Stochastic models for throughput analysis of randomly arriving elastic flows in the Internet (original) (raw)

On the Accuracy of Analytical Models of TCP Throughput

2006

Based on a large set of TCP sessions we first study the accuracy of two well-known analytical models (SQRT and PFTK) of the TCP average rate. This study shows that these models are far from being accurate on average. Actually, our simulations show that 70% of their predictions exceed the boundaries of TCP-Friendliness, thus questioning their use in the design of new TCP-Friendly transport protocols. Our study also shows that the inaccuracy of the PFTK model is largely due to its inability to make the distinction between the two packet loss detection methods used by TCP: triple duplicate acknowledgments or timeout expirations. We then use supervised learning techniques to infer models of the TCP rate. These models show important accuracy improvements when they take into account the two types of losses. This suggests that analytical model of TCP throughput should certainly benefit from the incorporation of the timeout loss rate.

A compound model for TCP connection arrivals: Empirical study within a general framework

Teletraffic Science and Engineering, 2001

Recent measurement and simulation studies have revealed that wide area network traffic displays complex statistical characteristics-possibly multifractal scaling-on fine timescales, in addition to the well-known property of self-similar scaling on coarser timescales. In this paper we investigate the performance and network engineering significance of these fine timescale features using measured TCP and MPEG2 video traces, queueing simulations and analytical arguments. We demonstrate that the fine timescale features can affect performance substantially at low and intermediate utilizations, while the longer timescale self-similarity is important at intermediate and high utilizations. We relate the fine timescale structure in the measured TCP traces to flow controls, and show that UDP traffic-which is not flow controlled-lacks such fine timescale structure. Likewise we relate the fine timescale structure in video MPEG2 traces to sub-frame encoding. We show that it is possibly to construct a relatively parsimonious multifractal cascade model of fine timescale features that matches the queueing performance of both the TCP and video traces. We outline an analytical method to estimate performance for traffic that is self-similar on coarse timescales and multi-fractal on fine timescales, and show that the engineering problem of setting safe operating points for planning or admission controls can be significantly influenced by fine timescale fluctuations in network traffic. The work reported here can be used to model the relevant characteristics of wide area traffic across a full range of engineering timescales, and can be the basis of more accurate network performance analysis and engineering.

Long-run performance analysis of a multi-scale TCP traffic model

IEE Proceedings - Communications, 2004

The long-run queueing performance of a multi-scale TCP traffic model, the HOO model, is analysed. Since the model links the multi-scale behaviour with practical traffic elements and approximates TCP traffic very well, the analysis is expected to provide insights into the physical interpretation of multi-scale traffic and to give useful results for performance prediction. To derive a meaningful solution and avoid the extreme difficulty of an exact analysis, the authors adopt several techniques to track the problem, among which are techniques to establish equivalent processes to the traffic process or the queue content process in two cases, the case of fast flows and the case of slow flows. Quantitative results for the queue tails are obtained in both cases, and a unified form is derived. It indicates that three levels of traffic elements in different time scales, i.e. the connection, the burst and the packet, all affect the asymptotic queueing performance. It shows quantitatively how the connection determines the index of the queue tail, and the burst and the packet contribute to the tail with their averages. Used with simple statistical inferences, the analytical result is shown to predict the queueing performance of real traffic well.

An empirical model of TCP transfers

2003

We propose a model of TCP performance that captures the behavior of a diverse set of network paths. The model uses more parameters than previous efforts, but we show that each feature of the model describes an effect that is important for at least some paths. We show that the model is sufficient to describe the datasets we collected with acceptable accuracy. Finally, we show that the model's parameters can be estimated using simple, application-level measurements.

Modeling TCP throughput: An elaborated large-deviations-based model and its empirical validation

Performance …, 2010

In today's Internet, a large part of the traffic is carried using the TCP transport protocol. Characterization of the variations of TCP traffic is thus an important issue, both for resource provisioning and Quality of Service purposes. However, most existing models are limited to the prediction of the (almost-sure) mean TCP throughput and are unable to characterize deviations from this value.

