Vitalik Buterin outlined a framework categorizing nodes into three types based on their roles and trust assumptions: Light nodes, which are capable of verifying chain correctness and availability, and accessing necessary data privately—assuming at least one honest heavy node exists to maintain liveness, while safety remains unconditional; Medium nodes, which Ethereum relies on with an n/2-of-n trust model, such as attesters in staking and FOCIL participants; and Heavy nodes, which the protocol trusts on a 1-of-n basis for functions like optimal block construction or proof generation.