58 research outputs found
Chinese Internet AS-level Topology
We present the first complete measurement of the Chinese Internet topology at
the autonomous systems (AS) level based on traceroute data probed from servers
of major ISPs in mainland China. We show that both the Chinese Internet AS
graph and the global Internet AS graph can be accurately reproduced by the
Positive-Feedback Preference (PFP) model with the same parameters. This result
suggests that the Chinese Internet preserves well the topological
characteristics of the global Internet. This is the first demonstration of the
Internet's topological fractality, or self-similarity, performed at the level
of topology evolution modeling.Comment: This paper is a preprint of a paper submitted to IEE Proceedings on
Communications and is subject to Institution of Engineering and Technology
Copyright. If accepted, the copy of record will be available at IET Digital
Librar
Correlated Resource Models of Internet End Hosts
Understanding and modelling resources of Internet end hosts is essential for
the design of desktop software and Internet-distributed applications. In this
paper we develop a correlated resource model of Internet end hosts based on
real trace data taken from the SETI@home project. This data covers a 5-year
period with statistics for 2.7 million hosts. The resource model is based on
statistical analysis of host computational power, memory, and storage as well
as how these resources change over time and the correlations between them. We
find that resources with few discrete values (core count, memory) are well
modeled by exponential laws governing the change of relative resource
quantities over time. Resources with a continuous range of values are well
modeled with either correlated normal distributions (processor speed for
integer operations and floating point operations) or log-normal distributions
(available disk space). We validate and show the utility of the models by
applying them to a resource allocation problem for Internet-distributed
applications, and demonstrate their value over other models. We also make our
trace data and tool for automatically generating realistic Internet end hosts
publicly available
Transport Protocol Throughput Fairness
Interest continues to grow in alternative transport protocols to the Transmission Control Protocol (TCP). These alternatives include protocols designed to give greater efficiency in high-speed, high-delay environments (so-called high-speed TCP variants), and protocols that provide congestion control without reliability. For the former category, along with the deployed base of ‘vanilla’ TCP – TCP NewReno – the TCP variants BIC and CUBIC are widely used within Linux: for the latter category, the Datagram Congestion Control Protocol (DCCP) is currently on the IETF Standards Track. It is clear that future traffic patterns will consist of a mix of flows from these protocols (and others). So, it is important for users and network operators to be aware of the impact that these protocols may have on users. We show the measurement of fairness in throughput performance of DCCP Congestion Control ID 2 (CCID2) relative to TCP NewReno, and variants Binary Increase Congestion control (BIC), CUBIC and Compound, all in “out-of-the box” configurations. We use a testbed and endto- end measurements to assess overall throughput, and also to assess fairness – how well these protocols might respond to each other when operating over the same end-to-end network path. We find that, in our testbed, DCCP CCID2 shows good fairness with NewReno, while BIC, CUBIC and Compound show unfairness above round-trip times of 25ms
A critical look at power law modelling of the Internet
This paper takes a critical look at the usefulness of power law models of the
Internet. The twin focuses of the paper are Internet traffic and topology
generation. The aim of the paper is twofold. Firstly it summarises the state of
the art in power law modelling particularly giving attention to existing open
research questions. Secondly it provides insight into the failings of such
models and where progress needs to be made for power law research to feed
through to actual improvements in network performance.Comment: To appear Computer Communication
Analysis on Differential Router Buffer Size towards Network Congestion: A Simulation-based
Network resources are shared amongst a large number of users. Improper managing network traffic leads to congestion problem that degrades a network performance. It happens when the traffic exceeds the network capacity. In this research, we plan to observe the value of buffer size that contributes to network congestion. A simulation study by using OPNET Modeler 14.5 is conducted to achieve the purpose. A simple dumb-bell topology is used to observe several parameter such as number of packet dropped, retransmission count, end-to-end TCP delay, queuing delay and link utilization. The results show that the determination of buffer size based on Bandwidth-Delay Product (BDP) is still applicable for up to 500 users before network start to be congested. The symptom of near-congestion situation also being discussed corresponds to simulation results. Therefore, the buffer size needs to be determined to optimize the network performance based on our network topology. In future, the extension study will be carried out to investigate the effect of other buffer size models such as Stanford Model and Tiny Buffer Model. In addition, the buffer size has to be determined for wireless environment later on
