In-depth Analysis of Ethereum Scalability Solutions: The Current State and Future of L2 Technologies

Ethereum, as a leader in the blockchain field, supports numerous decentralized applications, from DeFi to NFTs, and the ecosystem is thriving. However, behind this prosperity lie many challenges, such as high costs due to network congestion, extended transaction times, and increased failure rates, which severely affect user participation enthusiasm.

To address these challenges while maintaining the decentralized nature of the main chain, the community has proposed an L2 scaling solution. The core idea of L2 is to shift computation and transactions from the main network to a second-layer network, submitting only the final results to the main network. This approach not only improves transaction efficiency and reduces costs but also inherits the security of the main network.

Currently, the more well-known L2 solutions include Rollups and sidechains, among which Rollups can be further divided into Optimistic Rollups and Zero-Knowledge Rollups (ZK-Rollups).

Optimistic Rollups

Optimistic Rollups perform transaction computation and state updates on the L2 network, and then batch publish the compressed raw data to the mainnet. L2 nodes assume that these transactions are valid by default, similar to the presumption of innocence in the real world. This model significantly enhances transaction confirmation speed and efficiency.

After the transaction is submitted, if the validator finds an issue, they can submit a fraud proof within seven days. The mainnet smart contract will verify this proof. If there is indeed a problem, the relevant batches and subsequent batches will be rolled back, the malicious nodes will be punished, and the validators will receive rewards.

The "fraud proof" mechanism is like the sword of Damocles hanging over the nodes, with a deterrent effect far greater than the actual punishment. In practice, the submission of fraud proofs is extremely rare, due to reasons such as thorough testing of the project itself, a strict penalty mechanism, and the losses incurred from wrongdoing far exceeding the potential gains.

Compared to node malfeasance, issues caused by network fluctuations or software bugs are more common. The main drawback of Optimistic Rollups is that the seven-day challenge period may affect fund circulation, as well as the potential risk of centralization.

Zero-Knowledge Rollups

Unlike Optimistic Rollups, ZK-Rollups require validity proofs to be submitted along with the data. This method also processes transactions off-chain, but it requires computing the validity proof before the official submission.

Although ZK technology has existed for a long time, its advantages are fully realized in the application of blockchain. Blockchain can confine complexity within smart contracts, allowing users to trust decentralized smart contracts rather than any centralized entity.

The complexity of ZK-Rollups lies in the need to compile complex logic circuit diagrams based on transaction data and execution logic, and then generate quickly verifiable results through dedicated provers. This process typically requires powerful computing capabilities and specialized hardware.

Layer2 Cost Analysis

L2 networks aim to reduce the interaction cost for users on the mainnet, but they also come with their own costs.

The main costs of Optimistic Rollups include transaction fees for submitting compressed data to the mainnet and operating costs for L2 nodes. Ethereum's EIP-4844 upgrade significantly reduced the costs of interaction between L2 and the mainnet. In addition, maintaining nodes requires a large amount of capital to be locked up, which can lead to opportunity costs.

The main costs of ZK-Rollups come from the large amount of computing resources and specialized hardware required to generate zero-knowledge proofs. At the same time, it also needs to bear the transaction fees for submitting data to the mainnet. The demand for specialized hardware may lead to an increase in network centralization.

Looking to the Future

Both Optimistic Rollups and ZK-Rollups are important solutions for Ethereum to tackle scalability challenges. With the implementation of upgrades like Ethereum EIP-4844, the data publication costs for L2 have been significantly reduced, which will further unleash the potential of both solutions and promote the continuous development and innovation of the Ethereum ecosystem.