There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Stable non-Gaussian random processes , by G. Samorodnitsky and M. S. Taqqu. Pp. 632. £49.50. 1994. ISBN 0-412-05171-0 (Chapman and Hall).

The Transmission Control Protocol.

Stochastic differential equations and diffusion processes

Traffic classification technology has increased in relevance this decade, as it is now used in the definition and implementation of mechanisms for service differentiation, network design and engineering, security, accounting, advertising, and research. Over the past 10 years the research community and the networking industry have investigated, proposed and developed several classification approaches. While traffic classification techniques are improving in accuracy and efficiency, the continued proliferation of different Internet application behaviors, in addition to growing incentives to disguise some applications to avoid filtering or blocking, are among the reasons that traffic classification remains one of many open problems in Internet research. In this article we review recent achievements and discuss future directions in traffic classification, along with their trade-offs in applicability, reliability, and privacy. We outline the persistently unsolved challenges in the field over the last decade, and suggest several strategies for tackling these challenges to promote progress in the science of Internet traffic classification.

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Issues and future directions in traffic classification

In This work a fractal analysis study of VoIP traffic is presented. The characteristics of measured VoIP traffic on both call and packet level have been investigated. The results support the popular Poisson process for VoIP call arrival modeling but we argue that the call holding times follow heavy-tailed distributions rather than exponential distributions. We propose the generalized Pareto distribution for modeling the call holding times. At the packet level we have found that the exponential modeling of on and off periods is also inappropriate and heavy-tailed characteristics have been identified in case of all the investigated VoIP codecs. The generalized Pareto distribution can be used as an accurate model for the on and off periods too. In the analysis we revealed that the aggregated VoIP traffic has fractal characteristics and we suggest the fractional Gaussian noise model for the aggregated VoIP traffic.

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Fractal analysis and modeling of VoIP traffic

HTTP has been the protocol for transferring web traffic over the Internet since the 90s. However, over the past 20 years websites have evolved so much that today this protocol does not provide optimal delivery over the Internet and became a bottleneck in decreasing page load times. Google is pioneering in finding better solutions for downloading web pages and they implemented two new protocols: SPDY in 2009 and QUIC in 2013. Since the wide range deployment of SPDY clients and servers it has been revealed that in some scenarios SPDY can negatively affect the page transfer time mainly due to the fact that the protocol is working over TCP. To tackle these obstacles QUIC uses its own congestion control and based on UDP in the transport layer. Since QUIC is a very recent protocol, this paper could help further understand its operation and performance in a wide range of network scenarios. We present a comprehensive study about the performance of QUIC, SPDY and HTTP particularly about how they affect page load time. We found that none of these protocols is clearly better than the other two and the actual network conditions determine which protocol performs the best.

How quick is QUIC

Recent measurement studies report that a significant portion of Internet traffic is unknown. It is very likely that the majority of the unidentified traffic originates from peer-to-peer (P2P) applications. However, traditional techniques to identify P2P traffic seem to fail since these applications usually disguise their existence by using arbitrary ports. In addition to the identification of actual P2P traffic, the characteristics of that type of traffic are also scarcely known. The main purpose of this paper is twofold. First, we propose a novel identification method to reveal P2P traffic from traffic aggregation. Our method does not rely on packet payload so we avoid the difficulties arising from legal, privacy-related, financial and technical obstacles. Instead, our method is based on a set of heuristics derived from the robust properties of P2P traffic. We demonstrate our method with current traffic data obtained from one of the largest Internet providers in Hungary. We also show the high accuracy of the proposed algorithm by means of a validation study. Second, several results of a comprehensive traffic analysis study are reported in the paper. We show the daily behavior of P2P users compared to the non-P2P users. We present our important finding about the almost constant ratio of the P2P and total number of users. Flow sizes and holding times are also analyzed and results of a heavy-tail analysis are described. Finally, we discuss the popularity distribution properties of P2P applications. Our results show that the unique properties of P2P application traffic seem to fade away during aggregation and characteristics of the traffic will be similar to that of other non-P2P traffic aggregation.

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Identification and Analysis of Peer-to-Peer Traffic

TCP traffic round-trip delay measurements have been carried out in the Ericsson Corporate Network. Based on these data a comprehensive analysis has been performed to identify basic state changes in the network and to find the parametric distribution of the round-trip delay. The main finding of our research is that the round-trip delay can be well approximated by a truncated normal distribution. A method for parameter setting with the statistical tests for validation is also presented. Finally, we discuss the possible explanations of this result.

Sándor Molnár

Papers

Fractal analysis and modeling of VoIP traffic

How quick is QUIC

Identification and Analysis of Peer-to-Peer Traffic

On the distribution of round-trip delays in TCP/IP networks

Challenges and solution for measuring available bandwidth in software defined networks