The Department of Computer Science at the University of Cyprus cordially invites you to the Colloquium entitled:

Census and Survey of the Visible Internet


Speaker: Prof. Christos Papadopoulos
Affiliation: Colorado State University, USA
Category: Colloquium
Location: Room 148, Faculty of Pure and Applied Sciences (FST-01), 1 University Avenue, 2109 Nicosia, Cyprus (directions)
Date: Tuesday, December 22st, 2009
Time: 11:30-12:30 EET
Host: Andreas Pitsillides (andreas.pitsillides AT

Many Internet topology studies have appeared in the literature. However, such studies have for the most part, ignored the population of hosts. While many hosts are hidden behind firewalls and NATs, there is much to be learned from examining the population of "visible" Internet hosts -- one can better understand network growth and accessibility to help assess vulnerabilities, deployment of new technologies and improve network models. This paper is to our knowledge the first attempt to measure the population of visible Internet edge hosts. We measure hosts in two ways: via periodic Internet censuses, where we query all accessible Internet addresses every few months, and via surveys of a small fraction of the responsive address space, probing each address every 11 minutes for one week. These approaches are complementary: a census is effective at evaluating the Internet as a whole, while surveys validate the census and allow observation of the lifetime of typical address occupancy. Our findings include trends in address occupancy, an upper bound on the number of servers and an analysis of firewalled addresses and firewall block size. Joint work with John Heidemann, Yuri Pryadkin, Ramesh Govindan and Joseph Bannister.

Short Bio:
Christos Papadopoulos is currently an associate professor at Colorado State University. He received his Ph.D. in Computer Science in 1999 from Washington University in St. Louis, MO. His interests include network security, router services, multimedia protocols and reliable multicast. His current work includes signal processing techniques for network attack detection and participation in the PREDICT program to collect network traces for security research.

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Sponsor: The CS Colloquium Series is supported by a generous donation from Microsoft