Ethereum has become an essential platform for many decentralized applications. However, as its adoption increases, it faces significant challenges, primarily in scalability and transaction fees . During traffic spikes, fees can reach hundreds of euros for a single transaction. To address these issues, Layer 2 have been developed. These solutions accelerate transactions while reducing costs. This article explores in depth how Layer 2 works, its different types, and the associated challenges.
Table of contents
Understanding the concept of Layer 2
Definition and differences with Layer 1
Layer 1 refers to the main layer of a blockchain , such as Ethereum or Bitcoin. It is on this layer that all transactions are recorded and verified. Verifying a transaction involves confirming that it complies with the network rules, such as the availability of funds, the authorization of the digital signature, and the absence of double-spending. Validators ( or miners) on Layer 1 rely on these rules and consensus mechanisms, such as Proof of Work Work or Proof Proof of Stake , to confirm or reject a transaction.
However, Layer 1 has limitations in terms of scalability. Ethereum , for example, can process approximately 15 transactions per second ( TPS ), which quickly becomes insufficient when thousands of dApps dApp DeFi services are Layer 2 solutions come in.
Layer 2 is an additional layer that relies on the main blockchain (Layer 1) but processes transactions externally to relieve the load on the main network. Once processed, transactions are submitted to Layer 1 as batches or summaries, thus reducing the load on the main network and lowering fees.
Why did Layer 2 emerge as a solution?
With the exponential growth of dApps dApp DeFi services Ethereum network quickly reached its limits. Transactions became not only slower but also more expensive, making some applications unviable.
Layer 2 solutions, particularly rollups and sidechains , were developed to address these pressing needs. They increase transaction processing capacity while keeping costs much lower, thus making blockchain more accessible.
The different types of Layer 2 solutions
Rollups: Optimistic Rollups and ZK-Rollups
Rollups are one of Layer 2 - chain transactions to be processed before a summary of these transactions is submitted to the main chain (Layer 1).
Optimistic Rollups : These rollups operate on the assumption that all transactions are valid by default. However, if a network participant suspects fraud or an error, they can challenge the validity of a transaction by providing "fraud proof ." This challenge mechanism introduces a waiting period (usually between one and two weeks) to allow anyone to question the transaction's validity. This delay explains why withdrawing funds from Optimistic Rollups can be lengthy: the main blockchain must wait for the challenge period to end before confirming the transaction.
ZK-Rollups : Unlike Optimistic Rollups, ZK-Rollups (Zero Knowledge Rollups) use cryptographic proofs to verify the validity of off-chain transactions. These proofs, called ZK-SNARKs or ZK-STARKs , are submitted to the main chain, ensuring that transactions are compliant without needing to execute each transaction on Layer 1. This allows transactions to be validated almost instantly, without the dispute delays associated with Optimistic Rollups. A notable project using ZK-Rollups is zkSync , which stands out for its speed and low cost for fund transfers.
Sidechains: How they work and examples
Sidechains blockchains that operate in parallel with the main chain (Layer 1). They have their own consensus mechanism, allowing them to process transactions autonomously. However, this means they do not directly benefit from the security of Layer 1. Users can transfer assets between the sidechain and the main chain via bridges .
These bridges allow the two chains to be linked, but they also introduce additional security risks, particularly in the event of hacking or compromise of the bridge validators.
Although Polygon Proof of Stake (PoS) consensus mechanism , it relies on Ethereum for transaction finality and security 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 aggregated states of the sidechain (or Plasma chain in some implementations) and include a summary of transactions that have been validated on Polygon . Although transactions are processed and validated autonomously Polygon Ethereum ensures a form of transaction finality.
This means that, even though transactions are first validated via Polygon's PoS mechanism, the final state of the blockchain (or at least part of that state) is secured on Ethereum via these checkpoints, creating an additional validation layer.
2. Enhanced security thanks to Ethereum
By using Ethereum to anchor these checkpoints, Polygon benefits from the security of the Ethereum , including its immutability and the power of its decentralized network . This ensures that even if a problem occurs on Polygon Polygon 's PoS mechanism ), the data anchored on Ethereum remains reliable and can serve as a basis for restoring transactions to a consistent state.
The main difference between sidechains and rollups lies in the consensus mechanism. Sidechains manage their own security and consensus, while rollups rely on the security of the main chain (Layer 1) to validate final transactions. A well-known example of a sidechain is Polygon Ethereum sidechain that enables low-cost, high-speed transactions but requires the use of bridges to interact with Ethereum .
