Network Systems Lab

  Enabling Scalable Communication on the Internet   
  and Beyond


Three principal projects are conducted at the Network Systems Lab at Purdue University spanning QoS provisioning, traffic control, and network security. Each project follows a top-down approach, with theory at the top and system building at the bottom. The research projects are supported by grants from government and industry, including NSF, DARPA, Xerox, Intel, CERIAS, and ETRI.

Scalable QoS Provisioning

The Internet, in spite of an overprovisioned core, cannot deliver user-specified on-demand QoS: Mahatma, who has a 100 Mbps access link from his PC at Purdue, cannot make a telephone quality call to Sidharta, with similar access bandwidth, on the west coast; never mind TV quality video conferencing. What are the reasons underlying this limitation? How can they be overcome? What is a realizable solution for the Internet? The project tackles these questions, with the aim of enabling a QoS-enhanced Internet through Q-Bahn, a deployable technology where the "QoS rubber meets the road."

Workload-Sensitive Traffic Control

Internet traffic exhibits strong correlation at large time scales, whose cause is intimately tied to the structure of the payload being carried: most transfers are short-lived, but a few very long-lived transfers contribute the bulk of the total traffic. Our studies show that different protocols are suited for each type, predictive control for long-lived flows and optimistic control for short-lived flows. Workload-sensitivity helps mitigate the reactive cost of feedback controls, including TCP, in WAN environments where feedback latency is large.

Proactive Network Security

Securing the Internet against cyber attacks, including DDoS and worm attacks, is a pressing problem. Past approaches to network security have focused on localized solutions, targeted at shielding a single, confined entity from outside influences. The distributed nature of modern cyber attacks limits the effectiveness of localized methods, necessitating distributed solutions that protect the system as a whole through synergistic security actions. Our work in distributed filtering shows that significant protection, proactive and reactive, can be achieved through selective incremental deployment.

For further information or questions, please contact


 Purdue University