Ware Receives 2025 SIGCOMM Doctoral Dissertation Award

Monday, September 15, 2025 - by Aaron Aupperlee

CSD Ph.D. alum Ranysha (Ray) Ware was awarded the 2025 SIGCOMM Doctoral Dissertation Award.

Ranysha (Ray) Ware, who earned her Ph.D. from Carnegie Mellon University's Computer Science Department (CSD) in 2024 and is a first-year assistant professor at Swarthmore College, received the 2025 SIGCOMM Doctoral Dissertation Award at the ACM SIGCOMM conference in Coimbra, Portugal.

The award is the highest honor given to a dissertation in the field of computer networking worldwide. Ware’s dissertation focused on how fairly internet services share bandwidth.

“If you think of an internet connection like a pipe full of water, bandwidth is how wide the pipe is. The wider the pipe, the faster water can pass through it. Similarly, the more bandwidth a link has, the more quickly data can pass through it,” said Justine Sherry, an associate professor in CSD and Ware’s thesis co-adviser.

Because no one explicitly tells service providers how fast to send data, operators discover the available bandwidth using congestion control algorithms (CCAs). When multiple users share an internet connection, CCAs ultimately determine how bandwidth is shared between competing services, like Netflix and Google. If one service is too aggressive while another is too passive, one service performs well — by providing high-definition video, for example — while the other suffers and shows low-quality video.

Ware’s work sparked headlines in the popular press when she discovered that Google’s CCA, called BBR, was mathematically and provably unfair to other algorithms. Google, surprised by the discovery, quickly patched the problem and funded the next chapter of Ware’s work.

“Ray’s thesis has shown that the interactions between modern congestion control algorithms are poorly understood, and even the metrics and methodologies for measuring their interactions or fairness are not well defined,” said Srini Seshan, the head of CSD and a thesis co-adviser.

Following the discovery of BBR’s unfair interactions, Ware went on to argue that perfect fairness was a practically impossible goal and instead laid out new criteria for reasoning about whether CCAs should be considered acceptable for internet deployment.

“In a nutshell, she argued that new CCAs should be considered OK so long as they aren’t any more unfair than the CCAs that were already out there on the internet,” said Sherry. “It was a radically more pragmatic approach to thinking about CCA deployment than what we had previously seen in the literature.”

Ware's argument went on to receive the 2019 IRTF Applied Networking Research Prize, an honor bestowed by the research arm of the Internet Engineering Task Force (IETF), which governs how the Internet Protocol works. Ware presented at the global IETF meeting in 2020.

Jim Kurose, professor of computer networking at the University of Massachusetts, Amherst, and author of one of the most widely used networking textbooks worldwide, was one of Ware’s nominators for the dissertation award.

"CCAs are arguably the most fundamental control algorithms in all of networking. CCA fairness has been a concern for more than 25 years. Ray’s deep analysis of BBR fairness and her formulation of CCA classification in a time-series framework are tremendously insightful new ways to look at these important problems," Kurose said.

Learn more about Ware’s work and read her dissertation on her website.