Network Access Control via SYN Cookie Verification
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Solution Overview
Problem
Conventional Application Delivery Controllers (ADCs) face challenges in preventing denial of service attacks and unauthorized access due to overwhelming SYN packets, which can lead to resource exhaustion and malicious activities such as botnet attacks, as they typically allocate resources upon receiving SYN packets without adequate verification.
Innovation Solution
Implementing a system that uses SYN cookies in SYN/ACK packets to verify client devices, allowing only trusted sources to establish connections by including identifying information and incrementing sequence numbers, thereby preventing unauthorized access and SYN flooding attacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional ADCs allocate resources upon receiving SYN packets, then connection establishment is simplified, but the system becomes vulnerable to SYN flooding attacks and resource exhaustion
Solution Approach 1:
The patent implements SYN cookies as a preliminary action before full resource allocation. When a SYN packet is received, the ADC generates a SYN cookie containing encoded connection information and sends it in the SYN/ACK packet without allocating full resources. This preliminary verification mechanism prevents resource exhaustion from malicious SYN packets while maintaining legitimate connections.
Solution Approach 2:
The SYN cookie acts as an intermediary verification mechanism between the SYN packet reception and full resource allocation. The cookie encodes client identification and connection parameters, serving as a mediator that validates the connection request before committing system resources, thus resolving the contradiction between ease of connection establishment and resistance to attacks.
2Reliability
If the ADC verifies each SYN packet to prevent unauthorized access, then security is improved, but the processing time and complexity increase
Solution Approach 1:
The patent changes the verification parameter from complex multi-factor authentication to a compact SYN cookie containing encoded connection parameters. The cookie transforms verification from a complex process into a simple parameter matching operation, maintaining high security while reducing processing complexity and time.
Solution Approach 2:
The SYN cookie is a compact copy of essential connection information encoded in a verification token. Instead of verifying multiple separate parameters, the system uses this copied and encoded information to streamline the verification process, reducing complexity while maintaining security.
3Speed
If resources are allocated immediately upon SYN packet reception, then connection speed is improved, but the system is susceptible to denial of service attacks
Solution Approach 1:
The SYN cookie mechanism performs preliminary verification before full resource allocation, allowing the system to maintain fast connection establishment for legitimate users while preventing resource exhaustion from malicious attacks. The preliminary action of sending the cookie with encoded verification data enables rapid validation without compromising security.
Data Source
AI summary
Provided are methods and systems for network access control. A method for network access control may commence with determining whether a client device is a trusted source or an untrusted source. The determination may be performed using a SYN packet received from the client device. The SYN packet may include identifying information for the client device. When it is determined that the client device is neither the trusted source nor the untrusted source, the method may continue with transmitting a SYN/ACK packet to the client device. The SYN/ACK packet may include a SYN cookie and identifying information for a network device. The method may further include receiving an ACK packet from the client device that may include the identifying information for the client device, identifying information for the network device, and the SYN cookie. The method may continue with establishing a connection with a network for the client device.