Understanding CDN: Definition, Differences from Traditional Access, Use Cases, and Origin Host Configuration

CDN (Content Delivery Network) is a cache layer between users and servers that accelerates website access by distributing content across multiple edge nodes, balancing load, and reducing latency caused by cross‑operator or cross‑region traffic.

Typical problems solved by CDN include slow loading for distant users, server overload during traffic spikes, and limited bandwidth on shared hosting.

Using CDN improves access speed regardless of location or ISP, lowers infrastructure and operational costs, and can increase traffic, inquiries, and conversions.

Compared with traditional direct access, CDN routes requests to the nearest edge node, while traditional access goes directly to the origin server.

Common CDN use cases are static web pages, images, large file downloads, software distribution, video streaming, live streaming, application acceleration, mobile apps, and dynamic content acceleration.

When configuring CDN, the origin (source) server determines the IP address to which the CDN pulls content, while the origin host specifies which virtual host on that IP should serve the request.

Example 1: Origin is www.a.com, origin host is www.b.com – CDN requests the IP of www.a.com but retrieves the site hosted as www.b.com on that server.

Example 2: Origin is 1.1.1.1, origin host is www.b.com – CDN requests 1.1.1.1 and serves the site identified by www.b.com on that machine.

Setting the correct origin host allows a backend service without a bound domain (e.g., 127.0.0.1) to be accessed via CDN by adding the appropriate host (e.g., test.abc.com) in the CDN settings.

Testing steps include:

Directly curl the origin IP (e.g., 127.0.0.1) to verify if the site returns expected content.

Use the -H parameter with the service domain (e.g., api.vcloud.360.cn) to test; failure indicates the origin does not bind that domain.

Use the -H parameter with the test host (e.g., test.abc.com) to confirm it returns the site, then set this as the CDN origin host and retest the service domain.

Reference documents:

http://baike.so.com/doc/4157956-4357973.html http://www.enkj.com/idcnews/Article/20131029/3424