SubnetLayer
Learn networks, packet by packet.
Twelve protocols, taught as ideas first and then shown as traffic. Every lesson runs a deterministic, byte-accurate simulation you can pause, rewind, decode field by field, and export straight into Wireshark.
What a layer is. Why one machine has two different addresses. What /24 actually means. How a packet reaches a network nobody has heard of. Every module below assumes all of it — this page teaches it directly, with no captures to read. Tell it how much networking you already have and it will suggest where to start.
Five chapters, no packets →The order that works
Not a rule — every module stands alone, and each one names what it needs first. But this is the order that leaves the fewest gaps.
Protocols
See how they fit together →Finds the hardware address that owns an IP address on your own wire.
Start learning →Addresses and forwards packets across networks, with no promises about delivery.
Start learning →IP's way of reporting problems and testing whether a host is reachable.
Start learning →Ports and a checksum. Nothing else, on purpose.
Start learning →Turns unreliable packets into a reliable, ordered byte stream.
Start learning →Turns names people can remember into addresses machines can route to.
Start learning →Hands a machine its address, mask, gateway and resolver when it joins a network.
Start learning →Requests and responses carried over a TCP byte stream.
Start learning →Adds confidentiality, integrity and identity to a TCP connection.
Start learning →Not a separate protocol — HTTP inside TLS inside TCP inside IP inside Ethernet.
Start learning →Routers inside one organisation telling each other the shape of the network.
Start learning →How separate organisations exchange routes — the protocol that holds the internet together.
Start learning →