Quality of Service Guarantees in High Speed Networks A Research Project Funded by the National Science Foundation
Principal Investigator: R. L. Cruz
Summary of Results
- C. S. Chang and R. L. Cruz, "A Time Varying Filtering Theory for Constrained Traffic Regulation and Dynamic Service Guarantees," to appear in IEEE INFOCOM'99: (193K, postscript)
By extending the filtering theory under the (min,+)-algebra to the time varying setting, we solve the problem of constrained traffic regulation and develop a calculus for dynamic service guarantees. For a constrained traffic regulation problem with maximum tolerable delay d and maximum buffer size q, the optimal regulator that generates the output traffic conforming to a subadditive envelope f and minimizes the number of discarded packets is a concatenation of the g-clipper with g(t) = min[f(t+d), f(t)+q] and the maximal f-regulator. The g-clipper is a bufferless device which optimally drops packets as necessary in order that its output be conformant to an envelope g. The maximal f-regulator is a buffered device that delays packets as necessary in order that its output be conformant to an envelope f. The f-regulator is a linear time invariant filter with impulse response f, under the (min,+)-algebra.
To provide dynamic service guarantees in a network, we develop the concept of a dynamic server as a basic network element. Dynamic servers can be joined by concatenation, "filter bank summation," and feedback to form a composite dynamic server. We also show that dynamic service guarantees for multiple input streams sharing a work conserving link can be achieved by a dynamic SCED (Service Curve Earliest Deadline) scheduling algorithm, if an appropriate admission control is enforced.