128 lines
5.5 KiB
Markdown
128 lines
5.5 KiB
Markdown
# The Merge -- Networking
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This document contains the networking specification for the Merge.
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The specification of these changes continues in the same format as the network specifications of previous upgrades, and assumes them as pre-requisite. This document should be viewed as additive to the documents from [Phase 0](../phase0/p2p-interface.md) and from [Altair](../altair/p2p-interface.md)
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and will be referred to as the "Phase 0 document" and "Altair document" respectively, hereafter.
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Readers should understand the Phase 0 and Altair documents and use them as a basis to understand the changes outlined in this document.
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## Table of contents
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<!-- TOC -->
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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- [Warning](#warning)
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- [Modifications in the Merge](#modifications-in-the-merge)
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- [The gossip domain: gossipsub](#the-gossip-domain-gossipsub)
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- [Topics and messages](#topics-and-messages)
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- [Global topics](#global-topics)
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- [`beacon_block`](#beacon_block)
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- [Transitioning the gossip](#transitioning-the-gossip)
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- [The Req/Resp domain](#the-reqresp-domain)
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- [Messages](#messages)
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- [BeaconBlocksByRange v2](#beaconblocksbyrange-v2)
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- [BeaconBlocksByRoot v2](#beaconblocksbyroot-v2)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<!-- /TOC -->
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## Warning
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This document is currently illustrative for early Merge testnets and some parts are subject to change.
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Refer to the note in the [validator guide](./validator.md) for further details.
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# Modifications in the Merge
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## The gossip domain: gossipsub
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Some gossip meshes are upgraded in the Merge to support upgraded types.
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### Topics and messages
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Topics follow the same specification as in prior upgrades.
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All topics remain stable except the beacon block topic which is updated with the modified type.
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The specification around the creation, validation, and dissemination of messages has not changed from the Phase 0 and Altair documents.
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The derivation of the `message-id` remains stable.
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The new topics along with the type of the `data` field of a gossipsub message are given in this table:
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| Name | Message Type |
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| - | - |
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| `beacon_block` | `SignedBeaconBlock` (modified) |
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Note that the `ForkDigestValue` path segment of the topic separates the old and the new `beacon_block` topics.
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#### Global topics
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The Merge changes the type of the global beacon block topic.
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##### `beacon_block`
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The *type* of the payload of this topic changes to the (modified) `SignedBeaconBlock` found in the Merge.
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Specifically, this type changes with the addition of `execution_payload` to the inner `BeaconBlockBody`.
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See the Merge [state transition document](./beacon-chain.md#beaconblockbody) for further details.
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In addition to the gossip validations for this topic from prior specifications,
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the following validations MUST pass before forwarding the `signed_beacon_block` on the network.
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Alias `block = signed_beacon_block.message`, `execution_payload = block.body.execution_payload`.
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- If the execution is enabled for the block -- i.e. `is_execution_enabled(state, block.body)`
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then validate the following:
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- _[REJECT]_ The block's execution payload timestamp is correct with respect to the slot
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-- i.e. `execution_payload.timestamp == compute_timestamp_at_slot(state, block.slot)`.
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- _[REJECT]_ Gas used is less than the gas limit --
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i.e. `execution_payload.gas_used <= execution_payload.gas_limit`.
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- _[REJECT]_ The execution payload block hash is not equal to the parent hash --
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i.e. `execution_payload.block_hash != execution_payload.parent_hash`.
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- _[REJECT]_ The execution payload transaction list data is within expected size limits,
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the data MUST NOT be larger than the SSZ list-limit,
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and a client MAY be more strict.
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*Note*: Additional [gossip validations](https://github.com/ethereum/devp2p/blob/master/caps/eth.md#block-encoding-and-validity)
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(see block "data validity" conditions) that rely more heavily on execution-layer state and logic are currently under consideration.
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### Transitioning the gossip
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See gossip transition details found in the [Altair document](../altair/p2p-interface.md#transitioning-the-gossip) for
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details on how to handle transitioning gossip topics for the Merge.
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## The Req/Resp domain
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### Messages
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#### BeaconBlocksByRange v2
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**Protocol ID:** `/eth2/beacon_chain/req/beacon_blocks_by_range/2/`
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Request and Response remain unchanged.
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The Merge fork-digest is introduced to the `context` enum to specify the Merge block type.
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Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
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[0]: # (eth2spec: skip)
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| `fork_version` | Chunk SSZ type |
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| ------------------------ | -------------------------- |
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| `GENESIS_FORK_VERSION` | `phase0.SignedBeaconBlock` |
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| `ALTAIR_FORK_VERSION` | `altair.SignedBeaconBlock` |
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| `MERGE_FORK_VERSION` | `merge.SignedBeaconBlock` |
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#### BeaconBlocksByRoot v2
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**Protocol ID:** `/eth2/beacon_chain/req/beacon_blocks_by_root/2/`
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Request and Response remain unchanged.
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The Merge fork-digest is introduced to the `context` enum to specify the Merge block type.
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Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
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[1]: # (eth2spec: skip)
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| `fork_version` | Chunk SSZ type |
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| ------------------------ | -------------------------- |
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| `GENESIS_FORK_VERSION` | `phase0.SignedBeaconBlock` |
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| `ALTAIR_FORK_VERSION` | `altair.SignedBeaconBlock` |
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| `MERGE_FORK_VERSION` | `merge.SignedBeaconBlock` |
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