Reverse vs Forward Proxy

Proxy servers has become a common requirementin modern applications with distributed parts. For example, you’d have message brokers, event queues, serverless functions, virtual servers that require a single point of entry from a client.

In fact, consider this architectural diagram:

If you look at the diagram above, you’d see a proxy placed infront of the backend resources, leaving the client to interact with one point to get access to your app.

That’s exactly what a proxy is and does!

In fact, there’s two main types of proxies:

1. Forward Proxy
2. Reverse Proxy

So, let’s aim to explore these two proxies with greater detail in this article and see where it’s best useful for.

What is a reverse proxy?

A reverse proxy is a proxy server that sits between an application and a client. Consider this diagram:

The reverse proxy sits infront of your server resources. So, when you want to request a resource from a server, you communicate with the reverse proxy, which then sends the request to the relevant resource and returns the response back to you.

Simply put, a reverse proxy is a middleman between you and the websites you want to visit.
Due to this nature, it is used in various aspects like:

• Load Balancing: It helps distribute incoming traffic across several servers, which improves the speed and reliability of resources by spreading the load. This ensures no single server becomes a bottleneck, which can enhance the overall performance of the system.
• Security and Anonymity: Reverse proxies mask the characteristics and existence of backend servers, providing an additional layer of security. Additionally, they can act as application firewalls to protect against attacks such as SQL injection, cross-site scripting (XSS), and others. Thus, they can filter out requests before sending them to the backend.
• Content Caching: Reverse proxies cache outbound web content from a server and serve it directly to users upon request. This reduces the load on the server and speeds up response times since the content is delivered from a local cache rather than the origin server.

How does a reverse proxy work?

It’s important to understand how a reverse proxy works. In fact, its workings can be summarized into these simple steps:

• Client Request: The client will first request for a resource. When a request is made, it first goes to the reverse proxy server.
• Request Evaluation: The reverse proxy evaluates the request based on its rules and content. It decides whether to serve the request from its cache or send it to an actual server resource.
• Communication with Backend Servers: The reverse proxy forwards the request to the appropriate backend server, if it is not cached. If cached, it returns the response through the cache.
• Load Balancing: The reverse proxy uses load balancing algorithms to decide which server to route the request to, based on factors like the number of current connections, server response times, and server health.
• Request Processing: Once the backend server processes the request, it sends the response back to the reverse proxy.
• Caching: If caching has been enabled, the reverse proxy will cache the response generated through the resource.
• Response Delivery: The reverse proxy sends the response back to the client.

With this approach, it seems as if the reverse proxy is the origin of the content, not the backend server.

Pros of using a reverse proxy

Due to the nature explained above, a reverse proxy offers two main benefits to its users:

• Improved Security: As discussed earlier, reverse proxies help mask the internal server resources, giving system resources total anonymity. Additionally, with the additional layer of security, the reverse proxy can filter out requests before sending them to the server to ensure that only valid requests are processed.
• Enhanced Performance: Reverse proxies help with content caching and load balancing. This improves the overall system performance, as content is served quickly from the cache without straining system resources. It also utilizes server resources optimally by routing the request based on the load.

Cons of using a reverse proxy

However, a reverse proxy does carry some drawbacks:

• Complexity in Setup and Management: Setting up a reverse proxy isn’t always straightforward. It involves configuring network settings, managing traffic rules, and often integrating it with other network components. As a result, you usually need someone with good IT skills to handle it.
• Single Point of Failure: Since the reverse proxy sits between users and servers, it handles all the incoming and outgoing traffic. If it’s not set up with redundancies, and it goes down for some reason, all the traffic gets blocked. This means that no one can access your website or service until the problem is fixed.

What is a forward proxy?

On the other end of the spectrum, there’s the “forward proxy”, or simple known as a proxy server.

A forward proxy is an intermediary middleware between one or more user devices and the Internet. For example, consider the diagram:

As shown above, all requests go through the proxy before reaching the Internet. It acts on behalf of the client and routes the request to the destination. Next, it evaluates the response and forwards it back to the originating client.

