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A Content Delivery Network (CDN) is a globally distributed network of proxy servers expanded in multiple data centers. The goal of CDN is to provide better and faster web performance for end users. If your website visitors are from multiple countries or even multiple continents then using a CDN service is a good choice. CDNs are not for everyone, especially if you are running a localized website.When choosing a CDN you must analyze what are your requirements. Do you need on demand delivery, live or a combination, how much content you have and how much you plan to add from time to time. http://growthpixel.com/content-delivery-network-cdn-service-provider/
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Content Delivery Network Introduction Server Selection Policy Server Selection Mechanisms Conclusion
Content Delivery Network • A Content Delivery Network or Content Distribution Network is a globally distributed network of proxy servers deployed in multiple data centers. • The goal of a CDN is to serve content to end-users with high availability and high performance. • CDNs serve a large fraction of the Internet content today, including web objects (text, graphics and scripts), downloadable objects (media files, software, documents), applications (e-commerce, portals), live streaming media, on-demand streaming media, and social networks. • CDN Replicates the content: On many server spread throughout the internet. • Updating the Replicas: Updates pushed to replicas when the content changes.
Server Selection Policy. • Live server • For availability • Lowest load • To balance load across the servers • Closest • Nearest geographically, or in round-trip time • Best performance • Throughput, latency, … • Cheapest bandwidth, electricity,
Server Selection Mechanism • Routing : Any cast Routing. Advantages: No extra round trips. • Route to nearby server. Disadvantages: • Different packets may go to different servers. • Does not consider network or server load. • Naming: DNS-based server selection Advantages: Avoid TCP set-up delay. DNS caching reduces overhead. Disadvantages: Based on IP address of local DNS server. • “Hidden load” effect. 1.2.3.4 1.2.3.0/24 DNS query 1.2.3.5 1.2.3.0/24 local DNS server
Conclusion • The term CDN means many things to different people and is an umbrella term that covers a lot of different types of content delivery services. Video streaming, software downloads, web and mobile content acceleration, licensed/managed CDN, transparent caching, and services to measure CDN performance, load balancing, multi-CDN switching and analytics and cloud intelligence. It’s a complex ecosystem with a lot of vendors both large and small and some CDN vendors cross over into other industries like security and WAN optimization.