Re: Neighboring woes

From: Andreas Strotmann <>
Date: Wed, 9 Oct 1996 16:06:56 +0200

On Oct 8, 15:26, James R Grinter wrote:
> I did quite like that Netscape's proxy added Cache-last-checked to
> the headers.
> HTTP/1.0 200 OK
> Date: Sun, 06 Oct 1996 13:52:48 GMT
> Server: Apache/0.8.14
> Content-type: text/html
> Content-length: 4344
> Last-modified: Sat, 05 Oct 1996 07:59:14 GMT
> Accept-ranges: bytes
> Cache-last-checked: Tuesday, 08-Oct-96 11:26:32 GMT
> Proxy-agent: Netscape-Proxy/2.1b1
Hmm, yes, that's perhaps the easiest way to implement the kind of
functionality that I had in mind when I started this thread of discussion.


  Introduce ICP_OP_HIT_HEAD into the protocol (and the corresponding
option as well). It's just like HIT_OBJ, but will send the HTTP headers
only instead of the full object. NB: those headers are 'expected' to have
been augmented as by Netscape's proxy (or according to some HTTP 1.1
standard), as you suggested.

The idea is that just about every HTTP header will fit into a packet.
 Paranoid cache maintainers may even have an option at their disposal to
have their proxy disregard any neighbor's responses that do not include
the header information they require. The header information (Expires:,
Last-modified:, Cache-last-checked:, Date:,...) will be used by the proxy
to determine whether the neighbor has sent or has available an object that
fits its own time-to-live restrictions. It may also be used to figure out
which neighbor has the 'best' edition of the object if several answers are

An implementation would probably augment the in-memory cache index with
information about header size in addition to object size in order to speed
up this particular kind of response.

Best, Andreas

Andreas Strotmann       / ~~~~~~ \________________A.Strotmann@Uni-Koeln.DE
Universitaet zu Koeln  /| University of Cologne   \
Regionales Rechenzentrum| Regional Computer Center \
Robert-Koch-Str. 10    /|    Tel: +49-221-478-5524 |\   Home: -221-4200663
D-50931  Koeln        __|__  FAX: +49-221-478-5590 |__________~~~~~~~~~~~~   
Received on Wed Oct 09 1996 - 07:07:33 MDT

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