These are used in situations like:

• Privacy and Anonymity: A forward proxy binds its IP Address to a request, thereby, hiding a user’s real IP address. This is useful for individuals and organizations that want to browse the Internet without disclosing their location or identity.
• Security: Forward proxies can provide an additional layer of security by preventing direct connections between the Internet and internal network devices. This helps in protecting against malware and other security threats by scanning incoming data before it reaches the user’s device.
• Web Scraping: Forward proxies can be used in situations where you’d want to attempt web scraping. Certain sites have IP Based Blocking that can be avoided through forward proxies. They can route their requests through a forward proxy. This way, the websites don’t see the scraper’s original IP address but see the IP address of the proxy instead. And, with certain proxies, you have rotating IPs meaning every request would use a different IP Address, thus, making it harder for sites to block.

How does a forward proxy work?

This can be summarized in these five steps:

• Request Origination: The client first originates a request to the Internet.
• Proxy Verification: The request first enters the proxy server. It validates the request and ensures that there isn’t anything suspicious about it. Additionally, it checks if the user can view the resource and if the request requests are in its cache.
• Request Sending: If the request is valid the proxy will send it to the Internet. But, before doing so, it checks its cache and serves it from the cache if there’s a Cache Hit.
• Response Generation: The Internet generates a response and sends it back to the proxy.
• Response Delivery: The proxy would validate the response sent by the Internet and forward it back to the client if it’s valid and safe.

Pros of using a forward proxy

It’s evident that forward proxies are highly beneficial. By using forward proxies, you can:

• User Anonymity: Using a forward proxy gives users complete anonymity in the Internet as their IP address is not visible to anyone. Instead, the proxy IP address is used for communication, thus, keeping the user hidden.
• Adminsitrative Control: Forward proxies help in controlling what users connected to your network can view. For instance, a company might block access to streaming sites during work hours to keep employees focused. This helps maintain a productive environment and ensures that Internet use aligns with organizational policies.
• Content Filtering: A forward proxy can filter out unwanted or unsafe content from reaching the network’s users. This could mean blocking inappropriate or dangerous websites, stopping downloads that might contain viruses, or preventing access to phishing sites that try to trick you into giving up personal information, thus keeping the network safe and clean for all users.

Cons of using a forward proxy

But, using a forward proxy does have its pitfalls.

• Poor performance: Using a forward proxy can slow things down a bit. Since all the Internet traffic has to go through the proxy, it can become a bottleneck, especially if the proxy server isn’t very fast or is handling a lot of requests at the same time.
• Requires additonial management: Having a forward proxy also means there’s more stuff to manage. It needs to be properly set up, maintained, and monitored to make sure it’s doing its job without causing any new problems. This can require extra time and resources, and you might need someone with specific technical skills to handle it.

What should I use – Forward or a Reverse Proxy?

Given everything that was discussed, you might be wondering—what should I use? Would I benefit more from a forward or a reverse proxy?

Well, it’s important to know that there isn’t a right or wrong answer here. It depends on your use case and how you intend to use it. But here are some guidelines that you can consider before making your decision.

1. Consider Your Primary Goal: Are you looking to manage and secure your internal users’ internet access? If that’s your focus, a forward proxy is likely the way to go. It filters content, enforces policies, and maintains user anonymity. On the other hand, if you’re more interested in managing how external users access your servers, like balancing server load and protecting your servers, a reverse proxy would be more suitable.
2. Think About Security Needs: If your main concern is protecting your backend servers from exposure to threats, a reverse proxy can help by acting as a shield. It hides the true details of your servers from the outside world. However, if you want to secure and monitor outbound Internet requests from within your network, a forward proxy is your tool, as it can monitor and filter traffic going out.
3. Evaluate Performance Requirements: If server performance and uptime are critical (for example, if you run a high-traffic website), a reverse proxy can help distribute traffic and reduce load times. However, if the performance concern is more about controlling traffic flow from internal users, a forward proxy can manage this without impacting your core server operations.
4. Assess Management Capabilities: Consider your ability to manage and maintain these proxies. A reverse proxy might require more complex setup and management, but it is suitable if you have the IT resources to handle it. A forward proxy might be easier to implement but could require ongoing management to update rules and monitor user activity.
5. Understand the Scale of Your Operation: If you’re operating on a large scale, handling lots of user requests or managing heavy inbound traffic to your services, a reverse proxy can be essential. A forward proxy might be adequate and more cost-effective for smaller operations or when fewer internal users need to be managed.

Conclusion

Forward and reverse proxies are used in modern applications and organizations. They play a critical role in improving the overall performance and security of the context in which they are used.

However, the success of your implementation ultimately depends on the right proxy you’ve chosen. Therefore, evaluate your requirements first and then decide on the proxy you will use.

I hope you found this article helpful.

Thank you for reading.