What Is Reverse Proxy?

• Reverse Proxy Definition

  Reverse Proxy Definition

  A reverse proxy is an intermediary client-server architecture that protects the origin server's identity from the clients by masking its IP address. All the incoming connection requests pass through it before reaching the origin server; thereby, it acts as a gateway with built-in security tools. It also helps enhance the network performance with intelligent data compression, caching, and load balancing.
• How does reverse proxy server work?

  How does reverse proxy server work?

  The reverse proxy server typically sits between your corporate firewall and back-end servers and receives all the incoming HTTP requests. After receiving the connection requests at the network perimeter, it completes a three-way TCP handshake with clients and terminates the initial connections immediately. It then forwards those inward requests to the origin server, collects the server responses, and sends them back to the clients. Preventing illicit users or unauthorized traffic from reaching the origin server is the primary motive of intermediary servers.

  Compared to the forward proxy, reverse proxies secure the origin server with traffic scrubbing and preventing direct server interactions. On the other hand, forward proxy hides the client computers' identity by interacting with web servers on behalf of them. In short, forward proxy sits in front of client computers, whereas its counterpart is positioned before web or application servers. Nevertheless, both operate at the network edge and help optimize network security, efficiency, and performance.

  Implementing a reverse proxy involves several steps to configure a server to efficiently route client requests to the appropriate backend services and return responses. First, you need to choose a reverse proxy solution, such as Nginx, Apache, or a more advanced system like F5 BIG-IP or Radware’s Alteon ADC. Once you have your proxy server set up, you can start configuring it to handle various tasks.

  For performance optimization, enable caching by specifying which types of content should be cached and for how long. Use compression to reduce the size of data transferred, improving load times.

  For security, configure SSL offloading to handle encryption and decryption, and set up rate limiting to prevent abuse and ensure fair resource usage. Implement traffic splitting to distribute requests based on load or user attributes, and use geolocation to route users to the nearest data center, reducing latency.

  To maintain client IP information, add the X-Forwarded-For header to all forwarded requests.

  Additionally, for global applications, set up global server load balancing (GSLB) to ensure high availability and optimal performance across multiple data centers. Regularly monitor and log proxy activities to identify and address any issues, and scale your proxy horizontally as needed to handle increased traffic. By carefully configuring these features, you can create a robust and efficient reverse proxy that enhances the overall performance and security of your system.
• Why use a reverse proxy?

  Why use a reverse proxy?

  1. Load balancing: This is one of the primary functions of reverse proxies or intermediary servers, allowing them to distribute incoming traffic to multiple back-end servers to prevent website unresponsiveness or slowdown due to server overload. It’s especially beneficial for a high-traffic website running on multiple servers. In addition, intermediary servers can perform global server load balancing (GSLB) by routing the incoming traffic to servers geographically closest to end-users to reduce the website load times. They rely on load balancing algorithms, such as weighted round-robin and least connection, to help divert the traffic to the appropriate back-end server.
  2. Cyberattack prevention: Setting up an intermediary server makes it extremely difficult for attackers to launch a DDoS attack or exfiltrate valuable data from origin servers due to layered protection. Masking origin servers' IP addresses and intercepting every client request directed to back-end servers makes it an ideal solution for tightening network security controls. Further, it can enable basic HTTP access authentication for web servers. Security teams can install a web application firewall in reverse proxies to prevent malicious data packets from reaching back-end servers.
  3. Secure file transfer: Modern FTP servers leverage reverse proxies or gateways, enabling organizations to exchange files internally and externally in a safe, compliant, and automated way. Such gateways help security teams create a demilitarized zone (DMZ) to handle the connection requests from FTP clients outside the corporate firewall without exposing internal systems. In addition, gateways help ensure DMZ segments don’t contain sensitive data and reject all inbound connections to corporate LAN. This helps organizations stay compliant with PCI DSS and other data security standards.
  4. Web acceleration: Intermediary servers can eliminate website performance bottlenecks by offloading processor-intensive SSL encryption and decryption tasks from the origin server. They can decrypt inbound data packets and encrypt outbound messages for secure client-server communication. Similarly, they can use intelligent data compression to reduce the network bandwidth requirements of a web server, resulting in faster response times and improved user experiences.
  5. Content caching: This enables the reverse proxies to store the replica versions of frequently requested website content for rapid delivery. Compressing and caching content by an intermediary or local server takes the load off from origin servers and improves the website’s performance and availability.
• Reverse Proxy vs. Load Balancer

  Reverse Proxy vs. Load Balancer

  Both reverse proxies and load balancers serve as intermediaries to ensure seamless client-server communication and perform activities to enhance network efficiency. Both intercept the client HTTP requests before routing them to back-end servers. Organizations often find it difficult to distinguish between them due to their similar characteristics.

