Client–server Network model

Provides a common applications and data from servers to Clients connected in a network. 

Ex : Web Server , Email, Service, Accounting and Sales like Business Applications 

Peer-to-Peer (P2P) Network
In a peer-to-peer network nodes function both as "clients" and "servers" to the other nodes on the network.

P2P share twork loads between peers. 
Control how many members to allow at one time;
Control what services to offer
How many system resources to devote to the network.

Ex : BitTorrent . Skype, Napster

Peer-to-Peer Networks (no computer designated as the server)

• simple and cost efficient
• no server is needed
• each client computer acts as its own server
• each computer user manages its security and administration
• simple cable system connects computer to computer
• security is an issue

Client/Server Networks ( one or more computers on the network acts as a server)

• servers and software can be expensive
• sharing resources
• network cabling
• servers need a secure room
• central file management and backup
• central security administration
• user management and permissions
• security to protect the network from virus attacks

A hybrid Network (Start, Ring with P2P and Client Server Models)