Arbitrum Orbit and Rollup Scaling Developments

Offchain Labs recently launched Arbitrum Orbit, an extensible framework that allows developers to spin up new Layer 3 (L3s) that settle on either Arbitrum One or Arbitrum Nova. Put simply, Arbitrum Orbit can be considered an L3-as-a-service provider. This is analogous to rollups-as-a-service, except the settlement layer used in this case is an optimistic rollup (OR) instead of Ethereum. 

This calls to mind L3s that both StarkWare and Matter Labs have previously introduced, which leverage recursive validity proofs to confer security to the L3s. However, L3s on ORs have different security assumptions, and we will look into some of the advantages and disadvantages of building L3s on ORs.