TCP SYN Cookie Time Validation for Flood Attack Protection
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Solution Overview
Problem
Existing solutions for constructing and validating SYN cookies are inadequate, leading to high false validation rates and unsatisfactory protection against TCP SYN flood attacks, which deplete server resources and impact legitimate users by filling connection queues with phony TCP SYN packets.
Innovation Solution
A system and method for TCP SYN cookie validation that generates a transition cookie using data from the SYN packet, including a time value, and validates it by determining if the candidate transition cookie in the ACK packet is within a predetermined time interval, typically between one to six seconds, to ensure valid resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a hash function is used to construct the SYN cookie, then the SYN cookie can be generated quickly, but the false validation rate increases significantly
Solution Approach 1:
The patent changes the construction parameters of the SYN cookie from a simple hash function to a time-based validation mechanism. The SYN cookie includes a time value that must fall within a predetermined time interval, transforming the validation from a purely cryptographic check to a temporal verification that reduces false positives while maintaining generation speed.
Solution Approach 2:
The patent performs preliminary validation by checking whether the time value in the received SYN cookie falls within the expected time interval before proceeding with full connection establishment. This preliminary time-based filter prevents false validations early in the process, reducing the burden on subsequent validation steps.
2Productivity
If server resources are allocated immediately upon receiving SYN packet, then connection processing is fast, but server resources are depleted by flood attacks
Solution Approach 1:
The patent performs preliminary validation of the SYN cookie (including time interval verification) before allocating full server resources for connection establishment. This allows the server to quickly reject invalid packets without committing resources, while still maintaining fast processing for valid connections that pass the preliminary checks.
Solution Approach 2:
The SYN cookie with time validation acts as an intermediary mechanism between the SYN packet reception and full resource allocation. It serves as a gatekeeper that verifies the legitimacy of connection requests before the server commits its resources, preventing flood attacks from depleting server capacity.
3Quantity of substance
If connection queue size is increased to handle more SYN packets, then more connections can be tracked, but the queue fills up faster during attacks
Solution Approach 1:
The patent extracts the validation logic from the connection queue management process by implementing time-based SYN cookie verification. This separates the filtering function from the queue, allowing the queue to remain smaller since invalid packets are rejected before entering or remaining in the queue for extended periods.
Solution Approach 2:
The patent implements periodic time-based validation where the SYN cookie's time value is checked against the current time to determine if it falls within the expected interval. This periodic verification ensures that packets remain in the queue only for the necessary duration, preventing long-term occupancy by invalid connections.
Data Source
AI summary
Provided is a method and system for TCP SYN cookie validation. The method includes receiving a session SYN packet by a TCP session setup module of a host server, generating a transition cookie including a time value representing the actual time, sending a session SYN/ACK packet, including the transition cookie, in response to the received session SYN packet, receiving a session ACK packet, and determining whether a candidate transition cookie in the received session ACK packet comprises a time value representing a time within a predetermined time interval from the time the session ACK packet is received.