19,949 research outputs found
Average-Value Analysis of 802.11 WLANs with Persistent TCP flows
The widespread use of the IEEE 802.11 MAC as a layer-2 protocol for wireless local area networks has generated an extensive literature on its performance modeling. However, most of the available studies evaluate the capacity of WLANs in saturated conditions, while very little has been done on investigating the interactions between the 802.11 MAC protocol and the various transport protocols that are used to deliver users\u27 traffic. Recently there have been renewed efforts to understand and model the TCP dynamics in 802.11 WLANs. In general, these models employ multi-dimensional discrete-time Markov chains to analyze the distributions of the number of TCP packets enqueued in the stations\u27 buffers. Then, they exploit those distributions to derive both the average number of active TCP stations and the aggregate TCP throughput. However, this approach may rapidly lead to the explosion of the model state-space when the number of TCP flows is large. In this technical report we propose a novel modeling approach by developing an average-value analysis of TCP performance in 802.11 WLANs. Our model intuitively characterizes the equilibrium conditions for the network, and this method yields a precise estimate of the throughput of persistent TCP flows. Extensive simulations validate the accuracy of our analysis
PERFORMANCE CHARACTERISATION OF IP NETWORKS
The initial rapid expansion of the Internet, in terms of complexity and number of hosts, was
followed by an increased interest in its overall parameters and the quality the network offers.
This growth has led, in the first instance, to extensive research in the area of network monitoring,
in order to better understand the characteristics of the current Internet. In parallel, studies were
made in the area of protocol performance modelling, aiming to estimate the performance of
various Internet applications.
A key goal of this research project was the analysis of current Internet traffic performance from a
dual perspective: monitoring and prediction. In order to achieve this, the study has three main
phases. It starts by describing the relationship between data transfer performance and network
conditions, a relationship that proves to be critical when studying application performance. The
next phase proposes a novel architecture of inferring network conditions and transfer parameters
using captured traffic analysis. The final phase describes a novel alternative to current TCP
(Transmission Control Protocol) models, which provides the relationship between network, data
transfer, and client characteristics on one side, and the resulting TCP performance on the other,
while accounting for the features of current Internet transfers.
The proposed inference analysis method for network and transfer parameters uses online nonintrusive
monitoring of captured traffic from a single point. This technique overcomes
limitations of prior approaches that are typically geared towards intrusive and/or dual-point
offline analysis. The method includes several novel aspects, such as TCP timestamp analysis,
which allows bottleneck bandwidth inference and more accurate receiver-based parameter
measurement, which are not possible using traditional acknowledgment-based inference. The
the results of the traffic analysis determine the location of the eventual degradations in network
conditions relative to the position of the monitoring point. The proposed monitoring framework
infers the performance parameters of network paths conditions transited by the analysed traffic,
subject to the position of the monitoring point, and it can be used as a starting point in pro-active
network management.
The TCP performance prediction model is based on the observation that current, potentially
unknown, TCP implementations, as well as connection characteristics, are too complex for a
mathematical model. The model proposed in this thesis uses an artificial intelligence-based
analysis method to establish the relationship between the parameters that influence the evolution
of the TCP transfers and the resulting performance of those transfers. Based on preliminary tests
of classification and function approximation algorithms, a neural network analysis approach was
preferred due to its prediction accuracy.
Both the monitoring method and the prediction model are validated using a combination of
traffic traces, ranging from synthetic transfers / environments, produced using a network
simulator/emulator, to traces produced using a script-based, controlled client and uncontrolled
traces, both using real Internet traffic. The validation tests indicate that the proposed approaches
provide better accuracy in terms of inferring network conditions and predicting transfer
performance in comparison with previous methods. The non-intrusive analysis of the real
network traces provides comprehensive information on the current Internet characteristics,
indicating low-loss, low-delay, and high-bottleneck bandwidth conditions for the majority of the
studied paths.
Overall, this study provides a method for inferring the characteristics of Internet paths based on
traffic analysis, an efficient methodology for predicting TCP transfer performance, and a firm
basis for future research in the areas of traffic analysis and performance modelling
The Road Ahead for Networking: A Survey on ICN-IP Coexistence Solutions
In recent years, the current Internet has experienced an unexpected paradigm
shift in the usage model, which has pushed researchers towards the design of
the Information-Centric Networking (ICN) paradigm as a possible replacement of
the existing architecture. Even though both Academia and Industry have
investigated the feasibility and effectiveness of ICN, achieving the complete
replacement of the Internet Protocol (IP) is a challenging task.
Some research groups have already addressed the coexistence by designing
their own architectures, but none of those is the final solution to move
towards the future Internet considering the unaltered state of the networking.
To design such architecture, the research community needs now a comprehensive
overview of the existing solutions that have so far addressed the coexistence.
The purpose of this paper is to reach this goal by providing the first
comprehensive survey and classification of the coexistence architectures
according to their features (i.e., deployment approach, deployment scenarios,
addressed coexistence requirements and architecture or technology used) and
evaluation parameters (i.e., challenges emerging during the deployment and the
runtime behaviour of an architecture). We believe that this paper will finally
fill the gap required for moving towards the design of the final coexistence
architecture.Comment: 23 pages, 16 figures, 3 table
I Know Why You Went to the Clinic: Risks and Realization of HTTPS Traffic Analysis
Revelations of large scale electronic surveillance and data mining by
governments and corporations have fueled increased adoption of HTTPS. We
present a traffic analysis attack against over 6000 webpages spanning the HTTPS
deployments of 10 widely used, industry-leading websites in areas such as
healthcare, finance, legal services and streaming video. Our attack identifies
individual pages in the same website with 89% accuracy, exposing personal
details including medical conditions, financial and legal affairs and sexual
orientation. We examine evaluation methodology and reveal accuracy variations
as large as 18% caused by assumptions affecting caching and cookies. We present
a novel defense reducing attack accuracy to 27% with a 9% traffic increase, and
demonstrate significantly increased effectiveness of prior defenses in our
evaluation context, inclusive of enabled caching, user-specific cookies and
pages within the same website
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