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I'm a basic beginner.
The web three-layer structure is interpreted as the foundation built on the web server, webAP server, and database server.

In the case of images, I think that the web server and webAP server are not separated, but why can the following image be said to have a three-layer structure?

* Excerpted from the link below.
https://note.com/agw/n/n4ff3fc9f6bd9

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  • Answer # 1

    In the case of images, I think that the web server and webAP server are not separated, but why can the following image be said to have a three-layer structure?

    The Web three-tier model is an architecture that separates the presentation layer, application layer, and data layer.

    In the case of this figure, if you read the designer's intention deeply, you can read that ALB is the design that plays the role of the presentation layer. In fact, ALB can also return some HTTP response.

    However, in reality, it seems that the application server is a presentation. So it's not the classic three-tier structure, but the architecture where the presentation is separated into ALB and the application server.

  • Answer # 2

    I think that you can get an accurate explanation if you confirm it with the person who created the figure.

    In this figure, the WEB3 layer is only inside the central VPC 192.168.0.0/16 square.
    It is properly divided into three, and the IP addresses of 6 units in 3 layers are listed.

    The square (172.14. ~) outside it seems to be for maintenance and is not included in the WEB3 layer.
    Looking at the relevant page, it seems that this figure itself is intended to introduce the author's environment rather than explaining the WEB3 layer.

    Also, if you look at the citation source, there are several articles before the article in this image.
    If you want to understand this image properly, you may need to check these past articles.
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