Electra -- Networking

Note: This document is a work-in-progress for researchers and implementers.

Table of contents

• Introduction
• Modifications in Electra
  • Configuration
  • The gossip domain: gossipsub
    • Topics and messages
      • Global topics
        • beacon_block
        • beacon_aggregate_and_proof
        • blob_sidecar_{subnet_id}
      • Attestation subnets
        • beacon_attestation_{subnet_id}
  • The Req/Resp domain
    • Messages
      • BeaconBlocksByRange v2
      • BeaconBlocksByRoot v2
      • BlobSidecarsByRange v1
      • BlobSidecarsByRoot v1

Introduction

This document contains the consensus-layer networking specification for Electra.

The specification of these changes continues in the same format as the network specifications of previous upgrades, and assumes them as pre-requisite.

Modifications in Electra

Configuration

[New in Electra:EIP7691]

Name	Value	Description
MAX_REQUEST_BLOB_SIDECARS_ELECTRA	MAX_REQUEST_BLOCKS_DENEB * MAX_BLOBS_PER_BLOCK_ELECTRA	Maximum number of blob sidecars in a single request
BLOB_SIDECAR_SUBNET_COUNT_ELECTRA	9	The number of blob sidecar subnets used in the gossipsub protocol

The gossip domain: gossipsub

Some gossip meshes are upgraded in the fork of Electra to support upgraded types.

Topics and messages

Topics follow the same specification as in prior upgrades.

The beacon_block topic is modified to also support Electra blocks.

The beacon_aggregate_and_proof and beacon_attestation_{subnet_id} topics are modified to support the gossip of the new attestation type.

The attester_slashing topic is modified to support the gossip of the new AttesterSlashing type.

The specification around the creation, validation, and dissemination of messages has not changed from the Capella document unless explicitly noted here.

The derivation of the message-id remains stable.

Global topics

beacon_block

Updated validation

• [REJECT] The length of KZG commitments is less than or equal to the limitation defined in Consensus Layer -- i.e. validate that len(signed_beacon_block.message.body.blob_kzg_commitments) <= MAX_BLOBS_PER_BLOCK_ELECTRA

beacon_aggregate_and_proof

The following convenience variables are re-defined

• index = get_committee_indices(aggregate.committee_bits)[0]

The following validations are added:

• [REJECT] len(committee_indices) == 1, where committee_indices = get_committee_indices(aggregate).
• [REJECT] aggregate.data.index == 0

blob_sidecar_{subnet_id}

[Modified in Electra:EIP7691]

The existing validations all apply as given from previous forks, with the following exceptions:

• Uses of MAX_BLOBS_PER_BLOCK in existing validations are replaced with MAX_BLOBS_PER_BLOCK_ELECTRA.

Attestation subnets

beacon_attestation_{subnet_id}

The topic is updated to propagate SingleAttestation objects.

The following convenience variables are re-defined:

• index = attestation.committee_index

The following validations are added:

• [REJECT] attestation.data.index == 0
• [REJECT] The attester is a member of the committee -- i.e. attestation.attester_index in get_beacon_committee(state, attestation.data.slot, index).

The following validations are removed:

• [REJECT] The attestation is unaggregated -- that is, it has exactly one participating validator (len([bit for bit in aggregation_bits if bit]) == 1, i.e. exactly 1 bit is set).
• [REJECT] The number of aggregation bits matches the committee size -- i.e. len(aggregation_bits) == len(get_beacon_committee(state, attestation.data.slot, index)).

The Req/Resp domain

Messages

BeaconBlocksByRange v2

Protocol ID: /eth2/beacon_chain/req/beacon_blocks_by_range/2/

The Electra fork-digest is introduced to the context enum to specify Electra beacon block type.

Per context = compute_fork_digest(fork_version, genesis_validators_root):

fork_version	Chunk SSZ type
GENESIS_FORK_VERSION	phase0.SignedBeaconBlock
ALTAIR_FORK_VERSION	altair.SignedBeaconBlock
BELLATRIX_FORK_VERSION	bellatrix.SignedBeaconBlock
CAPELLA_FORK_VERSION	capella.SignedBeaconBlock
DENEB_FORK_VERSION	deneb.SignedBeaconBlock
ELECTRA_FORK_VERSION	electra.SignedBeaconBlock

BeaconBlocksByRoot v2

Protocol ID: /eth2/beacon_chain/req/beacon_blocks_by_root/2/

Per context = compute_fork_digest(fork_version, genesis_validators_root):

fork_version	Chunk SSZ type
GENESIS_FORK_VERSION	phase0.SignedBeaconBlock
ALTAIR_FORK_VERSION	altair.SignedBeaconBlock
BELLATRIX_FORK_VERSION	bellatrix.SignedBeaconBlock
CAPELLA_FORK_VERSION	capella.SignedBeaconBlock
DENEB_FORK_VERSION	deneb.SignedBeaconBlock
ELECTRA_FORK_VERSION	electra.SignedBeaconBlock

BlobSidecarsByRange v1

Protocol ID: /eth2/beacon_chain/req/blob_sidecars_by_range/1/

[Modified in Electra:EIP7691]

Request Content:

(
  start_slot: Slot
  count: uint64
)

Response Content:

(
  List[BlobSidecar, MAX_REQUEST_BLOB_SIDECARS_ELECTRA]
)

Updated validation

Clients MUST respond with at least the blob sidecars of the first blob-carrying block that exists in the range, if they have it, and no more than MAX_REQUEST_BLOB_SIDECARS_ELECTRA sidecars.

BlobSidecarsByRoot v1

Protocol ID: /eth2/beacon_chain/req/blob_sidecars_by_root/1/

[Modified in Electra:EIP7691]

Request Content:

(
  List[BlobIdentifier, MAX_REQUEST_BLOB_SIDECARS_ELECTRA]
)

Response Content:

(
  List[BlobSidecar, MAX_REQUEST_BLOB_SIDECARS_ELECTRA]
)

Updated validation

No more than MAX_REQUEST_BLOB_SIDECARS_ELECTRA may be requested at a time.