Show HN: I'm writing a free book called Computer Networks from Scratch

Thank you! Glad I didn't give up on the doodles (they take a lot longer than you'd think).

I feel like walkie talkies are something all network engineers need to play with. Furthermore, remember that real world telephone and radio networks were in fact... Networks. (Called 'nets' in the radio world)

Ethernet, and 802.11, are both based on the concept of a singular channel shared by many individuals. When Alice talks, she says 'I'm Alice calling Bob, can you hear me Over'.

Alice is the source address. Bob is the destination address. Over is the stop code/stop bit signifying the end of frame. The payload is 'can you hear me'.

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This is everything up to layer 3. But if you wanted to send a radio/telegram across the country, you need one more layer, IP4 or the ARRL protocol (American Radio Relay League meets on the air at predestinated times to pass messages to each other on Ham radio frequencies. It's a human network)

I'm Alice, calling the Eastern Operators. I'd like you to relay a message to Bob for me. The message is 'Can you Hear me', Over.

This is a radio frame like all others, but an additional layer has been added. The radio operator has its own protocol built on top of the Frames.

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Dave may overhear all of this chatter, but Dave knows to stay off the channel (otherwise he will cause interference). Only if Dave is addressed specifically would Dave respond (Ex: This is Alice, calling Dave. How are you doing? Over)

We can see that the operator is itself just another person on the network. The operator may have a message from the rest of the world.

This is the Eastern Operator calling Alice. I'm relaying a message from Bob. The message is 'I got your message Alice!'. Over.

This is how a router may take a message from the greater internet and pass it to your local network.

A classic, but I'm biased because my fav undergrad prof used it.

That’s a great summary! Thanks for taking the time to write it up.