As we can discuss how the blockchain seen as an immutable ledger. Then question getting that how does the blockchain communicate. With each block and how does the data stored on the block, defend itself from hacks or attacks on the data?

Since the blockchain technology necessitates decentralization. The infrastructural communications network underlying the blockchain should also be decentralized. Since the network follows a peer-to-peer (P2P architecture, and not a client-service model).

The architecture allows Blockchain to work and provides a blockchain with redundancy. In P2P distributed network stands for peer to peer, indicating a network comprehend of peers. The most of networks in place now are called server/client networks. The center square represents a server, with the boxes around it representing nodes. When you want to view a web page, you send a request from your node to a server. The server will make a response with the requested information.

While this works well, but it should some drawbacks. First, since the server is the central point of
communication and holding all the information (webpages, databases, etc). If the server goes slow, the network must have died. This is the idea behind more successful methods of a cyber attack. Blockchain did not use a server-client approach. Instead, it uses peer to peer network to function. In a peer to peer, the nodes (laptops, tablets, etc) communicate directly to each other. Instead of a server holding all the information, the data that makes up the blockchain is or distributed across all the different nodes. So more nodes are the part of the blockchain. It exists more copies.

Peer to Peer structure has the following features:
1. In P2P network Decentralization, Dispatched center and database does not exist.
2. Every node contains the same logic and state. There is no concept of client or server.
3. Unreliability-The connections between nodes are unreliable.

P2P architecture is naturally, therefore, it is suitable for the decentralized blockchain network. This will happens only at the network layer. In upper layers such as the application layer, roles of the node will different. Between full nodes and lightweight nodes. Since P2P networks are decentralized and do not have an authorized database. Nodes can join and split at any time.

As such, resource allotment becomes a major issue. The strategy to locate resources immediately and conclusively is known as content routing.

In search of a solution, the P2P network model has developed several different forms. Including centralized, pure distributed, hybrid, and structured.

The centralized model utilizes distributed storage, a master index, and strong-dependency index server. This model is not sufficiently reliable.

In a pure distributed model, nodes and resources are randomly distributed and disordered. Thus it is suffering from message flooding and storms in ease. Hybrid Network is a combination of super nodes and ordinary nodes. Where super nodes are more likely to influence the network.

The structured P2P network is generally based on a distributed hash table (DHT). Which hashes the resource to obtain the resource ObjectID and assign NodeID to each node in the network.

Conclusion:

In the discussion of P2P networks, it works great for redundancy. If you took out a couple of nodes in the network. It would be able to function as normal. Even if you hack and corrupt the blockchain in one of the nodes. Then copies of it exist on all the other nodes protect it from corruption.