Ah, the good old days.

Remember in class, when I played you the noise that the old dial-up 14.4/28.8kbps (kilobits per second) modems would make whenever you called in to an ISP? Remember how I said it was the process of (most) of the 7 layers of the OSI – Open System Interconnect – model doing their thing? In case you missed it, here’s the video again so you can relive the glory days of old.

But I’ve done you one better! The image below, which is pretty big so you can zoom way in, shows you each step of the handshake that sets up the connection. For each noise that is made, this diagram explains exactly what’s going on.

It’s somewhat complicated, I know. Mapping what’s happening in the video of the sounds to the image above isn’t exactly intuitive. So I’ve done you one MORE better! The video below is the image above, but with the sound superimposed over it, and it shows exactly what is happening as each noise is heard over the modem. This makes everything much easier to understand, although it’s still a lot.

The reason I’m showing you this is that even though we don’t have to hear that infernal modem noise anymore, modems still work the same way, cable or dial-up. This will help give you an idea of how machines make connections and send packets across a network, the process is still the same.