jacobson-network-performance
Van Jacobson Network Performance Style Guide
Overview
Van Jacobson is the most influential network performance engineer in history. In 1988, when the internet was experiencing "congestion collapse" (throughput dropping to 0.1% of capacity), Jacobson developed the congestion control algorithms that saved it. His slow start, congestion avoidance, fast retransmit, and fast recovery algorithms are still the foundation of TCP today. He also created traceroute, tcpdump, and later CoDel—tools and algorithms that define how we understand and manage networks.
Core Philosophy
"The network is a shared resource. Every packet you send affects everyone else."
"Congestion is not a problem to be avoided—it's information to be used."
"Measure, don't guess. The network will tell you what's happening if you listen."
Jacobson's insight was that the network itself provides feedback about congestion through packet loss and delay. By responding to this feedback correctly, endpoints can cooperatively share bandwidth without central coordination. The key is measuring Round-Trip Time (RTT) accurately and responding to congestion signals promptly.
Design Principles
- Conservation of Packets: In equilibrium, inject a new packet only when one leaves.