Tom Callahan Tom Callahan Email: tom at lastname dot us Current Status: Senior Director of Engineering at Elastic, where I lead the Elasticsearch development team Previous: Director of Platform Engineering at Explorys, an IBM Company (Part of Watson Health) Software Architect at Heureka Senior Software Engineer at Explorys Education: Ph.D., Computer Science, Case Western Reserve University, 2013. (dissertation) M.S., Computer Science, Case Western Reserve University, 2012. (thesis) B.S., Computer Science, Miami University (Ohio), 2008. Research Advisers: Prof. Michael Rabinovich and Prof. Mark Allman Research Projects Active DNS Measurement This project probes over 1 million devices providing recursive DNS service on the Internet. We analyze the devices to describe aspects of the client-side DNS system, including topology, security, and protocol compliance. Passive DNS Measurement In this project we examine packet-traces of client DNS traffic from a small community of users. We study both the behavior of clients as they interact with the DNS, as well as the behavior of the services clients interact with. Communicating without Fixed Infrastructure Transactions on today's Internet require some sort of fixed infrastructure to commence -- usually a DNS hostname or an IP address. In this project, we implement a system of communication that requires no fixed infrastructure. Based upon a secret key, we enable users to scan for and discover a common set of open recursive DNS servers. Further, we describe a several methods for storing arbitrary data in DNS caches using the secret key, without using any predefined domain name. Metadata Information Storage System (MISS) The Metadata Information Storage System is a new foundational naming service for the Internet centered around users. Users and their applications may name content, configuration items, and other computer objects, which the user may then make available to other users or on other devices. We explore the design and security requirements of the system and explore new functionality available to applications. HTTP Measurement (M.S. Research) In this work we provide a long-term characterization of web traffic using four years of HTTP traffic from a small research institute. We study characteristics of the traffic from client and server behavior to object and connection characteristics. Publications Kyle Schomp, Tom Callahan, Michael Rabinovich, Mark Allman. On Measuring the Client-Side DNS Infrastructure, ACM Internet Measurement Conference, October 2013. (To appear) (PDF) Tom Callahan, Mark Allman, Michael Rabinovich. On Modern DNS Behavior and Properties, ACM SIGCOMM Computer Communication Review, February 2013. (PDF) Tom Callahan, Mark Allman, Michael Rabinovich. Pssst, Over Here: Communicating Without Fixed Infrastructure, IEEE InfoCom Mini-Conference, March 2012. (PDF) Tom Callahan, Mark Allman, Michael Rabinovich. Pssst, Over Here: Communicating Without Fixed Infrastructure. Technical Report 12-002, International Computer Science Institute, January 2012. (PDF) Tom Callahan, Mark Allman, Michael Rabinovich, Owen Bell. On Grappling with Meta-Information in the Internet. ACM SIGCOMM Computer Communication Review, 41(5), October 2011. (PDF) Tom Callahan, Mark Allman, Vern Paxson. A Longitudinal View of HTTP Traffic. Passive and Active Measurement Conference, April 2010. (PDF)