Select a calendar:
Filter September Events by Event Type:
SUNMONTUEWEDTHUFRISAT
University Calendar
Events for September
-
PhD Defense - Tobias Flach
Thu, Sep 08, 2016 @ 11:00 AM - 01:00 PM
Thomas Lord Department of Computer Science
University Calendar
Title: Detecting and Mitigating Root Causes for Slow Web Transfers
Time: Sept 8 (Thursday), 11am - 1pm
Location: EEB 248
PhD Candidate: Tobias Flach
Committee:
Ramesh Govindan
Ethan Katz-Bassett
John Heidemann
Konstantinos Psounis
Abstract:
One of the key goals for Web service providers is the quick delivery of their content to customers.
Minimizing the latency between a user's service request and the delivery of the corresponding content is of paramount importance for Web services like search, shopping, or video streaming. This is motivated by the fact that users have a low tolerance for delays. Past studies verified a link between increasing latency for content delivery and corresponding reductions in user engagement and provider revenue. As a result content providers go to great lengths to minimize latency by improving their infrastructure, communication protocols, and proximity to the users. However, end-to-end latency can still suffer from other network limitations, some of which have their root causes outside of a content provider's control domain.
In this thesis we strive to get a better understanding of the performance-limiting factors that affect Web transfers. In addition we explore techniques to mitigate these factors. For this we conducted multiple measurement studies dissecting Web transfers from different angles to find and analyze the root causes for poor performance.
First, we present two measurement studies investigating how the Transmission Control Protocol (TCP) can introduce delays that adversely affect Web transfers. We use large-scale measurements that we obtained at Google frontends across the globe as well as through the widely distributed M-Lab measurement platform for this task. We start by evaluating how packet loss affects Google's content delivery and show that especially short-lived connections suffer from packet loss in the network. We then discuss the design, deployment, and evaluation of algorithms tailored reduce the frequency and impact of the costly losses.
As a follow-up we present a methodology to break down the delay incurred by a packet into components attributable to propagation delay and cross-traffic, loss recovery, and queuing. Moreover we investigate the degree to which queuing delays slow TCP's loss recovery. We find that many of the flows see packet delivery times of one second or more, with large regional differences, and with queuing being a key cause of delay.
Second, we take a look at structural limitations affecting Web latency. Specifically we analyze the impact of path inflation in mobile carriers where traffic between content providers and mobile customers is taking geographically circuitous routes. We attribute these pathologies to root causes like a lack of ingress points between a carrier's network and the wider Internet as well as limited peering arrangements with content providers. Based on longitudinal data we show that performance in some carriers improved over time with other regions continuing to suffer from path inflation.
Third, we look at a particular type of third-party interference as a contributor to delay. We analyze the prevalence and impact of traffic policing, a traffic management technique used to enforce pre-configured throughput limits on connections by dropping excess packets. Based on global-scale measurements taken at Google frontends we show that a substantial number of connections with packet loss are affected by policing. Moreover we demonstrate that policing negatively impacts user quality of experience. We conclude by designing and testing solutions for content providers and the policing ISPs to mitigate the negative effects of policers.
Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248
Audiences: Everyone Is Invited
Contact: Lizsl De Leon
-
ASBME BIOMED: Research Symposium
Thu, Sep 08, 2016 @ 05:30 PM - 08:30 PM
Viterbi School of Engineering Student Organizations
University Calendar
BIOMED is a beginning-of-the-year dinner meant to introduce incoming and current students of any background to medical issues that face our world today. This semi-formal event invites faculty and PhD students in the USC Department of Biomedical Engineering who will discuss their experiences in the field to students and also provide an opportunity for students to become better acquainted with their peers, faculty, and staff at USC. BIOMED will be taking place Thursday, September 8th in TCC 227. Dr. Ellis Meng will be the keynote speaker. Deposits of $10 are due to the front desk of DRB Wednesday, September 7th.
Location: Ronald Tutor Campus Center (TCC) - 227
Audiences: Everyone Is Invited
Contact: Associated Students of Biomedical Engineering
-
W.V.T. Rusch Engineering Honors Program Colloquium
Fri, Sep 09, 2016 @ 01:00 PM - 01:50 PM
Viterbi School of Engineering Student Affairs
University Calendar
Join us for a presentation by Professor. Omer Tamuz, Assistant Professor of Economics and Math, Caltech, Division of Humanities and Social Sciences titled "Aggregation of Information in Social Networks".
Location: Henry Salvatori Computer Science Center (SAL) - 101
Audiences: Everyone Is Invited
Contact: Julie Phaneuf
-
W.V.T. Rusch Engineering Honors Program Colloquium
Fri, Sep 23, 2016 @ 01:00 PM - 01:50 PM
USC Viterbi School of Engineering
University Calendar
Join us for a presentation by Professor Ellen Rothenberg, Professor of Biology, Cal Tech, Kerckhoff Library, titled "Design, Execution and the Control of a Program to Generate T-Cell Identity".
Location: Henry Salvatori Computer Science Center (SAL) - 101
Audiences: Everyone Is Invited
Contact: Julie Phaneuf
