In order to support QoS requirements, mechanisms should exist for ensuring that traffic gets the levels of assurance it requires. These mechanisms are usually referred to as "resource management" mechanisms. Support for QoS guarantees is usually provided by a set of policies for handling data in the networks. These data handlers work at the network routers. Data traffic is described in terms of flows, i.e. logical groupings of data packets that may belong to the same applications or the same sender/ receiver pair. The resource management mechanisms control how data from each flow interact and share resources such as the bandwidth, buffer, etc. The service guarantee for a given application, or a set of applications with similar requirements, can be obtained at the flow level. Packet scheduling algorithms determine how packets from different flows get transmitted on the outgoing links of a router. A large variety of scheduling algorithms have been proposed. The algorithms have to be simple to implement.

In order to meet the QoS requirements some form of resource reservation is needed. For a given flow to receive a level of service a state is associated with that flow. Such state includes rates reserved at the schedulers of the routers in the path of the flow, buffers and flow classification. Clearly, providing guarantees relies on non over-allocation of resources. Admission control mechanisms are used to make sure that given application does not capture the critical resources.

The whole area of quality service in the internet is a very active area of research. Indeed, the problem is very complex. However, only simple and effective policies are going to work.

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