eth/69 - Drop pre-merge fields

Abstract

After the merge a few fields (td) and messages (NewBlockHashes, NewBlock) in the networking protocol became obsolete. This EIP modifies the networking messages such that these fields are not sent anymore. Additionally we propose to remove the Bloom field from the receipts networking messages.

Motivation

We recently discovered that none of the clients store the Bloom field of the receipts as it can be recomputed on demand. However the networking spec requires the Bloom field to be sent over the network. Thus a syncing node will ask for the Bloom filters for all receipts. The serving node will regenerate roughly 530GB of bloom filters (2.3B txs * 256 byte). These 530GBs are send over the network to the syncing peer, the syncing peer will verify them and not store them either. This adds an additional 530GB of unnecessary bandwidth to every sync.

Additionally we propose to remove fields and messages that were deprecated by the merge, such as

• Removing the TD field in the Status message.

• Removing the NewBlockHashes message.

• Removing the NewBlock message.

Specification

Remove the NewBlockHashes (0x01) message.

Remove the NewBlock (0x07) message.

Modify the Status (0x00) message as follows:

• (eth/68): [version: P, networkid: P, td: P, blockhash: B_32, genesis: B_32, forkid]

• (eth/69): [version: P, networkid: P, blockhash: B_32, genesis: B_32, forkid]

Modify the encoding for receipts in the Receipts (0x10) message as follows:

• (eth/68): receipt = {legacy-receipt, typed-receipt} with typed-receipt = tx-type || receipt-data and

legacy-receipt = [
    post-state-or-status: {B_32, {0, 1}},
    cumulative-gas: P,
    bloom: B_256,
    logs: [log₁, log₂, ...]
]

• (eth/69): receipt = {legacy-receipt, typed-receipt} with typed-receipt = tx-type || receipt-data and

legacy-receipt = [
    post-state-or-status: {B_32, {0, 1}},
    cumulative-gas: P,
    logs: [log₁, log₂, ...]
]

We omit the bloom filter from both the legacy and typed receipts. Receiving nodes will be able to recompute the bloom filter based on the logs.

Rationale

After the merge, the TD field of the Status message became meaningless since the difficulty of post-merge blocks are 0. It could in theory be used to distinguish synced with unsynced nodes, but the same thing can be accomplished with the forkid as well. It is not used in the go-ethereum codebase in any way.

After the merge, the NewBlock and NewBlockHashes messages have not been used for block propagation, since block propagation post-merge happens solely on the consensus layer. These message types error out in the go-ethereum implementation. Getting rid of them would allow us to disconnect non-mainnet peers earlier.

Removing the bloom filters from the Receipt message reduces the cpu load of serving nodes as well as the bandwidth significantly. The receiving nodes will need to recompute the bloom filter. The recomputation is not very CPU intensive. The bandwidth gains amount to roughly 530GiB per syncing node or (at least) 95GiB snappy compressed.

Backwards Compatibility

Since this EIP removes the NewBlock and NewBlockHashes messages, private networks or forks that use them to distribute blocks can not update to this version. All private networks or forks that use a mechanism similar to ethereum mainnet, where the consensus layer takes care of block distribution can update to eth/69.

This EIP changes the eth protocol and requires rolling out a new version, eth/69. Supporting multiple versions of a wire protocol is possible. Rolling out a new version does not break older clients immediately, since they can keep using protocol version eth/68.

This EIP does not change consensus rules of the EVM and does not require a hard fork.

Security Considerations

None

Copyright

Copyright and related rights waived via CC0.