The Core Function of Data Availability in Layer2

Core Function of Layer2 Data Availability

Author: Haotian; Source: Author’s Twitter @tmel0211

Some friends asked me to analyze the newcomers outside the four big layer2 chains, such as Linea, Polygon zkEVM, Mantle, and Metis, known as the Four Little Dragons. After a brief review, I found that the core differences among most layer2 solutions lie in two aspects:

1) Whether Data Availability depends on the Ethereum mainnet;

2) How compatible they are with the EVM.

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The equivalence of the EVM determines the ease of ecological migration for developers. This article will explore what Data Availability is and why the DA layer is the core layer of layer2 from an introductory perspective. What trade-offs have third-party DAs like Celestia and Eigenlayer made?

-Firstly, let’s explain in simple terms what Data Availability is.

In simple terms, Data Availability refers to the availability of all historical data generated by the system in a blockchain network, which can be obtained by all nodes. Why is this important? Because blockchain is distributed, with records stored on different nodes. If certain critical data is lost or hidden, the security of the entire system will be compromised.

For example, if only a few nodes know the detailed information of a transaction and other nodes cannot access it, the transaction cannot be verified correctly by all validators. Similarly, when querying an account balance, all relevant historical transactions must be traversed to calculate the final result. If some transaction data is missing in the middle, the balance result will be incorrect.

Therefore, Data Availability ensures that any node can access all historical data for correct verification and querying, ensuring that the data in the blockchain system will not be lost or hidden and that all nodes can obtain complete data. If the DA layer fails to work properly, as in the case of Optimism, the 7-day challenge period cannot proceed because if the Calldata before and after the batch cannot be read normally, the Rollup contract cannot be confirmed. Ultimately, DA is to ensure the security of the blockchain ledger system.

-Analyzing the advantages and disadvantages of using Ethereum as the DA layer in layer2

Using Ethereum as the DA layer of layer2 indeed allows for the utilization of Ethereum’s security and data integrity, which is its biggest advantage. Otherwise, layer2 transactions would be subject to malicious tampering and disorderly accounting without any constraints, making it difficult for such layer2 networks to gain mainstream recognition. However, Ethereum itself has limited block capacity and transaction throughput, which may make it difficult to support high TPS layer2 networks in the long run.

This severe capacity mismatch means that a large number of layer2 transactions are queued and waiting for block confirmation, unable to complete DA verification in a timely manner. It also increases the competition for Ethereum block space by layer2, driving up gas fees.

Therefore, relying solely on the Ethereum mainnet as the DA layer will undoubtedly become a bottleneck for the development of layer2 in the long run. As a result, some mainstream DA solutions have emerged in the process of layer2 development:

1) Compressing state data to L1, such as zkSync submitting zkSNARK proofs to the mainnet, with a large amount of original transaction data maintained by L2;

2) Third-party public chain platforms such as Celestia providing DA layer solutions, with data submitted to third-party distributed networks for verification and synchronizing the resultant state to L1;

3) After the upgrade, Cancun added Blob additional storage space, which is encoded and validated using the KZB tool.

– Third-party DA modular solution trade-offs

When it comes to third-party DA modular solutions, the most well-known projects are Celestai and Eigenlayer (as well as Ethstorage).

The Celestia network itself can handle a large volume of transactions, ensuring the effectiveness of DAs generated by applications on layer2. It only uploads transaction statuses in batches to Ethereum, making it a highly modularized DA solution;

Eigenlayer separates transaction processing and data storage. Transaction processing is done quickly in rollup, while integrity data storage is done in a distributed network built by Eigenlayer. Rollup only uploads key data, such as block headers and Merkle tree roots, to Ethereum. When it needs to read complete data, the Rollup contract will read data from the Eigenlayer network in real-time.

Currently, these two modular DA solutions are quite popular. For example, Celestia is used as the DA layer for application chains in the Cosmos ecosystem, such as Eclipse and Cevmos, while Eigenlayer is used as the DA layer for layer2 networks such as Mantle.

It should be noted that modular DA solutions are more directed towards future DA solutions, as they embed third-party external consensus mechanisms and do not directly rely on Ethereum for DA consensus, which is stronger. Therefore, some propose to exclude projects that adopt third-party DA solutions from the layer2 ecosystem.

In essence, it depends on whether you trust this kind of externally embedded DA solution that can enhance capacity and performance. From my perspective, in the short term, Ethereum DAs will definitely be more popular, but in the long term, especially in the era of multi-chain applications, these third-party modular DA solutions may also emerge with strong consensus.

In this simple system, we discussed the impact of Data Availability on layer2. With the emergence of various layer2 solutions, the ideas and frameworks become clear. The differences between OP and ZK Rollup lie in the way they verify data state accuracy, while the adoption of third-party modular DAs is to address the capacity limitations of Ethereum as a DA. The additional extension of Blob after the Cancun upgrade is a compromise solution.

Based on this premise, we can then look at various cutting-edge layer2 solutions and have criteria for judging the basic cognitive framework.

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