Content delivery network

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A Content Delivery Network (CDN) is a system of servers that work together to deliver internet[2] content quickly. This is done by strategically locating servers in various places around the world, some networks having thousands of them. These servers store popular content to speed up response times and balance the load of web traffic[1]. They also direct requests for content to the most efficient source. CDNs use specific protocols to provide access to content services, and some even allow clients to contribute resources. They also employ various security[3] measures to ensure the integrity of the content and protect user privacy[4]. However, they can potentially breach privacy regulations. The industry is evolving with new trends like streaming video traffic and emerging technologies like virtualization. CDNs are a key component in the delivery of internet services, and ongoing research is being conducted to optimize their performance.

Terms definitions
1. web traffic. Web traffic, the main subject of this text, is an essential aspect of digital business. In simple terms, it refers to the number of people visiting a website. These visits, also known as 'hits,' provide valuable data about the website's popularity and performance. Analysis of this data, known as web analytics, helps businesses understand visitor behavior and optimize their online presence. Monitoring web traffic can also highlight potential issues, like traffic overload, which can slow or crash a website. Various tools and strategies, such as Search Engine Optimization (SEO) and online advertising, can increase web traffic. However, it's important to manage this growth carefully to ensure the website can handle increased activity and isn't overwhelmed. Additionally, limiting access to certain parts of the website or to certain users is another aspect of managing web traffic, which helps maintain security and performance.
2. internet. The Internet is a global system of interconnected computer networks that use standardized communication protocols, primarily the TCP/IP, to link devices worldwide. Originating from the term 'internetted' used in 1849, the term 'Internet' was later used by the US War Department in 1945. Its development began with computer scientists creating time-sharing systems in the 1960s and further progressed with the establishment of ARPANET in 1969. The Internet is self-governed, without a central authority, and its principal name spaces are administered by the Internet Corporation for Assigned Names and Numbers (ICANN). It has significantly transformed traditional communication media and has grown exponentially over the years, with internet users increasing 20% to 50% annually. In 2019, over half of the world population used the Internet. The Internet protocol suite, which includes TCP/IP and four conceptual layers, guides internet packets to their destinations. Essential services like email and Internet telephony operate on the Internet. The World Wide Web, a global collection of interconnected documents, is a key component of the Internet.

A content delivery network or content distribution network (CDN) is a geographically distributed network of proxy servers and their data centers. The goal is to provide high availability and performance by distributing the service spatially relative to end users. CDNs came into existence in the late 1990s as a means for alleviating the performance bottlenecks of the Internet as the Internet was starting to become a mission-critical medium for people and enterprises. Since then, CDNs have grown to serve a large portion 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 media sites.

(Left) Single server distribution
(Right) CDN scheme of distribution

CDNs are a layer in the internet ecosystem. Content owners such as media companies and e-commerce vendors pay CDN operators to deliver their content to their end users. In turn, a CDN pays Internet service providers (ISPs), carriers, and network operators for hosting its servers in their data centers.

CDN is an umbrella term spanning 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. CDN vendors may cross over into other industries like security, DDoS protection and web application firewalls (WAF), and WAN optimization.

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