Definition - What does Number of Tiers (N-tier) mean?
Number of tiers (n-tier) is an enterprise computing architecture in which the entire application is distributed across multiple tiers of hardware nodes. Number of tiers defines the distribution of logical layers of application, presentation and data management over physically tiered enterprise infrastructure.
In n-tier, "n" refers to the number of tiers being used, such as 2-tier, 4-tier, etc. By breaking an application into tiers, developers can modify or add layers without having to rewrite the entire application. Application architectures exist in the seventh layer of the OSI model.
A number of tiers architecture may also be refereed to as multi-tier.
Number of tiers is primarily used to describe the number of hardware layers required to execute, host and manage an enterprise-level application. Generally, there are three distinct tiers in such applications, with one layer being the user’s application interface, the other serving as the primary application and the last existing for storage and managing data/database. All of these layers are operated separately on different hardware tiers.
Generally, the computing architecture based on n-tier concepts are independent of each other. In other words, each tier - and its respective logical layer - can be modified, updated and executed separately. N-tier architecture is based on concepts from distributed computing and client/server computing architecture.