RE: Caching configuration and News Site (cnn.com)
- From: "Thomas W Shinder" <tshinder@xxxxxxxxxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Sat, 26 Apr 2003 16:49:00 -0500
Hi Shawn,
Your trenchant analysis here points out an important consideration. Most
of the time when people complain about the ISA Server cache not doing
whatever it is they expect it to do, the problem lies with the browser
cache. The browser cache needs to be emptied depending on what changes
are desired.
Thanks!
Tom
Thomas W Shinder
www.isaserver.org/shinder
ISA Server and Beyond: http://tinyurl.com/1jq1
Configuring ISA Server: http://tinyurl.com/1llp
-----Original Message-----
From: Quillman Shawn (RBNA/CIT1.1) *
[mailto:Shawn.Quillman@xxxxxxxxxxxx]
Sent: Friday, April 25, 2003 7:35 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Caching configuration and News Site (cnn.com)
http://www.ISAserver.org
Some more thoughts:
- you may want to create a destination set for news sites and have them
not
cached or at least updated frequently
- you may also want to set the browser to not cache at all, or at least
empty the browser cache frequently. In IE the best you can do is reduce
the
cache to 1MB. In Netscape you can set both disk and memory cache down
to 0
bytes which effectively disables it.
- to clarify something in my explanation below, a public cache is a
shared
cache. ISA's cache is a public cache since it is shared between your
users.
A browser cache is a private cache since it is only used by that one
person
using the browser.
-Shawn
-----
Shawn R. Quillman
Robert Bosch Corporation RBNA/CIT1.1
38000 Hills Tech Drive
Farmington Hills, MI 48331
(248) 553-1164 (P) (248) 848-2855 (F)
shawn.quillman@xxxxxxxxxxxx
-----Original Message-----
From: Quillman Shawn (RBNA/CIT1.1) *
Sent: Friday, April 25, 2003 8:07 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: Caching configuration and News Site (cnn.com)
http://www.ISAserver.org
Hi Jos,
Here are answers for those 2 sites you mentioned (cnn.com, anp.com) and
also
msnbc.com.
CNN.com Response Headers:
HTTP/1.1 200 OK
Via: 1.0 MYPROXY
Expires: Fri, 25 Apr 2003 11:49:15 GMT
Date: Fri, 25 Apr 2003 11:48:16 GMT
Content-Type: text/html
Server: Netscape-Enterprise/6.1 AOL
Last-Modified: Fri, 25 Apr 2003 11:48:15 GMT
Cache-Control: private,max-age=60
Private in the cache-control header means that a public cache must not
cache
it and the max-age means that a private cache (like a browser's) must
expire
it after 60 seconds. The time difference between the Date and Expires
headers reinforces that 60 second expiration. My guess is that other
objects sent by CNN have similar cache directives.
anp.com Response Headers:
HTTP/1.1 200 OK
Via: 1.0 MYPROXY
Date: Fri, 25 Apr 2003 11:50:17 GMT
Content-Type: text/html; charset=ISO-8859-1
Server: Apache/2.0.44 (Unix) PHP/4.3.1
Accept-Ranges: bytes
X-Powered-By: PHP/4.3.1
This is a cacheable response, however other objects and pages deeper in
the
site may have cache-control directives associated with them. I would be
suspicious of this site without further investigation.
Another site, msnbc.com (after following their redirects...):
HTTP/1.1 200 OK
Via: 1.0 MYPROXY
Expires: Thu, 24 Apr 2003 23:59:51 GMT
Date: Fri, 25 Apr 2003 11:59:50 GMT
Content-Type: text/html
Server: Microsoft-IIS/5.0
P3P: CP="BUS CUR CONo FIN IVDo ONL OUR PHY SAMo TELo"
Pragma: no-cache
Cache-Control: private
Accept-Ranges: none
Similiar to CNN, public cache must not cache but a private cache can
unless
it knows about the Pragma header. If it understands the Pragma header
then
it won't cache because of the no-cache directive. The content is set to
expire immediately upon loading (with an Expires header set to a date in
the
past) so a private cache will never return anything because its content
will
already be expired. I would guess that this is also the norm for the
majority of the content on this site.
Hope that helps!
-Shawn
-----
Shawn R. Quillman
Robert Bosch Corporation RBNA/CIT1.1
38000 Hills Tech Drive
Farmington Hills, MI 48331
(248) 553-1164 (P) (248) 848-2855 (F)
shawn.quillman@xxxxxxxxxxxx
-----Original Message-----
From: J.Beunk@xxxxxxxxxxxxxxx [mailto:J.Beunk@xxxxxxxxxxxxxxx]
Sent: Friday, April 25, 2003 4:53 AM
To: [ISAserver.org Discussion List]
Subject: [isalist] Caching configuration and News Site (cnn.com)
http://www.ISAserver.org
Hello,
Since a few months we've been using ISA server. One of my clients is
dependant on information published on news sites like: cnn.com, anp.com
etc. He came up with a question for which i can't provide the answer, so
I
share it with the group:)
- Are Newssites like cnn.com, anp.com being cached ?
- Does this mean that we don't see the last content of this site but
only
the content in the cache
- What is the refresh frequency of the cache ?
We use the following cache configuration:
- Enabled HTTP Caching - Less frequently (Reduced network traffic is
more
important)
I hope one of you has an answer tho these questions.
Kind regards,
Jos Beunk
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