More explicit "intro to networking" content

[illicitonion]

We should probably introduce:

• DNS
• IP addresses
• TCP / UDP, trade-offs between, shape of a TCP handshake
• HTTP
• The idea these packets are encapsulated in each other
• Why DNS is (typically) over UDP
• Importance/Difficulties in reducing round-trips (e.g. a simplified evolution from HTTP1-over-TCP to QUIC)

In particular, we should do this before we have people think about load balanceres.