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Troubleshooting poor performance for specific web sites?

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Troubleshooting poor performance for specific web sites? - 6.Jul.2009 11:52:23 AM   
mcr

 

Posts: 2
Joined: 6.Jul.2009
Status: offline
I'm using an ISA 2004 server as a simple cacheing proxy. Most of the time it works very well, but there are a small number of web sites that perform extremely poorly through the proxy. Examples are the KLM and Air France online checkin sites and Travelocity.

If I remove the proxy setting from Internet Explorer on the client PCs the same sites perform perfectly well, so it doesn't seem to be a problem with the web sites or our internet connectivity. The same sites perform poorly from any client machine using the proxy, it's not specific to individual clients.

There are no errors or alerts in the event logs on the proxy, no other problems with the network, and the vast majority of sites are not affected. The server is high spec, probably overpowered for it's task - CPU use and disk IO are negligible, memory utilisation is around 1.5Gb of 2Gb available (ISA is set to use 50% for the cache).

Does anybody have any suggestions where I go next to troubleshooting this problem?
Post #: 1
RE: Troubleshooting poor performance for specific web s... - 6.Jul.2009 4:19:01 PM   
Rotorblade

 

Posts: 1348
Joined: 27.Feb.2007
Status: offline
In Troubleshooting, have you tried creating a non-caching rule for the problem sites? In reference to “extreme poor performance” as you defined, are requests just slow or are you getting time-outs? There could be a few things to check and DNS would be my first and PMTU discovery is the second. Is DNS setup correctly on ISA using an internal DNS server configured as a forwarder? PMTU discovery should be enabled.

http://support.microsoft.com/kb/902347

http://blogs.isaserver.org/shinder/2006/05/09/general-approach-to-solving-performance-issues-with-the-isa-firewall-part-1/

http://blogs.isaserver.org/shinder/2006/05/10/general-approach-to-solving-performance-issues-with-the-isa-firewall-part-2/  

 HTH

RB

_____________________________

David Melvin
Ohio
MCSE: Security 2003, MCSA:Security 2003

(in reply to mcr)
Post #: 2
RE: Troubleshooting poor performance for specific web s... - 7.Jul.2009 5:50:27 AM   
mcr

 

Posts: 2
Joined: 6.Jul.2009
Status: offline
Thanks for those. PMTU was already enabled in the registry but there was no rule set up in the firewall, so I've created that. I'd already checked everything that's listed in the other two documents... good checklists.

I'll see if the PMTU change makes any difference, if not I'll move on to try rules to prevent cacheing.

(in reply to Rotorblade)
Post #: 3
RE: Troubleshooting poor performance for specific web s... - 7.Jul.2009 5:52:29 PM   
paulo.oliveira

 

Posts: 3472
Joined: 3.Jan.2008
From: Amazon, Brazil
Status: offline
Hi,

you can also run ISABPA.

Regards,
Paulo Oliveira.

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Microsoft Premier Field Engineer (PFE)
Blog: http://poliveirasilva.wordpress.com/
Twitter: https://twitter.com/poliveirasilva

(in reply to mcr)
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