Discussion topic for EIP-8070 [PR]
Description
Introduce custody-aligned sampling in the EL blobpool to vacate bandwidth.
Abstract
This proposal introduces the sparse blobpool, a construction that brings cell-level, custody-aligned sampling in the Execution Layer (EL). For every new type 3 (blob-carrying) transaction, an EL node fetches full blob payloads only with probability p = 0.15, and otherwise it merely samples the blobs, using the same custody assignment as its Consensus Layer (CL) counterpart. For full nodes, this means downloading as little as 1/8 of the data (8 out of 128 cells), so that the average bandwidth consumption compared to the (current) full blobpool is 0.15 + 0.85/8 ~ 0.25, a ~4x reduction. The choice of p = 0.15 balances reducing bandwidth consumption with guaranteeing the full propagation of txs, by ensuring that for each blob tx there exists a large connected backbone of nodes that have the full blob payload. At an individual node level, p = 0.15 translates to 98.6% probability of least 3/50 neighbours holding the full blob payload, only 0.03% chance of total unavailability. The sampling performed with probability 1 - p = 0.85 enables streamlined data availability checks during block validation, as well as enhancing the availability of the data.