Question

Distinguish between network and application architectures. (4 marks)

Answer 1

Let's understand the given terms first in layman langauge. But even before that, let's try to understand the word "Architecture".
An architecture is basically a model or set of components or a design structure about a certain entity. It shows the parts of that entity, how they are related, and how do they communicate(if possible). In the world of Computer Science, the architecture could be related to a software application (running on a hardware) or to a network.

If we talk about software application, its architecture will mean - how the software has been/will be built, what all major components constitute that application, how they communicate amongst one another, how/from where they receive some input, which components processes that input, and how the output is provided etc.

The Application architectures are in general layered architectures. It may consist of two or more of the following layers:

1. Presentation layer (how an end user will see/usr the application)
2. Business layer (Actual logic of how the information will be created and pushed to the presentation layer)
3. Service layer (Optional that interacts with the database)
4. Data layer (Actual Database)

Each layer does its own job and provides information to the layer above it.

Let's understand this via a simple example of a popular application called "Instagram":
The presentation layer within instagram tells you:

1. How your login interface will look like.
2. If someone likes your picture, how will you be notified
3. How will the presentation of an album look like if you are on phone and if you are on Desktop/laptop.
4. What should be the error messages thrown if there is a bad network or any other issues with the application.

and many more such thoughts that involve end user's direct interaction with Instagram.

The Business layer of Instagram tells you:

1. How to update the likes on a picture runtime without page refresh.
2. If you login, it will try authenticating you from the backend.
3. If you got any follower, your follower count has to be increased and saved in the database so that next time you get the updated count.

and many more such facilities, that end user doesn't have to know how it's happenening in the background, but he gets to know the result of the process.

The Service Layer in Instagram:

1. It exposes some methods(APIs) so that when business layer asks for some data, it can interact with the database and tell back

The Data layer in Instagram:

1. What database will be used
2. How many tables will be required
3. How many nodes should be kept
4. Should the database be replicated over multiple nodes
5. How database concurrency will be achieved

and many thing related to database, because it's the most crucial and most important thing about any application.

We now will talk about Network architectures. As the name suggests, this is an architecture about the network or network components. It could be with respect to an application or just a network buildup for a certain geographical area. It refers to how your network is built. It gives you the physical or/and logical connection of the various network devices and protocols.

For example: School computer lab.

When the lab was getting built in your school, the lab administrator or a group of administrators would have reached to a
network architecture of the lab. but how?
The factors that they would have considered are the following:

1. Which Internet SErvice Provider?
2. How many PCs?
3. How many private LANs?
4. Subnets required?
5. How many servers?
6. How many switches, routers, repeaters etc?

and many such factors depending on the requirement of the lab.
In all these questions, we never talked about any software application. Why? Because we are building a network and network consists of devices and conmmunication amongst them.

The network administrator after taking all these factors into consideration comes up with a graphical representation of the
network depicting the devices, network, protocols, ip addresses, ports etc to show how they will actually communicate.

To conclude, Application architecture talks about the structure of the software while network architecture deals with the structure of the network.

I hope the examples gave you a pretty clear picture around both the architectures. If you have any more questions on this, feel free to write back and I will be glad to clarify.

Thanks for asking :)