Ask HN: Favorite Networking Links? Help a TA

Hello HN! I will be TAing a course on Networking next semester, and my goal is to be able to complement each topic with some cool demonstration, application or article. Here is the course schedule: http://www-inst.cs.berkeley.edu/~cs168/fa15/ I've been mainly browsing HN for links, and here are some interesting ones I came across:

Passive TCP/IP Geo-Location - http://geoloc.foremski.pl/

DNS Enumeration - https://github.com/darkoperator/dnsrecon

"Why do we use the Linux kernel's TCP stack? - https://news.ycombinator.com/item?id=12021195

The History of the URL: Domain, Protocol, and Port - https://eager.io/blog/the-history-of-the-url-domain-and-protocol/

Levels of Abstraction: Net, Web, Graph - https://www.w3.org/DesignIssues/Abstractions.html

I'd love to see what cool things you all have found. Anything interactive is a big plus! (Also, there was this one site that talked about designing very efficient netcode for syncing two computers in this 3D visualizer with flying red cubes. I have unfortunately been unable to find it.)