Learnitweb

Forward Proxy vs. Reverse Proxy

1. Forward Proxy

Many businesses use proxy servers to route and secure traffic between networks. A proxy server, sometimes referred to as a forward proxy, is a server that routes traffic between client(s) and another system, usually external to the network. By doing so, it can regulate traffic according to preset policies, convert and mask client IP addresses, enforce security protocols, and block unknown traffic.

Proxy servers are commonly used in shared network environments like business organizations or data centers. They provide a unified interface for client interactions, simplifying network management by centralizing policy enforcement and routing logic. This eliminates the need for individual clients to handle these tasks, enhancing efficiency and maintainability.

1.1 How it works

  • A client sends a request to the forward proxy.
  • The proxy evaluates the request, applies any defined policies, and then forwards it to the target server.
  • The response from the server is returned to the client through the proxy.

1.2 Use Case Example

A business organization sets up a forward proxy to regulate employee internet usage, enforce security policies, and cache frequently accessed resources like company-specific web applications.

Client -> Forward Proxy -> Internet -> Target Server

2. What Is a Reverse Proxy?

A reverse proxy is a type of proxy server. Unlike a traditional proxy server, which is used to protect clients, a reverse proxy is used to protect servers. A reverse proxy is a server that accepts a request from a client, forwards the request to another one of many other servers, and returns the results from the server that actually processed the request to the client as if the proxy server had processed the request itself. The client only communicates directly with the reverse proxy server and it does not know that some other server actually processed its request.

A traditional forward proxy server enables multiple clients to route their traffic to external networks. For example, a company might use a forward proxy to filter and control employee access to the public internet.

In contrast, a reverse proxy operates on behalf of servers, acting as an intermediary between clients and application servers. It manages access policies, handles traffic routing, and shields the identity of the backend servers that process the requests, offering enhanced security and streamlined traffic management.

2.1 How it works

  • A client sends a request to the reverse proxy.
  • The reverse proxy processes the request and forwards it to one of the backend servers based on routing rules.
  • The response from the server is returned to the client through the reverse proxy.

2.2 Use Case Example

A popular e-commerce website uses a reverse proxy to manage millions of client requests, distribute traffic across multiple servers, and protect backend systems from direct exposure.

Client -> Reverse Proxy -> Backend Servers

2.3 Reverse proxy configuration

By routing client traffic through a reverse proxy, admins can simplify security administration. They can configure backend servers to only accept traffic directly from the proxy and then configure the granular access control configurations on the proxy itself.

For example, admins can configure the reverse proxy’s firewall to whitelist or blacklist specific IP addresses. All existing servers behind the proxy will be protected accordingly, and whenever admins add a new backend server to the network that is configured to only accept requests from the proxy server, the new backend server is protected according to the proxy configuration.

Using a reverse proxy can also allow administrators to easily swap backend servers in and out without disrupting traffic. Because clients interact directly with the proxy, they only need to know its hostname and don’t need to worry about changes to the backend network topology. In addition to simplifying client configuration, an admin can configure a reverse proxy to load-balance traffic so that requests can be more evenly distributed to the backend servers and improve overall performance.

2.4 Use Case: Onboarding and Off-boarding

When onboarding a new user to a network, administrators must configure access control and firewalls to ensure the user can access the appropriate resources. Traditionally, an admin has to configure each server for which users need access. In a large organization with many servers, this can be a time-consuming and error-prone process.

However, with a reverse proxy, administrators can configure the access rights directly on the proxy server and have the user route all traffic through it. As such, the backend servers only need to trust and communicate with the proxy directly. This greatly simplifies the configuration process and helps ensure access is granted and revoked correctly by doing so through a single source.

2.5 Setting up a Reverse Proxy for Access Management

While a reverse proxy can greatly simplify the process of managing access to a network, setting it up and configuring it properly can get complicated. It requires provisioning the host with appropriate specifications, configuring the operating system and firewall, deciding on which proxy software to use (such as NGINX or HAProxy), enumerating and configuring the downstream servers in the proxy configuration files, setting up audit logging, and configuring the firewalls in all the downstream servers.

3. When to Use Each Proxy

Use Cases for Forward Proxy:

  • Organizations that want to control or monitor internet usage by employees.
  • Users who need anonymity while accessing external websites.
  • ISPs providing web filtering services.

Use Cases for Reverse Proxy:

  • Websites and applications with high traffic needing load balancing.
  • Securing backend servers by hiding their identities.
  • Centralized SSL/TLS encryption to offload the processing burden from backend servers.

4. Key Differences

FeatureForward ProxyReverse Proxy
PurposeServes the clientServes the server
Use CaseRegulates client access to resourcesManages and optimizes server access
PlacementBetween clients and external serversBetween clients and backend servers
AnonymityHides the client’s IP addressHides the server’s IP address
Security FocusEnforces client-side securityProtects server infrastructure
Common UsageInternet filtering, cachingLoad balancing, SSL termination