Posted on 14th October 2012 by Tony Marston This article is in response to written by Anthony Ferrara which I feel gives only a very limited view of what can be a complex subject. Different people have different ideas on how an application can be split into tiers, and different ideas on the benefits which can be gained from making such a split. I have been designing and building multi-tiered applications in different languages for over a decade, so my exposure to this subject has been quite extensive. I would like to share with you my experiences on this subject and hopefully give you a more detailed picture. A 'tier' can also be referred to as a 'layer'. A wedding cake is said to have tiers while a chocolate cake is said to have layers, but they mean the same thing. In the software world Tiers/Layers should have some or all of the following characteristics: • Each tier/layer should be able to be constructed separately, possibly by different teams of people with different skills. Neodata 2009 full action movies.

• Several tiers/layers should be able to be joined together to make a whole 'something'. • Each tier/layer should contribute something different to the whole. A chocolate layer cake, for example, has layers of chocolate and cake. • There must also be some sort of boundary between one tier and another. You cannot take a single piece of cake, chop it up into smaller units and call that a layer cake because each unit is indistinguishable from the other units. • Each tier/layer should not be able to operate independently without interaction with other tiers/layers.

• It should be possible to swap one tier/layer with an alternative component which has similar characteristics so that the whole may continue functioning. • Although it is usual to run all of these layers on the same server, there may be benefits from running each layer on its own server. The idea of being able to swap components in one layer without having to modify components in other layers has enormous benefits. For example, you may start with a presentation layer component which extracts data from a business layer component and formats that data into HTML, but later on you add additional presentation layer components to format the data into CSV or PDF. These additional presentation layer components should be handled without having to make any changes to the business or data access layers. Similarly, if you start with a data access object which handles all the communication with a MySQL database it should be possible to switch to an alternative component for a different database engine, such as PostgreSQL, Oracle or SQL Server, without having to make changes to any components in the business or data access layers. There is no difference.

Some people refer to the N Tier Architecture where 'N' can be any number. I personally have found no use for any more than 3 tiers, which is why I always call it the 3 Tier Architecture. If you try to build an application with more than three layers then be aware that it may have a serious impact on performance, as discussed in. Some people consider that a web application is automatically 3 Tier as it has 3 separate components, as shown in.

A Web Application Although this would appear to satisfy the conditions outlined in, I feel that it fails on one important aspect. Just as a layer cake is made up of several layers of cake - you cannot combine a single piece of cake, a cake stand and a decoration and call it a 'layer cake' - you require several layers of 'cake'. In order for your application to be called multi-layered it is the application on its own - which excludes all external components such as the browser and the database - which must be broken down into several layers. I am discounting everything outside of the application itself for the following reasons: • The web browser can operate independently of the application, therefore it is not part of the application. Although it is possible for application code to be executed in the client's browser, such as JavaScript, Flash, or ActiveX controls, their usage is entirely optional and can be disabled.

The AWS Architecture Diagrams solution includes icons, sample and templates for 3 - Tier Auto-scalable Web Application Architecture 10 000 vector stencils;. See examples and learn how to make a network diagram from scratch. It interacts with can be done using a quality network diagram software like Lucidchart. Logical network diagrams correlate with the information contained in layer 3 (L3).