Three-Tier Client-Server Architecture

In more recent times, a middle tier was added to Client-Server implementations, effectively creating a three tier structure. In a three tier or N-Tier atmosphere, the client implements the presentation logic. On application servers, the business logic shall be implemented. Data is left to be situated on to database servers.

The following three component layers define a Multi Tier (or N-Tier) architecture.

First of all, there is the front end component. This component provides portable presentation logic.

Secondly, there is a middle tier, which enables users to share business logic and control it by isolating it from the application in question.

Then there is the back end component. This component provides users with access to services like database servers.

Multi Tier architecture augments Two-Tier structures in the introduction of middle tier components. The Client system then works with the middle tier through such standard protocols as RPC and HTTP. The central tier interacts with the backend server through such standard database protocols as JDBC, SQL, and ODBC, among others.

The vast majority of the application logic is contained in the middle tier. It is here where client calls are translated in to database queries, and data from the database is simultaneously translated in to client data.

This positioning of business logic on the application server maximizes scalability as well as the business logic’s isolation, which effectively handles a business’s rapidly evolving requirements. More open choice of database vendors are then allowed for.

Three tier architecture can extend to N-Tiers.  In the event that the middle tier is capable of providing connections to a variety of different services, while also integrating them and coupling them to the client, as well as to each other.

N-Tier Architecture

As Client-Server Models evolved throughout the decade, many Multi Tier architecture models began to appear, enabling computers on the client side to function as both clients and servers. Once software developers began to realize that smaller processes were a lot simpler to design, not to mention cheaper and faster to implement, then N-Tier models increased in popularity quite rapidly. The same principles applied to the client side were then applied to the server side. As a result, thinner, more specialized server processes evolved.

These days, N-Tier architecture seems to dominate the industry. The vast majority of new IS development is being created in the form of N-Tier systems.

It should be noted, however, that N-Tier architecture does not necessarily preclude the utilization of Two-Tier or Three-Tier models. Depending on the scale and requirements involved for a particular data, Two-Tier or Three-Tier models are very often used in departmental applications.

N-Tier computing is widely considered to be the most effective model these days, as it promotes integration of contemporary information technology in the form of a much more flexible model. It is widely believed that the percentage of applications utilizing an N-Tier model is going to grow four fold within the next two years.

Three-Tier and N-Tier systems are mainly able to do two things that 2 Tier systems are unable to do. They are the partitioning of application processing loads among several different servers, and the funneling of database connections. By centralizing application logic within the central tier, business logic can be readily updated by a developer without having to re-deploy an application to thousands of different desktops.

Distributed Processing

N-Tier computing attains a high level of synergy by combining different computer models and providing centralized common services in a single distributed atmosphere.

The multi level distribution architecture in question must rely on a back end host of some kind, an intelligent client, as well as several intelligent agents in order to control activities like Online Transaction Processing, message handling, transaction monitoring, etc.

Such forms of architecture tend to rely heavily on object oriented methodologies, which help to effect a maximum amount of interchangeability and flexibility.

TP monitors, distributed objects, and application partitioning tools can all contribute to spreading the processing load among a bevy of different machines, which supports an unlimited quantity of processing loads and users – quite a far cry from the Two-Tier architectural models of the past. Indeed, N-Tier is here to stay. At least for the foreseeable future.

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