This paper addresses the issues of charging, rate control and routing for a communication network carrying elastic traffic, such as an ATM network offering an available bit rate service. A model is described from which max–min fairness of rates emerges as a limiting special case; more generally, the charges users are prepared to pay influence their allocated rates. In the preferred version of the model, a user chooses the charge per unit time that the user will pay; thereafter the user’s rate is determined by the network according to a proportional fairness criterion applied to the rate per unit charge. A system optimum is achieved when users ’ choices of charges and the network’s choice of allocated rates are in equilibrium. 1

Mobile computing environments that seek to support communication-intensive applications need to provide sustained end-to-end networking resources to static and mobile flows in the presence of scarce and variable wireless bandwidth, bursty wireless channel error, and user mobility. In order to achieve this goal, we present the TIMELY adaptive resource management architecture and algorithms for resource reservation, advance reservation, and network layer and end-to-end adaptation in mobile computing environments. The key novelty of our approach is the coordination of adaptation between the different layers of the network in order to solve the problems introduced by scarce and dynamic network resources. 1 Introduction Mobile computing is becoming increasingly popular because of the availability of indoor and outdoor wireless packet networks such as Wavelan, Rangelan, RAM and CDPD. In order to effectively support communication-intensive applications such as web browsing and multime...

Supporting compressed video efficiently on networks is a challenge because of its burstiness. Although a large number of applications using compressed video allow adaptive rates, it is also important to preserve quality as much as possible. We propose a smoothing and rate adaptation algorithm for compressed video, called SAVE, that is used in conjunction with explicit rate based control in the network. SAVE smooths the demand from the source to the network, thus helping achieve good multiplexing gains. SAVE maintains the quality of the video and ensures that the delay at the source buffer does not exceed a bound. We show that SAVE is effective by demonstrating its performance across 28 different traces (entertainment and teleconferencing videos) that use different compression algorithms.

Abstract--We propose a novel explicit rate-flow-control algo-rithm intended for available-bit-rate (ABR) service on an ATM net-work subject to loss and fairness constraints. The goal is to guar-antee low cell loss in order to avoid throughput collapse due tore-transmission by higher level protocols. The mechanism draws on measuring the current queue length and bandwidth availability, as well as tracking tile current number of active sessions contending for capacity, to adjust an explicit bound on the source transmis-sion rates. We identify the factors that affect queue overflows and propose simple design rules aimed at achieving transmission with controlled loss in a dynamic environment. We also discuss how con-servative design rules might be relaxed by accounting for statistical multiplexing in bandwidth sharing among bursty ABR sources and variable-bit-rate (VBR) sources. Index Terms--ABR service, ATM networks, delay differential equations, explicit rate flow control. A

Corelite is a Quality of Service architecture that provides weighted max-min fairness for rate among flows in a network without maintaining any per-flow state in the core routers. There are three key mechanisms that work in concert to achieve the service model of Corelite: (a) the introduction of markers in a packet flow by the edge routers to reflect the normalized rate of the flow, (b) weighted fair marker feedback at the core routers upon incipient congestion detection, and (c) linear increase/multiplicative decrease based rate adaptation of packet flows at the edge routers in response to marker feedback.

In this paper, we present a novel control-theoretic explicit rate (ER) allocation algorithm for the MAX--MIN flow control of elastic traffic services with minimum rate guarantee in the setting of the ATM available bit rate (ABR) service. The proposed ER algorithm is simple in that the number of operations required to compute it at a switch is minimized, scalable in that per-virtual -circuit (VC) operations including per-VC queueing, per-VC accounting, and per-VC state management are virtually removed, and stable in that by employing it, the user transmission rates and the network queues are asymptotically stabilized at a unique equilibrium point at which MAX--MIN fairness with minimum rate guarantee and target queue lengths are achieved, respectively. To improve the speed of convergence, we normalize the controller gains of the algorithm by the estimate of the number of locally bottlenecked VCs. The estimation scheme is also computationally simple and scalable since it does not require per-VC accounting either. We analyze the theoretical performance of the proposed algorithm and verify its agreement with the practical performance through simulations in the case of multiple bottleneck nodes. We believe that the proposed algorithm will serve as an encouraging solution to the MAX--MIN flow control of elastic traffic services, the deployment of which has been debated long due to their lack of theoretical foundation and implementation complexity. Index Terms---Asymptotic decay rate, elastic traffic services, max--min flow rate, scalibility, stability. I.

