CDN

Edge Network Architecture

A CDN (Content Delivery Network) is a geographically distributed network of servers (edge nodes or points of presence) that caches and serves content to users from locations close to them. When a user requests a resource, DNSDomain Name System. The hierarchical, distributed naming system that translates human-readable domain names (e.g., example.com) into IP addresses (e.g., 93.184.216.34). Often called the "phonebook of the internet." resolves the domain to the nearest edge node — often using AnycastA network addressing method where the same IP address is assigned to multiple servers in different locations. Traffic is routed to the nearest or best-performing server, commonly used by CDNs and DNS providers. routing — rather than the origin server. The edge node serves the cached response directly, reducing round-trip distance and therefore LatencyThe time delay for a data packet to travel from source to destination, typically measured in milliseconds (ms). Lower latency is critical for real-time applications like video calls, gaming, and financial trading., while also absorbing traffic that would otherwise hit the origin.

What CDNs Cache and Accelerate

CDNs are most effective for static assets: images, CSS, JavaScript, fonts, and video. They also accelerate dynamic content through persistent TCP/TLS connections between edge and origin (connection reuse), HTTP/2 and HTTP/3 multiplexing, and regional caching of semi-dynamic pages. Modern CDNs additionally provide security services including DDoSDistributed Denial of Service. An attack that overwhelms a target server or network with massive traffic from many compromised sources (a botnet), rendering the service unavailable to legitimate users. mitigation, Web Application Firewall rules, and SSL/TLSSecure Sockets Layer / Transport Layer Security. Cryptographic protocols that provide encrypted, authenticated communication over a network. SSL is deprecated; modern implementations use TLS 1.2 or TLS 1.3. termination at the edge so the origin never needs to handle raw internet traffic.

CDN and DNS Interaction

CDN integration is almost always DNS-based: you point your domain's CNAME RecordA DNS record that creates an alias from one domain name to another (e.g., www.example.com -> example.com). The alias inherits all DNS records of the target, but cannot coexist with other record types at the same name. at the CDN's domain, and the CDN routes requests to the appropriate edge node. The edge node fetches content from your origin using the origin's Public IP AddressA globally unique IP address assigned by an ISP that is routable on the public internet. Every device directly accessible from the internet must have a public IP address., caches the response, and serves subsequent requests locally. CDN providers use AnycastA network addressing method where the same IP address is assigned to multiple servers in different locations. Traffic is routed to the nearest or best-performing server, commonly used by CDNs and DNS providers. to ensure the DNS resolution and the actual HTTP request both land on the same geographically optimal edge node. Use DNS Lookup to observe CDN CNAME chains in practice.