The principle of high-defense CDN is to build a content distribution network on the Internet. It relies on edge servers deployed in various places, and through the load balancing, content distribution, scheduling and other functional modules of the central platform, users can obtain the required content nearby without directly accessing the website source server. The principle is simply to set up multiple high-defense CDN nodes, and when there is an attack on a CDN node, each node bears it together. The website will not be inaccessible because a node is attacked and killed, and the website source IP can also be hidden.
　　Configuration and optimization of high-defense CDN
　　In order to achieve efficient acceleration and protection, correct configuration and optimization are essential. The following are some key configuration and optimization suggestions:
　　DNS configuration: Make sure that the domain name resolution points to the node address provided by CDN. Usually, CDN will provide CNAME records to point the website's domain name resolution to the CDN server.
　　Cache strategy configuration: Set appropriate cache time according to different types of resources. Static content (such as pictures, JS, CSS) can set a longer cache time, while dynamic content needs to be refreshed more frequently.
　　Content distribution strategy: Select appropriate content distribution rules. For some specific content (such as video streaming), you can use the video acceleration and real-time traffic optimization solutions provided by CDN.
　　SSL certificate configuration: Configure SSL certificates for the website to ensure secure communication with CDN nodes through the HTTPS protocol to protect user data from being stolen.
　　DDoS protection threshold setting: Set the DDoS protection threshold according to the traffic characteristics of the website. Ensure that the attack traffic can be identified in time and directed to the protection system when attacked.
　　WAF rule configuration: Configure appropriate WAF rules according to the business type of the website. For example, if it is an e-commerce website, you can strengthen the security protection of the payment interface.
　　Bot identification and interception: Enable the Bot management function of CDN to identify and intercept malicious automated traffic. The protection accuracy can be improved by enabling device fingerprint recognition, behavior analysis and other means.
　　Traffic analysis and monitoring: Regularly monitor traffic changes, detect abnormal traffic in time and respond to emergencies. High-defense CDN usually provides real-time traffic analysis reports to help website administrators identify potential security risks.
　　Optimize cache configuration: Regularly clean CDN cache and adjust cache strategy to ensure that frequently accessed resources can respond quickly, while less frequently accessed content reduces cache burden.
　　Compression and image optimization: Enable image compression and compression of static resources (such as Gzip compression) to reduce file size and increase loading speed.
　　HTTP/2 and QUIC protocols: Enable modern protocols such as HTTP/2 and QUIC to increase resource loading speed, especially in high-latency network environments.
　　Load balancing and fault tolerance: Enable intelligent load balancing to ensure that traffic can be reasonably distributed to healthy CDN nodes, and enable fault tolerance to cope with node failures.
　　DDoS attack defense methods:
　　Filter unnecessary services and ports: You can use tools such as Inexpress, Express, and Forwarding to filter unnecessary services and ports, that is, filter fake IPs on routers. Opening only service ports has become a popular practice for many servers. For example, for WWW servers, only port 80 is opened and all other ports are closed or blocked on the firewall.  
　　Abnormal traffic cleaning and filtering: Abnormal traffic is cleaned and filtered through DDOS hardware firewall. Through data packet rule filtering, data flow fingerprint detection filtering, and data packet content customized filtering, etc., top technologies can accurately determine whether the external access traffic is normal, and further prohibit abnormal traffic from filtering. A single load can defend 8-9.27 million syn attack packets per second.
　　Distributed cluster defense: This is an effective way to defend against large-scale DDOS attacks in the current network security industry. The characteristics of distributed cluster defense are that multiple IP addresses (load balancing) are configured on each node server, and each node can withstand DDOS attacks of no less than 50G. If a node is attacked and cannot provide services, the system will automatically switch to another node according to the priority setting, and return all the attacker's data packets to the sending point, making the attack source paralyzed.
　　High-defense intelligent DNS resolution: The perfect combination of high-intelligent DNS resolution system and DDoS defense system, it subverts the traditional practice of one domain name corresponding to one mirror, and intelligently resolves the DNS resolution request to the server of the user's network according to the user's Internet route. At the same time, the intelligent DNS resolution system also has a downtime detection function, which can intelligently replace the paralyzed server IP with a normal server IP at any time.
　　Related questions and answers
　　Q1: Does the CDN server support blocking IP?
　　A1: Yes. In order to avoid problems such as malicious attacks from abnormal IP addresses, CDN supports setting filtering policies for user request source IP addresses by configuring IP blacklists through the console. Please go to CDN console>Domain Management>Access Control>IP Blacklist and Whitelist to complete the configuration. For specific configuration methods, please refer to IP Blacklist Configuration.
　　Q2: Is there a speed limit for CDN services?
　　A2: Currently, there is no default speed limit for accelerated domain names connected to CDN.
　　Q3: Does the CDN server support directory acceleration?
　　A3: All domain names connected to CDN will be accelerated, and the CDN source station resources can be cached and refreshed through the directory.