Postdoc position at Orange Lab

TCP Troubleshooting on High-Speed Networks

Institution: Orange Labs (France Télécom R&D) – Sophia-Antipolis, France

Start date: ASAP

Duration: 1 year

Subject Definition

Standard TCP is unable to use efficiently the always increasing capacities in the networks (eg. FTTH, LTE). New congestion control mechanisms have been proposed and some of them are already implemented in widespread operating systems (Cubic, HighSpeed, and Compound TCP). We have previously developed several models to describe the actual behaviour and predict the performance of a single connection using one of these TCP variants [3][4][5].

A first objective of this post doctoral position is to consider more realistic traffic model with many TCP connections, to assess the interactions and the fairness between persistent greedy connections [1]; between Markovian short transfers; and between TCP connections and streaming flows. The impact of middleboxes, splitting the TCP connections in many parts [2], with possibly different TCP variants should also be considered. Another subject to investigate is the impact of the increase of the initial window on the performance and the stability of the network. Some recent studies suggest that increasing significantly aggressiveness of TCP will not actually lead to a catastrophic event. Still we need to check very carefully this hypothesis.

The study will be based on various complementary methods: analytical modelling, discrete event simulations, experiments on high-speed testbeds and passive analyses of operational traffic. So the aim of this study is not only to develop theoretical models, but above all to use them to diagnose and optimize the performance of TCP transfers on real networks.

Required Skills: Research experience in performance evaluation of queuing systems, or computer networks, Programming / scripting languages

Desired Skills: Traffic control mechanisms, Internet protocols, Experience on high speed networks

Education: A PhD in Computer Science, or Applied Mathematics.

Applications should include: detailed CV, publication list, and references. For more information, please contact Denis Collange (denis.collange@orange-

[1] “Parallel TCP Sockets: Simple Model, Throughput and Validation”, E. Altman, D. Barman, B. Tuffin and M. Vojnovic, Infocom, Barcelona (Spain), April 2006.

[2] “Proxy Caching in Split TCP: Stability and Tail Asymptotics”, F. Baccelli, G. Carofiglio, S. Foss, Infocom, Phoenix (USA), April 2008.

[3] “Comparing Some High Speed TCP Versions under Bernoulli Losses”, A. Blanc, K. Avrachenkov, D. Collange, International Workshop on Protocols for Future, Large-Scale and Diverse Network Transports (PFLDNet’09), Tokyo (Japan), May 2009.

[4] “Modelling an Isolated Compound TCP Connection”, A. Blanc, D. Collange, K. Avrachenkov, Advanced International Conference on Telecommunications (AICT’09), Venice (Italy), May 2009.

[5] “Compound TCP with random losses”, A. Blanc, K. Avrachenkov, D. Collange and G. Neglia, Networking 2009, Aachen (Germany), May 2009.

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