An empirical model of TCP performance

Modeling, Analysis, and Simulation of Computer …, 2005

We propose a model of TCP performance that captures the behavior of a set of network paths with diverse characteristics. The model uses more parameters than others, but we show that each feature of the model describes an effect that is important for at least some paths. We show that the model is sufficient to describe the datasets we collected with acceptable accuracy. Finally, we show that the model's parameters can be estimated using simple, application-level measurements.

On the Use of Queueing Network Models to Predict the Performance of TCP Connections

Lecture Notes in Computer Science, 2001

In this paper we describe an analytical approach to estimate the performance of greedy and short-lived TCP connections, assuming that only the primitive network parameters are known, and deriving from them round trip time, loss probability and throughput of TCP connections, as well as average completion times in the case of short-lived TCP flows. It exploits the queuing network paradigm to develop one or more 'TCP sub-models' and a 'network sub-model,' that are iteratively solved until convergence. Our modeling approach allows taking into consideration different TCP versions and multi-bottleneck networks, producing solutions at small computational cost. Numerical results for some simple single and multi-bottleneck network topologies are used to prove the accuracy of the analytical performance predictions, and to discuss the common practice of applying to short-lived TCP flows the performance predictions computed in the case of greedy TCP connections.

TCP performance modeling in wired and wired/wireless networks: single source models

LAMBERT Academic Publishing, 2011. 200 p.

From the early days of BSD Unix systems to desktop and server platforms of today, the TCP/IP protocol suite and, consequently, the Transmission Control Protocol (TCP) itself are an integral part of any operating system. Most popular applications and services, starting from FTP and Usenet before the World Wide Web was invented and up to YouTube and P2P these days, use TCP as the default transport layer protocol for providing reliable data delivery over best-effort IP networks. As a result, a large portion of Internet traffic is carried by TCP. Due to its widespread use, TCP performance has been extensively studied over the last decade, whereas analytical modeling has proven to be a powerful and cost-effective tool for examining the behavior of TCP. To be useful, these analytical models should be accurate and capture the most important TCP algorithms. In this book, we made an effort towards a better understanding of various aspects of TCP performance under different conditions and in different environments.

A compound model for TCP connection arrivals for LAN and WAN applications

Computer Networks, 2002

We propose a two level model for TCP connection arrivals in local area networks (LAN). The £rst level are user sessions whose arrival is timevarying Poisson. The second level are connections within a user session. Their number and mean interarrival are independent and biPareto across user session. The interarrivals within a user session are Weibull, and across all users are correlated Weibull. Our model has a small number of parameters which are inferred from real traf£c collected at a £rewall. We show that traf£c synthesized with our model closely matches the original data. We extend this approach to a general model involving shot noise and show it is asymptotically consistent with more common fractal models used in data networks. Finally, we show that this model extends to the wide area network applications without alteration and it predicts smoothing of wide area network traf£c pro£le due to spatial aggregation, which we observe experimentally by synthetically creating large aggregate TCP load.

TCP THROUGHPUT MODELING – A NEW APPROACH

TCP is the most dominant transport protocol that serves as a basis for many other protocols in wired and wireless networks. Interoperability with the TCP-dominant wireless or wired network is often critical to some ad hoc network applications using IEEE 802.11. TCP suffers from poor bandwidth utilization, and the utility of TCP in the multihop IEEE 802.11 network has been questioned. The signal interference in this environment, causes channel noise, delay and congestion in transmission which in turn affects the TCP performance. Then, to address these problems, propose two complementary mechanisms are proposed, that is, the TCP fractional window increment (FeW) scheme and the Routefailure nOtification using BUlk-losS Trigger (ROBUST) policy. The TCP FeW scheme is a preventive solution used to reduce the congestion-driven wireless link loss. The ROBUST policy is a corrective solution that enables on-demand routing protocols to suppress overreactions induced by the aggressive TCP behavior.