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What is CDN? (Content Delivery Network)
A comprehensive guide to Content Delivery Networks and caching strategies
Overview
Today, we’ll explore Content Delivery Networks (CDN), a crucial technology for optimizing web content delivery across the globe.
What is CDN?
A Content Delivery Network (CDN) is a geographically distributed network of servers designed to:
- Deliver web content from locations closer to users
- Improve loading speeds and reduce latency
- Cache content at various Points of Presence (PoP)
- Serve static files like images, videos, and web pages efficiently
Popular CDN providers include Akamai and AWS CloudFront.
Understanding Caching
Caching is the process of storing data locally for quick future access. In web browsers:
- Stores static data copies locally
- Reduces server requests
- Saves time and resources
- Perfect for static files (images, CSS, JavaScript)
Content Types
Static Contents
- Same data regardless of user/region
- Easily cacheable
- Examples: images, CSS files, JavaScript files
Dynamic Contents
- Data varies based on user/region
- Requires special caching strategies
- Examples: personalized content, real-time data
CDN Caching Methods
1. Static Caching
- Pre-copies content to cache servers
- Always serves from cache
- Ideal for unchanging content
2. Dynamic Caching
- Caches on first request
- Pulls from origin when needed
- Content may expire and be removed
How CDN Works
- First Request:
- Browser requests content
- Origin server provides content
- CDN caches the content
- Subsequent Requests:
- Browser requests content
- Nearest CDN server responds
- Faster response times
CDN Architectures
PoP (Point of Presence)
- Connection points between networks
- Access points for internet connectivity
- Distributed globally for better coverage
Push vs Pull Methods
Push Method:
- Content actively pushed to PoPs
- Requires manual updates
- Faster content delivery
- Lower error probability
- Content pulled on demand
- Easier initial setup
- Resource efficient
- May have slower first access
Architecture Types
1. Scattered Architecture:
- Multiple low-spec servers
- Minimized physical distance
- Lower latency
- Higher maintenance costs
2. Consolidated Architecture:
- Few high-capacity servers
- Cost-effective
- Better security
- More complex deployment
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