(1) Client/Server Model (C/S)

(2) P2P model

In the P2P model, there is no fixed division of clients and servers for each computer. In contrast, any pair of computers is called a Peer and communicates directly with each other. In essence, the P2P model still uses the client/server approach. Each node acts as a client to access the resources of other nodes, and also acts as a server to provide resources for other nodes to access. Popular P2P applications include PPlive, Bittorrent and Edonass.

Compared with C/S model, P2P model has the following advantages:

• Reduced server computing pressure, eliminated the rely solely on a server, the task can be assigned to each node, thus greatly improving the system efficiency and resource utilization (for example, streaming to the server when the pressure is too big, and by P2P model, can use a large number of clients to provide services).
• Documents can be shared directly between multiple clients.
• Scalability is good, traditional servers have response and bandwidth limitations, so can only accept a certain number of requests.
• The network is robust, and the failure of a single node does not affect other nodes.
• The P2P model also has drawbacks. When obtaining services, other nodes also need to provide services. Therefore, a large amount of memory is occupied and the system speed is affected.

For example, regular P2P downloading can also cause serious damage to hard drives. According to an Internet research institute statistics, P2P applications have accounted for 50 to 90 percent of the traffic on the Internet, making the network become very congested, so major ISPs (Internet service 2 providers, such as telecom, netcom, etc.) are generally opposed to P2P applications.