Policy-Based DNS Server for Selective Traffic Control

The patent applies local quality by making DNS responses non-uniform based on the source IP address. Different quality levels of responses are provided to different clients: legitimate clients receive valid IP addresses while malicious clients receive null routes or loopback addresses. This resolves the contradiction by maintaining accessibility for legitimate users while blocking malicious traffic, thereby improving security without compromising overall network accessibility.

The patent inverts the conventional DNS approach by not providing IP addresses to all clients by default, but instead selectively denying service to specific clients based on their source IP addresses. The system evaluates each query source and applies policy-based responses, inverting the traditional open-access model into a controlled-access model that prioritizes security while maintaining accessibility for authorized clients.

The patent applies preliminary action by pre-configuring policy rules that define which clients should receive which types of DNS responses. The policy engine is pre-programmed with security policies and evaluation criteria that automatically determine the appropriate response for each client based on their source IP address. This resolves the contradiction by establishing information distribution rules in advance, making traffic management systematic and controllable rather than complex and ad-hoc.

The patent changes the parameter of DNS response content based on the client's source IP address. Instead of providing uniform information to all clients, the system dynamically adjusts the response parameters (IP address, null route, loopback address) according to policy evaluations. This resolves the contradiction by enabling selective information availability through parameter variation, simplifying traffic management through policy-based control rather than complex individual handling.