Bitcoin Universe · Model 17
The Lightning routing machine
A payment can reach someone you have no channel with by hopping through people who are connected. Each hop can only pass on what sits on its side of the channel, so a connected path is not always a working one.
What happened
Change a channel
Routes the sender can see
| # | Route | Hops | Fees | Sender pays |
|---|
The sender ranks routes by fee using public information (channels, capacities, fee policies). It cannot see the liquidity split, so the cheapest route may fail; it then learns which hop failed and tries the next one.
Educational simplifications. A fixed network of seven nodes with demonstration capacities, splits and fees. Fees are a base fee plus a proportional fee (parts per million) per forwarding hop, rounded down to whole satoshis; real nodes count millisatoshis and also set time-lock deltas, HTLC limits and reserves, which are left out. The sender knows the public graph but not the liquidity split and tries routes cheapest first; real implementations differ in path-finding, use probabilistic estimates and may split payments into parts. The onion encryption of the route (BOLT #4), which hides the whole path from each hop, is not drawn. The payment hash is a real SHA-256 of a demonstration preimage.