Maintaining flow isolation in work-conserving flow aggregation

Abstract — In order to improve the scalability of scheduling protocols with bounded end-to-end delay, much effort has focused on reducing the amount of per-flow state at routers. One technique to reduce this state is flow aggregation, in which multiple individual flows are aggregated into a single aggregate flow. In addition to reducing per-flow state, flow aggregation has the advantage of a per-hop delay that is inversely proportional to the rate of the aggregate flow, while in the case of no aggregation, the per-hop delay is inversely proportional to the (smaller) rate of the individual flow. Flow aggregation in general is non-work-conserving. Recently, a work-conserving flow aggregation technique has been proposed. However, it has the disadvantage that the end-to-end delay of an individual flow is related to the burstiness of other flows sharing its aggregate flow. Here, we show how work-conserving flow aggregation may be performed without this drawback, that is, the end-to-end delay of an individual flow is independent of the burstiness of other flows. I

Stabilization of Max-Min Fair Networks without Per-Flow State

Let a flow be a sequence of packets sent from a source computer to a destination computer. Routers at the core of the Internet do not maintain any information about the flows that traverse them. This has allowed for great speeds at the routers, at the expense of providing only best-effort service. In this paper, we consider the problem of fairly allocating bandwidth to each flow. We assume some flows request a constant amount of bandwidth from the network. The bandwidth that remains is distributed fairly among the rest of the flows. The fairness sought after is max-min fairness, which assigns to each flow the largest possible bandwidth that avoids affecting other flows. The distinguishing factor to other approaches is that routers only maintain a constant amount of state, which is consistent with trends in the Internet (such as the proposed Differentiated Services Internet architecture). In addition, due to the need for high fault-tolerance in the Internet, we ensure our protocol is self-stabilizing, that is, it tolerates a wide variety of transient faults. Key words: networks stabilization, max-min fairness, quality of service, computer 1

SLBN: A Scalable Max-min Fair Algorithm for Rate-Based Explicit Congestion Control

The growth of the Internet has increased the need for scalable congestion control mechanisms in high speed networks. In this context, we propose a rate-based explicit congestion control mechanism with which the sources are provided with the rate at which they can transmit. These rates are computed with a distributed max-min fair algorithm, SLBN. The novelty of SLBN is that it combines two interesting features not simultaneously present in existing proposals: scalability and fast convergence to the max-min fair rates, even under high session churn. SLBN is scalable because routers only maintain a constant amount of state information (only three integer variables per link) and only incur a constant amount of computation per protocol packet, independently of the number of sessions that cross the router. Additionally, SLBN does not require processing any data packet, and it converges independently of sessions' RTT. Finally, by design, the protocol is conservative when assigning rates, even in the presence of high churn, which helps preventing link overshoots in transient periods. We claim that, with all these features, our mechanism is a good candidate to be used in real deployments

Networking Mechanisms for Delay-Sensitive Applications

The diversity of applications served by the explosively growing Internet is increasing. In particular, applications that are sensitive to end-to-end packet delays become more common and include telephony, video conferencing, and networked games. While the single best-effort service of the current Internet favors throughput-greedy traffic by equipping congested links with large buffers, long queuing at the congested links hurts the delay-sensitive applications. Furthermore, while numerous alternative architectures have been proposed to offer diverse network services, the innovative alternatives failed to gain widespread end-to-end deployment. This dissertation explores different networking mechanisms for supporting low queueing delay required by delay-sensitive applications. In particular, it considers two different approaches. The first one assumes employing congestion control protocols for the traffic generated by the considered class of applications. The second approach relies on the router operation only and does not require support from end hosts

Core-stateless guaranteed throughput networks

End-to-end throughput guarantee is an important service semantics that network providers would like to offer to their customers. A network provider can offer such service semantics by deploying a network where each router employs a fair packet scheduling algorithm to allocate network bandwidth to competing flows. Unfortunately, these scheduling algorithms require every router to maintain per-flow state and perform per-packet flow classification; these requirements limit the scalability of the routers. This paper makes two primary contributions: (1) We present the first tight analysis for deriving end-to-end throughput guarantees for a network of routers that employ per-flow fair scheduling algorithms. (2) We propose the Core-stateless Guaranteed Throughput (CSGT) network architecture that, without maintaining per-flow state or performing per-packet flow classification in core routers, provides to flows throughput guarantees that are within a constant of what is attained by a network of core-stateful fair routers.