What is Rate Limiting?

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Rate limiting is a control mechanism used in computer networks and applications. It regulates the number of requests a user, typically identified as an IP address, can make within a specified time frame. This approach helps manage the load on the network, prevents abuse of services, and ensures equitable resource distribution among users.

When a user exceeds the set request limit, their additional requests are either denied or delayed until the limit resets. This mechanism is vital for maintaining system stability and performance, particularly in scenarios with high user traffic or where resources are limited.

Key uses of rate limiting include managing access to web APIs, safeguarding against brute-force attacks in authentication systems, and controlling the overall traffic flow to web services. It's a balancing act between security and user experience, requiring careful calibration to avoid undue restrictions on legitimate users while still deterring malicious or excessive use.

Organisations typically determine rate limits based on factors such as their server capacity, anticipated traffic volumes, observed user behaviour, and security needs. Adjustments are often made in response to real-time monitoring and traffic analysis.

There are various algorithms for implementing rate limiting, such as fixed window, sliding window log, and token bucket. Each method has its unique way of tracking and managing requests.

The rise of proxy networks, and the use of CGNAT has limited the effectiveness of IP based rate limiting. Advanced rate limiting that allows counting by other request characteristics, like network fingerprints and headers is required to combat modern botnets and layer 7 ddos attacks.