EIP4844, Blob and Blob Gas: What you need to know about the Cancun upgrade

Written by: 0xjs@金财经

After the Ethereum Dencun upgrade, Ethereum will adopt EIP-4844, commonly known as proto-danksharding. This upgrade introduces Type-3 transactions (Note: Ethereum previously had Type-0, Type-1, Type-2 transactions), bringing new opportunities and complexities to the L2 network to optimize them Settlement method with the Ethereum base layer.

This article uncovers the details of EIP-4844 and explores its potential impact on L2 networks and the broader blockchain ecosystem.

Problem: High L2 Gas Fees 

L2 solutions improve scalability and reduce transaction costs by processing off-chain transactions and then settling them regularly on Ethereum L1 cost.

Currently, the settlement of L2 transactions on L1 is completed by publishing batches of L2 transaction information through L1 calldata. The cost associated with publishing via calldata is a significant expense for L2.

According to the Dashboard "Rollup Economics" created by Dune user niftytable, the L2 network spent more than 15,000 ETH in December 2023 and more than 10,000 ETH in February 2024 in order to submit transaction information to the Ethereum main network. , not even halfway through March 2024, more than 7,000 ETH have been spent.

< /p>

Solution: Blob Transactions

EIP-4844 solves Ethereum by creating space for data "blobs" For scalability issues, L2 can use these blob spaces instead of calldata for settlement. One major expected consequence is lower L2 fees.  

Some details about Type-3 transactions and blobs:

• Each block can have up to 6 blobs

• Each Type-3 transaction can have 1 or 6 blobs

• Each blob can store up to 128kb of data. The tx sender is still charged for the 128kb blob space if the entire 128kb is not used.

• Blob only needs to be stored for 4096 epochs (about 18 days). This is considered long enough to be retrieved by all participants of the L2, but short enough to keep hard drive usage manageable. This makes blobs cheaper than permanently stored calldata.

Blobs can be thought of as a new type of tool where Rollup can efficiently store transaction and proof data, thereby saving Gas fees when sending this information to the mainnet. This new type of transaction provides a better way for L2 to interact with L1 block space.

Preliminary A rough estimate shows that Blob will save Rollup transaction costs 10-100 times.

New transaction and block header fields

Type-3 transactions have two new fields:

• max_fee_per_blob_gas: The maximum fee a user is willing to pay per Blob Gas

• blob_versioned_hashes: A list of hash outputs for kzg_to_versioned_hash.  

In EIP-4844, the block header will also have two new fields:

< li>

blob_gas_used: The total amount of Blob Gas consumed by transactions in the block

• excess_blob_gas: The total amount of Blob Gas consumed before the block exceeds the target. This is used to set Blob Gas pricing.

Blob propagation

Ethereum has a memory pool mempool, which temporarily stores Type-0, Type-1 and Type-2 transactions. Type-3 transactions will also be in the mempool, but the actual contents of the blob will be propagated through the consensus client blob sidecar and will not reach the execution client. Type-3 transactions only contain a reference to the blob (hash), not the blob itself.  

Understanding Blob Base Charges

EIP-4844 creates a new Blob Gas market. The market operates similarly to EIP-1559, changing the blob base fee based on supply and demand.  

EIP- 4844 operates according to the following pricing rules:

• If the number of blobs in the block is more than the target (currently 3), increase the blob base fee .

• If there are fewer blobs in the block than the target, reduce the blob base fee.

• Do not change the blob base fee if the number of blobs in the chunk is the same as the target.

In addition to this new pricing mechanism, Type-3 transactions will still have the max_fee_per_gas and max_priority_fee_per_gas fields and be subject to the existing EIP-1559 market. In addition to blob space, Type-3 transactions still need to pay for the EVM space they use.

Impact on Ethereum L2

Blob is expected to significantly reduce the cost of publishing to the Ethereum mainnet, leading to a shift in the L2 market. Many in the ecosystem predict that blob base fees will be close to rock-bottom levels in most cases.  

However, this introduction will create new complexities for L2 operators, who will now need to decide between using Type-2 and Type-3 fee mechanisms to aggregate them Wind up. Sometimes, regular Type-2 batch transactions are more expensive than Type-3 Blob transactions and vice versa. Therefore, each L2 must monitor two independent markets to determine which market is more advantageous to use based on current network conditions.

In anticipation that L2 may not require the entire blob space, there may be L2 timing studies that: 1) wait for and completely fill a blob and/or 2) coordinate with other L2s to share the blob space.  

Dencun upgrade and EIP 4844 bring new opportunities to the L2 network, but will also bring more observability challenges to Ethereum. As Type-3 transactions enter the market, L2 will need to manage the new opportunities presented by these changes.