What is a difference "Protect API in Azure API Mgmt by OAuth 2.0 auth with AAD" vs secure API built with NET Core by the MS identity platform

Question

I am reading microsoft documentation and using their apps / api to secure api using Azure AD. But I got confused by two different approaches and as articles describe setting up the client app and Api.

1. This article describe " Protect a web API backend in Azure API Management using OAuth 2.0 authorization with Azure Active Directory"
   link: https://docs.microsoft.com/en-us/azure/api-management/api-management-howto-protect-backend-with-aad

2. I am following another tutorial and using built application for web app and api, this describe "How to secure a Web API built with ASP.NET Core using the Microsoft identity platform. This sample demonstrates a ASP.NET Core Web App calling a ASP.NET Core Web API that is secured using Azure AD".

It further describe "1. The client ASP.NET Core Web App uses the Microsoft Authentication Library (MSAL) to sign-in and obtain a JWT [Access Tokens]. 2. The [Access Tokens] is used as a bearer token to authorize the user to call the ASP.NET Core Web API protected by Azure AD .

So I am confused are they two different things if so when to use 2nd option or first 1. Both deals with the Azure AD and claims to protect an api.

Answer 1

The first article you're referring to uses Azure API management, where authentication is taken away from your API and completely configured in API management. This means you're adding an extra Azure resource type to your eco-system, most probably also adding costs.

In this article, you'll learn how to configure your Azure API Management instance to protect an API, by using the OAuth 2.0 protocol with Azure Active Directory (Azure AD).

Next tot this, API Management adds a lot of other functionality as well.

In the second article you learn how to implement authentication using Microsoft Identity Platform. This way you will not be adding Azure resource types, but you'll have to code the authentication yourself.