Core Protocol

Erasure Coding

A Reed-Solomon error-correction scheme applied to shreds during block propagation. The leader encodes each batch of 32 data shreds into 32 additional recovery (parity) shreds. Any 32 of the 64 total shreds are sufficient to reconstruct the original data, providing 50% loss tolerance during Turbine propagation.

IDerasure-codingAliasReed-Solomon

Plain meaning

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A Reed-Solomon error-correction scheme applied to shreds during block propagation. The leader encodes each batch of 32 data shreds into 32 additional recovery (parity) shreds. Any 32 of the 64 total shreds are sufficient to reconstruct the original data, providing 50% loss tolerance during Turbine propagation.

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Technical context

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Consensus, leader rotation, slots, epochs, and the runtime.

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Erasure Coding (erasure-coding)
Category: Core Protocol
Definition: A Reed-Solomon error-correction scheme applied to shreds during block propagation. The leader encodes each batch of 32 data shreds into 32 additional recovery (parity) shreds. Any 32 of the 64 total shreds are sufficient to reconstruct the original data, providing 50% loss tolerance during Turbine propagation.
Aliases: Reed-Solomon
Related: Shred, Turbine
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Branch

Shred

The smallest unit of block data propagated through the network via Turbine. Blocks are split into shreds of up to 1,228 bytes each (fitting in a single UDP packet). Shreds are Reed-Solomon erasure coded—typically 32 data shreds produce 32 recovery shreds—so blocks can be reconstructed even if up to half the shreds are lost.

Branch

Turbine

Solana's block propagation protocol inspired by BitTorrent. Instead of the leader sending a full block to every validator, Turbine organizes validators into a layered tree and propagates shreds through successive tiers. Each node forwards shreds to a small fanout set, reducing the leader's bandwidth requirement from O(n) to O(log n).

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Core Protocol

Shred

The smallest unit of block data propagated through the network via Turbine. Blocks are split into shreds of up to 1,228 bytes each (fitting in a single UDP packet). Shreds are Reed-Solomon erasure coded—typically 32 data shreds produce 32 recovery shreds—so blocks can be reconstructed even if up to half the shreds are lost.

Core Protocol

Turbine

Solana's block propagation protocol inspired by BitTorrent. Instead of the leader sending a full block to every validator, Turbine organizes validators into a layered tree and propagates shreds through successive tiers. Each node forwards shreds to a small fanout set, reducing the leader's bandwidth requirement from O(n) to O(log n).

Core Protocol

Fast Finalization

The sub-second transaction finality goal of the Alpenglow consensus protocol, targeting approximately 150 milliseconds from block production to irreversible confirmation. Fast finalization is achieved by replacing Tower BFT's exponential lockout mechanism (which requires ~31 confirmations over ~12.8 seconds) with Alpenglow's certificate-based approach where a single round of supermajority voting produces an irrevocable finality proof.

Core Protocol

Epoch

A period of 432,000 slots (approximately 2-3 days) that defines a staking cycle. At each epoch boundary, the leader schedule is recalculated based on stake weights, stake activations/deactivations take effect, and inflation rewards are distributed to validators and delegators.

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Core Protocolshred

Shred

The smallest unit of block data propagated through the network via Turbine. Blocks are split into shreds of up to 1,228 bytes each (fitting in a single UDP packet). Shreds are Reed-Solomon erasure coded—typically 32 data shreds produce 32 recovery shreds—so blocks can be reconstructed even if up to half the shreds are lost.

Core Protocolturbine

Turbine

Solana's block propagation protocol inspired by BitTorrent. Instead of the leader sending a full block to every validator, Turbine organizes validators into a layered tree and propagates shreds through successive tiers. Each node forwards shreds to a small fanout set, reducing the leader's bandwidth requirement from O(n) to O(log n).

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Core Protocol

Proof of History (PoH)

A clock mechanism that cryptographically proves the passage of time between events. PoH uses a sequential SHA-256 hash chain where each output becomes the next input, creating a verifiable ordering of events without requiring consensus. The leader produces ~400,000 hashes per slot (~400ms), and any validator can verify the sequence in parallel, enabling Solana's high throughput by removing the need for validators to agree on time.

Core Protocol

Tower BFT

Solana's custom BFT consensus algorithm built on top of Proof of History. Tower BFT uses PoH as a clock to reduce communication overhead in traditional PBFT from O(n²) to O(n). Validators vote on forks with exponentially increasing lockout periods—each consecutive vote doubles the lockout, making rollbacks progressively more expensive. A fork is finalized when it reaches supermajority (66.7%+ of stake).

Core Protocol

Slot

A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.

Core Protocol

Block

A set of entries produced by a leader during a single slot. A block contains transactions bundled into entries, each with a PoH hash proving ordering. Blocks are broken into shreds for network propagation via Turbine. Maximum block size is limited by compute units (48M CU cap per block) rather than byte size.