Blockchain technology is a way to have a peer-to-peer computing network to work in sync in order to store and upend a decentralized database – the distributed ledger that we often refer to when it comes to Web3 protocols.
A blockchain network is a network of interconnected computing devices known as blockchain nodes. Each node of a blockchain needs to run special software called a blockchain client, which allows the node to verify blocks and transactions.
How does a blockchain node work?
In the intro, we already alluded to the role of nodes in blockchain networks. A blockchain node can be any computing device that has an IP address. To be part of a blockchain network, the computing device has to run a software implementation known as blockchain client. A blockchain protocol can support multiple clients.
The client that a node runs determines the role of that node in the blockchain network. We have nodes that store full copies of the public ledger, maintain consensus and ensure that the network is synchronized. We also have nodes that are specifically optimized for efficient processing of transactions, as well as others that are even more specialized.
Types of blockchain nodes
We can have different types of modes depending on what functions they perform in a blockchain network. Some networks may have nodes that perform functions specific to their protocols and architecture. That said, there are a few types of blockchain nodes that are widely seen across different networks.
Full nodes form the backbone of a blockchain network. These are the nodes that are responsible for ensuring that the network behaves in an honest way. They validate new blocks, store and distribute blockchain data and make sure that the blockchain protocol is followed across the network. A full node is usually thought of as storing a copy of the entire history of the blockchain network. However, this is not always the case, as there are two types of full nodes.
Full nodes that store the entire blockchain ledger are called archive nodes. An archive node never deletes any data, starting from the genesis block of the network. But then we also have pruned full nodes, designed to store only recent data that fits within a certain memory limit. The node actually downloads the entire ledger at the start, but then undergoes a ‘pruning’ process, starting from the oldest entries in the ledger. The process continues until the ledger size is trimmed down to match the node’s memory limit. As new data is added to the node’s pruned copy of the ledger, the oldest entries are continuously deleted.
Light nodes’ main purpose is to process simple transactions quickly and efficiently, which is why they are widely used by crypto wallets. Instead of blocks, light nodes download block headers, which provide a summary of the data recorded in the blocks. This allows them to securely access the blockchain and verify independently the data they receive. For any additional information, they have to make requests to full nodes.
Light nodes cannot participate in the consensus of a blockchain network.
Other blockchain nodes
In some networks we also have blockchain nodes programmed to serve more specialized roles. Let’s see some examples:
1. Mining nodes
While in recent years we’ve seen a significant shift toward Proof-of-Stake, Proof-of-Work consensus still plays a prominent role in Web3, primarily thanks to Bitcoin. In PoW networks new blocks are added by ‘miners’ that compete to solve complex mathematical problems for the opportunity to add a new block to the blockchain and earn rewards. Mining nodes need to have considerable computing power in order to compete effectively for rewards. That’s why PoW networks today are largely dominated by mining pools where hundreds or even thousands of powerful machines work together.
2. Authority nodes
Some protocols utilize authority nodes to secure and moderate their networks. This model relies on a smaller number of select node operators, for example companies or other formal organizations. The main drawback of this approach is that it’s much more centralized than the models employed by networks like Bitcoin and Ethereum.
3. Collator nodes
These nodes are unique to the Polkadot network, which is a multi-chain protocol that aims to build an ecosystem of interconnected blockchains. To achieve that, Polkadot has a main chain called the Relay chain, which is designed to connect a multitude of individual shard chains known as ‘parachains’. Collator nodes are the linchpin of the network architecture as they are responsible for synchronizing parachains with the Relay chain. Collator nodes are able to do this because they run a node of their respective chain and a full Relay chain node simultaneously.
4. Mirror nodes
If you’re familiar with the Hedera Hashgraph you may have heard about mirror nodes. These play a similar role to the light nodes in other blockchain networks. They receive information from Hedera consensus nodes and do not contribute to the network’s consensus themselves. Mirror nodes provide a cost-efficient way to query historical data from the Hedera ledger.
As blockchain technology continues to evolve and mature, the role of the blockchain node is set to become even more important. Web3 developers continue to come up with novel blockchain architecture, which often creates a need for new types of blockchain nodes. Meanwhile, light nodes are an area of active development for networks like Ethereum, as Web3 developers are exploring ways to increase their utility. All this leads us to believe that there’s a lot to look for in this space.
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