Details of the Mumbai upgrade: rollups in the mainnet and block backing in 15 seconds!
The next protocol upgrade, Mumbai, will be Tezos' most notable improvement since switching to the Emmy* consensus algorithm in the Granada.
First, the rollups we’ve often written about will finally appear in the mainnet. Second, the validation pipelining project will reduce block creation time from 30 to 15 seconds!
Pipelining: reducing block creation time
Tezos nodes sequentially check the validity of operations (fast), apply them (slow), and only then start to propagate over the network (fast). Pipelining streamlines the process: the node first validates all operations, then distributes the block, and only then applies them.
In the Kathmandu upgrade, the developers activated Pipelining for manager operations: transactions, delegation, smart contract deployment, public key disclosure, and others. In the current Lima upgrade, the developers have enabled Pipelining for other possible operations.
In Mumbai, Pipelining will begin to be applied to block creation. This means that the baker will start distributing a new block on the network as soon as they have checked the validity of its contents. Only then will they begin resource-intensive applications of operations.
Using Pipelining in practice gave core developers the confidence that Tezos could work faster with it without compromising security. As a result, they decided to reduce the block creation time from 30 seconds to 15.
As a result, transactions will finalize faster, although the protocol will have to adjust epoch lengths, baking rewards, and some other variables.
Activating Smart Optimistic Rollups
Rollups are L2 solutions for scaling decentralized applications. Rollups receive transactions from users, execute them off-chain and regularly publish the results of all accumulated transactions to the L1 network. By being “detached” from L1, rollups achieve higher throughput with lower transaction fees than the core network.
In the last three protocol updates, core developers have advanced the implementation of testnet rollups: first TORUs just for transactions, then SCORUs to perform smart contracts, then Kernel-Based Optimistic Rollups with the ability to run L2 with any virtual machine.
Smart Rollups are just Kernel-Based Optimistic Rollups. They can be used to run an L2 node with an EVM, WASM, or another virtual machine in which users will work with programs written in any language.
Smart Rollups will help Tezos achieve throughputs of over one million transactions per second and give developers a basis for implementing fast applications. For example, games with a record of every action or decentralized derivatives exchanges with order books.
Smart Rollups are optimistic, meaning that the network automatically considers the rollup state in L1 valid unless someone proves it fraudulent. Therefore, Smart Rollups will have a refutation system to punish dishonest node operators. Users will only be able to withdraw funds from rollups after a dispute period.
Rollups on Tezos differ from other implementations because they are enshrined—built into the protocol. This makes them more accessible and cheaper to deploy and also enables valuable tools for handling them, like global inbox.
Epoxy: ZK rollups Tezos
Optimistic rollups need a dispute period and external checks. Their transactions take a long time to reach finality at L1.
ZK rollups use a different mechanism: they publish cryptographic proof of change validity when updating the state at L1. As a result, transactions in a ZK rollup are immediately considered valid at L1.
In addition, ZK rollups can be used to handle data that should not be written to L1. All transaction details will be stored on the rollup operators’ machines, and only zero-knowledge cryptographic proofs will be stored on the Tezos blockchain.
Nomadic Labs’ implementation of ZK rollups is called Epoxy. Subscribe to their blog to be the first to know the details. Also, subscribe to us; we’ll cover them when ZK rollups appear on Mondaynet.
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