184 lines
8.4 KiB
Markdown
184 lines
8.4 KiB
Markdown
# Bellatrix -- Networking
|
|
|
|
This document contains the networking specification for the Bellatrix.
|
|
|
|
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)
|
|
and will be referred to as the "Phase 0 document" and "Altair document" respectively, hereafter.
|
|
Readers should understand the Phase 0 and Altair documents and use them as a basis to understand the changes outlined in this document.
|
|
|
|
## Table of contents
|
|
|
|
<!-- TOC -->
|
|
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
|
|
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
|
|
|
|
- [Warning](#warning)
|
|
- [Modifications in Bellatrix](#modifications-in-bellatrix)
|
|
- [Configuration](#configuration)
|
|
- [The gossip domain: gossipsub](#the-gossip-domain-gossipsub)
|
|
- [Topics and messages](#topics-and-messages)
|
|
- [Global topics](#global-topics)
|
|
- [`beacon_block`](#beacon_block)
|
|
- [Transitioning the gossip](#transitioning-the-gossip)
|
|
- [The Req/Resp domain](#the-reqresp-domain)
|
|
- [Messages](#messages)
|
|
- [BeaconBlocksByRange v2](#beaconblocksbyrange-v2)
|
|
- [BeaconBlocksByRoot v2](#beaconblocksbyroot-v2)
|
|
- [Design decision rationale](#design-decision-rationale)
|
|
- [Gossipsub](#gossipsub)
|
|
- [Why was the max gossip message size increased at Bellatrix?](#why-was-the-max-gossip-message-size-increased-at-bellatrix)
|
|
- [Req/Resp](#reqresp)
|
|
- [Why was the max chunk response size increased at Bellatrix?](#why-was-the-max-chunk-response-size-increased-at-bellatrix)
|
|
|
|
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
|
|
<!-- /TOC -->
|
|
|
|
## Warning
|
|
|
|
This document is currently illustrative for early Bellatrix testnets and some parts are subject to change.
|
|
Refer to the note in the [validator guide](./validator.md) for further details.
|
|
|
|
# Modifications in Bellatrix
|
|
|
|
## Configuration
|
|
|
|
This section outlines modifications constants that are used in this spec.
|
|
|
|
| Name | Value | Description |
|
|
|---|---|---|
|
|
| `GOSSIP_MAX_SIZE_BELLATRIX` | `10 * 2**20` (= 10,485,760, 10 MiB) | The maximum allowed size of uncompressed gossip messages starting at Bellatrix upgrade. |
|
|
| `MAX_CHUNK_SIZE_BELLATRIX` | `10 * 2**20` (= 10,485,760, 10 MiB) | The maximum allowed size of uncompressed req/resp chunked responses starting at Bellatrix upgrade. |
|
|
|
|
## The gossip domain: gossipsub
|
|
|
|
Some gossip meshes are upgraded in Bellatrix to support upgraded types.
|
|
|
|
### Topics and messages
|
|
|
|
Topics follow the same specification as in prior upgrades.
|
|
All topics remain stable except the beacon block topic which is updated with the modified type.
|
|
|
|
The specification around the creation, validation, and dissemination of messages has not changed from the Phase 0 and Altair documents unless explicitly noted here.
|
|
|
|
Starting at Bellatrix upgrade, each gossipsub [message](https://github.com/libp2p/go-libp2p-pubsub/blob/master/pb/rpc.proto#L17-L24)
|
|
has a maximum size of `GOSSIP_MAX_SIZE_BELLATRIX`.
|
|
Clients MUST reject (fail validation) messages that are over this size limit.
|
|
Likewise, clients MUST NOT emit or propagate messages larger than this limit.
|
|
|
|
The derivation of the `message-id` remains stable.
|
|
|
|
The new topics along with the type of the `data` field of a gossipsub message are given in this table:
|
|
|
|
| Name | Message Type |
|
|
| - | - |
|
|
| `beacon_block` | `SignedBeaconBlock` (modified) |
|
|
|
|
Note that the `ForkDigestValue` path segment of the topic separates the old and the new `beacon_block` topics.
|
|
|
|
#### Global topics
|
|
|
|
Bellatrix changes the type of the global beacon block topic.
|
|
|
|
##### `beacon_block`
|
|
|
|
The *type* of the payload of this topic changes to the (modified) `SignedBeaconBlock` found in Bellatrix.
|
|
Specifically, this type changes with the addition of `execution_payload` to the inner `BeaconBlockBody`.
|
|
See Bellatrix [state transition document](./beacon-chain.md#beaconblockbody) for further details.
|
|
|
|
In addition to the gossip validations for this topic from prior specifications,
|
|
the following validations MUST pass before forwarding the `signed_beacon_block` on the network.
|
|
Alias `block = signed_beacon_block.message`, `execution_payload = block.body.execution_payload`.
|
|
- If the execution is enabled for the block -- i.e. `is_execution_enabled(state, block.body)`
|
|
then validate the following:
|
|
- _[REJECT]_ The block's execution payload timestamp is correct with respect to the slot
|
|
-- i.e. `execution_payload.timestamp == compute_timestamp_at_slot(state, block.slot)`.
