Ethereum has become an essential platform for many decentralized applications. However, as its adoption increases, it must take up major challenges, mainly in terms of scalability and transaction costs . During traffic peaks, costs can reach hundreds of euros for a single transaction. Layer 2 solutions have been developed. They accelerate transactions while reducing costs. This article deeply explores the functioning of Layer 2, its types and associated challenges.
Table of contents
Understand the concept of Layer 2
Definition and differences with Layer 1
Layer 1 designates the main layer of a blockchain, like Ethereum or Bitcoin. It is on this layer that all transactions are saved and verified. The verification of a transaction consists in validating that it respects the rules of the network, such as the availability of funds, the authorization of the digital signature and the absence of double expenditure. Validators (or minors) on Layer 1 are based on these rules and consensus mechanisms, such as proof of work ( Proof of Work ) or proof of stake ( of Proof of Stake ), to confirm or reject a transaction.
However, the Layer 1 has limits in terms of scalability. Ethereum , for example, can treat around 15 transactions per second ( TPS ), which quickly becomes insufficient when thousands of dApp S DEFI services request the network. During periods of high demand, transaction costs increased considerably. Layer 2 solutions intervene.
The Layer 2 is an additional layer based on the main blockchain (Layer 1) but treats transactions externally to relieve the latter. Once the transactions have been processed, they are subjected to the Layer 1 in the form of lots or summaries, thus reducing the load on the main network and reducing costs.
Why did the Layer 2 emerge as a solution?
With the exponential development of dApp S and DEFI services Ethereum network has quickly reached its limits. Transactions became not only slower, but also expensive, making certain applications not very viable.
Layer 2 solutions, in particular rollups and sidechains , have been developed to meet these pressing needs. They increase the processing capacity of transactions while maintaining much lower costs, making the blockchain more accessible.
The different types of Layer 2 solutions
Rollups: Optimistic Rollups and ZK-Rollups
Rollups are one of the most used Layer 2 technologies They make it possible to treat off -chain transactions before submitting a summary of these main channel transactions (Layer 1).
Optimistic Rollups : These Rollups work by assuming that all transactions are valid by default. However, if a participant in the network suspects fraud or error, he can contest the validity of a transaction by providing "evidence of fraud" ( fraud proof ). This dispute mechanism leads to a waiting period (generally between one and two weeks) to allow any person to question the validity of the transaction. This period explains why the withdrawal of funds from the optimistic rollups can be long: the main blockchain must wait for the end of the protest period before confirming the transaction.
ZK-Rollups : Unlike Optimistic Rollups, ZK-Rollups ( Zero Knowledge Rollups) use cryptographic evidence to prove the validity of off-chain transactions. This evidence, called ZK-Snarks or ZK-Starks , are subject to the main channel, ensuring that transactions are in accordance with without having to execute each transaction on the Layer 1. This allows to validate the transactions almost instantly, without dispute, as is the case for optimistic rollups. A notable project using ZK-Rollups is zkSync , which is distinguished by its speed and low cost for fund transfers.
Lateral chains (sidechains): operation and examples
Sidechains are independent blockchains that work in parallel with the main channel (Layer 1) . They have their own consensus mechanism, which allows them to treat transactions independently. However, this means that they do not benefit directly from the safety of the Layer 1.. Users can transfer assets between the sidechain and the main channel via bridges (bridges) .
These bridges make it possible to link the two channels, but they also introduce additional security risks, in particular in the event of hacking or compromise of the bridge validators.
Although Polygon has its own consensus mechanism based on the Proof of Stake (POS) , it is based on Ethereum for the purpose and safety of transactions in a specific way. Here's how it works:
1. Periodic anchoring of checkpoints on Ethereum
Polygon regularly sends checkpoints to Ethereum . These checkpoints represent aggregate states of Sidechain (or plasma chain in certain implementations) and include a summary of transactions that have been validated on Polygon . Although transactions are processed and validated on Polygon independently, anchoring on Ethereum ensures a form of "purpose" of transactions.
This means that even if the transactions are first validated via the POS mechanism of Polygon, the final state of the blockchain (or at least part of this state) is secure on Ethereum via these checkpoints, creating an additional validation layer.
2. Increased security thanks to Ethereum
Using Ethereum for the anchoring of these checkpoints, Polygon benefits from the Ethereum network , in particular its immutability and the power of its decentralized network . This ensures that even if a problem occurs on Polygon (like a 51% attack on the POS mechanism of Polygon ), the data anchored on Ethereum remains reliable and can be used as a basis for restoring transactions in a coherent state.
