Satadal Sengupta will present his Pre-FPO "Protocol-Aware Telemetry For In-Network Control" on June 11th, 2025 at 12:30pm in Friend 125 and Zoom. Committee: Jennifer Rexford (Advisor) Ravi Netravali (Examiner) Maria Apostolaki (Examiner, Princeton ECE) David Walker (Reader) Hyojoon Kim (Reader, University of Virginia CS) Zoom: https://princeton.zoom.us/j/2332835952?pwd=tYVB2ta8EI4aC3eX4biZCbu4VyYK0J.1 Abstract: The average Internet user consumes a staggering 4 GB of data per day in 2025, compared to just 1 MB per month in 1993 when the web went public. Yet, despite major improvements, the underlying infrastructure still does not guarantee performance or security, and is afflicted by issues such as packet loss, excessive latency, and suboptimal paths. To address these deficiencies, sophisticated network protocols have been developed: for example, TCP aims to provide reliable delivery of on-demand traffic, and WebRTC addresses timely delivery of interactive traffic—together accounting for over 80% of all Internet traffic. These protocols rely on the Border Gateway Protocol for policy-driven routing. Despite the effectiveness of these protocols, significant performance and security problems still persist. Among these problems, short‑lived or stealthy issues are particularly damaging because they often go undetected by traditional coarse‑grained (flow‑level or packet sampling-based) monitoring, yet cause disproportionate impacts on network performance and security. For example, nearly a quarter of business users of video-conferencing applications report lags during peak hours due to transient network congestion, and billions of dollars are lost yearly to stealthy hijacks of cryptocurrency services. Tackling these problems requires protocol‑aware methods to monitor and control the network in real time at a fine granularity (i.e., packet level). This is a challenging task at Internet scale. State-of-the-art networking hardware, such as programmable switches, is characterized by Tbps-scale speed and programmability, offering the only practical opportunity for fine‑grained, real‑time network visibility and control. However, their high speed comes at the cost of limited programmability in the form of stringent memory and computational constraints. This makes it challenging to analyze traffic governed by complex protocols since the hardware cannot retain complete protocol state under such tight resource constraints. In this dissertation, we address these challenges by developing efficient, hardware‑amenable techniques for real-time network monitoring and control. First, we measure a critical packet‑level metric—TCP round‑trip time (RTT)—to enable prompt detection and mitigation of stealthy long‑distance routing attacks. Second, we analyze popular, representative video‑conferencing applications, such as Zoom (proprietary) and MediaSoup (open‑source, WebRTC‑based), and extract detailed packet‑level performance metrics. Our insights drive the design of a scalable, hardware‑software co‑designed architecture for video‑conferencing, significantly improving performance and reducing operational costs compared to conventional software solutions. In summary, this work advances scalable, protocol‑aware techniques for network monitoring and control to enhance the performance and security of the Internet.