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What is a Peer-to-Peer (P2P) Architecture?
A peer-to-peer architecture is a framework that outlines how nodes (peers) in a decentralized peer-to-peer network can communicate, interact, and share resources.
P2P architectures are commonly used to build distributed ad hoc networks, mesh networks, and P2P overlay networks that don’t rely on a central server or authority to mediate interactions.
Key Takeaways
- Peer-to-peer architectures provide a framework for building P2P decentralized networks.
- They can be unstructured, structured, or a hybrid combination of both.
- Virtual peer-to-peer networks overlay a P2P architecture on top of a client-server network like the Internet.
- Originally, P2P architectures were used to build networks where every node was both a client and a server.
- Today, many P2P architectures have some degree of centralization to improve scalability and network performance.
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Types of P2P Architectures
The specific implementation of a P2P architecture determines how network connections are managed, how data flows, the roles and responsibilities of each network node, and how resources are shared.
There are currently three main types of P2P architectures:
Unstructured P2P
Each node can act as both a client and a server.Structured P2P
Each node is assigned a specific role for locating and maintaining data.Hybrid P2P
Supernodes act as centralized hubs for certain network management functions, but the actual data exchange happens directly between peers.
Overlay Models in P2P Architectures
An overlay P2P architecture is a framework for building virtual P2P networks on top of another network like the Internet. The overlay facilitates specific P2P interactions like routing and data storage.
Overlay network architectures can be unstructured, structured, or hybrid, depending on how peers are connected and how data is managed.
How Peer-to-Peer Architecture Works
The way a P2P architecture works depends largely on how network nodes connect.
- In an unstructured architecture, nodes randomly connect and search the network for resources.
- In a structured P2P architecture, the connections between nodes are based on a specific algorithm or distributed hash table (DHT) like Kademlia.
- In a hybrid P2P architecture, node connections can be either random or hierarchical, depending on the network’s purpose.
Peer-to-Peer Protocols
Peer-to-peer (P2P) network architects can tailor P2P protocols to ensure their decentralized? networks can support specific use cases. The purpose of the protocols is to ensure that data is efficiently distributed across the network and that nodes can locate and exchange data with each other.
| P2P Protocol | Purpose |
|---|---|
| BitTorrent | File sharing |
| Tor | Anonymous communication |
| Kademlia | Distributed hash table (DHT) for resource location and routing |
| IPFS (InterPlanetary File System) | Decentralized file storage and sharing |
| Freenet | Anonymous communication, file sharing, and publishing |
| Ethereum | Decentralized applications (DApps) and smart contracts |
| I2P (Invisible Internet Project) | Anonymous communication |
| RetroShare | Instant messaging and file sharing |
| Syncthing | File synchronization |
P2P Architecture Use Cases
Because peer-to-peer architectures are fundamentally decentralized, they have a wide variety of use cases.
One of the most common use cases is allowing end users to share files directly with each other without the need for a central server.
The architecture is also integral to distributed computing projects like SETI@home, where computational tasks are divided and processed across numerous peers to take advantage of idle resources.
P2P architectures also play an important role in the design of cryptocurrency platforms,? content delivery networks, and real-time communication apps.
| P2P Use Case | Purpose | Example |
|---|---|---|
| File sharing | Allow network peers to exchange files directly. | Gnutella |
| Cryptocurrency | Conduct P2P financial transactions. | Bitcoin |
| Distributed computing | Use idle computing power from multiple devices to solve complex problems. | Folding@home |
| Content distribution | Allow network peers to transfer multimedia directly. | LivePeer |
| Communication | Enable anonymous user-to-user communication. | Wire |
| Decentralized marketplaces | Support P2P commerce. | Origin Protocol DeFi products |
| Gaming overlays | Allow players to communicate directly with each other during gameplay over a peer-to-peer connection. | AmongUsP2P |
| Blockchain | Enable decentralized ledgers. | Ethereum |
| P2P lending | Facilitate direct lending and borrowing between individuals. | Prosper |
Challenges of Peer-to-Peer Architecture
P2P architectures can have challenges related to cybersecurity because without a central authority, it can be challenging to enforce security controls uniformly across all peers.
Because each peer can potentially be both a client and a server, P2P security depends on the security posture of each individual peer, which can vary widely and lead to potential vulnerabilities.
If even one node in the network uses weak passwords or has outdated software or misconfigured settings, a threat actor could use it to distribute malware or engage in other harmful activities.
Peer-to-Peer Architecture Pros and Cons
While the lack of central control is an important advantage of using a peer-to-peer architecture, it also makes it challenging to identify and isolate compromised nodes, especially if their IP address is masked by a virtual private network (VPN).
Whether the pros outweigh the cons depends on the specific application and its requirements.
- There is no single point of failure (SPoF) since the network is not dependent on a central server. If one node fails, the network can still function
- P2P networks will naturally scale out network resources as more peers join
- Since there is no need for a central server, the cost of setting up and maintaining the network can be lower
- P2P networks can offer a degree of anonymity and privacy since there is no central authority controlling or monitoring the network
- Without a central authority, it can be challenging to enforce network security policies uniformly across all nodes
- It can be difficult to ensure data integrity across all peers if nodes randomly join and leave
- While P2P networks can scale easily, the performance can degrade if too many peers need to access the same resources simultaneously
- Without central control, it can be difficult to prevent the distribution of harmful or unethical content
The Bottom Line
Peer-to-peer architectures, by definition, are supposed to be decentralized. In real life, however, many P2P networks have structured or hybrid architectures that incorporate some level of centralization to balance the benefits of decentralization with the practical requirements for network performance in the real world.
FAQs
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References
- SETI Institute (Seti)
