Minlan Yu will present her preFPO on Wednesday November 24 at 9AM in Room 402. The members of her committee are: Jennifer Rexford, advisor; Mike Freedman and Albert Greenberg (Microsoft), readers; Vivek Pai and Ed Felten, nonreaders. Everyone is invited to attend her talk. Her abstract follows below. ---------------------------------- Title: Supporting Flexible Policies in Large Enterprise and Data-Center Networks Abstract: Enterprise and data center networks are growing larger and becoming more complicated to manage. These networks consist of two layers: the management layer that defines routing, enforces high-level policies, and diagnoses performance problems; the data plane that forwards packets, applies fine-grained rules, and monitors traffic. To make management layer simpler and easier to operate, people have proposed flat addressing to support host mobility, shortest-path routing to improve performance, and flow-based switches to enable fine-grained policies. However, these techniques raise scalability challenges in the data plane with many hosts, switches, flow rules, and applications, forcing the use of expensive switches with large, power-hungry memory for processing and monitoring data packets. This thesis proposes a new scalable data plane for enterprises and data centers. We improve the scalability of enterprise networks through a combination of new data structures that make effective use of limited memory, traffic indirection that minimizes the state required at each switch, and end-host based monitoring to reduce the overhead at switches. Our proposed system consists of three parts: (i) BUFFALO: A scalable packet forwarding architecture that uses Bloom filters to reduce the switch memory usage, and gracefully handles false positives by sending packets through a slightly longer path. (ii) DIFANE: A distributed management architecture that leverages emerging flow-based switches to scalably forward packets based on policies. (iii) SNAP: A network performance diagnosis architecture for data center applications that passively logs traffic statistics in the end-host network stack and pinpoint problems that occur at the network device, network stack and the application software. BUFFALO and DIFANE can be easily implemented with small modifications in today's switches, as demonstrated by our prototypes built using the Click modular router. SNAP was deployed in a large data center networks and helped operators and developers to pinpoint performance problems.