789958
Myths about Congestion Management in High Speed Networks
Weaknesses in several recently proposed ideas about congestion control and avoidance in high-speed netwroks are identified. Both sides of the debate concerning prior reservation of resources versus walk-in service, open-loop control versus feedback control, rate control versus window control, and router-based control versus source-based control are presented. The circumstances under which backpressure is useful or not are discussed, and it is argued that a single congestion scheme is not sufficient, but that a combination of several schemes is required for complete congestion management in a network.
5474275
Overload based explicit rate switch schemes with MCR guarantees
An explicit rate switch scheme monitors the load at each link and gives feedback to the sources. We define the overload factor as the ratio of the input rate to the available capacity. In this paper, we present three overload-based switch schemes which provide MCR (minimum cell rate) guarantees for the ATM (asynchronous transfer mode) ABR (available bit rate) service. The switch schemes proposed use the overload factor and other terms including current source rate and target utilization to calculate feedback rates. A dynamic queue control mechanism is used to achieve efficient usage of the link, control queues and, achieve constant queuing delay at steady state. The proposed algorithms are studied and compared using several configurations. The configurations were chosen to test the performance of the algorithms in the presence of link bottlenecks, source bottlenecks and transient sources. Finally, a comparison of the proposed algorithms based on the simulation results is given.
822716
A Timeout-Based Congestion Control Scheme for Window Flow-Controlled Networks
During overload, most networks drop packets due to buffer unavailability. The resulting timeouts at the source provide an implicit mechanism to convey congestion signals from the network to the source. On a timeout, a source should not only retransmit the lost packet, but it should also reduce its load on the network. Basedon this realization, we have developed a simple congestion control scheme using the acknowledgment timeouts as indications of packet loss and congestion. This scheme does not require any new message formats, therefore, it can be used in any network with window flow control, e.g., ARPAnet or ISO.
52864471
A binary feedback scheme for congestion avoidance in computer networks
We propose a scheme for congestion avoidance in networks using a connectionless protocol at the network layer. The scheme uses a minimal amount of feedback from the network to the users, who adjust the amount of traffic allowed into the network. The routers in the network detect congestion and set a congestion-indication bit on packets flowing in the forward direction. The congestion indication is communicated back to the users through the transport-level acknowledgment. The scheme is distributed, adapts to the dynamic state of the network, converges to the optimal operating point, is quite simple to implement, and has low overhead. The scheme maintains fairness in service provided to multiple sources. This paper presents the scheme and the analysis that went into the choice of the various decision mechanisms. We also address the performance of the scheme under transient changes in the network and pathological overload conditions.
6846204
Improving explicit congestion notification with the mark-front strategy
Abstract Delivering congestion signals is essential to the performance of networks. Current TCP/IP networks use packet losses to signal congestion. Packet loss not only reduces TCP performance, but also adds large delay. Explicit congestion notification (ECN) delivers a faster indication of congestion and has better performance. However, current ECN implementations mark the packet from the tail of the queue. In this paper, we propose the mark-front strategy to send an even faster congestion signal. We show that mark-front strategy reduces buffer size requirement, improves link efficiency and provides better fairness among users. Simulation results that verify our analysis are also presented.
1305
Design Considerations for the Virtual Source/Virtual Destination (VS/VD) Feature in the ABR Service of ATM Networks
Abstract The Available Bit Rate (ABR) service in ATM networks uses end-to-end rate-based flow control to allow fair and efficient support of data applications over ATM networks. One of the architectural features in the ABR specification [ATM Forum, ATM Traffic Management Specification Version 4.0, April 1996] is the Virtual Source/Virtual Destination (VS/VD) option. This option allows a switch to divide an end-to-end ABR connection into separately controlled ABR segments by acting like a (virtual) destination on one segment, and like a (virtual) source on the other. The translation and propagation of feedback in the VS/VD switch between the two ABR control segments (called “coupling”) is implementation specific. In this paper, we model a VS/VD ATM switch and study the issues in designing the coupling between ABR segments. We identify a number of implementation options for the coupling and show that the choice of the implementation option significantly affects the system performance in terms of (a) the system stability in the steady state, (b) the time to respond to transient changes and converge to the steady state, and (c) the buffer requirements at the switches.
