This is a write-up on an idea first suggested by Mark on Discord here. Key considerations in ePBS are the time allowed for block execution and the time allowed for propagation. Positioning the payload timeliness committee (PTC) vote earlier allows more time for execution and positioning it later allows more time for propagation. A short time for propagation of blobs is particularly unfortunate, given the amount of data that must be propagated before the deadline. However, it turns out that we actually do not need to strictly compromise between either propagation or execution, because the PTC can be instructed to have dual deadlines. The PTC first observes the timeliness of the payload, ensuring it arrives early in the slot, allowing time for more execution. At a later point in the slot, the PTC also checks if the blob data is available (for example in custodied columns, depending on the state of DAS), and casts a positive vote if both deadlines were met. Figure 1 illustrates the design. Note that time indications are tentative and subject to change. Figure 1. A dual-deadline PTC vote in ePBS. The design enforces that the payload is available early in the slot to allow time for execution, but leaves room for blob data to propagate over a longer time. As shown in Figure 1, by staggering the deadlines, the majority of the slot can be used for: execution of the payload, propagation of blobs,
6/27/2025EIP-7918 introduces the constant BLOB_BASE_COST, constituting the reserve price for a blob expressed in EL gas. The reserve-price design fulfills two separate functions: To ensure a functioning fee market, by keeping the blob base fee in a range where its adjustment affects the demand for blobspace. To charge at least a fraction of the cost for the compute imposed on nodes, at the prevailing market rate. The preliminary setting is: BLOB_BASE_COST = 2**14 # 16384 This means that the blob reserve price is slightly below the cost of a simple tx and that the reserve blob base fee is 1/8 (2**14/2**17) of the execution base fee. The setting balances the two stated goals of the EIP, where (1) is ensured already at a lower setting (e.g., $2^{11}$ or $2^{12}$) and (2) can be satisfied with an even higher setting (e.g., $2^{15}$). During the SFI decision, we left the door open to adjust BLOB_BASE_COST after testing the core functionality in devnets. I will here outline why the preliminary setting was selected and the range of settings that could be considered.
6/19/2025During the discussion phase for EIP-7918, Ben Adams has suggested that we compute the minimum blob base fee from the cost of POINT_EVALUATION_PRECOMPILE_GAS, as opposed to using TX_BASE_COST with amortization across blobs. The design seems worthwhile, and I will here analyze it, based on discussion with—and feedback from—Ben, Francesco D'Amato, Justin Traglia, Toni Wahrstätter and Marius Van Der Wijden. Summary The threshold in the if-clause is changed by switching constants, but EIP-7918 remains two lines of spec code. The original constants establish a low minimum blob base fee that still ensures a functioning fee market. The suggested new constants would raise the minimum blob base fee by charging closer to the workload that blobs impose on nodes, still also ensuring a functioning fee market. The rest of this document simply discusses the underlying rationale and implications, illustrating the total workload imposed by blobs on nodes relative to the workload of one point evaluation. Background EIP-4844 (Dencun) EIP-4844 introduced the first phase of Ethereum's data availability sampling (DAS) roadmap. Validators on the consensus layer (CL) verify that the KZG commitments in the payload correspond to the provided blobs by cryptographically verifying the accompanying KZG proofs. Furthermore, execution layer (EL) nodes must also validate the tx_payload_body and verify the wrapped data (blobs, commitments, and proofs) for every blob entering a node's tx pool. MEV-boost also performs similar checks on blobs via the flashbots_validateBuilderSubmission endpoint when they are included in the payload (at least in Nethermind). The computational requirements for verifying a KZG proof for an entire blob are slightly higher than those for verifying a KZG proof for a single point on that blob; the latter is the specific operation covered by the POINT_EVALUATION_PRECOMPILE_GAS (50000) charged to smart contracts. While blobs arriving directly via MEV-boost do not subject EL nodes to the burden of this p2p verification, MEV-boost is an out-of-protocol solution. The protocol should ideally charge users according to the regular (worst-case) scenario of blob txs propagating p2p. This is also the most common behavior today given limited MEV in blobs.
5/26/2025When the if-clause in EIP-7918 evaluates to true, the fee update is operating in the thresholded regime, and should not decrease the blob base fee further. The function then returns: return parent.excess_blob_gas + parent.blob_gas_used // 3 This produces a positive linear response in blob_gas_used that has the same maximum increase as when the if-clause evaluates to false. Two alternatives will be outlined here. Incorporating max blobs in the equation As previously mentioned, computing // 3 ensures that the maximum increase stays the same as in the regular update. Specifically, // 3 compensates for the fact that 1/3 of the max blob gas remains after subtracting TARGET_BLOB_GAS_PER_BLOCK. This is expressed as the equation: (max - target) / max = 1/3. It would be convenient to encode the relationship, which is easily achieved if the EL has access to blobSchedule.target and blobSchedule.max from EIP-7892. In this case, the return statement can be modified to: return parent.excess_blob_gas + parent.blob_gas_used * (blobSchedule.max - blobSchedule.target) // blobSchedule.max If EIP-7892 is confirmed for Fusaka with accessible constants, this return statement could be pursued.
5/20/2025