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Current Projects:

Architecting Latency Sensitive Applications for the Cloud:

Cloud computing offers IT organizations the ability to create geo-distributed, and highly scalable applications while providing attractive cost-saving advantages. Yet, architecting, configuring, and adapting cloud applications to meet their stringent performance requirements is a challenge given the rich set of configuration options, shared multi-tenant nature of cloud platforms, and dynamics resulting from activities such as planned maintenance. A unique area of focus of our research is interactive multi-tier applications (e.g., enterprise applications, web applications) which have received limited attention from the community. We are developing novel methodologies, and systems that can enable application architects to (1) judiciously architect their applications across multiplecloud data-centers while considering application performance requirements, cost saving objectives, and cloud pricing schemes guided by performance and cost models of cloud components such as key-value datastores; (2) create applications that can adapt to ongoing dynamics in cloud environments through transaction reassignment over shorter time-scales. Our research if successful can enable IT organizations to significantly reduce costs by optimally moving their operations to the cloud. We are also working on creating benchmarks based on operationally deployed applications and collecting workload traces which will be made available to the research community.

Towards Automated and Assurable Enterprise Network Migration:

Enterprise network operators must frequently change the design of their networks to reflect new organizational needs (e.g., company mergers). Redesigning enterprise networks is challenging given theneed to change hundreds of interdependent low-level configurations. Configuration errors can have catastrophic consequences (e.g., large-scale network outages). The project is investigating systematic frameworks to help operators redesign their networks to meet desired high-level objectives. Optimization problems are formulated that trade-off the benefits of a redesign task with the reconfiguration costs involved. Algorithms for the redesign tasks are derived by exploring synergies with theoretical work in the operations research community. We are devising ways to map high-level network design to low-level configuration complexity metrics, and investigating algorithms to minimize the complexity of network designs. The techniques are being applied to important and unexplored problem domains such as migrating security policies from enterprise data centers to a cloud computing model, reorganizing routing designs on mergers, and service differentiation policies. The research if successful will change how operators manage their networks, leading to large cost-savings for IT organizations, and the creation of more reliable and secure networks. The research will foster innovation by lowering the risks in migration to new enterprise network architectures such as cloud computing and clean-slate architectures such as those based on Software-Defined Networks.

Past Projects:

Dissecting State-of-the-Art Video Distribution Networks:

We are conducting a detailed study of the YouTube CDN with a view to understanding the policies used to determine which data centers users download video from. Our analysis is conducted using unique week-long datasets simultaneously collected from the edge of five networks - two university campuses and three ISP networks - located in three different countries. Our analysis employs state-of-the-art delay-based geolocation techniques to find the geographical location of YouTube servers. Our results indicate that the RTT between users and data centers plays a prominent role in the video server selection process. More interestingly however, our results reveal a variety of factors besides RTT can influence server selection including load-balancing, diurnal effects, DNS misconfiguration, limited availability of rarely accessed video, and the need to alleviate hot-spots that may arise due to popular video content.


Trustworthy Peer-to-Peer Networks:

Peer-to-peer systems are rapidly maturing from being narrowly associated with copyright violations, to a technology that offers tremendous potential to deploy new services over the Internet. In many ways, peer-to-peer systems are beginning to herald a paradigm shift in this decade, in much the same way as HTTP in the 1990's. In this project, we are studying challenges in designing peer-to-peer systems in a safe, secure and robust manner, and considering new issues to Internet management due to the proliferation of peer-to-peer systems.

We are currently working in three areas of peer-to-peer systems design. (i) feasibility of generating DDoS attacks using widely deployed peer-to-peer applications and establishing design principles that could make these systems robust against such vulnerabilities, (ii) design and deployment of a monitoring system for automatic detection of malicious users in peer-to-peer applications; and (iii) enabling data confidentiality in an overlay broadcasting system. More..


Heterogeneity and Incentives for Peer-to-Peer Video Broadcasting

We propose the design of bandwidth-demanding broadcasting applications using overlays in environments characterized by hosts with limited and asymmetric bandwidth, and significant heterogeneity in outgoing bandwidth. Such environments are critical to consider to extend the applicability of overlay multicast to mainstream Internet environments where insufficient bandwidth exists to support all hosts, but have not received adequate attention from the research community. We leverage the multi-tree framework and design heuristics to enable it to consider host contribution and operate in bandwidth-scarce environments. Our extensions seek to simultaneously achieve good utilization of system resources, performance to hosts commensurate to their contributions, and consistent performance. We have implemented the system and conducted an Internet evaluation on PlanetLab using real traces from previous operational deployments of an overlay broadcasting system. More..


Abstractions for Enterprise Network Management

Our focus is on the management of enterprise networks.  Despite their critical importance, and their striking differences and diversity compared to carrier networks, enterprise networks have been largely unexplored by networking researchers. We envision a three-pronged research process that involves:
(i) capturing the goals operators have for their networks, through interactions with operators, and "bottom-up'' studies of actual network designs, (ii) elevating the design patterns we observe into abstractions; and (iii) demonstrating that abstractions can simplify both top-down network design, and validation of network properties.

A distinguishing feature of this research is its "white-box'' methodology to studying network designs. Rather than infer network characteristics with limited support from network operators as is common practice today, we will capitalize on our extensive ties with real network operators, and conduct studies using data such as router configuration files obtained with their support, and iterative interactions with them.

We are currently designing abstractions in two areas that are critically important, and widely prevalent in enterprises. (i) use of virtualization, in particular VLANs, to simplify management goals; and (ii) network evolution through planned maintenance. More..

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