Fiber DocsHow Fiber Network Works
Fiber Network uses payment channels to move frequent transfers off-chain while using CKB for settlement and enforcement. Participants lock assets on-chain when opening a channel, exchange signed state updates directly while the channel is active, and return to Layer 1 when closing or disputing the channel.
This page explains the core mechanisms behind Fiber: payment channels, multi-hop routing, and the difference between off-chain transfers and on-chain settlement.
Payment Channels
A payment channel is a direct relationship between two participants. To open a channel, both participants lock assets into a shared on-chain Script. This funding transaction defines the initial state of the channel.
After the channel is opened, participants can start exchanging payments off-chain. Instead of sending every payment to Layer 1, they keep track of the latest balance between themselves and only submit the final result when the channel is closed.
When both participants agree to close the channel, the latest mutually signed state is submitted on-chain for settlement. If one participant attempts to close with an outdated state, the on-chain Script enforces the dispute rules and allows the counterparty to challenge it.
The simulator below illustrates the lifecycle of a payment channel.
Note: For visual clarity, this demo allows up to 7 channels between Node 1 and Node 2. In practice, multiple channels can exist between the same pair of nodes.
Use the simulator to observe the channel lifecycle:
- Select Node 1 and Node 2.
- Click "Open Channel" to simulate a Layer 1 funding transaction.
- Send off-chain updates and observe the Layer 2 transaction count.
- Select a channel and click "Close Channel" to simulate Layer 1 settlement.
Multi-Hop Routing
While a payment channel enables transfers between two participants, Fiber operates as a network of interconnected channels. A direct channel between sender and receiver is not required; if a path with sufficient liquidity exists, a payment can be forwarded through intermediate participants.
For example, Alice does not need a direct channel with Carol. If Alice has a channel with Bob, and Bob has a channel with Carol, Bob can forward the payment as an intermediate node.
In a multi-hop payment, each intermediary forwards a conditional transfer to the next hop along the route. These transfers are locked under cryptographic conditions and can only be claimed if a required secret is revealed within a defined time window. This ensures that all hops along the path either complete successfully or are safely reverted.
Only the nodes involved in the selected path participate in the transaction, and no network-wide consensus is required. Payments therefore traverse the network off-chain while remaining cryptographically enforceable.
The simulator below demonstrates multi-hop routing. By clicking "Trigger Sample Transaction," you can observe a transaction being forwarded across intermediate nodes without interacting with Layer 1.
Interactive Network Simulation
This simulator combines the previous concepts in one view. You can open and close channels, trigger routed payments, and observe when activity happens off-chain versus when it requires Layer 1 settlement.
Note: For visual clarity, this demo displays only one channel between two nodes. In practice, multiple channels can exist between the same pair of nodes.
Experiment by:
- Opening channels between unconnected nodes
- Triggering transactions across connected paths
- Closing channels and observing Layer 1 settlement
Notice that:
- Layer 2 transaction count increases during off-chain transfers.
- Layer 1 operations change only when channels are opened or closed.