Some designs are more sophisticated and consist of three different kinds of nodes: clients, application servers which process data for the clients, and database servers which store data for the application servers. This configuration is called a three-tier architecture, and is the most commonly used type of client-server architecture. Designs that contain more than two tiers are referred to as multi-tiered or n-tiered.
The advantages of n-tiered architectures is that they are far more scalable, since they balance and distribute the processing load among multiple, often redundant, specialized server nodes. This in turn improves overall system performance and reliability, since more of the processing load can be accommodated simultaneously.
The disadvantages of n-tiered architectures include:
1. More load on the network itself, due to a greater amount of network traffic.
2. More difficult to program and test than in two-tier architectures because more devices have to communicate in order to complete a client's request.
Another type of network architecture is known as peer-to-peer, because each node or instance of the program can simultaneously act as both a client and a server, and because each has equivalent responsibilities and status. Peer-to-peer architectures are often abbreviated using the acronym P2P.
Both client-server and P2P architectures are in wide usage today.
While classic Client-Server architecture requires one of communication endpoints to act as a server, which is much harder to implement, Client-Queue-Client allows all endpoints to be simple clients, while the server consists of some external software, which also acts as passive queue (one software instance passes its query to another instance to queue, e.g. database, and then this other instance pulls it from database, makes a response, passes it to database etc.). This architecture allows greatly simplified software implementation. Peer-to-Peer architecture was originally based on Client-Queue-Client concept.
* In most cases, a client-server architecture enables the roles and responsibilities of a computing system to be distributed among several independent computers that are known to each other only through a network. This creates an additional advantage to this architecture: greater ease of maintenance. For example, it is possible to replace, repair, upgrade, or even relocate a server while its clients remain both unaware and unaffected by that change. This independence from change is also referred to as encapsulation.
* All the data is stored on the servers, which generally have far greater security controls than most clients. Servers can better control access and resources, to guarantee that only those clients with the appropriate permissions may access and change data.
* Since data storage is centralized, updates to those data are far easier to administer than would be possible under a P2P paradigm. Under a P2P architecture, data updates may need to be distributed and applied to each "peer" in the network, which is both time-consuming and error-prone, as there can be thousands or even millions of peers.
* Many mature client-server technologies are already available which were designed to ensure security, 'friendliness' of the user interface, and ease of use.
* It functions with multiple different clients of different capabilities.