Glossary: Cybersecurity Terms & Definitions

What is the difference between a reverse proxy and a load balancer?

Reverse Proxy Servers and Load Balancers

Reverse proxy servers and load balancers are integral components of the client/server computing architecture. Both serve as intermediaries between clients and servers, enhancing efficiency in communication. While they can be implemented as dedicated hardware devices, modern web architectures increasingly rely on software applications running on general-purpose hardware.

Here are their basic definitions:

  • Reverse Proxy: Receives client requests, forwards them to the appropriate backend server, and then returns the server's response to the client.
  • Load Balancer: Distributes client requests among a group of servers and ensures that responses from selected servers are directed back to the proper client.

While the definitions might seem similar, their functions differ, which often causes confusion. To clarify, we will explore when and why each is deployed for web services.

Load Balancing

A load balancer is typically deployed when a single server cannot handle a high volume of requests efficiently, requiring multiple servers to manage the load. By distributing requests across multiple servers, load balancers eliminate single points of failure and improve the reliability of websites. Most of the servers in such an environment host identical content.

The role of the load balancer is to maximize the utilization of server resources, distribute workloads evenly to prevent overloading any single server, and deliver faster responses to clients. When a server goes offline, the load balancer detects it and reroutes requests to the remaining servers.

Advanced health checks allow load balancers to evaluate server health more effectively by sending specific requests and analyzing responses, rather than relying solely on intercepted error responses.
Some load balancers also offer session persistence, ensuring all requests from a specific client are directed to the same server. This is especially useful for stateful applications like e-commerce platforms, where functionality, like shopping carts, requires maintaining consistent session states.

Reverse Proxy

While load balancers are typically deployed in multi-server environments, reverse proxies are often beneficial even with a single web or application server. Acting as the "public face" of a website, a reverse proxy is positioned at the network edge, receiving requests for hosted content from browsers and mobile apps.

Key benefits include:

  • Improved Security: Reverse proxies protect backend server information from being visible to external networks, preventing direct server access by malicious actors. Additionally, most reverse proxies can block traffic from specific IP addresses, limit connection attempts, and guard against DDoS attacks.
  • Enhanced Scalability and Flexibility: With only the reverse proxy's IP address visible to clients, the backend infrastructure can be freely modified. This setup is particularly useful in load-balanced environments, allowing seamless scaling in response to traffic fluctuations.

Reverse proxies also significantly enhance web acceleration, reducing the time required to generate responses to client requests through techniques like:

  • Compression: Compressing server responses (e.g., using gzip) before transmitting them reduces bandwidth usage and speeds up transfers.
  • SSL/TLS Termination: Encrypting traffic protects data transmitted over public networks like the internet. However, encryption and decryption demand considerable computing power. By handling these processes, reverse proxies free up backend servers to focus on content delivery.
  • Caching: Stores frequently requested content, reducing response times for clients and alleviating backend server loads.

How Can NGINX Plus Help?

NGINX Plus and NGINX are world-class load balancing solutions, trusted by high-traffic websites such as Dropbox, Netflix, and Zynga. More than 450 million websites globally rely on NGINX Plus and NGINX Open Source for fast, reliable, and secure content delivery.

NGINX Plus provides extensive load balancing and reverse proxy functionalities, improving a website's performance, reliability, security, and scalability. Being a software-based solution, it offers these features at a fraction of the cost of hardware-based solutions. With NGINX Plus, you can create highly optimized application delivery networks.