Cisco CCIE Security 350-701 – Application Programming Interface – API

1. Application Programming Interface – API

Is. So probably in this section we’ll talk about API application program rule interface. Probably in the later on topics. Like in the section we’ll try to first understand what is an API and then we’ll also see some of the general examples of the API as well as also we’ll try to understand how it works with a simple example and then types of APIs. And then we’ll come to the API, how it is going to be used in our Sdn, because the API is general topic.

But again, we are going to use APIs, how we are going to use in our Sdn and how they correlate with our Sdn topics. And again, we’ll try to understand the difference between northbound API and the southbound APIs. So let’s get started here. So what is API? As I said, API is going to be stands for Application Programmable Interface or programming interface. Now, it is a piece of code which is going to allow two different applications to talk to each other. Or we can say another way like API is responsible for providing the connectivity between the two different applications so that they can exchange the information.

Or we can also say that it is a kind of messenger which is going to take the request from one application and it is going to forward the request to the next application and then get back the result. So to understand an API, we’ll take a simple general example. If you take a simple example of a hotel where a user probably you are visiting a restaurant where you got a user and this user is sitting on a table and he has the menu in front in general to choose the choice of food, right? And whatever the choice of food, he is going to prefer probably who is going to prepare that particular food. So again, there is a kitchen inside the restaurant which is a part of the system which is going to prepare your food. So probably they are responsible for preparing the food. But now the question is like how we are going to get the food on your table or how we are going to send out a request to the Quichel to prepare so and so forth. Now, there must be some kind of mediator in between. And that’s where your API or in our example, the waiter is going to be considered as an API here.

Now, the waiter waiter is actually a messenger. Or we can say it is a kind of piece of code which is responsible for providing the communication between the end user and then forwarding his request back to the kitchen and getting your food and prepared. And that food will be coming back again. So this waiter is your missing link, which is going to communicate between your order to the kitchen and ensure that you get delivered your food back on your table. Okay, so this is a general example of an API so API is, again as I said, the same definition. API is a kind of code or a messenger. We can say which is going to take your request and forward it to the other application. Like in this example, this is one kind of application, this is another application. Now these two applications can talk to each other, communicate with each other with the help of some kind of code. And that code will be referred as an API. Now, this is your daily example.

You can consider whenever you talk about API, you can simply consider this example, but how the API is going to relate in your real network. Now, if you take a real time example or a real example, if you are searching, if you’re probably familiar with the process of search engine flights, if you go to any airline website, like let me see if I can go to any specific airline website here. So you can see this is a Soviet. com website. Now on any airline website probably you get this kind of portal where you’re going to enter from, where the departure city, probably where you want to go, the class, plenty of details, all the details, what you have to fill in general.

So once you fill in these details and after filling the details, probably you’re going to click on search button or whatever the option over there and it is going to interact with the database. So probably it is going to interact with your airline database. Whatever the airline website you are sitting over there. And then it is going to check the database and going to return back with all the details about the availability of the flights and the availability of the seats. So what is the cost? Probably all those details you will get back. Okay, so this is another example of an API where the website is interacting with the airline database to the website API. Or we can say whatever the program used in the website is interacting with the centralized airline database to get back with the information. Probably take an example, what if the database is being retried? What if you are taking an example of any online travel service where you are going to book the flight. Now the same thing.

So I’m going to specific website MakeMyTrip. com here, which is a kind of online travel agent or travel service from where I can book the flight. Now we provide the same details here as well. So probably what we are doing is we are going to provide all the details, specific dates, and then we are going to search and all the information. Probably this travel agent, we can say the agent or the service. Now this agent is actually not hosting any kind of information. So this is not your airline service here. Now what the agent application is going to interact with the database of multiple airlines. So probably it’s going to connect to the database of multiple airlines and get all the details like interacts with multiple airlines APIs to get the information completely based on whatever the inputs we are providing here. And when you click on specifically search like this, you probably get all the details. So now you can see the API is making to see all the travel sites.

