Thesis

Monolithic vs Modular

There are four layers in a blockchain:

• Execution layer

• Settlement layer

• Consensus layer

• Data Availability layer

"Modular blockchain" is a paradigm that combines these separated layers, and allows us to build a scalable blockchain.

Data Availability layer

In short, the Data Availability (DA) layer plays a role of storing transaction data of Layer 2 blockchains until the L2 transactions are finalized in the L1 blockchain.

Combinations of layers

Conventional rollup

Example of Optimism:

Execution layer	Optimism
Settlement layer	Ethereum
Consensus layer	Ethereum
Data Availability layer	Ethereum

Smart contract rollup with altDA

Example of Eclipse:

Execution layer	Eclipse
Settlement layer	Ethereum
Consensus layer	Ethereum
Data Availability layer	Celestia

Sovereign rollup

Example of Gluon:

Execution layer	Gluon
Settlement layer	Gluon
Consensus layer	Sunrise
Data Availability layer	Sunrise