Forward Proxy and Reverse Proxy

Forward proxies and reverse proxies are both intermediary servers that sit between a client and a server. However, they serve different purposes and are used in different contexts. Here’s a detailed comparison of the two:

Forward Proxy

A forward proxy, often simply called a proxy server, acts on behalf of clients (e.g., users' computers) to fetch data from servers.

Use Cases:

1. Anonymity and Privacy: Hides the client's IP address from the server, providing anonymity.

2. Content Filtering: Enforces policies such as blocking access to certain websites.

3. Caching: Stores frequently accessed resources to reduce bandwidth usage and speed up access.

4. Access Control: Allows or denies internet access based on IP addresses or user authentication.

5. Security: Protects clients from malicious sites by filtering requests and responses.

Workflow:

1. A client makes a request to access a particular resource on the internet.

2. The request is sent to the forward proxy.

3. The proxy server forwards the request to the internet server on behalf of the client.

4. The internet server sends the resource back to the proxy server.

5. The proxy server sends the resource back to the client.

Reverse Proxy

A reverse proxy, on the other hand, acts on behalf of servers to handle requests from clients.

Use Cases:

1. Load Balancing: Distributes client requests across multiple backend servers to ensure no single server is overwhelmed.

2. Caching: Caches content to reduce the load on backend servers and improve response times for clients.

3. SSL Termination: Handles SSL encryption/decryption, freeing backend servers from the computational load.

4. Security: Protects servers by acting as a barrier, filtering requests for malicious content, and preventing direct access to the backend servers.

5. Global Server Load Balancing: Directs clients to the nearest or most appropriate server based on various criteria, such as geographical location.

Workflow:

1. A client makes a request to access a resource.

2. The request is sent to the reverse proxy.

3. The reverse proxy determines which backend server should handle the request.

4. The proxy forwards the request to the selected backend server.

5. The backend server processes the request and sends the resource back to the reverse proxy.

6. The reverse proxy sends the resource back to the client.

Key Differences

• Direction of Proxying:

  • Forward Proxy: Sits between the client and the internet, serving requests from clients.

  • Reverse Proxy: Sits between the client and internal servers, serving requests from clients to servers.

• Primary Purpose:

  • Forward Proxy: Used mainly for client-side purposes like privacy, filtering, and caching.

  • Reverse Proxy: Used mainly for server-side purposes like load balancing, security, and caching.

• Visibility:

  • Forward Proxy: The server is unaware of the client's identity.

  • Reverse Proxy: The client is often unaware that they are interacting with a reverse proxy.

Examples

• Forward Proxy: Squid, Privoxy

• Reverse Proxy: NGINX, HAProxy

In summary, while both forward and reverse proxies serve as intermediaries, they are used in different scenarios and serve different purposes, enhancing the functionality, performance, and security of networks and applications in distinct ways.