Alberto Medina, Ph.D. 10 Moulton St Cambridge MA, 02138 617-8736203 medina at bbn dot com EDUCATION ========= Boston University, Boston, MA. May 2003. Ph.D. in Computer Science Dissertation: "Practical Estimation of Internet Traffic Matrices". Specialization: Computer and Data Communication Networks GPA: 4.0/4.0 Northeastern University, Boston, MA. July 1997. M.S. in Computer Science Areas of concentration: Theory, Programming Languages, Networking GPA: 4.88/5.0 Central University of Venezuela, Caracas, Venezuela. June 1992. B.S. in Computer Science Areas of Concentration: Systems, Networking AWARDS ====== 1. Postdoctoral Fellowship, International Computer Science Institute, 2003-2004. 2. Full Ph.D. Scholarship, Boston University 1999-2003. 3. Full M.S. Scholarship, INTEVEP (Venezuela's Oil Research Institute) 1996-1997.. TEACHING EXPERIENCE =================== 1. Boston University Teaching Assistant - Course: Computer Architectures. Fall 1999. 2. Northeastern, University Instructor. Course: Introduction to Comp. Science. Summer 1996, 1997. 3. Central University of Venezuela Teaching Assistant. Course: Numerical Calculus. 1990-1991. 4. Central University of Venezuela Teaching Assistant. Course: Discrete Mathematics. 1989-1990. RELATED EXPERIENCE ================== 1. Network Scientist, BBN Technologies Cambridge, MA 2004- 2. Postdoctoral Researcher, ICSI Center for Internet Research (ICIR). Berkeley, CA 2003-2004 Research: The Transmission Control Protocol (TCP) is the transport protocol most used for data communications in the Internet. For example, the very popular Hyper Text Transfer Protocol (HTTP), used by the World Wide Web uses TCP as the underlying transport protocol providing it with reliable data transfers. Therefore, the stability of the Internet depends on the correctness and performance of the TCP implementations used by applications running on the Internet. Despite the fact that there exist a standard specification of TCP adopted by the Internet Engineering Task Force (IETF), TCP implementers have certain degrees of freedom for certain aspects of the protocols and consequently there exist varying implementations of the protocol interacting in the Internet these days. In addition to variations allowed by the standard specification, there are possibilities as well of having bogus implementations as well as malicious implementations that seek to obtain higher performance from the network at the expense of degrading the performance of the general Internet community. My research at ICSI has focused on the evolution and performance of existing TCP implementations, as well as the evolution of the Internet communication platform. In a nutshell, the main strategy of my work is the transparent interaction with a vast population of web servers providing significant amounts of data that flows in the network. By exerting control on the characteristics of the communication between our Web clients and the existing servers, we are able to deduce the type of implementation of the TCP stack at the server. In addition we have been able to detect bugs in the target implementation, as well as the characteristics of the parameters set for the data transfers. Furthermore, we have designed tests to detect the presence of devices ?external? to the client-server communication and how such devices may affect the performance characteristics of the end-to-end communications. These external devices are often called middleboxes because they are placed in the middle of the communication paths between the client and the servers. Examples of middleboxes are firewalls, load balancers, network address translators, etc. Besides of gaining understanding regarding the evolution of the Internet and the protocols that carry data though it, my research at ICSI aims at providing mechanisms that enable researches to characterize different aspects of Internet behavior and use such characterizations in the development and parameterization of more accurate simulation models. 3. Research Intern, SPRINT Burlingame, CA June 2001 ? December 2002 Research: Any Internet Service Provider (ISP) such as Sprint owns a set of Points of Presence (PoPs) in cities across the geographical area covered by its data communication network. A PoP is a set of routers co-located in a single place (e.g. a building). Each POP received an aggregated of data coming from customers located in the corresponding city. In addition, a PoP may receive data coming from peering connections to other ISPs. Many traffic engineering and performance management tasks performed by an ISP benefit directly or indirectly from knowledge regarding the amount of data exchanged by any pair of PoPs in the network. However, obtaining such information is extremely challenging because of the very large amount of data that traverses each PoP. My research at Sprint focused on alternative techniques to enable network operators to gather the necessary traffic exchange information without having to directly measuring it. My research led to the proposal of an approximation mechanism based on Economic Consumer Theory, in which the traffic exchanged between PoPs is modeled in terms of the engineering characteristics of the participating PoPs. Using this approach, only partial data needs to be directly measured from the network and the rest is filled using appropriate statistical methods. My Ph.D. dissertation thesis was the result of this work. 4. Research Assistant, Boston University 1999-2001 Research: My research work at the Computer Science department of Boston University centered on the development of models and software tools to generate representative synthetic Internet topologies to be used in Internet studies and simulations. The main outcome of this research was the development of a universal topology generator, called BRITE (see Software Section below). 5. Visiting Scholar, Massachusetts Institute of Technology Cambridge, MA 1997- 1998 Research: Cilk is a language for multithreaded parallel programming based on ANSI C designed and developed at the Supercomputing Technologies group at MIT Laboratory for Computer Sciences. Cilk is designed for general-purpose parallel programming, but it is especially effective for exploiting dynamic, highly asynchronous parallelism, which can be difficult to write in data-parallel or message-passing style. My research on Cilk centered around integrating the capabilities of the language with existing mathematical tools such as Matlab in order to make asynchronous paralleling processing capabilities offered by Cilk available to these tools. 