Stills from the net

These images depict servers in a computer network.

Image 1: When a server opens a TCP connection, it sends a special message indicating the intention to connect. This message is called a “SYN” and is the first part of the three-way handshake. Home excercise: use three-way handshaking with real people.

Image 2: 192.168.0.1 is called an IP address, and describes a location the server is trying to connect to (or: reach). Computers will often indicate to users they “cannot reach” something. As a side note, this specific address often appears in private networks, and is likely an address of your router.

Image 3: Tunnelling is a system admin practice of estabishing a connection to one server, and then establishing a second connection through the first one to reach an otherwise unreachable destination.

Image 4: This is just a poetic approximation of what happens when a server sleeps. It’s entirely fictitious, as servers don’t sleep.

Image 5: TCP, ICMP, UDP and DNS are important communication protocols used on computer networks underlying the Internet. This image depicts a poor server with a disconnected network cable, unable to communicate. As a sidenote, the author was pretty lazy and inconsistently selected protocols from different OSI layers. If it bothers you, do send him a message, preferrably using UDP.