A traffic shaper for supporting CBR and VBR services in ATM networks

The proposed ATM traffic shaper consists of a regulator and a scheduler. It can shape multiple incoming CBR and VBR cell streams simultaneously. The impact of cell emission conflicts is considered and resolved by using an earliest-due-date (EDD) scheduler. In addition, for VBR services, there exists a feedback signal from the EDD scheduler to the regulator. It guarantees that the shaped VBR streams always conform to the GCRA-based traffic descriptor when the cells depart for the ATM output link. Both the cell delay bounds and the call admission control (CAC) conditions for assuring shaper performance are derived. With our CAC mechanism, this traffic shaper can operate with no jitter violation for CBR cells and provide a predictable overall delay bound for VBR cells, and the derived bounds of the proposed traffic shaper are tight for both CBR and VBR.