> ## Documentation Index
> Fetch the complete documentation index at: https://cosmos-docs-sync-security-docs.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Block Sync

## Channel

Block sync has one channel.

| Name             | Number |
| ---------------- | ------ |
| BlocksyncChannel | 64     |

## Message Types

There are multiple message types for Block Sync

### BlockRequest

BlockRequest asks a peer for a block at the height specified.

| Name   | Type  | Description               | Field Number |
| ------ | ----- | ------------------------- | ------------ |
| Height | int64 | Height of requested block | 1            |

### NoBlockResponse

NoBlockResponse notifies the peer requesting a block that the node does not contain it.

| Name   | Type  | Description               | Field Number |
| ------ | ----- | ------------------------- | ------------ |
| Height | int64 | Height of requested block | 1            |

### BlockResponse

BlockResponse contains the block requested.
It also contains an extended commit *iff* vote extensions are enabled at the block's height.

| Name      | Type                                                                        | Description                     | Field Number |
| --------- | --------------------------------------------------------------------------- | ------------------------------- | ------------ |
| Block     | [Block](/cometbft/latest/spec/core/Data_structures#block)                   | Requested Block                 | 1            |
| ExtCommit | [ExtendedCommit](/cometbft/latest/spec/core/Data_structures#extendedcommit) | Sender's LastCommit information | 2            |

### StatusRequest

StatusRequest is an empty message that notifies the peer to respond with the highest and lowest blocks it has stored.

> Empty message.

### StatusResponse

StatusResponse responds to a peer with the highest and lowest heights of any block it has in its blockstore.

| Name   | Type  | Description                                                       | Field Number |
| ------ | ----- | ----------------------------------------------------------------- | ------------ |
| Height | int64 | Current Height of a node                                          | 1            |
| Base   | int64 | First known block, if pruning is enabled it will be higher than 1 | 2            |

### Message

Message is a [`oneof` protobuf type](https://developers.google.com/protocol-buffers/docs/proto#oneof). The `oneof` consists of five messages.

| Name                | Type                                | Description                                                  | Field Number |
| ------------------- | ----------------------------------- | ------------------------------------------------------------ | ------------ |
| block\_request      | [BlockRequest](#blockrequest)       | Request a block from a peer                                  | 1            |
| no\_block\_response | [NoBlockResponse](#noblockresponse) | Response saying it doe snot have the requested block         | 2            |
| block\_response     | [BlockResponse](#blockresponse)     | Response with requested block + (optionally) vote extensions | 3            |
| status\_request     | [StatusRequest](#statusrequest)     | Request the highest and lowest block numbers from a peer     | 4            |
| status\_response    | [StatusResponse](#statusresponse)   | Response with the highest and lowest block numbers the store | 5            |