Active Projects

• Data consistency in DHTs
• A DHT (Distributed Hash Table) is distributed key-value storage system. Although DHTs have been thoroughly researched, they are in dire need of applications. One of the reasons for this is their typically abysmal performance, loose consistency and lack of availability guarantees. This project aims to design and implement a DHT that has strict data consistency guarantees. This project is an evolution of prior work by the systems community on improving performance of DHTs, and prior work by the theory of distributed systems community on the efficiency of distributed consistency algorithms such as Paxos and its variants.


• SatelliteLab
• This project is based at the Max Planck Institute for Software Systems and is part of my Summer 2007 internship work with Krishna P. Gummadi. The goal of SatelliteLab (SatLab) is to design and implement a system that improves the heterogeneity of existing internet testbeds (e.g. PlanetLab, RON) by including internet edge-nodes. Nodes located in edge-networks (e.g. residential networks) are typically unreliable, cover a wide range of software and hardware configurations, and have widely varying network connectivity characteristics. These dimensions of heterogeneity are especially important for accurately testing distributed system prototypes. Today such prototypes are developed in highly homogeneous testbed environments that hinder their readiness for realistic deployment. SatLab makes it easier to evaluate, debug, and explain the observed performance of distributed systems in the wild.


• Governance in Wikipedia
• I am also interested in analysis of social networks. This includes both quantitative analysis (e.g. member graph structures, activity patterns) as well as qualitative analysis (e.g. intensive study of activity samples, interviews). I am nourishing this interest by studying Wikipedia's policy mechanism and the interactions between wikipedia editors on discussion pages as they employ policies to arrive at consensus and make progress in their work.

Past Projects

• VFER
• VFER is a congestion controlled transport protocol that enables client applications to define a 'functional' level of reliability with a callback reliability function. VFER has a delay-based congestion control scheme that attempts to achieve the theoretical optimum by monitoring delay variations and applying control theory to packet spacing. VFER is an experimental protocol that aims to be TCP-friendly and robust in heterogeneous network latency environments. At the moment, VFER has a C library implementation and a reliable file transfer scp-like test application. This project was initially brainstormed with Matei Ripeanu, before becoming a Google Summer of Code 2005 implementation project at Internet2 with Stanislav Shalunov as my mentor. It continued as an internship with the transport group at Internet2 and received three new students under the Google Summer of Code 2006 program, one of whom was mentored by me.
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  SPRUCE (Special PRiority and Urgent Computing Environment)
• Modeling and simulation using high-performance computing are playing an increasingly important role in decision making and prediction. For time-critical emergency decision support applications, such as influenza modeling and severe weather prediction, late results may be useless. A specialized infrastructure is needed to provide computational resources quickly. SPRUCE, is a system for supporting urgent computing on both traditional supercomputers and distributed computing Grids. Currently deployed on the TeraGrid, SPRUCE provides users with ``right-of-way'' tokens that can be activated from a Web-based portal in the event of an urgent computing need. Tokens are transferrable and can be restricted to specific resource sets and priority levels. Once a session is activated, job submissions may request elevated priority. Based on local policy, computing resources can respond, for example, by preempting active jobs or raising the job's priority in the queue.


• ZeptoOS
• A Linux distribution effort for petascale cluster Operating Systems centered at Argonne National Labs. Currently deployed on the Compute and IO nodes of Argonne's BG\L machine, it is a massive undertaking that resulted in a GPLed codebase and promises to become a mainstream distribution for future IBM's BlueGene family clusters. My involvement with this project has been work done during the summer 2005 internship at ANL on ZOID, the ZeptoOS IO Daemon. The ZOID codebase I developed emulates the IO\Compute node syscall redirection on x86 clusters.
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  Wireless Sensor Networks at ANL
• This effort started with a couple of classes at UChicago, and escalated into a ANL building 221 sensor-net over my summer 2005 internship at ANL. The network is two stargates with hallway mounted MicaZ motes, all running the fantastic TinyOS.

Publications

Presentations