SWAN: Software-driven wide area network


July 30, 2013


Ratul Mahajan


Microsoft Research


I will describe SWAN, a system that boosts the utilization of inter-datacenter networks beyond 95%, by centrally controlling when and how much traffic each service sends and frequently re-configuring the network’s data plane to match current traffic demand. Done simplistically, network reconfigurations can also cause severe, transient congestion because different switches may apply updates at different times. We develop a new technique that leverages a small amount of scratch capacity on links to apply updates in a provably congestion-free manner, without making any assumptions about the order and timing of updates at individual switches. Further, to scale to large networks in the face of limited forwarding table capacity, SWAN greedily selects a small set of entries that can best satisfy current demand. It updates this set without disrupting traffic by leveraging a small amount of scratch capacity in forwarding tables. Experiments using a prototype and simulations of two production networks show that SWAN carries 60% more traffic than the current practice.


Ratul Mahajan

Ratul Mahajan is a Senior Researcher at Microsoft Research and an Affiliate Professor at the University of Washington. His research interests include all aspects of networked systems. His current work focuses on smart home technologies, software-defined networks, and network verification, and his past work spans Internet routing and measurements, incentive-compatible protocol design, and wireless and vehicular networks. He has published over 30 papers in top-tier venues such as SIGCOMM, SOSP, MobiSys, and CHI. He is a winner of the ACM SIGCOMM Rising Star award, the William R. Bennett prize, the SIGCOMM best paper award, and Microsoft Research Graduate Fellowship.