What is the consensus layer?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 5 min
In short
The consensus layer is where the network agrees on which block is canonical. On Ethereum it is separated from the execution layer and handles validator management, attestations and finality. If it stops, the chain cannot advance even if transactions could still be executed.
Key points
- Where the network agrees on the canonical block
- Also manages validators entering and exiting
- Accumulates attestations to determine finality
- If it stalls, the chain stops advancing
Definition
The layer where participants agree on which blocks form the canonical chain, handling validator management, attestations and the determination of finality.
When Ethereum moved to proof of stake, its agreement mechanism was split off from the execution environment. The consensus client tracks the set of staked validators, selects a proposer for each slot, and tallies the attestations other validators broadcast.
Once enough attestations accumulate, a block becomes irreversible. Unlike proof of work, where confidence grows probabilistically, finality here is declared by rule. Reversing it would require rule violations that cause large amounts of stake to be slashed.
It connects to the execution layer over a dedicated interface: the consensus side asks for a block to be processed, and the execution side returns the result. Running only one of the two clients will not sync a node — both have to be up.
Watch out for
- · Running a validator exposes your stake to slashing if the rules are broken
- · Until finality is reached, recent blocks can still be reorganised away
- · If the consensus side halts, no new block finalises even when execution would work