Jason But

Passive TCP stream estimation of RTT and jitter parameters

There exist many tools to passively monitor a link for traffic flows. They are typically used near the edge of the network, but not necessarily at the termination point of data flows - usually within a few hops of end-points. Round trip time (RTT) values for individual flows is of interest for network management purposes and can be used to indicate user experienced network delay, and in network design decisions. Determining the RTT when not at an end-point of a data flow is complicated by the fact that packets may be seen out of order and that witnessed packets may not reach their destination. In this paper we present an algorithm to estimate running RTT and jitter characteristics of TCP streams monitored at the midpoint of a TCP flow

Issues with network address translation for SCTP

A Stream Control Transmission Protocol (SCTP) capable Network Address Translation (NAT) device is necessary to support the wider deployment of the SCTP protocol. The key issues for an SCTP NAT are SCTPs control chunk multiplexing and multi-homing features. Control chunk multiplexing can expose an SCTP NAT to possible Denial of Service attacks. These can be mitigated through the use of chunk and parameter processing limits. Multiple and changing IP addresses during an SCTP association, mean that SCTP NATs cannot operate in the way conventional UDP/TCP NATs operate. Tracking these multiple global IP addresses can help in avoiding lookup table conflicts, however, it can also result in circumstances that can lead to NAT state inconsistencies. Our analysis shows that tracking global IP addresses is not necessary in most expected practical installations. We use our FreeBSD SCTP NAT implementation, alias_sctp to examine the performance implications of tracking global IP addresses. We find that typical memory usage doubles and that the processing requirements are significant for installations that experience high association arrival rates. In conclusion we provide practical recommendations for a secure stable SCTP NAT installation.

Outsourcing automated QoS control of home routers for a better online game experience

Consumer network access links can become bottlenecks when faced with heterogeneous network traffic where real-time traffic from network games finds itself competing with nongame traffic for access to bandwidth. We would like to prioritize network game traffic over these bandwidth restricted links. However, the limited resources of consumer access devices make this problematic. We propose a solution whereby the classification of flows is outsourced to an ISP-based system. The access device is then notified of flow classifications and can apply a simple flow prioritization rule. We have developed a prototype of this system and found it viable in terms of functionality, timeliness of classification, and scalability.

Rapid Identification of BitTorrent traffic

BitTorrent is one of the dominant traffic generating applications in the Internet today. The ability to identify BitTor-rent traffic in real-time could allow network operators to better manage network traffic and provide a better service to their customers. In this paper we analyse the statistical properties of BitTorrent traffic and select four features that can be used for real-time classification using Machine Learning techniques. We then train and test a classifier using the C4.5 algorithm. Our results show that based on statistics calculated on 150-packet sub-flows, we can classify BitTorrent traffic with Recall of 98.2% and Precision of 96.5%. We then show that 98.1% of sub-flows from other client-server bulk transfer applications are correctly classified as non-BitTorrent.

Designing a scalable video-on-demand system

As network access costs, especially over the last mile, decrease and broadband access becomes more available to the home user, the idea of video-on-demand (VoD) as an application has made a comeback. Previously, VoD systems could only be supported on a local intranet; however, when considering deploying a global VoD service, the issue of scalability becomes important. Indeed, many low-bitrate Internet streaming services have led the way in distributed video server design. We need to re-examine the issues of designing a global VoD service that is not only scalable, but also cost effective - the most important driver in deciding whether VoD will survive its latest incarnation, or whether it will fade away to bide its time again.

Implementing encrypted streaming video in a distributed server environment

Technical issues are not the only ones preventing large scale introduction of online streaming video services. Unlike generic web browsing applications, streaming video imposes greater demands on network resources. Caching of content through the use of distributed servers has been proposed as a solution to reduce resource requirements and improve scalability. Video caching presents a unique challenge to copyright protection schemes, particularly if we consider provision of functionality such as indexed and high-speed playback modes. This paper discusses the issues involved in implementing copyright protection for cached streaming video, concluding with a set of requirements for any proposed scheme.

The brave new world of online digital home entertainment

The emergence of widespread broadband home Internet connectivity is leading to a change in patterns of home user online behavior. Innovative networked applications (e.g., online multimedia and gaming) are making their mark. Will the next killer Internet applications be new forms of online digital home entertainment? Can the Internet support a widespread explosion in the use of such applications? In this article we explore potential problems in running interactive multimedia and game applications over existing Internet and home access network infrastructures. We also discuss the issues both network and application developers should consider when designing new Internet entertainment applications such that widespread usage becomes a possibility.

Rapid and generalized identification of packetized voice traffic flows

In this paper we describe the construction and performance of classifiers able to identify Variable Rate VoIP traffic flows rapidly, reliably and independently of the application version that generated it. We show that features calculated on short sequences of packets extracted from the flow (sub-flows) are sufficient to identify VoIP flows with Recall of 99% and Precision of 90%. The features we used are based on mean packet length, autocorrelation and the ratio of data transmitted in either direction of a bi-directional flow. Even though the codecs we use to generate VoIP traffic are quite different, we show that by using selected features that capture the nature of variable bit rate voice traffic, a classifier trained on traffic generated by one version of VoIP can reliably recognize traffic generated by another version.

Automated network games enhancement layer: a proposed architecture

In this paper we present the design of the Automated Network Games Enhancement Layer (ANGEL), a novel architecture for meeting Quality of Service (QoS) requirements of real-time network game traffic across consumer broadband links. Consumer access links can become bottlenecks when faced with heterogeneous network traffic (e.g. simultaneous use of online games and peer-to-peer file sharing) and the online gaming experience can be significantly affected by bottleneck queuing. Implementing QoS on these links provides improvement by reducing latency and jitter. In our approach network servers automatically identify traffic that might benefit from QoS and then trigger provisioning of QoS by signaling network elements such as access routers. By placing intelligence within the network, QoS decisions can be transparently made for the game applications without imposing an additional processing cost at the access link router. Our system uniquely uses machine learning methods to perform traffic classification.

Evaluating the impact of DNS and HTTP session characteristics on consumer ISP web traffic

Web caches are generally considered useful because they reduce replication of network traffic flowing from original content sources. In this paper we experimentally characterise the network and transport layer consequences of Web caching in the consumer ISP context. We instrumented a small number of Australian, broadband-attached homes to collect round-trip time (RTT) and hop count statistics for their HTTP/TCP sessions, and collect DNS lookup statistics associated with each HTTP exchange. We estimated the impact of DNS lookup delays on overall HTTP session times, and use our RTT and hop count statistics to show that consumer ISPs would benefit greatly from local caching, particularly in Australia where speed of light delays have a large impact on session times when retrieving international content.