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Maintaining the Blockchain – Network, and Nodes
The blockchain is maintained by a peer-to-peer network. The network is a collection of nodes that are interconnected to one another. Nodes are individual computers that take in input and performs a function on them and gives an output. The blockchain uses a special kind of network called “peer-to-peer network” which partitions its entire workload between participants, who are all equally privileged, called “peers”. There is no longer one central server, now there are several distributed and decentralized peers.

Why do people use the peer-to-peer network?
One of the main uses of the peer-to-peer network is file sharing, also called torrenting. If you are to use a client-server model for downloading, then it is usually extremely slow and entirely dependent on the health of the server. Plus, as we said, it is prone to censorship.

However, in a peer-to-peer system, there is no central authority, and hence if even one of the peers in the network goes out of the race, you still have more peers to download from. Plus, it is not subject to the idealistic standards of a central system, hence it is not prone to censorship.

If we were to compare the two:

Blockchain technology: decentralized downloading

Image courtesy: Quora

The decentralized nature of a peer-to-peer system becomes critical as we move on to the next section. How critical? Well, the simple (at least on paper) idea of combining this peer-to-peer network with a payment system has completely revolutionized the finance industry by giving birth to cryptocurrency.

The use of networks and nodes in cryptocurrencies.
The peer-to-peer network structure in cryptocurrency is structured according to the consensus mechanism that they are utilizing. For cryptocurrency like Bitcoin and Ethereum which uses a normal proof-of-work consensus mechanism (Ethereum will eventually move on to Proof of Stake), all the nodes have the same privilege. The idea is to create an egalitarian network. The nodes are not given any special privileges, however, their functions and degree of participation may differ. There is no centralized server/entity, nor is there any hierarchy. It is a flat topology.

These decentralized cryptocurrencies are structured like that is because of a simple reason, to stay true to their philosophy. The idea is to have a currency system, where everyone is treated as an equal and there is no governing body, which can determine the value of the currency based on a whim. This is true for both bitcoin and Ethereum.

Now, if there is no central system, how would everyone in the system get to know that a certain transaction has happened? The network follows the gossip protocol. Think of how gossip spreads. Suppose Alice sent 3 ETH to Bob. The nodes nearest to her will get to know of this, and then they will tell the nodes closest to them, and then they will tell their neighbors, and this will keep on spreading out until everyone knows. Nodes are basically your nosy, annoying relatives.

So, what is a node in the context of Ethereum? A node is simply a computer that participates in the Ethereum network. This participation can be in three ways:

By keeping a shallow-copy of the blockchain aka a Light Client
By keeping a full copy of the blockchain aka a Full Node
By verifying the transactions aka Mining
However, the problem with this design is that it is not really that scalable. Which is why a lot of new generation cryptocurrencies adopt a leader-based consensus mechanism. In EOS, Cardano, Neo, etc. the nodes elect leader nodes or “supernodes” who are in charge of the consensus and overall network health. These cryptos are a lot faster but they are not the most decentralized of systems.

So, in a way, cryptos have to make the trade-off between speed and decentralization.

Who Will Use The Blockchain?
As a web infrastructure, you don’t need to know about the blockchain for it to be useful in your life.

Currently, finance offers the strongest use cases for the technology. International remittances, for instance. The World Bank estimates that over $430 billion US in money transfers were sent in 2015. And at the moment there is a high demand for blockchain developers.

The blockchain potentially cuts out the middleman for these types of transactions. Personal computing became accessible to the general public with the invention of the Graphical User Interface (GUI), which took the form of a “desktop”. Similarly, the most common GUI devised for the blockchain are the so-called “wallet” applications, which people use to buy things with Bitcoin, and store it along with other cryptocurrencies.

Transactions online are closely connected to the processes of identity verification. It is easy to imagine that wallet apps will transform in the coming years to include other types of identity management.

Blockchain and Mainstream Adoption
The impact of blockchain technology is genuinely far-reaching and has far more use-cases than being a facilitator for transactions. Several industries have discovered the benefits of blockchain integration. While Bitcoin and Ethereum are examples of public blockchains, most of these industries require specific functionalities out of their distributed ledger architecture. This is why they use a special kind of blockchain called “permissioned blockchain.”