Control difuso de la tasa de transferencia de extremo a extremo en protocolos de transporte de Internet
La dinámica del tráfico de extremo a extremo en Internet es un problema complejo para el cual los modelos disponibles son, en el mejor de los casos incompletos. Esta comunicación describe nuevos mecanismos para regulación de la tasa de transferencia de extremo a extremo en la capa de transporte por medio de sistemas difusos. Se describen una generalización basada en lógica difusa de los mecanismos de control de flujo y congestión de TCP (Transport Control Protocol), el diseño de un regulador difuso basado en mecanismo de ventana para TCP, así como la metodología de diseño empleada para simular e implementar de manera experimental el sistema. Se resume un estudio comparativo del regulador difuso presentado frente a los mecanismos tradicionales. El regulador difuso resulta útil como enfoque de modelado y proporciona significativas mejoras de prestaciones respecto a un conjunto de criterios.Ministerio de Educación y Ciencia TEC2005-04359/MICJunta de Amdalucía TIC2006-63
Discrete-time heavy-tailed chains, and their properties in modeling network traffic
This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in ACM Transactions on Modeling and Computer Simulation , http://dx.doi.org/10.1145/10.1145/1276927.1276930The particular statistical properties found in network measurements, namely self-similarity and long-range dependence, cannot be ignored in modeling network and Internet traffic. Thus, despite their mathematical tractability, traditional Markov models are not appropriate for this purpose, since their memoryless nature contradicts the burstiness of transmitted packets. However, it is desirable to find a similarly tractable model which is, at the same time, rigorous at capturing the features of network traffic.
This work presents discrete-time heavy-tailed chains, a tractable approach to characterize network traffic as a superposition of discrete-time “on/off” sources. This is a particular case of the generic “on/off” heavy-tailed model, thus shows the same statistical features as the former, particularly self-similarity and long-range dependence, when the number of aggregated sources approaches infinity.
The model is then applicable to characterize a number of discrete-time communication systems, for instance, ATM and optical packet switching, to further derive meaningful performance metrics such as average burst duration and the number of active sources in a random instant.The authors would like to acknowledge the support of the UKLight MASTS
project (EPSRC, UK) and the DIOR project (MEC, Spain) to this work
Large-Sample comparison of TCP congestion control mechanisms over wireless networks
As new congestion control mechanisms are developed, their performance relative to existing mechanisms needs to be understood; in particular over wireless networks. This study aimed to evaluate existing TCP congestion control mechanisms using a comprehensive and reproducible methodology designed to be representative of real world usage of wireless networks. The study sought to investigate whether any existing mechanism could provide significant performance benefits over CUBIC and be recommended for adoption.
The findings of this study showed that YeAH demonstrated an increase in throughput of 3%–5% over CUBIC, with no penalty to latency. While this small improvement may assist applications requiring the highest available performance, it is unlikely that it will provide a significant improvement over existing congestion control mechanisms. As such, it is the conclusion of this study that use of alternate congestion control mechanisms would not provide noticeable improvements in performance in most applications
Discrete-time heavy-tailed chains, and their properties in modelling network traffic
The particular statistical properties found in network measurements, namely self-similarity and
long-range dependence, cannot be ignored in modelling network and Internet traffic. Thus, despite
their mathematical tractability, traditional Markov models are not appropriate for this purpose,
since their memoryless nature contradicts the burstiness of transmitted packets. However, it is
desirable to find a similarly tractable model which is, at the same time, rigorous at capturing the
features of network traffic.
This work presents the discrete-time heavy-tailed chains, a tractable approach to characterise
network traffic as a superposition of discrete-time “on/off” sources. This is a particular case of
the generic “on/off” heavy-tailed model, thus showing the same statistical features as the former;
particularly, self-similarity and long-range dependence, when the number of aggregated sources
approaches infinity.
The model is then applicable to characterise a number of discrete-time communication systems,
for instance ATM and Optical Packet Switching, and further derive meaningful performance met-
rics, such as the average burst duration and the number of active sources in a random instant
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