This page contains a series of images for comparing tier models when using the Web Interaction Model to conceptualize the full range of web components.
The front end (Tier 1) consist of the user's computer and software, and the back end (Tier 2) consists of a Web server, along with other hardware and software. No attempt is made to illustrate complexities on either tier.
The 3-tier model acknowledges more complexity than the 2-tier model. A typical example is the separation of a Web server from a database server that provides information for specific applications. Note that tier 1 is unchanged, and only back-end complexity is explored in this model.
The N-tier model encompasses a full range of back-end complexities, including components such as routers and firewalls. This model is especially valid for e-commerce and business-to-business Web Applications, extending the back-end complexity by allowing for the inclusion of a third party application service provider. a) Storefront/Catalog Pages, b) ASP.net, c) Windows 2018 Server
While this model accounts for the many different servers and applications that are involved in organizing and providing content to the user, note by the time we arrive at the n-tier, the user is pushed to the model's periphery. The N-tier model recognizes that there are often more tiers than simply the user and the Web server.