State Channels: Usefulness and Functioning
State Channels are another Layer 2 that allows two parties to process off-chain transactions. They work by opening a channel where transactions are conducted directly between the parties. Only when the channel is closed is the final state of the transactions recorded on the main chain. This allows for multiple transactions to be carried out quickly and without fees, as long as the channel remains open.
A popular example of a State Channel is Bitcoin 's Lightning Network , which enables fast and inexpensive payments without overloading the main blockchain. Transactions are processed off-chain, and only final interactions, such as channel closure, are submitted to the blockchain.
The advantages of using Layer 2
Transaction fee reduction
Layer 2 solutions significantly reduce transaction fees by moving operations off the main chain. Rather than paying high fees for each transaction on Layer 1, users only pay for validating batched transactions on Layer 2. This is particularly important for DeFi applications or blockchain games, where many small transactions are required.
Improved scalability
Layer 2 increases network capacity by increasing the number of transactions that can be processed simultaneously. For example, Ethereum can process approximately 15 TPS on Layer 1. With solutions like zkSync or Optimism , this number can climb to several thousand TPS, making transactions faster and more accessible.
Comparison between Layer 1 and Layer 2
Major differences
Layer 1 offers maximum security by processing each transaction directly on the blockchain, but at the cost of low scalability and high fees. Layer 2 improves scalability and reduces costs, but can sometimes compromise security. For example, Optimistic Rollups introduce a delay for contesting transactions, which can expose the network to fraud attempts. Similarly, sidechains can be vulnerable if their consensus mechanism or the 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 enables fast, low-cost transactions on Ethereum . By using cryptographic proofs to validate transactions, zkSync ensures high security while reducing fees. It is an ideal platform for applications requiring frequent and rapid transfers.
Optimism: Why is it a popular solution?
Optimism is one of the leading implementations of Optimistic Rollups on Ethereum Ethereum smart contracts , allowing dApp to easily migrate to the network while reducing fees. However, users must wait until the end of the dispute period before withdrawing their funds from the network.
Polygon : An example of a popular sidechain
Polygon , formerly Matic, is an Ethereum sidechain Ethereum speed, low-cost transactions. However, because 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.
The challenges of Layer 2
Risk of compromising security
Layer 2 solutions improve scalability and reduce costs, they are not without risk. Optimistic Rollups introduce delays for contesting transactions, which can lead to fraud attempts during this waiting period. Furthermore, sidechains and their bridges Layer 1 security . A breach of a sidechain's validators could result in significant losses.
Complexity and delays in withdrawing funds
One of the main criticisms of Optimistic Rollups concerns the waiting time required to withdraw funds. Indeed, once a user wishes to withdraw their funds, they must wait for the dispute period to end before the transaction is confirmed on the main chain. This can take several days, making the process less seamless.
The future of Layer 2 solutions
Towards wider adoption of roll-up banners
With the growing popularity of dApps dApp DeFi services , rollups are becoming the standard solution for Ethereum . In particular, ZK rollups , such as zkSync , offer enhanced security and faster validation times, which could drive their widespread adoption.
FAQ
What is Layer 2 in simple terms? Layer 2 is a technological solution that allows transactions to be processed outside the main blockchain, thus reducing fees and accelerating transactions while submitting the results to the main chain.
Why is Layer 2 crucial for Ethereum ? It solves scalability and high fees, enabling mass adoption and smoother use of dApp and DeFi services.
How do cryptographic proofs work in ZK-Rollups? ZK -Rollups use cryptographic proofs called ZK-SNARKs to prove the validity of transactions without needing to execute them on the main chain.
What is the main difference between rollups and sidechains? Rollups rely on the security of the main chain to validate transactions, while sidechains have their own consensus mechanism and operate more independently, which can introduce additional risks.
Cryptocurrency investments are risky. Crypternon investment advice .
Some links in this article are affiliate links, which means that if you purchase a product or sign up through these links, we will receive a commission from our partner. These commissions do not incur any additional cost to you as a user, and some even allow you to take advantage of promotions.
AMF recommendations. There is no guaranteed high yield, a product with high performance potential implies a high risk. This risk taking must be in line with your project, your investment horizon and your ability to lose part of this savings. Do not invest if you are not ready to lose all or part of your capital .
To go further, read our pages legal notices , privacy policy and general conditions of use .
Yoann
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.
