A2.2.3 — Networking Models
Client-Server Model
A server hosts, delivers, and manages most resources and services, which are requested by clients. Characterised by a request/response model.
| Advantages | Disadvantages | |
|---|---|---|
| Control | Central management so easy to enforce policies, manage resources, ensure data consistency. | If server is not properly maintained |
| Scalability | Feasible to scale by upgrading server resources or adding more servers. | Scaling is investmen in infrastructure. |
| Security | Centralised security measures — straightforward to administer, better protection against unauthorised access. | Centralised servers are targets for cyberattacks. |
| Efficiency | Servers optimised for specific tasks. Improves data processing and resource allocation. | High client demand can overload servers, causing bottlenecks and reduced performance. |
| Reliability | Professional maintenance and infrastructure , high reliability. | Single point of failure - server. |
Peer-to-Peer (P2P) Model - Torrent
A decentralised model where each participant (peer) has equal capabilities and responsibilities. No dedicated server — each peer can act as both client and server, sharing resources directly with other peers.
| Advantages | Disadvantages | |
|---|---|---|
| Control | No central authority — resilience, no single point of failure. Control distributed among peers. | Problems are harder to track down. Usage metrics difficult to gather without central authority. |
| Scalability | Adding more peers increases the network's resource pool and computational power at minimal cost. | Network performance varies significantly depending on the number and capacity of peers. |
| Security | P2P models are anonymous — can be seen as a benefit for privacy. | Anonymity means threats are harder to identify. Lack of accountability makes P2P susceptible to distribution of malware, illegal, or unethical content. |
| Efficiency | Efficient distribution of resources among peers reduces load on individual nodes. | Inefficient resource usage if not properly managed — redundancy and excessive overhead. |
| Reliability | Network continues even if some peers fail — enhances overall reliability. | Reliability compromised by transient nature of peers — potential data availability issues. |
Real-world examples:
- BitTorrent: Files shared directly between users' computers. No central server. Faster for large files as multiple peers transfer simultaneously. Less control over security.
- Skype (early): Direct P2P connections for voice calls. Scalable without infrastructure investment. Drawback: reliability depends on peer connection quality.
- Bitcoin/Blockchain: Each node holds a copy of the transaction ledger. Decentralised — enhances security, reduces fraud risk. Drawback: significant energy consumption, slower transactions.
Summary: Client-server = centralised, controlled, single point of failure. P2P = decentralised, resilient, harder to manage/secure.