Optimism Bedrock: An Early Guide

L2 chains are doing great for scaling Ethereum, and while we do have many different chains, the most prominent ones have been Optimism, ZkSync, and Arbitrium, to name a few.

The name which you’ll see everywhere is Optimism when it comes to Optimistic rollups.

Optimism is an EVM compatible rollup, which has an upgrading coming out in Q4 of 2022 named Optimism bedrock.

In this publication, we will talk about the upcoming optimism upgrade, “Bedrock.”

Bedrock:

First and foremost, what is bedrock? Simply put, it is an optimistic roll-up architecture built by Optimism. But we already have an OP rollup, so what does Bedrock offer? 

It offers “Ethereum equivalence.” You’ve read that right. Ethereum equivalence and not EVM equivalence. 

Let’s go through the difference between Ethereum and EVM equivalence real quick.

EVM equivalence is the complete compliance with the Ethereum yellow paper, the formal definition of the protocol. In contrast, Ethereum equivalence is compliance to geth, so the execution will have a lesser difference.

Optimism: A look back:

In this blog, I will assume that you are familiar with rollups or L2 and have some idea about the optimistic rollup. 

But, just to refresh, Optimism is an optimistic rollup; the name comes from its proof algorithm. It assumes that every transaction is valid until and unless stated otherwise. 

The otherwise is stated via fraud proofs. Fraud proofs are a claim that some state transaction was not done correctly. If the fraud proof turns out to be valid, the transition is reverted. Theoretically, all the other transitions which came after that invalid transition will also be reverted. Still, we have yet to see that, as currently, the sequencers used are honest because they are built by the rollups themselves. Decentralization has yet to enter the rollup chat.

Learn more about the basic OP architecture in this tweet.

Bedrock: Differences

Moving towards the bedrock version. Let's have a look at some differences which it renders.

1. Block time

The block time of optimism is 13 seconds if pending transactions exist. Bedrock will reduce it to 2 seconds. So the BLOCKNUMBER and TIMESTAMP will be updated after every 2 seconds.

2. Gas Cost

Team Optimism is optimistic when it comes to the gas cost of communication between layers. Although the cost is estimated to change, probably for the better, more accurate numbers will be presented once the test net goes live in the last quarter of 2022.

3. Faster Deposits

The deposit transactions currently take 10 to 20mins. With bedrock, this will reduce by 2 or 2.5 mins. This is because in Bedrock, there should usually be with a small confirmation depth of 10-12 Blocks L1 blocks, so 12*10 = 120secs and 12*12 = 144sec, hence a range of 2-2.5mins.

4. Transaction Types

Optimism bedrock has 3 types of transactions

1. The normal transactions
2. L1 Attribute transactions: These transactions register l1 block attributes such as timestamp, blocknumber, etc. to L2
3. User Deposit transactions: These are the transactions derived from L1 to drive the L2 chain.

5. Transaction Fees

Bedrock uses the same manner at EIP-1559 to determine the transaction fees.

6. Processing

It uses the rollup node and execution node for the sake of processing.

Bedrock Infrastructure:

The rollup node derives and broadcasts L2 blocks created from the L1 data. It appends the block to the canonical chain via the Engine API. The P2P network works like every other synchronization method. The rollup node further handles the L1 chain reorganization.

The Bedrock Geth node is a Geth 1.10.x instance, although it has some altering to make it work for optimism. It is used as an execution engine. Bedrock uses Geth’s built-in transaction pool to sync unconfirmed transactions and uses Geth’s built-in snap sync mechanism to sync state. It serves the Engine API to the Rollup Node and receives instructions from the rollup node.

Then we have Legacy Geth, which is a pre-bedrock L2 Geth node. The legacy node serves historical data to the Daisy Chain.

The Daisy Chain is an RPC request router that sends requests for historical chain data to the Legacy Geth node and requests for current chain data to the Bedrock Geth node.

Bedrock, combined with Cannon, is the only rollup architecture that can support multiple fault proofs and client implementations, and is a core component of the quest to remove upgrade keys from rollup proof-of-failures.

With Bedrock, Optimism will be the first EVM-based rollup to deliver Ethereum-level security guarantees.

Tl:dr Bedrock offers

• Significant reduction in average transaction fees.
• Significant improvement in throughput.
• Advanced optimization of deposits and withdrawals
• Faster sync speed than Optimism node

Testnet:

Bedrock’s testnet is live for developers to test contracts and for node operators.

You can use it with this guide.

Also, read about Ethereum Merge.