What is a reverse proxy server?
Reverse proxy servers are connection points that sit in front of web servers and work as gateways for the client requests. They are deployed to intercept these requests, forward them to web servers, and transmit the responses back to clients. Reverse proxies are distributed geo-strategically, with functionalities geared toward optimizing the performance, reliability and security posture of all web servers within a network.
How does reverse proxy differ from forward proxy?
Both proxy types act as intermediaries between the client and the origin server. The difference is in their placement along the schematic of the network architecture, which in turn defines each proxy’s functionalities.
When proxy servers sit in front of clients they are referred to as forward proxy servers. Their functions stem from shielding the identity of the client making requests and managing that client’s access to the internet. This could be useful, for example, when faced with government-imposed firewalls regarding parts of the Internet — the proxy’s IP may be used to circumvent such censorship.
On the other hand, a reverse proxy server sits in front of a web server on which the application is running. From its positioning it can also act as a firewall, masking any website’s IP address, but its abilities go beyond just beefing up security. Reverse proxies can also work as a load balancer, efficiently distributing requests across servers in a given network; cache the content from the origin so that distance to responses is reduced and performance accelerated; and decrypt incoming requests/encrypt outgoing responses, which frees up computational resources of the origin servers.
Here is a sample scenario to explain how the reverse proxy server works:
A user is browsing on a laptop and then opens a new website. This user’s action sends a request to the backend infrastructure of the website to retrieve data. But before the request can arrive at the origin server, the reverse proxy intercepts it. The reverse proxy then forwards that request to the origin server. Once the response comes back from the origin, the reverse proxy routes the appropriate response to the client’s browser.
On the technical side, the reverse proxy has to parse the request, decode the URL, normalize the path, do a TCP three-way handshake, and apply rules before forwarding the request to the backend.
Useful functionalities of a reverse proxy server
Reverse proxies have several features that make them essential components of any modern internet infrastructure. Let’s discuss them in detail.
When a distributed network of reverse proxy servers starts caching content from a web server, we refer to it as a content delivery network (CDN). A CDN’s purpose is to reduce latency and improve site performance, and the process goes like this:
Mary lives in New York and visits a website hosted in Paris. The distance between Mary and the website server increases the latency and makes page loading annoyingly slow. If Mary is the first user from her region to visit the site, the caching server that proxies her request to Paris has an opportunity to save a copy of the website content to its cache.
Peter also lives in New York and visits the website right after Mary. His user experience will be much better when visiting the website, because the biggest part of the content his browser will receive will be delivered via the NY proxy server with significantly reduced latency.
Since the reverse proxy intercepts the request midway, it reduces the load on the origin server and other backend infrastructure. It also increases the speed of responses. In general, reverse proxies use caching to enhance content availability, even during web server downtimes.
Reverse proxy can also work as a load balancing tool to disburse specified amounts of network traffic to the application servers.
Load balancing is crucial when handling increased user pools and unpredictable application workloads. For websites looking to scale, reverse proxies can help distribute the load to additional servers as traffic demand grows.
Furthermore, load balancing prevents web servers from being overloaded, even during traffic surges. As a result, applications have more availability because their backend infrastructure components work consistently and smoothly.
Protection against cyberattacks
By filtering all incoming traffic, reverse proxies can be configured to safeguard your network—its role as an intermediary between users and your backend infrastructure means it is positioned to absorb the brunt of a DDoS attack, thereby protecting the main servers in the process.
One mechanism reverse proxies employ is the use of a web application firewall (WAF) to prevent various file injections and other application attacks. While geared to repel hackers trying to exploit the network, the WAF also adheres to policies that help prevent data leakage and theft from the backend infrastructure.
When all incoming traffic travels through a reverse proxy server, the initial connection is terminated before re-emerging via the proxy IP. As a result, people outside the network will see the proxy’s IP address instead of the address of the origin server. This layer of anonymity is one method of IP masking.
As mentioned earlier, IP masking makes it difficult for malicious actors to launch pinpoint DDoS attacks on your network. Since they only have access to a spoofed address, the origin server’s IP remains anonymous, and any malicious traffic will head to your reverse proxy server.
Live monitoring and logging
Because of its placement, a reverse proxy is where monitoring software can oversee all incoming traffic and log all network events and changes. It keeps track of all data leaving the backend architecture. By analyzing this data, you can learn more about your business and clients, as well as figure out how to make data-driven adjustments.
A typical application of this feature is in e-commerce. Online shopping platforms can track the real-time activity on their network to find out the best way to optimize performance and improve user experience.
Reverse proxies may also have encryption functionalities to safeguard the privacy of client-server communications. Configured to decrypt incoming requests and encrypt outgoing responses, they function as an endpoint for SSL/TLS keys and certification.
By sitting in front of web servers and tasked with encrypting all client communications, the reverse proxy frees up computational resources at the origin server and offsets the expense that encryption would otherwise require to secure those web servers.
Drawbacks of using a reverse proxy
We’ve covered the essential features of a reverse proxy. But like every other internet system (hardware or software), reverse proxies may present drawbacks as well, and even potential risk factors.
Here are a few worth considering:
- The addition of any hardware or software means factoring in respective costs. This will vary, of course, according to your unique business requirements and global/regional network demands. Whether it’s an added on-premise appliance or cloud-based SaaS offering, incorporating a reverse proxy is an added expense.
- Implementing a reverse proxy means the network architecture as a whole will become more complicated (though, ideally, far more efficient and secure in the process). It is imperative to have an expert maintenance team in place. Failure to do so is a recipe for headaches down the road.
- Generally speaking, a reverse proxy is an additional network component, introducing another “hop” in the communication route. This equates to (potentially) having a higher degree of latency for clients accessing content. However, as we mentioned above, reverse proxy can optimize the distribution of network traffic to web servers, helping reduce latency, particularly during surges.
Reverse proxies act as important intermediaries placed between the web server and users. Their positioning provides an array of highly useful functionalities: from caching content closer to end users and serving as a load balancer to increase website availability and performance, to monitoring and filtering all incoming and outgoing traffic in order to maintain the security of the backend infrastructure.
You can also mask your IP address and encrypt your communications with the help of a proxy server. And during DDoS attacks, a reverse proxy can help your website stay active by absorbing the brunt of the impact.