6. Research Staff, INTEVEP 1994 -1995 Duties: INTEVEP is the research branch of the oil company of Venezuela, PDVSA. I was awarded a scholarship by INTEVEP to pursue my Ph.D. studies and prior to my coming to the U.S. I was assigned to the Geophysics department. My duties were mainly related to analyzing the domains of the oil exploration business that would benefit from parallel and distributed computation capabilities. 7. Networking Consultant Seyer Consulting Group Caracas, Venezuela, 1992-1994 Duties: Design and implementation of corporate networking plans. Customers included both public and private sector companies and institutions. My consulting tasks included studying client?s needs for infrastructure and software solutions, proposing technological avenues to meet their computational and networking demands, and laying out detailed designs of the proposed solutions. Once networking infrastructures were in place, my duties included the setup, configuration and maintenance of the computational platform. PUBLICATIONS AND TECHNICAL REPORTS ================================== * N. Riga, A. Medina, I. Matta, C. Partridge, J. Redi, I. Castineyra. Transport Protocols for Energy Constrained Environments. WIP Session. ACM SIGCOMM 2005, Philadelphia, PA. August 22-26 2005. * Alberto Medina, Sally Floyd, Mark Allman. Measuring the Evolution of Transport Protocols in the Internet. ACM Computer Communications Review. April 2005. * Alberto Medina, Sally Floyd, Mark Allman. Measuring the Interaction between Transport Protocols and Middleboxes. Internet Measurement Conference. Taormina, Italy. October 2004. * Alberto Medina, K. Salamatian, N. Taft, I. Matta, C. Diot. A Two-step Statistical Technique for Estimating Network Traffic Demands. BU-CS-TR-2003-004. * Alberto Medina, C. Fraleigh, N. Taft, S. Battacharyya, C. Diot. A Taxonomy of Traffic Matrices. SPIE Workshop on Scalability and Traffic Control in IP Networks II. Boston, MA. July 29-August 1, 2002. * Alberto Medina, N. Taft, K.Salamatian, S. Bhattacharyya, C. Diot. Traffic Matrix Estimation Techniques: Existing Techniques Compared and New Directions.To appear on proceedings of SIGCOMM 2002, Pittsburgh, PA. August 2002. * Alberto Medina, N. Taft, K.Salamatian, S. Bhattacharyya, C. Diot. Comparative Analysis of Traffic Matrix Estimation Methods. DIMACS Workshop on Internet and WWW Measurement, Mapping and Modeling. February 13-15 2002. * Alberto Medina, Anukool Lakhina, Ibrahim Matta and John Byers. BRITE: An Approach to Universal Topology Generation. In Proceedings of MASCOTS 2001. IEEE Computer Society, IEEE Computer Society. August 2001. * Alberto Medina, Ibrahim Matta, and John Byers. On the Origin of Power Laws in Internet Topologies. ACM Computer Communications Review, April 2000. Also BU-CS-TR-2000-004. January 21, 2000. * Alberto Medina, Anukool Lakhina, Ibrahim Matta and John Byers. BRITE: Universal Topology Generation from a User's Perspective. BU-CS-TR-2001-003. April 05, 2001. * Alberto Medina and Ibrahim Matta. BRITE: A Flexible Generator of Internet Topologies. BU-CS-TR-2000-005. January 21, 2000. SOFTWARE ======== 1. BRITE: Boston University Representative Internet Topology Generator Overview: Effective engineering of the Internet is predicated upon a detailed understanding of issues such as the large-scale structure of its underlying physical topology, the manner in which it evolves over time, and the way in which its constituent components contribute to its overall function. Unfortunately, developing a deep understanding of these issues has proven to be a challenging task, since it in turn involves solving difficult problems such as mapping the actual topology, characterizing it, and developing models that capture its emergent behavior. Consequently, even though there are a number of topology models, it is an open question as to how representative the topologies they generate are of the actual Internet. Our goal is to produce a topology generation framework which improves the state of the art and is based on design principles which include representativeness, inclusiveness, and interoperability. Representativeness leads to synthetic topologies that accurately reflect many aspects of the actual Internet topology (e.g. hierarchical structure, degree distribution, etc.). Inclusiveness combines the strengths of as many generation models as possible in a single generation tool. Interoperability provides interfaces to widely-used simulation applications such as ns, SSF and OmNet++ as well as visualization applications. We call such a tool a universal topology generator. As part of my Ph.D. research at Boston University, I co-authored a topology generator called BRITE which aimed at satisfying the described design goals. Information about BRITE can be found at http://www.cs.bu.edu/brite. 2. TBIT: TCP Behavior Inference Tool Overview: TBIT is a software tool written in C which has the aim of inferring server and network behavior for actual hosts in the Internet. TBIT uses an active but non-hostile, not-intrusive approach to gather the required information. This is achieved by acting as a fully-compliant web client with added components to exert control on important aspects of the communications taking place such as packet losses and generation of ICMP packets. The development of TBIT was started by Stephan Savage at the University of Washington, and continued by Jitendra Padhye at ICIR. As a part of my postdoctoral research at ICIR, I have continued the deployment of TBIT by extending its core to support IP options, emission of ICMP packets, and adding new components to test specific server and network behaviors. REFERENCES ========== 1. Ibrahim Matta. Associate Professor. Computer Science Department at Boston University. [email: matta@cs.bu.edu] 2. Nina Taft. Intel Research at Berkeley. [email: nina.taft@intel.com] 3. Sally Floyd. ICSI Center for Internet Research (ICIR) [email: floyd@icir.org] 4. Mark Allman. ICSI Center for Internet Research (ICIR) [email: mallman@icir.org] 5. Prof. Mark Crovella. Associate Professor. Computer Science Department at Boston University. [email: crovella@cs.bu.edu] 6. Prof. John Byers. Assistant Professor. Computer Science Department at Boston University. [email: byers@cs.bu.edu]