5 results for Alcock, Shane

  • Measuring and characterising inbound sessions in residential DSL traffic

    Alcock, Shane; Nelson, Richard (2011)

    Conference item
    University of Waikato

    It has been assumed that the need for successful NAT traversal discourages residential DSL users from running services or applications that require them to accept connections from remote hosts. However, there are now numerous approaches for NAT traversal but there have been no studies measuring the prevalence of DSL users accepting inbound sessions. This paper presents an analysis of TCP and UDP flows initiated by remote clients to a group of residential DSL users, using packet traces captured from a New Zealand ISP between 2009 and 2011. Our analysis reveals that over half of all measured users accepted at least one inbound TCP or UDP session. There was no dominant port being used to accept sessions and port usage was spread over thousands of different ports. Skype and BitTorrent were the most popular application protocols observed and had increased in popularity over time. We also report on the use of dual SYNs to perform TCP NAT traversal in our data.

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  • The RIPE NCC internet measurement data repository

    McGregor, Anthony James; Alcock, Shane; Karrenberg, Daniel (2010)

    Conference item
    University of Waikato

    This paper describes datasets that will shortly be made available to the research community through an Internet measurement data repository operated by the RIPE NCC. The datasets include measurements collected by RIPE NCC projects, packet trace sets recovered from the defunct NLANR website and datasets collected and currently hosted by other research institutions. This work aims to raise awareness of these datasets amongst researchers and to promote discussion about possible changes to the data collection processes to ensure that the measurements are relevant and useful to the community.

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  • Passive detection of TCP congestion events

    Alcock, Shane; Nelson, Richard (2011)

    Conference item
    University of Waikato

    Detailed passive analysis of TCP sender behaviour requires accurate identification of congestion events. Previous tools that attempt to provide such information do not incorporate the behaviour of recent operating systems and TCP features and are therefore of little use to researchers analysing contemporary TCP traffic. In this paper, we present a new tool for identifying and classifying TCP congestion events from a passive packet trace, called tcpcsm, which understands modern operating system TCP behaviour. We discuss the major problems that occur when passively identifying TCP congestion events and describe how tcpcsm solves them. We also show that tcpcsm is more accurate than previous tools using a series of controlled experiments involving a variety of operating systems.

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  • Measuring the impact of the copyright amendment act on New Zealand residential DSL users

    Alcock, Shane; Nelson, Richard (2012)

    Conference item
    University of Waikato

    The Copyright (Infringing File Sharing) Amendment Act 2011 (CAA) is a New Zealand law that aims to provide copyright holders with legal recourse when content is illegally shared over the Internet. This paper presents a study of residential DSL user behaviour using packet traces captured at a New Zealand ISP before, shortly after and several months after the CAA coming into effect. We use libprotoident to classify the observed traffic based on the application protocol being used to identify and examine any changes in traffic patterns that may be a result of the new law. We find that the use of peer-to-peer applications declined significantly once the CAA was in effect, suggesting a strong correlation. We also found that there were increases in tunneling, secure file transfer and remote access traffic amongst a small segment of the user population, which may indicate an increased uptake in the use of foreign seedboxes to bypass the jurisdiction of the CAA.

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  • Libtrace: A packet capture and analysis library

    Alcock, Shane; Lorier, Perry; Nelson, Richard (2012)

    Journal article
    University of Waikato

    This paper introduces libtrace, an open-source software library for reading and writing network packet traces. Libtrace offers performance and usability enhancements compared to other libraries that are currently used. We describe the main features of libtrace and demonstrate how the libtrace programming API enables users to easily develop portable trace analysis tools without needing to consider the details of the capture format, file compression or intermediate protocol headers. We compare the performance of libtrace against other trace processing libraries to show that libtrace offers the best compromise between development effort and program run time. As a result, we conclude that libtrace is a valuable contribution to the passive measurement community that will aid the development of better and more reliable trace analysis and network monitoring tools.

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