You can see all the information from different airlines here. Now, the same goes with all the interactions between any two applications. So this is just a general example I’m taking. But if you take any application, any two applications are talking to each other which are extracting the data or between the devices. With respect to here we’ll be talking about the Sdn and the Sdn controller communicating with the device. That’s where the API is again used. So talk about how it’s going to relate with an Sdn here. So now, whenever you think about an API, you just simply think about an example of the reader which I have given is like a messenger or the code which is allowing you to interact between the different applications. So there are some other general examples.

What you see with an API like if you are going with the travel bookings, the example which I do just now, or you’re using your phone or online, you are checking the weather probably. So your application, your phone have an application which is going to display probably the weather, interact with the database of the weather probably, and then get the information back to display on your screen. Or whenever you are trying to log into any of your Facebook account. Or you get these login options, that is also again at the back end you have something like API. Or if you take an example of any kind of Twitter bots, twitter bots application where the accounts will automatically tweet or follow or send some kind of direct messages based on some software instructions. There is one more example of an API. Or if you are using any kind of paper when you are doing some kind of payments, you click on the link which is going to redirect to the payment option and where your order where again it is just like redirecting from your website to the banking website from where maybe the payment option is done.

So that is also one more example of an API. So there are plenty of examples or even when you’re logging to any kind of online options like let’s say you’re watching your videos probably on a Uremi, or probably you’re logging to any of your account and it is going to redirect to check. Let’s say you’re using some kind of online account and probably you’ll be redirect to some kind of portal page where you need to check whether that particular user is already logged in. If not, it is going to pop up with a portal page to log in. Okay, so that is also one example of an API in simple API. Technically, if you say how the API is going to work is API. Let’s take an example on my mobile phone.

And here I’m going to run an application. And this application is going to connect to the centralized server. So whatever the server it is, whatever the information you’re trying to get back. So that application is going to allow you to connect. And who is going to allow you to do that? The API is acting as an intermediate to allow you to connect to that particular server and send out the request. Now the server is going to get that information, probably retrieve the information, and then it is going to send it back to the API and then send it back to the phone. So the API is again going to ensure that your data, whatever is being sent by the server is actually displayed in a format which the end user can understand kind of more readable way. And this is what an API is going to do.

2. API Types

So the next thing we’ll try to understand about the API types. Now mainly we have two types of APIs. The APIs within the local system or the local applications, and the APIs between the different applications. So our focus will be on API remote applications. So let’s try to understand first the API within the local system. Now, if you take a simple example of in a computer, let’s say here, I got a web browser here and then I got a notepad here. Let’s say now these are two different applications here. So one is your web page from where you can it’s a kind of another application which displays your website. And another is a simple text editor, a simple notepad.

So what I’m doing is I’m just trying to copy some of the text from the web application and then I’m going to paste it over to the notepad again. Now, here also there is some kind of API involved here. So whenever you are doing some kind of copy paste of these things, or generally if you take a simple example inside your computer system, you will be having multiple applications and every application will do a different job. And there must be something to talk between these two applications. So this is also one kind of API. But the difference is in this API, this actually works within the same system and there is no networking device is actually involved here. It’s completely inside your system. Okay, so there may be one or more APIs. Again, I’m not specifically saying there’s one API, maybe one or more APIs present inside your system which are allowing these two applications to talk to each other.

So this is the first one and the second one, the APIs which are used as a messenger or to talk between two different applications. Now, the concept, what we are going to see in the Sdn, probably they all come under the second category. Now, if you remember the examples of this API with the remote applications have taken an example in the previous definition of the airline probably, or any kind of login account or any kind of paper accounts which redirects to a different portal page. They all are example of this API which are used between two different applications, right? So when you are going with the airline example, so the travel agent website or the database is going to interact with the airline and it’s going to talk between them.

So for this we need to have IP reachability, like in case of travel agent or online service, you need to have some kind of internet connection so that you can reach the airline database because you are not sitting in your local system. So, similar way in Sdn also when we are trying to ensure that the controller is going to talk with applications and the controller is going to instruct the devices. So there is some kind of API involved here. And here also in our networking. There SD networking as well. Now, the communication, the API allows you to interact, but at the same time you need to have some kind of IP reachability between them. So you must have a network which is being built and you must have reachability between the applications.

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