TipSet

In a TipSet, multiple blocks proposed at the same blockchain height are aggregated, rather than forcing the network to choose a single canonical block. This structure is fundamental to Expected Consensus (EC) mechanisms, which are designed to improve network throughput and reduce the inefficiency of orphaned blocks common in single-chain protocols. By allowing several blocks to be valid simultaneously, a TipSet increases the chain's bandwidth and supports more concurrent transaction processing.

The formation of a TipSet relies on a weighting function that evaluates the collective chain of TipSets, not individual blocks. This weight is typically calculated from the cryptographic proofs provided by validators (e.g., storage proofs in Filecoin or attestations in Ethereum). The heaviest chain—the chain with the highest cumulative TipSet weight—is considered the canonical one. This approach decouples block production from immediate finality, enabling faster block times without compromising security.

From an implementation perspective, a TipSet is a directed acyclic graph (DAG) of blocks at a specific epoch. Clients and nodes must validate all blocks within a TipSet, checking their proofs and parent references. This validation ensures that even though multiple blocks exist at one height, they all adhere to the protocol's rules. The parent tipset of a new block is often the entire set of blocks at the previous height, creating a robust and interlinked chain structure.

The primary advantages of the TipSet model include improved scalability through parallel block validation and reduced wasted work, as less computational effort is discarded compared to networks where only one block per round succeeds. It also enhances network liveness by making chain reorganizations less disruptive, as multiple valid branches can be merged. This makes TipSets particularly suitable for proof-of-stake and proof-of-space-time consensus models.

For developers, interacting with a TipSet-based chain requires understanding APIs that return sets of blocks. For instance, querying chain head data will return a TipSet object containing multiple block headers (CIDs). Smart contracts and chain analysis tools must be designed to account for this multiplicity, as state computations may need to consider transactions across all blocks within the canonical TipSet for a given height.

A TipSet is a set of blocks that share the same parent block and epoch height, meaning they are considered for inclusion in the chain concurrently. Unlike traditional blockchains that enforce a strict linear sequence, a TipSet-based consensus mechanism allows multiple miners to produce valid blocks for the same slot. This design directly combats the inefficiency of orphaned blocks (blocks that are mined but not included in the canonical chain), as multiple blocks can be incorporated, increasing the network's transaction processing capacity and reducing wasted computational work.

The security and finality of a chain built with TipSets rely on a weighting function, often based on a variant of Proof-of-Stake or Proof-of-Space-Time. In Filecoin's Expected Consensus, for example, each block in the TipSet contributes to the chain's weight based on the storage power it represents. The canonical chain is then selected as the one with the heaviest cumulative weight from its TipSet history, not simply the longest chain. This encourages convergence as honest actors naturally extend the heaviest chain they observe.

From a practical perspective, nodes maintain a TipSet cache and a directed acyclic graph (DAG) of block headers. When a new valid block is received, it is grouped with its siblings at the same height to form a new TipSet. Clients and smart contracts interact with a logical 'head' of the chain, which is the TipSet with the greatest weight. This abstraction means applications see a single consistent state, even though the underlying data structure is composed of multiple parallel blocks, enabling significant scalability improvements over linear blockchains.

A TipSet is a set of valid blocks that share the same parent block height and are mined concurrently. This structure is a core innovation of Expected Consensus mechanisms, allowing multiple miners to propose blocks for the same epoch without creating a fork. Instead of selecting a single canonical chain, the protocol treats the entire TipSet as the valid head of the chain, increasing network throughput and liveness. This design contrasts with single-chain protocols, where only one block can occupy each height.

The primary function of a TipSet is to aggregate the collective weight of parallel block production. Each block in the set contains a collection of messages (e.g., transactions or storage deals), and the network considers all messages across the TipSet as confirmed. This aggregation is secured by the underlying consensus rules, which validate that all blocks in the set reference the same parent and meet the protocol's cryptographic and economic requirements. The chain selection rule then chooses the heaviest TipSet (often measured by total storage power or stake) as the canonical predecessor for the next epoch.

From a practical standpoint, TipSets make blockchain networks more resilient and efficient. They reduce the 'wasted work' of orphaned blocks common in Proof-of-Work chains, as concurrent valid blocks are incorporated into consensus. For developers, this means understanding that the chain head is often a set of blocks, not a single one. Analysts monitor TipSet size (the number of blocks per epoch) as a key metric for network activity and health, indicating the level of parallel participation and potential chain capacity.