|
|
|
|
### Transitioning the gossip
|
|
|
|
See gossip transition details found in the [Altair document](../altair/p2p-interface.md#transitioning-the-gossip) for
|
|
details on how to handle transitioning gossip topics for Bellatrix.
|
|
|
|
## The Req/Resp domain
|
|
|
|
### Messages
|
|
|
|
#### BeaconBlocksByRange v2
|
|
|
|
**Protocol ID:** `/eth2/beacon_chain/req/beacon_blocks_by_range/2/`
|
|
|
|
Request and Response remain unchanged unless explicitly noted here.
|
|
|
|
Starting at Bellatrix upgrade,
|
|
a global maximum uncompressed byte size of `MAX_CHUNK_SIZE_BELLATRIX` MUST be applied to all method response chunks
|
|
regardless of type specific bounds that *MUST* also be respected.
|
|
|
|
Bellatrix fork-digest is introduced to the `context` enum to specify Bellatrix block type.
|
|
|
|
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
|
|
|
|
[0]: # (eth2spec: skip)
|
|
|
|
| `fork_version` | Chunk SSZ type |
|
|
| ------------------------ | -------------------------- |
|
|
| `GENESIS_FORK_VERSION` | `phase0.SignedBeaconBlock` |
|
|
| `ALTAIR_FORK_VERSION` | `altair.SignedBeaconBlock` |
|
|
| `BELLATRIX_FORK_VERSION` | `bellatrix.SignedBeaconBlock` |
|
|
|
|
#### BeaconBlocksByRoot v2
|
|
|
|
**Protocol ID:** `/eth2/beacon_chain/req/beacon_blocks_by_root/2/`
|
|
|
|
Request and Response remain unchanged.
|
|
Bellatrix fork-digest is introduced to the `context` enum to specify Bellatrix block type.
|
|
|
|
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
|
|
|
|
[1]: # (eth2spec: skip)
|
|
|
|
| `fork_version` | Chunk SSZ type |
|
|
| ------------------------ | -------------------------- |
|
|
| `GENESIS_FORK_VERSION` | `phase0.SignedBeaconBlock` |
|
|
| `ALTAIR_FORK_VERSION` | `altair.SignedBeaconBlock` |
|
|
| `BELLATRIX_FORK_VERSION` | `bellatrix.SignedBeaconBlock` |
|
|
|
|
# Design decision rationale
|
|
|
|
## Gossipsub
|
|
|
|
### Why was the max gossip message size increased at Bellatrix?
|
|
|
|
With the addition of `ExecutionPayload` to `BeaconBlock`s, there is a dynamic
|
|
field -- `transactions` -- which can validly exceed the `GOSSIP_MAX_SIZE` limit (1 MiB) put in place in
|
|
place at Phase 0. At the `GAS_LIMIT` (~30M) currently seen on mainnet in 2021, a single transaction
|
|
filled entirely with data at a cost of 16 gas per byte can create a valid
|
|
`ExecutionPayload` of ~2 MiB. Thus we need a size limit to at least account for
|
|
current mainnet conditions.
|
|
|
|
Geth currently has a [max gossip message size](https://github.com/ethereum/go-ethereum/blob/3ce9f6d96f38712f5d6756e97b59ccc20cc403b3/eth/protocols/eth/protocol.go#L49) of 10 MiB.
|
|
To support backward compatibility with this previously defined network limit,
|
|
we adopt `GOSSIP_MAX_SIZE_BELLATRIX` of 10 MiB for maximum gossip sizes at the
|
|
point of Bellatrix and beyond. Note, that clients SHOULD still reject objects
|
|
that exceed their maximum theoretical bounds which in most cases is less than `GOSSIP_MAX_SIZE_BELLATRIX`.
|
|
|
|
Note, that due to additional size induced by the `BeaconBlock` contents (e.g.
|
|
proposer signature, operations lists, etc) this does reduce the
|
|
theoretical max valid `ExecutionPayload` (and `transactions` list) size as
|
|
slightly lower than 10 MiB. Considering that `BeaconBlock` max size is on the
|
|
order of 128 KiB in the worst case and the current gas limit (~30M) bounds max blocksize to less
|
|
than 2 MiB today, this marginal difference in theoretical bounds will have zero
|
|
impact on network functionality and security.
|
|
|
|
## Req/Resp
|
|
|
|
### Why was the max chunk response size increased at Bellatrix?
|
|
|
|
Similar to the discussion about the maximum gossip size increase, the
|
|
`ExecutionPayload` type can cause `BeaconBlock`s to exceed the 1 MiB bounds put
|
|
in place during Phase 0.
|
|
|
|
As with the gossip limit, 10 MiB is selected because this is firmly below any
|
|
valid block sizes in the range of gas limits expected in the medium term.
|
|
|
|
As with both gossip and req/rsp maximum values, type-specific limits should
|
|
always by simultaneously respected.
|