The main difference between the sidechains and the Rollups lies in the consensus mechanism. The sidechains manage their own safety and consensus, while the Rollups are based on the security of the main channel (Layer 1) to validate the final transactions. An example of well -known sidechain is Polygon , an Ethereum which allows low -cost and high speed transactions, but which requires the use of bridges to interact with Ethereum .
State channels (state channels): utility and operation
The status channels are another Layer 2 which allows two parts to treat outside chain transactions. They operate by opening a channel where transactions are carried out directly between the parties. It is only when the channel is closed that the final state of the transactions is recorded on the main channel. This makes it possible to perform several transactions quickly and at no cost, as long as the canal remains open.
A popular example of State Channel is Bitcoin 's Lightning Network , which allows you to make fast and inexpensive payments without overloading the main blockchain. Transactions are processed out of chain, and only final interactions, such as closing the canal, are subject to blockchain.
The advantages of using Layer 2
Reduction of transaction fees
Layer 2 solutions make it possible to significantly reduce transaction costs by moving operations outside the main channel. Rather than paying high fees for each transaction on Layer 1, users pay only for the validation of grouped transactions on Layer 2. This is particularly important for DEFI applications or Blockchain Games, where many small transactions are necessary.
Improved scalability
Layer 2 increases network capacity by increasing the number of transactions that can be treated simultaneously. For example, Ethereum can treat around 15 TPS on the Layer 1. With solutions like zkSync or Optimism , this figure can increase to several thousand TPS, making transactions faster and more accessible.
Comparison between Layer 1 and Layer 2
Major differences
The Layer 1 offers maximum security by treating each transaction directly on the blockchain, but at the cost of low scalability and high costs. Layer 2 improves this scalability and reducing costs, but it can sometimes compromise security. For example, Optimistic Rollups introduce a delay to contest transactions, which can expose the network to fraud attempts. Likewise, sidechains can be vulnerable if their consensus mechanism or bridges used to transfer assets are compromised.
The main Layer 2 projects on Ethereum
zkSync : a promising solution for Ethereum
zkSync ZK-Rollup solution that allows fast and low cost transactions on Ethereum . By using cryptographic evidence to validate transactions, zkSync guarantees high security while reducing costs. It is an ideal platform for applications requiring frequent and fast transfers.
Optimism: Why is it a popular solution?
OPTIMIME is one of the main implementations of Optimistic Rollups on Ethereum . Ethereum smart contracts , allowing dApp to easily migrate to this network while reducing costs. Users must however wait until the end of the protest period before withdrawing their funds from the network.
Polygon : an example of popular sidechain
Polygon Ethereum Matic, is an Ethereum sidechain which allows high -speed and low cost transactions. However, given that it operates with its own consensus mechanism, it does not directly benefit from Ethereum . Users must use bridges to transfer assets between Polygon and Ethereum , which can introduce additional security risks.
Layer 2 challenges
Risk of safety compromise
Layer 2 solutions improve scalability and reduce costs, they are not exempt from risks. Optimistic Rollups introduce deadlines to contest transactions, which can give rise to fraud attempts during this waiting period. In addition, the sidechains and their bridges are vulnerable to attacks because they do not directly use the safety of the Layer 1 . Piracy of the validators of a sidechain could cause loss of funds.
Complexity and deadlines for the withdrawal of funds
One of the main criticisms of optimistic rollups concerns the waiting time necessary to withdraw funds. Indeed, once a user wants to withdraw his funds, he must wait until the protest period was completed before the transaction is confirmed on the main channel. It can take several days, making the process less fluid.
The future of Layer 2 solutions
Towards a wider adoption of the Rollups
With the growing popularity of dApp S and DEFI services , Rollups are about to become the reference solution for Ethereum . In particular, ZK-Rollups , like zkSync , offer increased safety and faster validation times, which could promote their large-scale adoption.
Faq
What is the Layer 2 in simple terms? Layer 2 is a technological solution that makes it possible to deal with transactions outside the main blockchain, thus reducing costs and accelerating transactions while subjecting the results to the main channel.
Why is Layer 2 crucial for Ethereum ? It solves the problems of scalability and high costs, allowing massive adoption and more fluid use of the dApp S and DEFI services.
How do cryptographic evidence work in ZK-Rollups? ZK -Rollups use cryptographic evidence called ZK-Snarks to prove the validity of transactions without the need to execute them on the main channel.
What is the main difference between rollups and sidechains? Rollups main channel to validate transactions, while sidechains have their own consensus mechanism and operate more independently, which can introduce additional risks.
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Noah
Training engineer, I quickly became interested in the field of finance. Convinced that decentralized finance has a bright future ahead of it, I participate in its democratization by developing Crypternon.