5420102
Dynamic RDT Model for Data Mining
7565598
Towards coarse-grained mobile QoS
Supporting Quality of Service is an important objective for future mobile and wireless systems, and requires resource reservation and admission control to achieve. In this paper, we introduce a novel coarse grained approach to admission control termed Virtual Bottleneck Cell. Our approach is designed to scale to many users and handoffs, while simultaneously controlling “hot spots” and system bottlenecks. The key technique is to hierarchically control the virtual system, ensuring QoS objectives are satisfied without requiring models or accurate predictions of the users’ future locations. We develop a simple analytical model to study the system and illustrate several key components of the approach. Finally, we perform simulations in a two-dimensional network to compare the performance obtained with Virtual Bottleneck Cell with alternate schemes, including the optimal off line algorithm.
47572575
The Art of Computer Systems Performance Analysis
the art of computer systems performance analysis by is one of the most effective vendor publications worldwide? Have you had it? Not at all? Ridiculous of you. Currently, you can get this impressive book simply here. Locate them is layout of ppt, kindle, pdf, word, txt, rar, as well as zip. Just how? Merely download and even read online in this site. Now, never ever late to read this the art of computer systems performance analysis. Whatever our proffesion, the art of computer systems performance analysis can be good source for reading. Find the existing reports of word, txt, kindle, ppt, zip, pdf, and also rar in this website. You can absolutely read online or download this book by right here. Currently, never miss it. Our goal is always to offer you an assortment of cost-free ebooks too as aid resolve your troubles. We have got a considerable collection of totally free of expense Book for people from every single stroll of life. We have got tried our finest to gather a sizable library of preferred cost-free as well as paid files. GO TO THE TECHNICAL WRITING FOR AN EXPANDED TYPE OF THIS THE ART OF COMPUTER SYSTEMS PERFORMANCE ANALYSIS, ALONG WITH A CORRECTLY FORMATTED VERSION OF THE INSTANCE MANUAL PAGE ABOVE.
16168118
Defect-aware design paradigm for reconfigurable architectures
With advances in process technology, the feature sizes are decreasing, which leads to higher defect densities. More sophisticated techniques, at increased costs are required to avoid defects. If nanotechnology based fabrications are applied, the yield may even go down to zero, as avoiding defects during fabrication will not be a feasible option. Hence, future architectures have to be defect-tolerant. Most of the current defect-tolerance schemes introduce redundancy in architecture to combat defects. Alternatively we can introduce defect tolerance in the design-flow. In this paper we analyze the bottlenecks faced by current design-methodologies while addressing defect tolerance. We study the performance of present place and route tools on a defective fabric in terms of area and critical delay penalty, and explore routing aware placement in this context. We have proposed a new cost function, CA-RISA for improving the performance in a defect-aware environment
13296348
Variability in the execution of multimedia applications and implications for architecture
Multimedia applications are an increasingly important workload for general-purpose processors. This paper analyzes frame-level execution time variability for several multimedia applications on general-purpose architectures. There are two reasons for such an analysis. First, it has been conjectured that complex features of such architectures (e.g., out-of-order issue) result in unpredictable execution times, making them unsuitable for meeting real-time requirements of multimedia applications. Our analysis tests this conjecture. Second, such an analysis can be used to effectively employ recently proposed adaptive architectures.
We find that while execution time varies from frame to frame for many multimedia applications, the variability is mostly caused by the application algorithm and the media input. Aggressive architectural features induce little additional variability (and unpredictability) in execution time, in contrast to conventional wisdom.
The presence of frame-level execution time variability motivates frame-level architectural adaptation (e.g., to save energy). Additionally, our results show that execution time generally varies slowly, implying it is possible to dynamically predict the behavior of future frames on a variety of hardware configurations for effective adaptation.