Understand how the internet actually works
Interactive protocol simulators built from the ground up — every behaviour traced to the open-source implementations that run the real internet.
Running at default parameters. Open the simulator to drive it yourself.
You know what TCP is. You've read the RFC. But when a 2% packet loss rate collapses HTTP/2 throughput on all streams simultaneously, it takes hours to debug because the failure looks like an application problem. zerohop builds the mental model that lets you trace the cascade before you open the ticket.
See parameters change in real time
Drag a slider and watch the simulation respond instantly — packet loss, RTT, window size, hold timers. No replays, no canned scenarios.
Watch the cascade across layers
A server-side correlation engine computes how one component's state ripples into the next, so you see the failure propagate — not just the symptom.
Build judgment with katas
Predict the outcome, observe what actually happens, then reflect on the gap. Repetition turns protocol facts into debugging instinct.
Available modules
TCP Connection Lifecycle
net/ipv4/tcp_input.c
BGP Session Lifecycle
bgpd/bgp_fsm.c
Validated against:
- Linux kernel 6.x
- FRRouting bgpd
- BoringSSL
- Chromium Blink