Long delays when accessing certain websites through ISA 2004 & Proxy?

[ADB100]

I have a weird problem when accessing certain websites through ISA 2004 and with the client configured to use the proxy. If I access sites such as eBay or Microsoft the initial page usually appears but subsequent pages are delayed or timeout, this isn't always but about 50% of the time and is really annoying for users. If I disable Proxy on the clients everthing works. ISA is the exit point to the Internet for all traffic, its External interface is behind a Cisco PIX Firewall. If I place a client on the PIX Firewall segment it works fine.
On the clients on the Inside network I have Auto Discovery enabled and I know this works as the open TCP connections always show TCP port 8080 connections to the ISA Server. I have also tried hard-coding the clients for the Proxy but the problem still persists. I have also tried enabling HTTP 1.1 connections through Proxy but the problem is still there.

I have looked at Packet traces but can't see anything obvious.

Anyone have any idea?

Thanks

Andy

 

[ADB100]

To add:

There is no Authentication enabled and I have tried deleting the Cache file as well.

Andy

 

[marky99]

As anyone found a solution to this problem. We are experiencing the same issue.

 

[coco10]

what happen when your client have the firewall client install?

coco10

 

[ADB100]

We don't use (or want to use) the Firewall Client - SecureNAT is what we are using.

I have been messing around with this for a while and it seems that the MTU settings have been altered on the ISA Server as well as some clients. I think the Cisco VPN Client was installed on a few Clients and this changes the MTU to 1300 for all installed adapters. I have no idea who or what changed the MTU settings on the server as it is not manageable by anyone else or remotely.
I have reset the ISA Server and the clients MTU back to default (i.e. removed the setting in the registry) they are now all 1500. This has improved access to eBay but other sites are still problematic - for example Microsofts own site is a nightmare to navigate if Proxy is enabled on the client. Disable proxy and bang everything works.....

Andy

 

[coco10]

Check this , disable the cache in the isa server an try if without cache its work erase cache (delete de content of the directory)

coco10

 

[ADB100]

I have just deleted the cache but it is almost immediately re-created. The problem is still there though. I think I have tried this previously though and it didn't make any difference.

If I browse Microsofts website initially everything is OK, but I will click on a link or click back and nothing will happen, the progress bar at the bottom of the screen will show about 3 bars and stop. It can happen on the first page, 2 pages in or not until after several pages. But when it stops it stops for good. If I click the stop and then refresh the page may come back.

I have just tried the MS Mobile pages (microsoft.com/windowsmobile) and after about 5 pages the browser window is now empty and the pointer has a hour-glass next to it and nothing is happening. If I disable the proxy on the client the problem goes away.....

Andy

 

[coco10]

you try to disable web proxy filter?

coco10

 

[ADB100]

I will give it a shot and see what happens....


Andy