The focus of this dissertation is on congestion control algorithms in rate-based networks. We consider the problem of how to allocate available bandwidth fairly between competing flows and the effect of such allocation on window-based transport protocols, such as TCP. We study TCP behavior and analyze its performance in both one-way and two-way traffic scenarios, not only in pure rate-controlled environments, but also, in an environment where classical IP datagram networks are interconnected by rate-controlled segments. We develop an explicit rate allocation algorithm for ATM switches, that achieves max-min fair allocation of the available bandwidth, and can satisfy minimum bandwidth requests. The algorithm can support a large number of connections since it performs a constant amount of work for each resource management cell received by the switch. We examine the behavior of the algorithm with both simple cell sources as well as with TCP trafc and demonstrate that the allocation is fair and maintains high network efficiency. The source of a connection responds to the explicit rate feedback received from the network by adjusting the rate of transmission using and increase/decrease policy. We analyze the source policy, derive approximate analytical closed-form expressions to describe the rate increase process, and use these approximations to analyze the impact of the source algorithm on the TCP slow-start process when operatiNext, we examine the behavior of a window-based congestion control algorithm over a rate-controlled channel (for example, TCP operating over ABR service). The bunching of acknowledgements (ack compression) in the end systems in such an environment under two-way traffic can lead to significant loss of throughput and unfairness. We develop anng over a rate-controlled network analytical model for the IP queue behavior at the end systems and use it to estimate the throughput of the TCP connections. We explore solutions to the ack compression problem. This is particularly important in asymmetric environments, with the widespread deployment of cable and high-speed DSL (Digital Subscriber Line) access networks to homes and businesses. We demonstrate that the asymmetry in link bandwidth has an even more dramatic effect on the performance of the connection going through the faster down-link in a two-way trafc scenario. We study three approaches to improve the throughput of the connections: (i) transmitting acknowledgments at a higher priority than data, (ii) using a connection-level backpressure mechanism to limit the maximum amount of data buffered in the outgoing IP queue of the source of the low-bandwidth connection, and (iii) using a scheduling mechanism to allocate bandwidth between data and acks. We show that only the third approach is able to provide isolation and to control the connection throughputs precisely. Finally, we study the performance of TCP in an internetwork consisting of both rate- controlled and non-rate-controlled segments. A common example of such an environment occurs when the end systems are part of IP datagram networks interconnected by a rate- controlled segment, such as an ATM network using the ABR service. In the absence of congestive losses TCP keeps increasing its window to its maximum size. Mismatch be- tween the TCP window and the bandwidth-delay product of the network will result in accumulation of large queues and possibly buffer overows in the devices at the edges of the rate-controlled segment, causing degraded throughput and unfairness. We evalu- ate the effectiveness of intelligent packet discard policies such as Random Early Detection (RED) and Drop-from-Front in improving the TCP throughput and fairness in such environments. We also develop an explicit feedback scheme based on modifying the receiver's advertised window in TCP acknowledgments returning to the source. Our results show that this explicit window adaptation scheme results in superior throughput and fairness over the packet discard policies studied. where the rate allocation is performed explicitly in the switches.

Traditional ABR flow control mechanisms share, in a fair way, the available bandwidth according to the instantaneous peak rate requirements of active traffic streams. Such an approach does not allow bursty users, who besides the peak rate value additional measures of burstiness (e.g., the mean rate), to express their true preferences for network usage. Furthermore, fair sharing is achieved at the short time scales of the duration of the bursts, and cannot express fairness properties defined over longer time scales, such as average throughput. We describe an approach where resource sharing is done according to effective usage. Users bid for some amount of effective bandwidth, and the network controls the effective bandwidth of their traffic by adjusting the explicit rate ER (maximum rate the user is allowed to send traffic) in order to achieve economically fair resource sharing. The feedback loop operates in much longer time scales than the round trip delays, and its performance relies ...

ATM was the focus of active research and significant investment in the early to mid 1990’s. This paper discusses several visions for ATM prevalent at the time, and analyzes how ATM evolved during this period. The paper also considers the implications of this history for current connection-oriented technologies, such as optical transport networks and MPLS.

We have been examining the transport of compressed video over rate-controlled networks, and have developed a smoothing and rate adaptation algorithm, called SAVE (Smoothed Adaptive Video over Explicit rate networks). SAVE attempts to preserve quality as much as possible, by exercising control over the source rate only when essential, when the delay at the source may exceed a bound. Understanding the impact on the quality of the video using rate adaptation is important and we begin to examine some quantitative measures of video quality in this context. For the form of source rate adaptation we advocate, it appears necessary to evolve the quality metrics typically used to evaluate the efficacy of mechanisms to transport video. We also attempt to understand the dynamic nature of the reduction in the encoded rate, since any prolonged impairment is likely to be noticeable. We study the sensitivity of SAVE to its parameters and network characteristics. Finally, the utility of a proposed sche...