I’m sure this is posted in other blogs, but just in case … if you are running SBS2003 and ISA2004, after installing ISA’s service pack (SP2 or SP3), you may find that you can no longer access iTune’s store. The reason is that with ISA 2004 SP2, users had to disable the compression filter. But with SP3 you have to turn it back on.
The cause of the problem is that iTune sends back compressed HTML data, whether or not you (as the client) requested compressed data. You can see the error if you monitor activity from the ISA management console. You will see the following failed connection in the ISA logs:
Log type: Web Proxy (Forward) Status: 50 The request is not supported. Rule: SBS Internet Access Rule Source: Internal Destination: External (xx.xx.xx.xx:80) Request: GET http://ax.phobos.apple.com.edgesuite.net/……..
You can fix the problem in two easy steps through the ISA Management Console:
1. Enable compression – on the left frame drill down Configuration > Add-Ins, right click on Compression Filter, click Enable, then click Apply along the top
2. Identify the iTunes Servers to ISA: on the left frame click on Configuration > General. Click on the Define HTTP Compression Preferences in the middle frame. Click Add to add a new computer set. Name the new set iTunes (or iTunes Servers). Click on the Add button and then add in the following IP ranges:
Click on Apply and you should be good to go.
Note: iTunes will frequently use different IP ranges. So, if access to the iTune store stops working in the future, simply monitor ISA for the IP range being used, and then add the new IP address range to the computer set.
Hope this helps!