  A load balancer adequately distributes incoming traffic across multiple servers, enabling organizations to host websites in multi-server environments. It can be a physical device or a software application that organizations typically deploy in web farms. It relies on various algorithms, such as round-robin, least traffic, and least connection, for intelligent traffic distribution and optimal utilization of each server's capacity. Load balancers also monitor web servers' health by frequently detecting error responses to regular client requests. If a server is unavailable to handle a request, it automatically diverts the client requests to other servers in the web farm to prevent downtime. Additionally, load balancers provide session stickiness or persistence capability by routing all incoming requests from a client to a particular back-end server to enhance the end-user experience.

  In contrast, a reverse proxy server is a more powerful intermediary than a load balancer with advanced features such as SSL encryption and data compression. Unlike load balancers, organizations can employ a reverse proxy server with a single web server for traffic routing and network security. It can obfuscate the back-end server to prevent direct connections.

  Implementing configuration changes or scaling resources in the back-end environment also becomes straightforward with reverse proxies. It creates a secure client-server communication channel by encrypting the incoming and outgoing messages. This frees up valuable resources on origin servers from SSL encryption tasks. Further, it can compress and cache web server responses to optimize website performance and response times. Reverse proxies can also provide load balancing capabilities, preventing single-point failure in modern web architectures.
• Advanced Reverse Proxy Techniques

  Advanced Reverse Proxy Techniques

  Reverse proxies are versatile tools that can handle a wide range of complex and specialized tasks beyond simple request forwarding. These advanced techniques can significantly enhance the performance, security, and reliability of your distributed systems. Here’s a detailed look at some of these techniques and how they can be implemented:

  Traffic Splitting

  Traffic splitting involves distributing incoming requests to different backend servers or services based on specific criteria. This can be used for load balancing, A/B testing, or gradually rolling out new features. Suppose you are rolling out a new feature to a subset of users. You can configure the reverse proxy to split traffic, sending 90% of requests to the current production environment and 10% to the new feature environment. This allows you to test the new feature in a controlled manner without affecting the majority of users.

  Geolocation

  Geolocation involves routing traffic based on the geographic location of the client. This can be useful for content localization, compliance with data residency laws, or optimizing performance by directing users to the nearest server.

  Caching

  Caching involves storing frequently accessed data in a temporary storage area to reduce the load on backend servers and improve response times. By caching static content like images, CSS, and JavaScript files, the reverse proxy can serve these resources directly, reducing the number of requests to the backend servers. This not only improves performance but also reduces server load and bandwidth usage.

  Denial-of-Service (DoS) and Distributed Denial-of-Service (DDoS) Attacks

  Reverse proxies can help mitigate DoS and DDoS attacks by filtering out malicious traffic and distributing the load across multiple servers. Implementing rate limiting and IP blacklisting can prevent a single client from overwhelming your system with too many requests. Additionally, reverse proxies can use advanced algorithms to detect and block suspicious traffic patterns, ensuring that your backend servers remain accessible and responsive.

  Rate Limiting

  Rate limiting involves controlling the number of requests a client can make within a certain time frame to prevent abuse and ensure fair usage of resources. You can set up rate limiting rules to restrict the number of requests from a single IP address or user. For example, you might limit a user to 100 requests per minute. This helps prevent abuse and ensures that no single client can monopolize your resources.

  Virtual Hosts

  Virtual hosts allow a single server to host multiple domain names or applications, each with its own configuration and settings. By configuring virtual hosts, you can manage multiple applications or domains on a single reverse proxy server. Each virtual host can have its own set of rules for routing, security, and performance optimization, making it easier to manage a diverse set of services.

  X-Forwarded-For

  The X-Forwarded-For header is used to identify the original client IP address when a request passes through a proxy server. This is important for logging and security purposes. When a request passes through a reverse proxy, the original client IP address can be lost. By adding or modifying the X-Forwarded-For header, you can preserve the original IP address in your logs and security systems. This is crucial for tracking user behavior and detecting potential security threats.
• Advanced Configurations and Best Practices

  Advanced Configurations and Best Practices

  1. Hybrid Environments: In a hybrid environment that combines on-premises and cloud resources, a reverse proxy can help manage traffic between these different environments. By intelligently routing requests, you can ensure that the system remains efficient and responsive, regardless of where the resources are located.
  2. Security Enhancements: Reverse proxies can be configured to enhance security by implementing features like SSL offloading, where the proxy handles the SSL encryption and decryption, freeing up backend servers to focus on application logic. Additionally, they can perform content inspection and filtering to block malicious requests before they reach the backend.
  3. Performance Optimization: Techniques like caching and compression can be applied at the reverse proxy level to improve performance. Caching frequently accessed content reduces the load on backend servers, while compression reduces the amount of data that needs to be transferred, improving response times.
  4. Monitoring and Logging: Advanced reverse proxies can generate detailed logs and metrics, which are essential for monitoring the health and performance of your system. By analyzing these logs, you can quickly identify and resolve issues, ensuring that your system remains stable and efficient.
  5. Scalability: Reverse proxies can be scaled horizontally to handle increased traffic. By adding more proxy servers, you can distribute the load and ensure that your system can handle a growing number of users without performance degradation.