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Missing in Action: Gone but Not Forgotten
ISA Server 2004 offers some great new features and many improvements and enhancements to features that were present, but less functional or less friendly, in ISA Server 2000. However, we would be remiss if we didn't mention that there are a few features you might have used in ISA Server 2000 that are 'missing in action' when it comes to ISA Server 2004.
Most ISA Server firewall administrators won't miss these features, as they were ones that either were not used much or didn't work well in ISA 2000. However, take note, and if you have a specific need for these features, you might consider not upgrading to ISA 2004, or adding a third-party product that can handle these functions. The most significant 'gone but not forgotten features' are:
Live media stream splitting
The H.323 gateway
Bandwidth control
Active caching
Let's briefly address what each of these features does and why Microsoft chose not to include them in ISA Server 2004.
Live Media Stream Splitting
ISA Server 2000 was able to split live media streams using Windows Media Technologies (WMT) to reduce the amount of bandwidth used for streaming audio or video, depending on the number of internal clients that were viewing the same streaming media. If a large number of people within your organization often viewed or listened to the same streaming media source, this could be beneficial. The feature could be applied to streams that used a WMT server located on the internal network, or you could install the WMT server on the ISA Server itself.
According to customer feedback, most companies implementing ISA Server did not use the streaming media splitting feature, so Microsoft did not include it in ISA Server 2004.
H.323 Gateway
The H.323 gateway is used for call handling and routing of Voice over IP (VoIP) calls. VoIP allows you to make voice calls over the Internet instead of using telephone company lines. This can result in a big savings in long distance charges for organizations that must make many long distance calls.
Problems were reported with memory leaks in the ISA Server gatekeeper service when malformed packets were directed at the service. These attacks had no effect if the H.323 gateway was not configured on the ISA Server. Although the problem was corrected with ISA Server 2000 Service Pack 1, many users stopped using the H.323 gateway service or did not use it because of these problems and because configuration of the H.323 gateway was difficult for many ISA Server users to figure out. Further, many newer VoIP products use the Session Initiation Protocol (SIP) instead of H.323. SIP is less complex and was designed as an alternative to H.323. Cisco and other vendors market IP phones that are based on SIP (Cisco also has its own proprietary VoIP protocol called Skinny). In order for H.323 to be effective, both sides of the connection have to have an H.323 gateway.
Microsoft dropped support for the H.323 gateway in ISA Server 2004 because of low usage due to these causes.
Bandwidth Control
ISA Server 2000 included a bandwidth control feature. You could right-click on the Bandwidth Rules node and check a box to enable bandwidth control, then set an effective bandwidth in Kbps. Effective bandwidth refers to either the actual bandwidth used by a device such as a modem, or overall network bandwidth. You could use bandwidth rules to specify which connections would have priority over others.
Although it seemed like a good idea, users complained that bandwidth controls in ISA Server 2000 didn't work, or didn't work as expected. Users expected bandwidth controls to limit the amount of bandwidth that could be used by each connection. This was not how it worked. Instead, the bandwidth rules were used by the quality of service (QoS) packet scheduling service to determine how connections should be prioritized. More disconcertingly, even when you understood what the bandwidth rules did and didn't do and configured them correctly, there were widespread problems with the rules ceasing to work over time. The only solution seemed to be to reformat and reinstall the operating system and ISA Server-not something that the average firewall administrator wants to do on a regular basis.
For these reasons, support for the bandwidth control feature was dropped in ISA Server 2004.
Active Caching
ISA Server 2000 supported not only forward/reverse and distributed/hierarchical caching types, but also supported active caching. This feature would automatically initiate requests to update objects that were stored in cache without any intervention from the user. These updates could be triggered based on the amount of time the object had been cached or when it had last been retrieved from the source server. When active caching was enabled, ISA Server would automatically refresh the cache content before objects expired. The ISA server kept track of which objects in the cache were most popular, and re-cached them even if no one had requested them.
You were able to configure the active caching policy to determine how frequently objects should be updated to balance the need for up-to-date cached objects with network performance concerns.
Although active caching can ensure that frequently-requested objects are kept up to date, it also can use a lot of network bandwidth and impact overall network performance. Active caching was not enabled by default in ISA Server 2000, and input from customers indicated that it was not a feature that was important to most Microsoft ISA Server users. In keeping with Microsoft's emphasis on firewall functionality in ISA Server 2004, the active caching feature was left out.
