Author: 0xmiddle

AO can be understood as a network with unlimited sharding and unlimited expansion. Each Process is a shard.

AO is not a blockchain in the traditional sense. Its unconventional and counter-intuitive design can easily cause researchers who have just learned about AO to get confused at certain points, especially when researchers try to frame AO using the traditional blockchain architecture:

1. Non-PoS, non-PoW, what kind of consensus mechanism is the "holographic consensus" mentioned by AO?

2. Without a hash chain or even a block, how does AO ensure that data is immutable?

3. Without a coordination center, how can AO ensure the consistency of the global state?

4. Without a redundant calculation mechanism, who will ensure the reliability of calculations? What should I do if I make a calculation error?

5. Without shared security, how to ensure interoperability between Processes?

I will use 3 perspectives and concepts that everyone is already familiar with in the blockchain to help everyone travel from the known to the unknown and turn the unknown into the known. , understand AO on a perceptual level.

Fragmentation perspective

Through Ethereum 2.0, Polkadot, Near and other public chains In education, everyone should be familiar with "sharding".

The concept of sharding: In blockchain, sharding is a solution to improve network scalability by splitting the network into multiple shards. Each shard independently verifies and processes transactions and generates its own blocks, thereby improving overall network efficiency. Synchronous interoperation can be achieved within shards, and asynchronous interoperation can be achieved between shards through a certain communication protocol.

Polkadot is the most typical sharding architecture. In Polkadot, each parachain is a shard. The parachain independently collects and packages its own blockchain, and the relay chain randomly assigns a validator.verified by a panel of witnesses. The unified XCM message format is used to communicate between parallel chains to achieve interoperability.

AO's ultimate fragmentation

From the perspective of fragmentation, AO can be understood It is the ultimate "sharding": each Process is a shard. Imagine what it would be like if every smart contract in Ethereum ran on a separate shard? Yes, this is AO. Each Process is independent, and calls between Processes are message-driven and performed in a completely asynchronous manner.

Modular perspective

But we found a key, in the design of Polkadot, there is A "relay chain", there is also a "beacon chain" in ETH2.0, their role is to serve as a unified consensus layer to provide shared security. The unified consensus layer is responsible for providing direct or indirect verification services for all shards and message transmission between shards. AO does not seem to have this component, so how is the consensus layer of AO designed?

AO's consensus layer is actually Arweave. From a modular perspective, AO can be understood as the L2 of Arweave, with Arweave as the Rollup of L1. The logs of all messages generated during the operation of the AO network will be uploaded to Arweave for permanent storage, that is, on Arweave There is an immutable record of the operation of the AO network. So you may ask, Arweave is a decentralized storage platform and does not have much computing power. How does Arweave verify the data uploaded from the AO network?

The answer is: Arweave does not verify, the AO network itself will have an optimistic arbitration mechanism. Arweave accepts all message data uploaded from the AO network. Each message will carry its sender process id and the signature of the CU (Computing Unit) that runs it, as well as the SU (Sorting Unit) that sorts it. )'s signature. When a dispute occurs, you can rely on the immutable message records on Arweave to introduce more nodes for re-operation to create a correct fork, discard the original wrong fork, and penalize the wrong CU in the correct fork or Deposit for SU. It should be noted here that MU is only responsible for collecting the pending messages of Process, passed to SU, is trustless, requires no deposit, and does not involve forfeiture.

AO is very similar to Optimistic Rollup with Arweave as L1, except that the verification challenge process does not occur on L1, but in the AO network itself.

However, there is still a problem here. It is impossible to wait for every message to be included in Arweave before confirming it. In fact, the final formation time of Arweave It takes more than half an hour. Therefore, AO will have its own soft consensus layer, just like Ethereum's Rollups, which will have its own soft consensus layer. Most transactions will not wait for L1 confirmation before being credited.

The Process in AO actually determines the verification strength independently.

As the message receiver, Process needs to decide whether to wait for Arweave confirmation before processing the message, or to process the message after confirmation by the soft consensus layer, even if In the soft consensus layer confirmation process, Process can also adopt a flexible strategy. It can be processed immediately after confirmation by a single CU, or it can be redundantly confirmed by multiple CUs and processed after cross-validation. The redundancy is also determined by Process.

In practical applications, verification strength is often related to the amount of the transaction, for example

Small For medium-amount transactions, adopt a quick verification strategy and process them after single-point confirmation

For medium-amount transactions, according to the specific amount, adopt multi-point confirmation and post-processing with different degrees of redundancy Strategy

For large-amount transactions, adopt a cautious verification strategy and process them after confirmation by the Arweave network

This is what AO calls "holographic consensus"+" "Elastic Verification" model, by decoupling "verifiability" and "verification" behaviors themselves, AO adopts a completely different approach to consensus issues from traditional blockchains. The responsibility for message verification does not lie with the network itself, but with the receiver. Process itself, or rather the application developer.

It is precisely because of adopting such a consensus model that AO is able to adopt"Ultimate sharding" hub-less, infinite expansion model.

