Balaji Prabhakar : 2011 Plenary Session


Tuesday, April 12, 2011
Location: Fisher Conference Center, Arrillaga Alumni Center

"Buffers: The Great Boon and Bane of Packet Switching"
3:00pm - 3:30pm


Packet switching technology has greatly boosted networking: it has enabled many heterogenous services on a common networking platform. It is the ability to buffer packets that makes packet switching possible and distinguishes it from circuit switching. However, every time we want to provide quality assurances, especially latency guarantees, we hanker for circuit switching and find packet buffers a huge nuisance.

Can packet switching be rid of buffers? At first glance, this appears impossible. Packet transport mechanisms (like TCP), and high-bandwidth switch schedulers rely on buffering. Even the hosts/NICs require buffers for CPU offloading.

We discuss a combination of techniques for getting rid of buffers from data center fabrics: new packet transport protocols (QCN and DCTCP), hardware packet pacing, and 'phantom queues' which create a "bandwidth headroom" by systematically under-running links. These techniques make it possible to build data center fabrics that are essentially free of queues using commodity equipment. As a result, fabric latency is reduced by a few orders of magnitude at the cost of a programmable amount of bandwidth.


Balaji Prabhakar is a faculty member in the Departments of Electrical Engineering and Computer Science at Stanford University. His research interests are in computer networks; notably, in designing algorithms for the Internet and for Data Centers. Recently, he has been interested in Societal Networks: networks vital for society's functioning, such as transportation, electricity and recycling systems. He has been involved in developing and deploying incentive mechanisms to move commuters to off-peak times so that congestion, fuel and pollution costs are reduced.

He has been a Terman Fellow at Stanford University and a Fellow of the Alfred P. Sloan Foundation. He has received the CAREER award from the U.S. National Science Foundation, the Erlang Prize, the Rollo Davidson Prize, and delivered the Lunteren Lectures. He is a co-recipient of several best paper awards.