Consensus
The purpose of consensus in blockchains is to agree on a consistent order and ensure the availability of transactions.
On Sui, consensus has a straightforward API. Validators submit different user transactions to consensus concurrently. The consensus outputs a consistent stream of transactions across all well-behaving validators.
Sui uses the Mysticeti protocol to optimize for both low latency and high throughput. Mysticeti provides the following benefits:
- Supports multiple validators proposing blocks in parallel, which uses the full bandwidth of the network and provides censorship resistance. These are features of DAG-based consensus protocols.
- Requires only three rounds of messages to commit blocks from the DAGs. This is the same as practical Byzantine Fault Tolerance and matches the theoretical minimum.
- Allows voting and certifying leaders on blocks in parallel, which reduces median and tail latencies.
- Tolerates unavailable leaders without significantly increasing commit latencies.
Transaction throughput
Compared to other state-of-the-art consensus protocols, Mysticeti can theoretically handle more than twice as many transactions with half the observed latency. In a controlled environment using 10 nodes, Mysticeti handles 300,000 transactions per second (TPS) before latency crosses the one-second marker. With 50 nodes, test results show 400,000 TPS before latency exceeds one second. In the same tests, other top performing consensus mechanisms do not reach 150,000 TPS and their observed latency starts at about two seconds.
On average, testing shows Mysticeti reaches consensus commitment in about 0.5 seconds with a sustained throughput of 200,000 TPS.
Decision rule
The decision rule at the core of Mysticeti optimizes operational efficiency. Traditional consensus decision rules require explicit block validation and certification. This process increases communication overhead because validators must sign and broadcast votes to reach consensus. By contrast, Mysticeti provides implicit commitment, which reduces inter-node communication and lowers bandwidth usage.
Finality
Finality is the guarantee that a transaction or block, after confirmation, is permanently added to the network and cannot be altered or reversed. In traditional blockchain consensus, confirming transactions can take time because they rely on other transactions to reference them before they are considered final. This process slows down if network activity decreases or if there are many competing transactions. Mysticeti simplifies this process by finalizing transactions immediately upon inclusion in the structure. As a result, there is no need to wait for additional confirmations or network activity, which makes Mysticeti faster and more reliable for confirming transactions in less active or challenging network conditions.
For more details, including correctness proofs, see the MYSTICETI: Reaching the Latency Limits with Uncertified DAGs whitepaper.
Related links
The life of a transaction on the Sui network has some differences compared to those from other blockchains.
Sui is designed to provide very high security guarantees to asset owners. Assets on Sui can be used only by their owners, according to the logic pre-defined by smart contracts that can be audited, and that the network will be available to process them correctly despite some of the validators operating Sui not following the protocol correctly (fault tolerance).
Whitepaper that documents the Mysticeti protocol.