CDN Fundamentals & Anycast
Understand Content Delivery Networks: Global edge caching, Anycast BGP routing, origin shielding, cache invalidation, and dynamic content acceleration.
01.1. What is a Content Delivery Network (CDN)?
A Content Delivery Network (CDN) is a geographically distributed network of proxy servers and data centers (known as Points of Presence / PoPs) deployed at the edge of the internet, physically close to end users.
The Physics Problem:
If your origin server is located in Northern Virginia (AWS us-east-1), a user in Sydney, Australia attempting to download a 5MB JavaScript bundle faces:
- Transpacific undersea cable physical propagation delay: ~160ms RTT.
- TCP 3-way handshake + TLS 1.3 key exchange: ~320ms latency before the first HTTP byte is received.
- Total download time over high-latency links: 2 to 4 seconds.
The CDN Solution: The Australian user's request is intercepted by a CDN Edge PoP in Sydney:
- TCP + TLS termination occurs locally over a 3ms fiber loop.
- The 5MB bundle is served directly from the local Sydney edge SSD/RAM cache.
- Total load time drops from 3,500ms down to <80ms (40x faster!).
CDN Edge PoP Architecture & Origin Shielding Pipeline ð
CDN Edge PoP Architecture & Origin Shielding Pipeline ð
How BGP Anycast routes global users to geographically nearest Points of Presence (PoPs), serving cached assets in <10ms and shielding origin servers from thundering herd spikes.
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