What is a Reverse Proxy Server?

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By Vinay Khatri

A proxy server is an intermediary solution that helps steer requests for web pages and content from many clients to innumerable servers distributed all through the internet. A reverse proxy server is one that is perched inside a private network at the back of the firewall. It is used for directing requests from clients to the proper backend server. The reverse proxy server also comes up with an extra abstraction level to ensure a smooth, unbroken flow of traffic between servers and clients in the network.

What are the Basic Functions of a Reverse Proxy Server?

A reverse proxy server comes into the scene to eventually forward requests initiated by users or web browsers to the web servers. But, while doing so, the reverse proxy server contributes to protecting the identity of the web servers. Also, a reverse proxy server lends a helping hand to the web servers by strategically moving requests on their behalf. This action helps augment the web servers’ performance, reliability, and security.

Reverse proxy servers help in:

  • Disguising the existence and characteristics of origin servers
  • Making initial takedowns
  • Removing malware easily
  • Supporting TLS acceleration hardware
  • Allowing TLS acceleration hardware to execute encryption and augment security to websites
  • Sharing and distributing a load of incoming requests evenly to many servers that support their corresponding application areas
  • Performing as a web acceleration server to cache static as well as dynamic content
  • Decreasing the load on origin servers
  • Compressing and optimizing content
  • Reducing web page or content loading times
  • Carrying out A/B and multivariate testing without the need to insert JavaScript in web pages
  • Inserting basic authentication to web servers to access HTTP
  • Feeding dynamically generated web pages and content step-by-step to clients even if all of them are produced in one go
  • Allowing automatic closure of programs that generate web pages and content
  • Freeing up server resources in the course of the transfer of content
  • Reviewing several incoming requests using one public IP address
  • Delivering incoming requests to more than one web servers housed inside a LAN

How Reverse Proxy Servers are Commonly Used?

Let us consider a company with a massive e-commerce website. With just a single web server, it is impossible for the website to come to grips with the ever-increasing traffic.

Therefore, it makes use of a reverse proxy server to hand over user requests to a server having adequate resources. This server usually resides within a pool of servers and takes control of the gradual surge in traffic. Traffic from the proxy server is directed via a common method called round-robin load balancing.

A reverse proxy server garners significant merit by concealing the identity of the main server that is in charge of the website. It offers a powerful safeguard against malicious cyber attacks by spammers, hackers, and cybercriminals. The website is typically shown to be hosted by multiple servers. In the case of a cyber-attack, only the frontend servers are affected keeping the safety of the backend server intact.

How does a reverse proxy server stand out in the crowd?

reverse proxy server

The reverse proxy server is installed facing one or multiple web servers. Its main function is to intercept or listen to requests from clients. In the presence of a reverse proxy server, the requests sent from clients to a website’s origin server are intercepted at the edge of the network. Then, the reverse proxy begins sending requests to and receiving responses from the website’s origin server.

Even though there is only a subtle difference between forward and reverse proxy servers, it is significant. To put it simply, a forward proxy server is positioned facing a client-server. It makes sure there is no direct communication between the origin server and a particular client-server.

On the contrary, the reverse proxy server is placed before the origin server to ensure no client-server ever directly communicates with its anterior origin server. It works through the processes of:

  • Receiving a connection request from a user
  • Wrapping up a three-way TCP handshake and discontinuing the initial connection
  • Setting up a connection with the origin server and directing its request

The functioning of a reverse proxy server can be simply illustrated with the help of the following example.

  • D: The number of home computers of a user
  • E: The reverse proxy server
  • F: A single or multiple origin servers

What is the Reverse Proxy Flow?

Usually, every request originating from D will land directly in F. Also, F will be directly making responses to D. In the presence of a reverse proxy server, every request originating from D will first directly go to E. It is E that will start sending the requests to and receiving responses from F. Finally, E will relay proper responses to D.

Benefits of a Reverse Proxy Server

1. Load balancing

It is almost impossible on the part of a hugely popular website to manage the deluge of incoming traffic with just one origin server. The website is expected to be visited by millions of users on a daily basis. In place of a traditional setup, it is possible to distribute the website in a pool comprising multiple servers. Each of them will be in control of requests to be sent to or be received from by the same website respectively.

In such a scenario, the reverse proxy server can facilitate load balancing to uniformly spread out the incoming traffic within the pool. This averts the possibility of anyone server getting overloaded. If any of the servers in the pool malfunctions or completely breaks down, others can take over its share of traffic and evenly manage the distribution.

2. Protection from cyber attacks

The advantage of the placement of a reverse proxy server is that any websites or services never really need to disclose the IP addresses of the origin servers handled by them. When the incoming traffic is routed via a reverse proxy server, connections with the origin server are first broken off by the proxy and then re-established with the backend server. During this sequence of events, the IP address of the origin server remains masked. This makes it more difficult for spammers and cybercriminals to plan and execute an attack against the setup. Such an attack is often referred to as a distributed denial-of-service (DDoS) attack.

Instead, potential hackers will be left with the only choice to target the reverse proxy server, for example, the content delivery network (CDN) from Cloudflare. But, such a comprehensive network has more robust security and added resources to prevent a likely cyber-attack.