Of course, elastic verification leads to different verification strengths of different processes. In complex interoperation, it may lead to a break in the trust chain and a longer call chain. The failure of individual links will lead to the failure or error of the overall transaction. In fact, during the AO test network stage, such problems have been exposed. I think AO should set a minimum verification intensity standard for all verification tasks. Let us wait and see what new design AO will have in its upcoming official network.

Resource perspective

In traditional blockchain systems, resources are abstracted into "areas "Block space", block space can be understood as a collection of storage, computing and transmission resources provided by nodes, and is organically combined with on-chain blocks to provide a carrier for on-chain applications to run. Block space is a limited resource. In traditional blockchains, different applications need to compete for block space and pay for it, and nodes make profits through this payment.

There is no concept of blocks in AO, and naturally there is no concept of "block space". But like smart contracts on other chains, each Process on AO also needs to consume resources when running. It requires nodes to temporarily store transactions and status data, and it also requires nodes to consume computing resources to perform computing tasks for it. The outgoing message requires MU and SU to be transmitted to the target Process.

In AO, nodes are divided into three categories, CU (computing unit), MU (message unit), and SU (sequencing unit), where CU is the computing unit. core of the mission. MU and SU carry communication tasks. When a process needs to interact with other processes, a message will be generated and stored in the outbound queue. The CU running the process will sign the message. The MU will extract the message from the outbound queue and submit it to SU. SU will assign the message A unique serial number and uploaded to Arweave for permanent storage. MU then delivers the message to the inbound queue of the target process, and the message delivery is completed. MU can be understood as the collector and deliverer of messages, and SU can be understood as the sequencer and uploader of messages.

As for storage resources, the MU in the AO network only needs to store the temporary data required for calculation, which can be discarded after the calculation is completed. Responsible for permanent storage is Arweave, although Arweave cannot be expanded horizontally, its storage performance ceiling is extremely high. The storage requirements of the AO network will not be able to touch the ceiling of Arweave in the foreseeable future.

We found that the computing resources, transmission resources, and storage resources in the AO network are all decoupled. In addition to the unified storage resources provided by Arweave, computing resources and transmission Resources can be expanded horizontally without any restrictions.

The more and higher-performance CU nodes join the network, the network will have higher computing power and can support more Process operations; similarly ,The more ,higher performance MU and SU nodes join the network, the ,faster the transmission efficiency of the network will be. In other words, the "block space" in AO can be continuously created. For applications, you can either purchase public CU, MU, or SU node services in the open market, or you can run your own private nodes to serve your own applications. If the application's business expands, it can completely improve performance by expanding its own nodes, just as Web2 applications do. This is unimaginable on traditional blockchains.

At the resource pricing level, AO can be flexibly adjusted through supply and demand, thus allowing the supply of resources to expand and contract according to demand. This adjustment will be very sensitive, and nodes can be added and exited very quickly. If we look back at Ethereum, we will find that when resource demand rises sharply, everyone has no choice but to endure high gas fees, because Ethereum cannot improve its performance by expanding the number of nodes.

Summary

Above, we started with concepts familiar to most encryption researchers, such as "Sharding", "Modularization", "Rollup", "Block Space", etc., cut into the principles and mechanisms of AO, helping everyone understand how AO achieves almost unlimited expansion through disruptive innovation.

Now looking back at the first few questions, do you understand them?

1. Non-PoS, non-PoW, what kind of consensus mechanism is the "holographic consensus" mentioned by AO?

AO's consensus mechanism is actually a design close to Op Rollup. At the level of hard consensusAccording to Arweave, at the soft consensus level, each Process can independently decide the verification intensity and how many CU nodes perform redundant calculations.

2. Without a hash chain or even a block, how does AO ensure that data is immutable?

DA data uploaded to Arweave is immutable, providing verifiability for all calculations and transmission processes on AO. AO itself does not need to limit the processing capacity per unit time, so there is no need to set blocks. "Hash chain" and "block", these structures used to ensure the immutability of data, are available in the Arweave chain.

3. Without a coordination center, how can AO ensure the consistency of the global state?

Each Process is an independent "shard" that manages its transactions and status independently. Processes interact in a message-driven manner. Therefore global state consistency is not required. Arweave's permanent storage provides global verifiability and historical traceability, combined with an optimistic challenge mechanism, which can be used for dispute resolution.

4. Without a redundant calculation mechanism, who will ensure the reliability of calculations? What should I do if I make a calculation error?

AO does not have a globally enforced redundant calculation mechanism. Each Process can decide on its own how to verify the reliability of each message sent. If a calculation goes wrong, it can be discovered and corrected in the form of an optimistic challenge.

5. Without shared security, how to ensure interoperability between Processes?

Process needs to manage the credit of each Process it interoperates with, and can use different levels of verification strength for Processes with different security levels. For interoperations with relatively complex call chains, in order to avoid higher error correction costs caused by a broken trust chain, AO may have a minimum verification strength requirement.