Update EIP-7642: add earliestBlock and update receipts encoding

EIPS/eip-7642.md

@@ -1,7 +1,7 @@
 ---
 eip: 7642
-title: eth/69 - Drop pre-merge fields
-description: Drop unnecessary fields after the merge
+title: eth/69 - history expiry and simpler receipts
+description: Adds history serving window and removes bloom filter in receipt
 author: Marius van der Wijden (@MariusVanDerWijden), Felix Lange <[email protected]>
 discussions-to: https://ethereum-magicians.org/t/eth-70-drop-pre-merge-fields-from-eth-protocol/19005
 status: Stagnant
@@ -13,35 +13,46 @@ requires: 5793
 
 ## Abstract
 
-After the merge the `td` field in the networking protocol became obsolete.
-This EIP modifies the networking messages such that this field is not sent anymore.
-Additionally we propose to remove the `Bloom` field from the receipts networking messages.
+This EIP modifies the 'eth' p2p protocol to announce the historical block range served by
+the node. We also simplify the handshake to remove total difficulty information, which
+isn't used anymore after the merge. Additionally we propose to remove the `Bloom` field
+from receipts transfered over the protocol.
 
 ## 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.
+### Removing Bloom in Receipts
 
-Additionally we propose to remove the field that was deprecated by the merge, namely
-the `TD` field in the `Status` message. 
+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.
+
+### earliestBlock in Status message
+
+In the history expiry working group, it was decided that clients may drop pre-merge
+history from their storage after May 1, 2025. For clients that want to sync history
+through the 'eth' protocol, it is essential to know whether a peer still serves old
+history. A similar idea was proposed in [EIP-7542](./eip-7542.md) but was later withdrawn
+because a political decision on history expiry had not been reached at the time.
 
 ## Specification
 
 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]`
+- (eth/69): `[version: P, networkid: P, blockhash: B_32, genesis: B_32, forkid, earliestBlock: P]`
 
 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
+- (eth/68): `receipt = {legacy-receipt, typed-receipt}` with
 
 ```
+typed-receipt = tx-type || rlp(legacy-receipt)
+
 legacy-receipt = [
     post-state-or-status: {B_32, {0, 1}},
     cumulative-gas: P,
@@ -50,32 +61,48 @@ legacy-receipt = [
 ]
 ```
 
-- (eth/69): `receipt = {legacy-receipt, typed-receipt}` with `typed-receipt = tx-type || receipt-data` and
+- (eth/69): `receipt = [tx-type, post-state-or-status, cumulative-gas, logs]`
 
-```
-legacy-receipt = [
-    post-state-or-status: {B_32, {0, 1}},
-    cumulative-gas: P,
-    logs: [log₁, log₂, ...]
-]
-```
+## Rationale
 
-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.
+### Status changes
 
-## 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.
+
+The new `earliestBlock` field is technically not required for history expiry, but there
+are a couple reasons why adding it can help:
+
+- It improves peer finding for clients that still want to sync history from p2p after the
+  agreed-upon removal of pre merge history has taken place. Without `earliestBlock`, the
+  client would have to perform a request for history to check if the earlier range exists,
+  and assume that a failed request means it's not there.
+- The new field can be used for census in a specialized crawler. We will be able to see
+  how many users/nodes enable history, and in which implementation.
+- It prepares us for a future where the history expiry window is dynamic.
+
+### Receipts changes
 
-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.
+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 in order to fully verify the receipt hash. The recomputation is not very
+CPU intensive. The bandwidth gains amount to roughly 530GiB per syncing node or (at least)
+95GiB snappy compressed.
 
-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. 
+In Ethereum consensus, the encoding of receipts differs between legacy transactions and
+typed transactions. Typed transaction receipts are 'opaque' and have the data wrapped in a
+byte array. However, all receipt types ultimately contain the same four fields. With the
+removal of the bloom filter, the networking protocol now deviates from the encoding used
+by consensus, and there is no need to replicate the weird and expensive encoding used
+there. The proposed receipt encoding is just a flat list of the required data fields.
 
 ## Backwards Compatibility
 
-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 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.