Blockchain Technology for Kids: nodes are nosy gossips
Yesterday we learned that the blockchain is a ledger of information that's not controlled by anyone. It's also not located in any one place. The blockchain exists on the many distributed nodes that build it. So what's a node?
A node is an individual computer participating on the blockchain and creating new blocks for it. Each of these computer nodes talk to other nodes in a system called P2P (peer to peer). So each computer node is a "peer" to the others. Your peers, as you probably know, are people in your community with the same status as you. So in the community of the blockchain, each node is talking to other nodes similar status. These nodes are all peers. There isn't one boss node and a bunch of worker nodes -- they're all on the same level.
Nodes are located all over the world, and there are even some bitcoin nodes located out in space! We refer to all of them as distributed nodes. But this doesn't mean the nodes are distributed by someone or something. It means that these nodes are involved in a distributed system: “A distributed system is a model in which components located on networked computers communicate and coordinate their actions by passing messages.” (~ Wikipedia)
So far, we have a network of computers talking to their peers on a distributed system called the blockchain, that's tracking (in the case of bitcoin) cryptocurrency transactions. And these networked computers are called “nodes.” So what do the nodes actually do?
They build the blockchain by creating blocks. Using the bitcoin blockchain as an example, inside each block is data verifying and broadcasting bitcoin transactions. And each node acts as an authority to verify these transactions. So if Jack sends a bitcoin to Jill, nodes will verify that the transaction occurred and will broadcast or write into the block's data that it's now Jill, and no longer Jack, who owns that bitcoin.
Each node will also communicate with its peers, but it does so with an important caveat: nodes don't trust each other. So a node views all the other nodes suspiciously! And it's the job of a node to check up on its peers.
Let's say we have a node. We'll call her Nancy. Every time Nancy the Node receives a block from a fellow peer announcing that a bitcoin transaction is occurring, she questions it suspiciously. Nancy will then check for herself and verify the transaction, to make sure it happened exactly the way it was told to her.
Nodes are like a bunch of nosy gossips, each trying to verify that what they're hearing is true. And the community of nosy, gossiping nodes is always changing. Some join the community, some leave. But each one is busy verifying and synchronizing its copy of the blockchain with the copies of its peers.
It's important to realize that as the number of nodes increases, so does the blockchain's security and reliability. You'll never see an error message that a blockchain is “down.” Why? Because it's always being held up by many, many nodes. One individual node may go down, but they'll never all go down at once.
Next time we'll look at what happens when a piece of node gossip turns out to be a lie!
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@geke, I'm loving your handle and your explanations! I'm still a little fuzzy on how new blocks can be written and verified at the same time. It seems that enough nodes have to have information about a new transaction for it to be verified. But how do we know that all of those nodes aren't simultaneously getting bad information?
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Fantastic....thanks for sharing @geke