HP's WebQOS 2.2, which was released in July for HP-UX, Windows NT and Windows 2000, assigns priority to Web browsing sessions based on transaction activity. When site traffic spikes, priority can automatically shift from browsing sessions to revenue-producing transactions, Chiovari explains. But QOS involves more than specifying which traffic gets through the gate first. It's the foundation for policy-based networking. A policy defines how to use network resources under specific conditions and how much bandwidth to allot.
Policies can recognize that some data flows vary in amount and importance at different times.
For example, sales traffic could be given precedence over accounting except at the end of every quarter, when the accounting department must calculate and generate reports. Policy definitions depend on several existing QOS standards. Depending on these requirements and on the policies that have been set for routers along the path, resources are either reserved for or denied to the transmission. RSVP ropes off network resources even if they're not fully used. That's good for applications like telephony, where dropped packets can make a transmission unintelligible.