How CDN Technology Supercharges Web Performance and Reduces Latency

1. What is CDN

CDN (Content Delivery Network) adds a cache layer to the Internet, publishing website content to edge nodes closest to users, improving response speed by reducing bandwidth constraints, high traffic, and uneven distribution.

In simple terms, CDN caches resources from the origin server on globally distributed nodes; when users request resources, the nearest node serves the cached content, avoiding round‑trip to the origin, reducing congestion and load.

Solves the “first mile” problem on the server side

Alleviates bottlenecks between different ISPs

Reduces provincial outbound bandwidth pressure

Relieves backbone network pressure

Optimizes distribution of hot content online

2. CDN Working Principle

Traditional Access Process

Traditional access without CDN involves the user’s OS querying Local DNS, then ROOT DNS, then the authoritative DNS, obtaining the IP address, and finally contacting the origin server, which returns the content.

User enters the domain name; the operating system queries Local DNS for the IP address.

Local DNS queries ROOT DNS for the domain’s authoritative server (assuming Local DNS cache has expired).

ROOT DNS returns the domain’s authoritative DNS record to Local DNS.

Local DNS queries the authoritative DNS for the domain’s IP address.

The authoritative DNS responds with the IP record.

Local DNS returns the IP address to the user.

The user accesses the origin server using the IP address.

The origin server responds and returns the content to the client.

CDN Access Process

With CDN, after DNS resolution, the smart scheduling DNS selects the optimal CDN node IP based on algorithms and policies, and the CDN node serves cached content to the client.

User enters the domain name; the operating system queries Local DNS for the IP address.

Local DNS queries ROOT DNS for the domain’s authoritative server (assuming cache expiration).

ROOT DNS returns the authoritative DNS record to Local DNS.

Local DNS obtains the authoritative record and queries the authoritative DNS for the IP address.

The authoritative DNS returns a CNAME record, which Local DNS forwards.

Local DNS queries the smart scheduling DNS for the best CDN node IP.

Smart scheduling DNS selects the nearest CDN node based on static topology, capacity, etc., and returns its IP to Local DNS.

Local DNS returns the CDN node IP to the user.

User accesses the origin server using the IP address.

The CDN node responds, returning the cached content to the client (the cache server stores the data locally for future requests).

To make CDN usage transparent to ordinary users, DNS is used to direct requests to cache servers, providing the simplest and most effective acceleration method.

Components of CDN Network

Each CDN node acts like a web server placed near users.

Through DNS takeover, user requests are transparently directed to the nearest node, which responds like the origin server, resulting in faster response times.

The CDN layer sits between the user side and the origin server.

Smart scheduling DNS (e.g., F5 3DNS) is a key system; when a user accesses a CDN‑enabled site, the DNS request is finally handled by the smart scheduling DNS, which, based on predefined strategies, provides the nearest node address and maintains communication with all nodes to track health, capacity, and ensure optimal request distribution.

Cache services include load‑balancing devices (e.g., LVS, F5 BIG‑IP), content cache servers (e.g., Squid), and shared storage.

3. Glossary

CNAME Record

CNAME (Canonical Name) maps one domain to another; DNS follows the alias until reaching the final A or PTR record.

Example: you have resources at

docs.example.com

and want

documents.example.com

to access the same resources. Adding a CNAME record that points

documents.example.com

to

docs.example.com

makes all requests to the former resolve to the latter, delivering identical content.

CNAME Domain

When you add an accelerated domain in a CDN provider’s console, you receive a CDN‑assigned CNAME domain. You must add a CNAME record in your DNS to point your accelerated domain to this CDN CNAME, so all requests are routed to CDN nodes for acceleration.

DNS

Domain Name System translates domain names to IP addresses. Common DNS providers include Alibaba Cloud DNS, DNSPod, Route53 (AWS), Dyn, Cloudflare, etc.

Origin Host

The origin host determines which specific site on the origin server the request is forwarded to.

Example 1: Origin domain www.a.com with origin host www.b.com results in requests being sent to the IP of www.a.com but served as www.b.com . Example 2: Origin IP 1.1.1.1 with origin host www.b.com results in requests to 1.1.1.1 serving the site www.b.com .

Protocol Origin

Protocol origin means the CDN uses the same protocol (HTTP or HTTPS) as the client when fetching uncached resources from the origin server.