The Connext protocol is composed of a set of smart contracts and offchain agents.
Connext's smart contracts are the interfaces between the protocol and the wide gamut of different users in the ecosystem. There are contracts for handling
xcall, managing asset registration, and provisioning liquidity for routers and stableswap LPs.
The full contract stack consists of the following components.
Dispatches and handles messages related to sending funds across chains. Custodies funds for canonical assets, fast liquidity, and stable swaps.
Manages asset enrollment, stores mappings of adopted <-> local assets, exposes liquidity caps functions, and specifies stableswaps for assets.
xcalland enables destination-side calldata execution.
Holds all the functionality needed for Connext's messaging layer to reconcile cross-chain transfers.
Provides a basic access control mechanism.
Manages whitelisting of relayers.
Manages whitelisting of routers and keeps track of router owners/recipients.
A StableSwap implementation that custodies closely pegged assets (eg. group of stablecoins).
Manages only-admin controls for the StableSwapFacet.
Functions for adding, removing, and replacing facets.
Required by the Diamond standard. Implements the DiamondLoupe interface which allows for inspection of a Diamond contract's various facets and their functions.
The various contracts required to manage merkle roots containing hashed transfer data and send them through a hub-and-spoke architecture. The messaging architecture includes:
- Connector. A connector is an abstraction around an underlying transport layer. The
IConnectorinterface requires a
processMessagemethod implemented for handling incoming messages.
Connectoris an abstract contract that is inherited by the following contracts:
- SpokeConnector. The
SpokeConnectoris deployed on spoke domains and implements a
sendmethod to send the Merkle root of all the messages that originate from the spoke domain to the hub domain. For example,
ArbitrumSpokeConnectoris deployed on the Arbitrum L2.
- HubConnector. The
HubConnectoris deployed on hub domains for each spoke and implements a
sendMessagemethod to send the aggregated Merkle root of all the received spoke Merkle roots to the configured destination domain. For example
ArbitrumHubConnectoris deployed on Ethereum L1.
Each AMB implementation requires us to create and deploy
SpokeConnectorcontracts for that flavor of AMB, calling into the internal bridge infrastructure.
Routers are liquidity providers that enable instant liquidity for the user on the destination chain in return for a fee. Anybody can participate in the protocol as a router and there is no minimum liquidity required! Routers provide a crucial service to the Connext protocol.
The sequencer collects bids from all chains and randomly selects router(s) to fulfill them. Any number of routers can fulfill a single transaction, which is especially useful for large transfers. The sequencer will post batches of these bids to a relayer network to submit them to chain.
Relayers are a decentralized network of infrastructure operators that can execute smart contract transactions on behalf of a user in exchange for a small fee. Because the last leg of a cross-chain transaction requires execution on the destination domain, relayers play an important role in completing the full flow.