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Clean Slate Research Projects

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8.) Flow-level Models for the Internet

Started: September 2006

Internet research largely consists of a cycle involving design and validation. Of the two validation methodologies---simulation and theoretical modeling, simulation has been by far the better developed and, hence, the more successful. Indeed, the highly-used simulation platform ns allows detailed transaction-level modeling of the Internet. But, the very detail that has endeared ns to researchers has made it difficult to simulate large-scale networks.
On the other hand, existing successful theoretical methods have two major drawbacks.

(i) They do not incorporate end-to-end semantics. For example, packet switching theory consists exclusively of packet level models and there is no notion of a flow. This is because packet switches operate on the individual packets that constitute a flow and not directly on the flow itself. This theory, therefore, ignores that packets do not arrive exogenously in an open-loop fashion, that the arrival of future packets depends on the outcome of scheduling and drop decisions on current packets.

(ii) They do not model flow-level dynamics. For example, the theory of Internet congestion control algorithms is primarily concerned with the stability of the closed-loop system with transport protocols like TCP on the one end and network routers on the other. This theory studies the ``unit step response'' of the network; that is, buffer occupancies and link utilization when infinitely long-lived flows are applied as input to the network at time 0. Such an input process does not capture a dynamic situation where flows arrive and depart, and cannot model the effect link sharing mechanisms on a flow's delay.

This proposal is aimed at obtaining flow-level theoretical models for the Internet, a topic which has generated much interest and excitement in the theoretical research community.


Balaji PrabhackarBalaji Prabhakar
(Faculty) Associate Professor departments of Electrical Engineering & Computer Science

Amin SaberiAmin Saberi
(Faculty) Assistant Professor, Management Science and Engineering


This research is funded by the Clean Slate Project.

We will post papers/progress reports on this page.

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