A content delivery network (CDN) is a geographically distributed server (also known as an edge server) thatRapid distribution of static and dynamic content. Let's see how it works.
Suppose Bob, who lives in New York, wants to access an e-commerce site deployed in London. If the request is sent to a server in London, the response time will be quite slow. Therefore, we deploy a CDN server near Bob's place of residence and the content will be loaded from the nearby CDN server.
The diagram below illustrates the process.
initial step
Bob types www.myshop.com into his browser and the browser looks up the domain name in the local DNS cache.
second step
If the domain name does not exist in the local DNS cache, the browser will go to a DNS resolver to resolve the domain name.The DNS resolver is usually located in theInternet Service Provider (ISP) (ISP).
third step
The DNS resolver recursively resolves the domain name. Finally, it requests authoritative name servers to resolve the domain name.
fourth step
Without CDN, the authoritative name server returns the IP address of www.myshop.com. However, with CDN, the authoritative name server will have an alias pointing to www.myshop.cdn.com (the domain name of the CDN server).
fifth step
The DNS resolver asks the authoritative name servers to resolve www.myshop.cdn.com.
sixth step
The authoritative name server returns the domain name of the CDN load balancer www.myshop.lb.com.
seventh step
The DNS resolver asks the CDN load balancer to resolve www.myshop.lb.com. The load balancer selects the best CDN edge server based on the user's IP address, the user's ISP, the requested content, and the server load.
eighth step
The CDN load balancer returns the IP address of the CDN edge server to www.myshop.lb.com.
ninth step
Now that we finally have the actual IP address we want to access the DNS resolver will return the IP address to the browser.
Step 10
Browsers access CDN edge servers to load content There are two types of content cached on CDN servers: static content and dynamic content. The former includes static pages, images and videos; the latter includesedge computingThe results of the
Step 11
If the edge CDN Server CacheIf the content is not found in the CDN server, it is uploaded to the regional CDN server. If the content is still not found, it goes up to the central CDN server or even to the origin - the London web server. This is called CDN distribution networkThe servers in it are deployed geographically.
How to prevent piracy of videos cached on CDN?
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Video encryption and watermarking
Encryption: Encrypts video files so that only authorized clients can decrypt and play them. Standard encryption algorithms such as AES can be used.
Dynamic watermarking: Add traceable dynamic watermarks to videos that change as they play, making it possible to trace the source of piracy.
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Signature and Token Verification
Use signatures and tokens (Token) to ensure that each request is authenticated. For example, adding a timestamp and encrypted signature to a video link ensures that it is only valid for a specific period of time and that unauthorized requests will be denied.
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Limit Cache Length
Set a short cache expiration time to avoid storing video content on CDN nodes for long periods of time. You can avoid storing video content on the CDN node for a long period of time by controlling the TTL (Time To Live) or cache clearing strategies to reduce the risk of piracy by reducing the cache survival time of videos.
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anti-theft chain
Configure CDNs and servers to restrict where video content can be accessed. For example, use HTTP Referer header inspection to ensure that only requests from legitimate websites or applications can access the video.