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Stanford University Networking Seminar


Monia Ghobadi (Microsoft Research)
Programmable Topologies

11:00am, Thursday, May 25 2017
Gates 104

About the Talk

As cloud computing grows, network efficiency becomes imperative. In this talk, I will present two projects that provide efficiency by leveraging programmability in the optical layer. First, I will explain a radically different approach for building data center interconnects: using free-space optics between racks. Our design enables all rack-pairs to communicate via direct links. We use a digital micromirror device (DMD) and mirror assembly combination as a transmitter and a photodetector on top of the rack as a receiver. We built a prototype that points to the feasibility of our approach. Simulations and analysis show that, for realistic data center workloads, it can improve mean flow completion time by 30-95%, while reducing cost by 25-40%. Next, I will present the results of the first ever large scale study on performance of optical links in a backbone network carrying live traffic. Our data-driven analysis coupled with simulations showed that existing fiber deployment can be driven towards much greater efficiency by enabling programmable modulations. For example, 99% of Microsoft’s 100 Gbps channels can be augmented to 150 Gbps, by simply changing the modulation formats at the two ends without touching the fiber or intermediate amplifiers. Even better, 43% can double their capacity and carry up to 200 Gbps. This way, using the same fiber paths, we get more bits, less space, and less power. This project has moved the industry into adopting bandwidth variable transponders in the WAN.

About the Speaker

Monia Ghobadi is a researcher at Microsoft Research, Redmond, WA. Her research interests include all aspects of networked systems. Currently, she leads the optical networking research in Redmond lab. Her past work spans data center congestion control, RDMA, software-defined networks, and network measurement. She received her Ph.D. from the University of Toronto and worked at Google’s data center team before joining Microsoft Research. Many of the technologies that she has helped develop are part of real-world systems at Microsoft and Google. Her papers have won best dataset award (IMC’16), Google research excellent paper award (USENIX ATC’12), and best paper award (IMC’08). https://www.microsoft.com/en-us/research/people/mgh/