> For the complete documentation index, see [llms.txt](https://docs.lighter.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lighter.xyz/evm/interop/message-passing.md).

# Message passing

The Lighter protocol supports message passing across all three of its domains.

[EVM and Core](/evm/interop/message-passing/evm-and-core.md) communicate through stateful write streams, one in each direction. These streams are [settled on L1](/evm/technical-architecture.md#batch-lifecycle-and-finalization) together with Core and EVM state, allowing the sequencer to fulfill cross-domain write requests without waiting for L1 finality.

Message passing between [L1 and Core](/evm/interop/message-passing/l1-and-core.md) and between [L1 and EVM](/evm/interop/message-passing/l1-and-evm.md) goes through the [`ZkLighter`](https://github.com/elliottech/lighter-contracts/blob/lighter-evm-devnet/contracts/ZkLighter.sol) bridge on L1. The bridge maintains a separate priority queue for messages sent from L1 to each domain. It also handles messages arriving on L1 from Core and EVM, called **L1 calls**.

A batch may contain many **L1 calls** generated by Core and EVM. Once such a batch has been [executed on L1](/evm/technical-architecture.md#batch-lifecycle-and-finalization), anyone can call the bridge to execute the included L1 calls. Batch execution makes the calls eligible but does not execute them itself.

Each **L1 Call** carries the following fields.

```solidity
struct L1Call {
    // Sender on the originating domain, authenticated by the bridge.
    address l2Sender;

    // L1 address to call.
    address to;

    // Amount of ETH to send with the call, in wei.
    uint256 value;

    // Nonce that distinguishes this call from other calls.
    uint256 msgNonce;

    // Calldata to pass to the L1 target.
    bytes data;
}
```


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