3. Global Server Load Balancing (GSLB)

This type of load balancing brings to the fore a setup where a global distribution of a website can be accomplished through numerous servers. Clients will be sent by the reverse proxy to the geographically nearest server. Therefore, the website loading time is greatly minimized.

4. Content caching

With the help of a reverse proxy server, it is also possible to cache content. This results in speedier performance. For instance, if a user in London pays a visit to a website that has its web servers stationed in Los Angeles, the user could possibly get connected to a reverse proxy server situated locally in London. It will then have to establish communication with an origin server located in Los Angeles. This enables the proxy server to cache or temporarily preserve the response data. So, when other users from London browse the same website they will be able to access the locally cached data from the reverse proxy in London. Consequently, the user will be able to access the website much faster.

5. SSL encryption

The computation processes of encryption and decryption of protocols such as Secure Sockets Layer (SSL) or its successor Transport Layer Security (TLS) are very costly as far as an origin server is concerned. A suitable configuration of the reverse proxy server can be designed and put into effect for encrypting every outgoing response and decrypting every incoming request. This frees up the origin server’s valuable resources to a great extent.

6. Traffic scrubbing

Since the ideal location of a reverse proxy server is in the front of all backend servers, it has the capability to scrub all types of incoming traffic before they are passed on to the backend servers. This helps mitigate a DDoS attack as the distribution of the incoming traffic happens within a secure mesh of reverse proxies and subdues its overall impact. It also provides web application security through the appropriate positioning of a web application firewall and expels malicious data packets containing hacker requests and bad bots.

Limitations of a Reverse Proxy Server

On the flip side, a reverse proxy server can pose a substantial security risk. This is because it is capable of monitoring all the traffic that passes through it and changing the data as per its own logic. Here are some of its limitations:

  • If HTTP traffic needs to be passed through a reverse proxy server, the data needs to be decrypted and subsequently encrypted. This implies a reverse proxy server must have the SSL/TLS private keys in its possession. So, in case the reverse proxy is compromised by any fraudster, the website can be injected with malware and destroyed.
  • If the main server cannot be directly accessed, employing a reverse proxy can be the sole cause of failure. For instance, when a reverse proxy is set up as the front for serving multiple domains, its outage can result in all the connected domains shutting down simultaneously.
  • If the operation and maintenance of the reverse proxy server are outsourced to a third party, then all sensitive information relevant to the website is passed on to the third party. Even though they can be relied upon, there is no certainty what it will possibly lead to.
  • The restoration of backups and making sites live may exert additional pressure on the reverse proxy server thereby causing it to load improperly. The installation of a WordPress Multisite on a reverse proxy is fairly complicated and not recommended. Even the maintenance of the site poses many problems.

How can a Reverse Proxy Server be Implemented?

A few companies develop their proprietary reverse proxy servers. This calls for numerous weeks to plan, procure, and deploy the specialized hardware. It also requires intensive software resources to be put in place. These own-built reverse proxy solutions can be costly investments. Furthermore, they involve complex operational steps to make the servers work successfully.

One of the simplest and most affordable ways to take advantage of a reverse proxy server is by teaming up with an eminent third-party service provider. They incorporate multi-cloud environments and ultra-modern applications in building reverse proxy servers that are simple yet offer high performance and also boost the security of websites.

Which Vendors Provide Reverse Proxy Servers?

Many companies are offering high-end reverse proxy servers with some of them mentioned as follows:

  • A10 Networks
  • Akamai
  • Amazon CloudFront
  • ArvanCloud
  • CDNetworks
  • Citrix Systems
  • Cloudflare
  • DDoS-Guards
  • DOSarrest
  • F5 Networks
  • Fastly
  • Imperva
  • Microsoft Azure
  • Qrator
  • Radware
  • StackPath
  • Sucuri
  • VMware

Do Reverse Proxy Servers Offer Absolute Security?

A reverse proxy is most effective in offering complete protection to systems against web-based susceptibilities. This is achieved through the addition of an extra layer of security. The server takes a seat between internal services and external clients. This precludes anyone from directly getting admittance to the network. It is important to expose the supporting IT infrastructure as little as possible. This will minimize the traction potential hackers may grab against confidential information.

The risk is lowered on account of two reasons:

  1. Better protection is offered to the server from bad bots.
  2. Hackers are more inclined to meddling with easy-to-access websites. One with extensive security will encourage them to leave it and move on.

The reverse proxy server is the face of a general web presence. So, it can be accorded the responsibility of hosting SSL/TLS certificates and handling the appropriate negotiations for the sake of each of the internal servers. This indicates managing multiple certificates or encrypting internal networks will no longer remain essential requirements.

To bring in more security, a firewall can be put into action. Therefore, if needed, a basic reverse proxy server can be exchanged with one having supplemental firewall features. This will not involve any change in the working of the internal services.

Bottom line

A reverse proxy server puts forward a number of benefits to businesses and web administrators. It improves server efficiency and is easy to maintain. It also provides an additional, necessary layer to render cybersecurity and privacy when users are online. Thus for real online privacy, a reverse proxy server is the quintessential go-to.

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