5 min read · Sep 10, 2023
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In the ever-evolving landscape of web applications, managing and optimizing web traffic is a critical task. Microsoft Azure offers a powerful solution for this challenge through its Application Gateway (AGW) service. AGW is a versatile tool that works at Layer 7 of the OSI model, allowing it to handle HTTP/S traffic with finesse. In this article, we will dive into the key features and functionalities of Azure Application Gateway and explore how it can empower your web applications.
But first, let’s look at the application gateway components. The diagram below shows the different components of AGW.
Frontend IP
This component defines the IP address and port (listener) that clients use to connect to the Application Gateway. Multiple frontend IP configurations can be used to support different scenarios, such as multi-site hosting.
Listener
This component defines the IP address and port (listener) that clients use to connect to the Application Gateway. Multiple frontend IP configurations can be used to support different scenarios, such as multi-site hosting.
Backend Pool
A backend pool is a collection of backend servers or virtual machines that host the web applications. Application Gateway distributes incoming traffic among the servers in the backend pool based on the configured load-balancing rules.
Backend Pool Servers
These are the actual backend servers or virtual machines where your web applications are hosted. Application Gateway forwards incoming requests to these servers after processing.
HTTP Settings
HTTP settings define how Application Gateway communicates with the backend servers. They include details like port, protocol (HTTP or HTTPS), and other settings like request timeout and cookie-based affinity.
Health Probes
Health probes periodically check the status of backend servers to ensure they are responsive and healthy. If a server fails a health probe, Application Gateway stops sending traffic to that server until it is deemed healthy again.
Web Application Firewall (WAF) Configuration
If you enable the Web Application Firewall feature, this component includes configuration settings for WAF rules, which help protect your web applications from common web exploits and attacks.
Frontend Port
Frontend ports define the ports on which Application Gateway listens for incoming traffic. Multiple frontend ports can be associated with a frontend IP configuration to support different protocols or scenarios.
Authentication and Authorization
Application Gateway can be configured to perform authentication and authorization checks on incoming requests. You can use this feature to control access to your applications based on user identities and policies.
Custom Error Pages
Application Gateway enables you to configure custom error pages for specific HTTP status codes. This feature helps improve the user experience by providing informative error messages.
Overview of how an Application Gateway Works
Load Balancing and Beyond
At its core, AGW provides robust load balancing capabilities. It serves as a traffic manager for your web applications, helping you distribute incoming requests across multiple backend servers or pools. This load balancing ensures improved availability and scalability for your applications, making them more resilient to traffic spikes and failures.
Intelligent Routing
One of AGW’s standout features is its ability to make routing decisions based on URI paths and host headers. For instance, you can configure AGW to route traffic depending on the incoming URL. Requests with “/images” in the URL can be directed to a specific server pool, while “/video” requests can be sent elsewhere. This granular control over routing optimizes how your application handles different types of requests.
TLS/SSL Termination
TLS/SSL encryption is crucial for securing web traffic, but it can be computationally intensive. AGW can handle TLS/SSL termination, meaning it decrypts incoming HTTPS traffic and forwards it to backend servers over an unencrypted connection. This offloads the resource-intensive encryption and decryption tasks from your servers, resulting in improved performance.
End-to-End Encryption
While TLS/SSL termination is advantageous for performance, there are situations where end-to-end encryption is non-negotiable due to security and compliance requirements. AGW has you covered, as it supports end-to-end TLS/SSL encryption. This means data remains encrypted from the client to the backend servers, ensuring the highest level of security throughout the communication path.
Web Application Firewall (WAF)
Security is a top concern for web applications. AGW includes a Web Application Firewall (WAF) that acts as a shield against common exploits such as SQL injection and cross-site scripting (XSS) attacks. With WAF, your applications are safeguarded against a wide range of threats, bolstering their security posture.
Application Delivery Controller (ADC)
AGW also functions as an Application Delivery Controller (ADC) as a service. This extends its capabilities beyond load balancing and includes features like session affinity, content-based routing, and health probes. These features optimize the performance and availability of your web farm, ensuring a smooth user experience.
In conclusion, Azure Application Gateway is a comprehensive solution for managing, securing, and optimizing web traffic for your applications. Its ability to handle Layer 7 traffic, coupled with features like load balancing, intelligent routing, TLS/SSL termination, end-to-end encryption, Web Application Firewall (WAF), and Application Delivery Controller (ADC) functionalities, make it an asset in your Azure toolbox. By leveraging AGW, you can enhance the performance, scalability, and security of your web applications, ultimately providing a better experience for your users.
