Polymer Labs has launched a real-time interoperability protocol for connecting all Ethereum rollups, known as Polymer Hub. 

The new protocol verifies and stores the headers of all connected rollups by streaming messages, states, and logs over IBC primitives (equivalent to Web2’s TCP/IP). This allows it to prove any arbitrary state across rollups at a low cost.

Before now, Rollup/L2 ecosystems were connected only within their walled gardens. ...