Virtual Time Reference System : A Unifying Scheduling Framework

| We propose and develop a novel virtual time reference system as a unifying scheduling framework to provide scalable support for guaranteed services. This virtual time reference system is designed as a conceptual framework upon which guaranteed services can be implemented in a scalable manner using the DiiServ paradigm. The key construct in the proposed virtual time reference system is the notion of packet virtual time stamps, whose computation is core stateless, i.e., no per-ow states are required for its computation. In this paper, we lay the theoretical foundation for the deenition and construction of packet virtual time stamps. We describe how per-hop behavior of a core router (or rather its scheduling mechanism) can be characterized via packet virtual time stamps, and based on this characterization , establish end-to-end per-ow delay bounds. Consequently , we demonstrate that, in terms of its ability to support guaranteed services, the proposed virtual time reference system has the same expressive power and generality as the IntServ model. Furthermore, we show that the notion of packet virtual time stamps leads to the design of new core stateless scheduling algorithms, especially work-conserving ones. In addition, our framework does not exclude the use of existing scheduling algorithms such as stateful fair queueing algorithms to support guaranteed services.