QoS enhancement with partial state

Considerable work has been done in devising mechanisms for providing service guarantees within a network. These schemes can be broadly classified into two categories, schemes that require maintaining state for each flow and schemes that do not require maintaining state for each flow within the network. Both the approaches have their advantages and proponents. This paper looks at a scheme that falls in between these two extremes, where a network switch may be able to maintain state for a fixed number of flows (possibly less than the number of flows it serves). This paper looks at the services that can be provided by a limited amount of state. As a first step, it presents SACRED, a method that employs sampling and caching in addition to RED at a router to enhance the QoS. The proposed mechanism uses caching to deal with the limited amount of state, and uses sampling to select flows. It is shown that this approach can be effective in containing non-responsive flows. It is also shown that SACRED is scalable in the sense of providing increased function with increased amount of state.