Justine Sherry's Homepage

I am a Computer Science graduate student in the PhD program at UC Berkeley. My advisor is Sylvia Ratnasamy, and my research interests are primarily in computer networks. I received my Master's from Berkeley in December 2012; my thesis focused on new deployment models for middleboxes.


I'm interested in big networking questions surrounding middleboxes, Internet-scale systems, measurement, Internet architecture, and cloud computing. Some of my past and current projects are below; a full list of my work is on my CV.

Making Middleboxes Someone Else's Problem

In a study of 57 enterprise networks, we found that middleboxes like firewalls and caches are expensive, failure-prone, and difficult to manage. To resolve these challenges, we built APLOMB, a service which allows enterprises to ditch their middleboxes entirely. With APLOMB, cloud providers offer middleboxes as a "service" to enterprise clients who tunnel their traffic to a nearby datacenter to receive security and performance processing services.

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Recursively Cautious Congestion Control

At startup, congestion control algorithms must carefully balance the desire to send aggressively -- making best use of available resources -- and to send cautiously -- in order to avoid congestion, heavy packet loss, and unfairness. TCP slow start takes the cautious route, sending only 4-10 packets in the first round trip time, and only slowly ramping up the sending rate from there. We propose RC3, which allows senders to send aggressively without the threat of heavy congestion or unfairness. RC3 `keeps the pipe full' from the very first RTT, sending additional traffic (beyond what TCP might send) at strictly lower priorities than normal traffic. We find that RC3 improves flow completion times in the wide area by 40-80%.

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Services like firewalling, protocol acceleration, and caching are widely available today through the deployment of middleboxes. However, these capabilities are not exposed to end host applications through the `interface' the network exposes to them. We designed netcalls to allow end hosts to invoke and configure the advanced capabilities offered in any network their traffic traverses; for example, we built a web server which invokes inter-domain DDoS defense when it detects it is under attack.

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Internet Measurements with IP Timestamps

IP timestamps are a little-known feature of every packet that traverses the Internet, allowing a client to request a simple timestamp from any router which handles the packet. We showed that IP timestamps are supported by a substantial fraction of routers on the Internet -- about 30% -- and that IP timestamps can be used for a number of useful measurements: measuring parts of the reverse path a packet takes from server to client, identifying when two IP addresses belong to the same router, and measuring course-grained link latencies.

Reverse Traceroute
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IP Aliases
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Bachelor's Thesis
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