We covered quite a bit in Season 1. For some "Go Deeper" resource suggestions for each topic, check the notes below.

Episode 1: How email travels

Episode 2: OSI model. Internet

Network Engineer Specialization: https://www.coursera.org/specializations/computer-communications
1. The first course is relevant here: https://www.coursera.org/learn/fundamentals-network-communications?specialization=computer-communications
2. GeeksforGeeks article: Layers of OSI Model - GeeksforGeeks
3. Cloudflare: What is the OSI Model? | Cloudflare
Youtube Series: Network Fundamentals by Network Direction channel: https://www.youtube.com/watch?v=cNwEVYkx2Kk&list=PLDQaRcbiSnqF5U8ffMgZzS7fq1rHUI3Q8
Computer Networking book

Episode 3 & 4; Interview with Marwan Fayed (Cloudflare)

Episode 5: TCP/IP

Episodes 6 & 7: Interview with Aaron Blum and Raphael Poss (Cockroach Labs)

Welcome to Data & Dev with Jon and Mel