The defense principle of anti-ddos CDN servers involves multi-layered security strategies and technologies to protect networks and websites from various network threats, especially distributed denial-of-service (DDoS) attacks. The following are the key points of the defense principles of anti-ddos CDN servers:

　　Distributed Denial of Service (DDoS) attack defense: One of the main tasks of a anti-ddos CDN server is to prevent DDoS attacks. It protects against DDoS attacks in the following ways:

　　-Traffic filtering: The anti-ddos CDN server monitors incoming traffic, detects abnormal traffic patterns and separates malicious traffic to ensure that only legitimate traffic reaches the source server.

　　-Load balancing: anti-ddos CDN servers can distribute traffic to multiple servers to share the load and ensure that the network will not be overwhelmed.

　　-Distributed network: anti-ddos CDN servers usually have distributed networks that can resist large-scale DDoS attacks because they have multiple edge nodes to handle traffic.

　　Caching technology: anti-ddos CDN servers use caching technology to store static content (such as images, style sheets, and scripts) on edge nodes. This reduces the number of requests to the origin server, reducing the load on the origin server and improving website performance.

　　SSL/TLS encryption: The anti-ddos CDN server supports SSL/TLS encryption to ensure that data is safe during transmission. This helps protect user privacy and sensitive information.

　　Web Application Firewall (WAF): anti-ddos CDN servers usually have WAF functionality, which is used to detect and block common vulnerabilities and attacks in web applications, such as SQL injection and cross-site scripting attacks.

　　Bot detection and blocking: anti-ddos CDN servers can detect and block malicious bots and crawlers to reduce unnecessary traffic and requests to the website.

　　IP blocking and whitelisting: The anti-ddos CDN server can be configured with IP blocking and whitelisting to allow or block access from specific IP addresses to increase security.

　　Network monitoring and analysis: The anti-ddos CDN server monitors and analyzes network traffic in real time to detect abnormalities in time and take measures to provide better security and performance.

　　Fast content delivery: By storing content on edge nodes, the anti-ddos CDN server reduces data transmission time and provides faster content delivery speed, thereby improving user experience.

　　Generally speaking, the defense principle of anti-ddos CDN servers is multi-layered, including the comprehensive application of multiple technologies and strategies such as DDoS attack defense, caching, encryption, WAF, Bot detection, IP blocking and whitelisting. Together, these technologies and strategies ensure high availability, performance, and security of networks and websites. anti-ddos CDN servers provide comprehensive protection for websites and applications by combining security with performance.