A versatile model for TCP bandwidth sharing in networks with user heterogeneity.

ABSTRACT
Enabled by the emergence of various access technologies (such as ADSL and wireless LAN),
the number of users with high-speed access to the Internet is growing rapidly, and their
expectation with respect to the quality-of-service of the applications has been increasing
accordingly. With TCP being the ubiquitous underlying end-to-end control, this motivates the
interest in easy-to-evaluate, yet accurate, performance models for a TCP-based network shared by multiple classes of users. Building on the vast body of existing models, we develop a novel
versatile model that explicitly captures user heterogeneity, and takes into consideration
dynamics at both the packet level and the flow level. It is described how the resulting multiple
time-scale model can be numerically evaluated. Validation is done by using NS2 simulations as a benchmark. In extensive numerical experiments, we study the impact of heterogeneity in the
round-trip times on user-level characteristics such as throughputs and flow transmission times, thus quantifying the resulting bias. We also investigate to what extent this bias is affected by the networks' 'packet-level parameters', such as buffer sizes. We conclude by extending the singlelink model in a straightforward way to a general network setting. Also in this network setting the impact of heterogeneity in round-trip times is numerically assessed.
2000 Mathematics Subject Classification: 60K25, 68M20

Keywords and Phrases: TCP; user heterogeneity; performance; throughput; round-trip times; packet level; flow level; acyclic networks
Note: The work of H. van den Berg and M. Mandjes was partially funded by the Dutch Ministry of Economic Affairs (through its agency SENTER/NOVEM) under the programme `Technologische Samenwerking ICT Doorbraakprojecten', project TSIT 2031 EQUANET. M. Mandjes is also with Korteweg-de Vries Institute, University of Amsterdam, Amsterdam, the Netherlands, and EURANDOM, Eindhoven, the Netherlands.
D. Abendroth is currently with Bayerische Motor Werke, München, Germany.