Guaranteed Throughput in Work-Conserving Flow Aggregation Through Deadline Reuse

Abstract — The Internet traditionally provides best effort service to all applications. While elastic applications are satisfied by this service, inelastic applications such as interactive audio and video suffer from end-to-end delay guarantees. Although Guaranteed Rate schedulers were developed to provide such guarantees, their scalability has been a concern because they maintain per-flow state. In an effort to reduce per-flow state, two methods have been proposed: stateless core networks and flow aggregation. Stateless core networks require no per-flow state at the routers, while flow aggregation maintains state for a small number of aggregate flows. Although flow aggregation maintains more state, it provides a lower end-to-end delay bound than stateless core networks. The original proposals of these two techniques did not provide guaranteed throughput, that is, flows could be temporarily denied service if they exceeded their reserved rates at earlier times. Recently, guaranteed throughput has been incorporated into the stateless core model through the reuse of deadlines. This is similar to the deadline reuse found in earlier stateful protocols that provide guaranteed throughput. In this paper, we propose adding deadline reuse to flow aggregation networks. In this way, guaranteed throughput can be achieved while maintaining a lower end-to-end delay bound. In addition, we revise the deadline reuse method for stateless core networks. I

Universal Timestamp Scheduling for Real-Time Networks

Consider a network of computers interconnected by point-to-point communication channels. Before generating network packets, each source in the network reserves a fraction of the packet rate of each output channel in the path to its destination. We define a family of scheduling protocols, called Universal Timestamp-Scheduling, to forward packets in this network such that all members of the protocol family provide the same upper bound on packet delay as Virtual Clock scheduling. That is, the packets from a source will exit the output channel of a computer no later than the time they would exit an output channel whose rate equals the source's reserved rate and whose input is exclusively the packets from this source. The protocol family is called universal because it encompasses a wide variety of protocols. To show this, we prove that many scheduling protocols in the literature are members of the protocol family, and thus provide the above guarantee. In addition, we show that the protocols in the literature have only considered one side of the spectrum of possible scheduling protocols, and that there is another side of the spectrum that deserves attention and remains to be investigated. 1

www.elsevier.comrlocatercomnet Universal Timestamp-Scheduling for real-time networks

Consider a network of computers interconnected by point-to-point communication channels. For each flow of packets through the network, the network reserves a fraction of the packet rate of each channel along the path of the flow. We define a family of scheduling protocols, called UniÕersal Timestamp-Scheduling, to forward packets in this network, such that all members of the protocol family provide the same upper bound on packet delay as the well-known packet delay of Virtual Clock scheduling. The protocol family is called uniÕersal because it encompasses a wide variety of protocols. To show this, we prove that many scheduling protocols in the literature are members of the protocol family, and thus provide the above guarantee. In addition, we show that the protocols in the literature have only considered one side of the spectrum of possible scheduling protocols, and that there is another side of the spectrum that deserves attention and remains to be investigated