System requirements

Functional:

1. Peer Discovery: Nodes must be able to discover other peers on the network using a defined protocol (e.g., multicast or distributed hash table).
2. Data Sharing: Peers should be able to share files and data with each other directly without needing a centralized server.
3. Data Integrity: Implement checksum or hash verification mechanisms to ensure data has not been altered during transmission.
4. Dynamic Node Management: The network should handle nodes joining and leaving gracefully, redistributing responsibilities as needed.
5. Resource Availability: Nodes must allow others to request and access resources, and define policies for resource sharing.

Non-Functional:

1. Scalability: The system should efficiently handle an increasing number of nodes and data without performance degradation.
2. Security: Implement encryption for data transmitted over the network and mechanisms to protect against malicious nodes (e.g., reputation systems).
3. Redundancy: The system should ensure that data is not lost when nodes leave and that copies exist across multiple peers.
4. Fairness: The network should provide fair access to resources among peers to prevent monopolization by any single node.
5. Performance: The system should ensure low latency and high throughput during data sharing operations.

API design

Based on these functional requirements, we can categorize the APIs into the following groups:

1. Peer Management APIs

• JoinNetwork(network_id): Joins a specific P2P network.
• LeaveNetwork(): Leaves the current P2P network.
• DiscoverPeers(): Discovers other peers in the network.
• GetPeerInfo(peer_id): Retrieves information about a specific peer.
• EstablishConnection(peer_id): Establishes a direct connection with a peer.

2. Data Management APIs

• ShareFile(file_path, metadata): Shares a file with the network.
• SearchFile(keywords): Searches for files based on keywords or metadata.
• RequestFile(file_id, peer_id): Requests a file from a specific peer.
• ReceiveFile(file_id, peer_id): Receives a file from a specific peer.
• VerifyFileIntegrity(file_id): Verifies the integrity of a file.

3. Resource Management APIs

• OfferResource(resource_type, capacity): Offers a resource to the network.
• RequestResource(resource_type, required_capacity): Requests a resource from the network.
• AllocateResource(resource_id, peer_id): Allocates a resource to a peer.
• ReleaseResource(resource_id): Releases a previously allocated resource.

4. Security APIs

• GenerateKeyPair(): Generates a public/private key pair for the peer.
• EncryptData(data, recipient_public_key): Encrypts data using the recipient's public key.
• DecryptData(encrypted_data, private_key): Decrypts data using the peer's private key.
• VerifySignature(data, signature, sender_public_key): Verifies the authenticity of data.

Database design

Defining the system data model early on will clarify how data will flow among different components of the system. Also you could draw an ER diagram using the diagramming tool to enhance your design...

High-level design

In the high-level design of a peer-to-peer (P2P) network, we'll focus on how the components will work together to form the entire system. Here’s an overview of the key elements in the design and their interactions.

High-Level Design Elements:

1. Peer Communication: Establish a direct communication channel between peers. Peers can send requests and responses using a design pattern, such as sockets or Websockets for real-time communication.
2. Data Distribution: Use techniques like sharding or partitioning where data is distributed across peers based on some criteria, improving load balancing and efficiency.
3. Discovery Protocol: Implement a discovery protocol (like Kademlia or another DHT-based method) to maintain a list of peers and enable efficient lookups for resources.
4. Security Mechanisms: Incorporate encryption (e.g., TLS or end-to-end encryption) for data transmission and a reputation system to assess peer trustworthiness and mitigate the impact of malicious nodes.
5. Fault Tolerance: Ensure redundancy in data storage by replicating data across multiple peers, allowing the network to recover if some peers go offline.
6. User Interface: Provide an interface for users to interact with the system, allowing them to upload, download, and manage resources.
7. Resource Index: Maintains metadata about shared resources (files, computing power, storage, etc.), including location, availability, and other relevant information. This enables efficient search and discovery.
8. Routing Algorithm: Determines the optimal path for data transfer between peers, considering factors like network congestion, peer load, and data proximity.

Supporting Components

• Incentive System: Motivates peers to contribute resources and participate actively in the network. This could involve reputation systems, token-based rewards, or other mechanisms.
• Monitoring and Management: Collects network metrics, detects anomalies, and provides tools for network administration and troubleshooting.
• Trust Management: Evaluates the trustworthiness of peers based on their behavior and reputation.
• Anonymity Layer: Protects user privacy by obfuscating their identity and traffic patterns.

Request flows

This sequence diagram clearly outlines the dynamic interactions in the process of searching for a file, searching for peers, downloading the file and joining the P2P network.

Description of the Sequence Diagram:

1. User sends a search query to the DiscoveryService.
2. The DiscoveryService responds with a list of peers.
3. The User then connects to Peer1 and Peer2, requesting the desired file from each.
4. Peer1 and Peer2 respond by sending the file data back to the User.
5. The User sends the received data to the DataIntegrityModule for validation.
6. The DataIntegrityModule confirms whether the data is valid or not and returns this confirmation to the User.
7. Finally, the User joins the network as a new peer.

Trade offs/Tech choices

Explain any trade offs you have made and why you made certain tech choices...

Failure scenarios/bottlenecks

Try to discuss as many failure scenarios/bottlenecks as possible.

Future improvements

What are some future improvements you would make? How would you mitigate the failure scenario(s) you described above?