How CDN Architecture Boosts Internet Application Quality and Reduces Latency

1 Internet Application Quality Overview

1.1 Internet Application Quality

QoE metrics include service success rate, service establishment time, latency, audio/video stutter, and image clarity.

1.2 Network Performance – Latency

Full latency consists of terminal processing delay → network delay → server response delay → network delay → terminal response processing delay.

Network delay includes routing processing, ADU transmission, server processing, and distance‑induced transmission delay.

Transmission delay = frame length / transmission rate.

Propagation delay = distance / propagation speed.

Processing delay = time routers/servers need to examine packet headers and decide forwarding.

Queueing delay = sum of waiting times in transmission links.

1.3 Network Performance – QoS

Delay, jitter, bandwidth, and packet loss together form QoS indicators, reflecting underlying packet transmission performance.

2 Common Internet Application Deployment

2.1 Centralized Deployment

Centralized deployment suffers from single points of failure, hinders scaling, and can cause high network latency.

2.2 Website Mirroring for Acceleration

Mirroring copies whole or part of a site to other servers, sharing traffic load, but is cumbersome for frequently updated content and rarely used by commercial sites.

2.3 CDN Acceleration

CDN combines intelligent mirroring, caching, and traffic scheduling. Its main advantages include:

Alleviating origin server load.

Optimizing hotspot content distribution and reducing backbone traffic.

Improving user access quality and speed.

Enhancing reliability and handling traffic spikes.

Resolving inter‑operator connectivity issues.

Increasing security against abnormal traffic attacks.

3 CDN Basic Concepts

3.1 Definition

A Content Delivery Network adds a layer to the existing network, delivering origin content to edge locations near users, thereby speeding up response.

Content includes static and dynamic assets.

Distribution uses strategies to place content on the nearest node.

CDN consists of thousands of distributed servers communicating over ISP backbone networks.

3.2 Basic Principles

By placing cache servers worldwide and using global scheduling, CDN moves content closer to users, turning inefficient IP networks into high‑performance, reliable smart networks, improving congestion and response time.

4 CDN Working Process

4.1 Basic Workflow

Content injection: injecting origin content into CDN.

User request scheduling: directing user requests to the optimal CDN node.

Content distribution: delivering content from CDN to users or pulling from upstream nodes.

Content service: delivering content from the nearest node to the end user.

4.2 CDN Content Access

Content storage access: pre‑injecting content into CDN for permanent storage until explicit deletion.

Content pre‑injection: temporary caching without permanent storage, with intelligent eviction based on popularity.

Real‑time pull: fetching content from origin on demand when not cached.

4.3 CDN User Request Scheduling

Global scheduling routes requests to the nearest node based on geographic location.

Local scheduling operates within a region, considering server health and load to assign tasks to the most suitable device.

4.4 CDN Content Distribution

Push method: CDN proactively pushes content from origin to edge nodes using protocols such as HTTP or FTP.

Tip: Push is ideal for hot content, enabling targeted delivery.

Pull method: CDN pulls content on demand when a user request misses the edge cache.

Tip: Pull suits less concentrated, on‑demand content.

Hybrid: combines push pre‑distribution with pull on‑demand fetching.

4.5 CDN Content Service

CDN serves both static and dynamic content.