Peer-to-Peer (P2P) Systems

Decentralized architecture, distributed hash tables, peer discovery, and resilience in peer-to-peer networks

75 minutes

7Detailed Sections

Senior Level

P2P (Peer-to-Peer): every node is equal; no central server. Benefits: decentralization (no single point of failure), scalability (add nodes, add capacity), censorship resistance, latency (peers near you), cost (no massive data centers).

Challenges: discovering peers, network partitions, malicious peers, consistency (eventual vs strong). Architecture: each node stores data and routes requests.

Compare client-server: client depends on server uptime (single point of failure); P2P: node goes down, network continues.

Real-world: BitTorrent (decentralized file sharing), Bitcoin (decentralized currency), DHTs (Distributed Hash Table: decentralized key-value store).

P2P networks solve Byzantine agreement (consensus with faulty/malicious nodes) and partition tolerance (network splits must not lose availability).

Key Takeaways

P2P Architecture: No central server; all nodes equal; peer discovers and connects to other peers

Advantages: Decentralization (no SPOF), scalability, censorship resistance, low latency

Challenges: Peer discovery, network partitions, malicious peers, data consistency

Failure Mode: Nodes leave/fail; P2P must self-heal without central coordinator

Consistency: Eventual consistency preferred over strong consistency (no central authority)

Real-world: BitTorrent (600M+ users), Bitcoin (longest running P2P system), IPFS

Visual Diagram

Peer A <-> Peer B <-> Peer C <-> Peer D (all connected, all route)

All Tutorials Practice Questions

Peer-to-Peer (P2P) Systems

Table of Contents

P2P Fundamentals: Decentralized Architecture

Key Takeaways

Visual Diagram

Distributed Hash Tables (DHT) and Kademlia

Peer Discovery and Network Formation

Gossip and Epidemic Protocols

BitTorrent: Practical P2P File Sharing

Consistency and Conflict Resolution in P2P

Case Studies: P2P at Scale