Separation principle of dynamic transmission and enqueueing priorities for real- and nonreal-time traffic in ATM multiplexers

In order to efficiently utilize network resources while still providing satisfactory QoS to both real-time and nonreal-time applications, prioritizing these two types of traffic according to their service requirement becomes necessary. Several slot-oriented transmission priority schemes applicable to the output queue of ATM switches have been proposed. We studied the slot-oriented queueing disciplines that further involve the buffer management of the output queue of ATM switches. A fundamental principle called the separation principle is presented, which asserts that (1) the QoS (measured by the time-cumulative cell loss for each traffic class) region of the efficient disciplines (provide the best QoS tradeoff between the two types of traffic) can be divided into two mutually exclusive ones by the QoS of a special efficient discipline called R*; and (2) the efficient disciplines may involve either dynamic transmission priority or dynamic enqueueing priority but not both depending on which of the two mutually exclusive QoS regions is desired. The QoS region of less time-cumulative nonreal-time cell loss than R* is shown to be approximately linear in the space of time-cumulative cell loss vector when the real-time traffic is well regulated. The suboptimal but simple disciplines which are functions of only a small set of system parameters are also investigated to achieve less time-cumulative nonreal-time cell loss than R*