Behlendorf <>says:
On Mon, 22 Aug 1994, Sarr Blumson wrote:
> Rob Raisch, The Internet Company, says:
> [Putting his publisher hat on]
> Let's see how this goes if we substitute "book store" for "caching server"

Analogies are like paper mache - you can make anything out of them. I
don't think contrary arguments to Rob's post are served by comparing
caching servers to book stores.

I didn't intend this as an analogy, but to suggest that, when Rob Raisch was
being critical of caching servers because they _intrinsically_ are incapable
of solving certain problems, he is asking them solve problems that paper
publishing can't solve either.

Book stores are still limited by stock
on hand, and they always provide accountability for the number of items
sold (discounting fraud).

My claim was that a technical solution (caches identify themselves as such,
provide an accounting of _their_ clients if asked, and respect expiration
times) addresses the problem Rob raised. I thought his concerns were about
preventing fraud, and my point was that we shouldn't insist that electronic
mechanisms be any _better_ at preventing fraud than paper publishing.

Caching servers, on the other hand, provide no
such accountability on their own. In fact, from the provider's
perspective accesses from caching servers are almost indistinguishable
from regular accesses (ignoring the fact that I can find them through the
USER_AGENT CGI variable).

I agree that the current protocol does not. I beleive, though, the sorts of
changes required are straightforward. Rob believes (I think) that they are
fundamentally impossible.

We're not on the charge-for-access model either, and until secure
transaction protocols become standard we won't even think about it.
Thus, given the choice between

1) a user not getting the page, or
2) a user getting the page without our knowledge

I'd choose the latter.

I (being a reader rather than a publisher) would agree. I also believe that
refusing to use caches is equivalent to (1) because an electronic market with
only point to point distribution will collapse under its own weight, just as a
physical market would; some sort of hierarchical distribution mechanism is a

Sarr Blumson
voice: +1 313 764 0253 FAX: +1 313 763 4434
CITI, University of Michigan, 519 W William, Ann Arbor, MI 48103-4943