Experimental Physics and
Industrial Control System

"J. Lewis Muir" <[email protected]> · Tue, 06 Mar 2012 10:33:40 -0600

On 3/6/12 7:40 AM, [email protected] wrote:
> I'm guessing that at some time in the last couple of weeks the
> web server for www.aps.anl.gov has been upgraded.  At present
> at Diamond we are unable to access any pages on this site, our
> web proxy reports (after a long timeout): "ICAP protocol
> error".
>
> Our IT support folk say:
>
> 	"The problem is that [www.aps.anl.gov] uses an updated
> 	version of the ICAP protocol.  The problem is that this
> 	version is not compatible with anything else."

Hi, Michael.

Could your IT support give a more detailed explanation?  This is
pretty vague.  They must be able to determine exactly what is
failing.  Also, I don't know this, but I would expect that the
ICAP protocol is versioned like the HTTP protocol is, so
shouldn't it be backwards compatible?  If not, then shouldn't it
be very clear what version of the ICAP protocol the APS is using
and what version Diamond is using?

As a workaround, couldn't the Diamond IT support just not use
ICAP for accessing www.aps.anl.gov?  I mean, come on, it's just
HTTP.  I can access www.aps.anl.gov from a non-proxied computer
on the Internet by simply doing the following:

===
$ telnet www.aps.anl.gov 80
GET / HTTP/1.1
Host: www.aps.anl.gov

===

I get the response header followed by the content:

===
HTTP/1.1 200 OK
Server: Sun-ONE-Web-Server/6.1
Date: Tue, 06 Mar 2012 16:14:53 GMT
Content-type: text/html
Expires: Mon, 26 Jul 1997 05:00:00 GMT
Last-modified: Tue, 06 Mar 2012 16:14:53 GMT
Cache-control: no-store, no-cache, must-revalidate
Cache-control: post-check=0, pre-check=0
Pragma: no-cache
Transfer-encoding: chunked

...
===

This is just a regular HTTP 1.1 request over a TCP/IP socket on
port 80.  Certainly the Diamond web proxy can be configured to
just do that until the ICAP problem can be solved, no?

Lewis

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System