Hi, everyone. Welcome to the fourth chapter in our Tencent Cloud practitioner course, introduction to CDN. At the end of this chapter, you will have a better understanding of the basics of CDN and how it works, the architecture of Tencent Cloud CDN, the security mechanisms of Tencent Cloud CDN, Tencent Cloud CDN products, and Tencent Cloud CDN billing plans. In this chapter, we'll cover five sections; CDN basics, Tencent Cloud CDN architecture, Tencent Cloud CDN security mechanisms, Tencent Cloud CDN products, and Tencent Cloud CDN billing plans. This video will cover the first section, CDN basics. Subsequent videos will cover the remaining four sections. Let's get started with Section 1, CDN basics. In this video, we'll cover what a CDN is, why people use CDNs, a brief history of CDNs, and Tencent Cloud CDN. What exactly is a CDN? A CDN or content delivery network, is a cluster of distributed servers that accelerate the delivery of content to users in different locations. It consists of nodes and different geographic locations and delivers content to users based on their locations, the origin of the desired content, and the node that host the content. Why use a CDN? Well, a CDN is very useful in the following network scenarios. The first scenario is when the user and the server are physically distant, which involves multiple forwarding events, resulting in high latency and unstable connection. The second scenario is when packets are forwarded between different carriers because the user and the server are in different carrier networks. The third scenario is when network bandwidth and processing capacity are limited for a single server or a group of servers hosted in the same region. As the number of requests increases, the server responsiveness and availability decrease. Before CDN, under a traditional network if you needed to access a website such as TECH.QQ.COM, then the browser would find the DNS server and the DNS server would request the QQ.COM domains authoritative DNS server QQ to the COM domain, and then request the TECHCVM to QQ. The browser would use the obtained IP address to send a data access request to the domain name server CVM, and would display the content of the webpage according to the data returned by the domain name host. This is a diagram that describes the process of using a CDN. First, the user enters a domain name in the browser and the browser sends the resolution request to the local DNS. Second, the resolution request is forwarded to the authoritative DNS server, which uses CNAME to forward the request to GSLB. Third, the GSLB resolves the request and returns the IP address of the preferred CDN node. Fourth, the user receives the IP address of the preferred node. Fifth, the user connects to the preferred CDN node and obtains the requested resources. Sixth, if the node does not have the requested resources, it requests them from the origin server, saves a copy of these resources on the node for future requests and sends them to the user. Here is a diagram that explains how CDN is implemented at a technical level while the user is using it. First, DNS resolves www.test.com. Then DNS recursively queries www.test.com.cdn.dnsy1.com. Then Tencent DNS returns the IP address of the preferred node to the local DNS, after which the local DNS returns the IP address of the preferred node to the user. After the user initiates a request for 1.jpg to the CDN node. Here, if the corresponding CDN node has cached 1.jpg, then it will send the data directly back to the user completing the request. However, if the CDN node cache has not cached 1.jpg, then it performs internal routing to the CDN intermediate server. Then the CDN intermediate server forwards the request to the origin server, which returns data back to the CDN intermediate server. Finally, the CDN node obtains and caches the data to the CDN node from which the user obtains the data. Now, let's take a look at a brief history of CDNs. CDNs first emerged during the first major period of Internet development in 1998. However, after the dot-com bubble burst in 2000, the development of CDNs slowed down before picking back up with the development of Web 2.0 in 2004 and the development of the mobile Internet in 2007. Later, the rapid development of online video games in 2011 led to a surge in demand for CDNs, which gained increased recognition for its growth potential. Five notable CDN trends in the last few years have been lower prices, industry solutions, standardization, edge computing, and smart CDNs. CDNs have been becoming cheaper as a result of increased competition among Cloud vendors, and the breadth of its potential industry solutions have expanded to include live streaming videos, VR and AR games and more. CDN has also experienced increased standardization with regards to its supervision, technology, experience, and quality. In addition, CDN has been met with increased applications in the field of Edge computing, with CDNs providing data processing and security protection services on Edge nodes to combat didas and web attacks and ensure business security. Lastly, CDNs have become smart by integrating with cutting edge technologies such as Cloud computing, AI, Big Data, H265, P2P and Quick. Now, let's take a look at the current CDN market landscape. At present, China's CDN coverage rate is only 17.2 percent, while in a mature market like North America it has reached 50 percent. Driven by videos, VR and AR games, e-commerce, IoT, edge computing, and other online applications. The CDN market is expected to grow rapidly at an average annual rate of 35 percent over the next five years. Here are some of Tencent cloud CDN's milestones. Tencent has been working on CDN technology for eight years, while Tencent Cloud has been launched for three years. As of now, Tencent Cloud has deployed over 1,100 nodes in China, over 120 terabytes per second bandwidth of resources and over 1,000 nodes internationally, and has garnered a customer base of 100,000 users. Tencent Cloud CDN is available globally. Tencent Cloud has deployed over 1,100 acceleration nodes across China, covering more than a dozen ISPs with over 100 terabytes per second bandwidth. It has also deployed over 1,000 cache nodes overseas, covering over 50 countries and regions worldwide. Now let's move on to Tencent Cloud CDN's performance. Tencent Cloud CDN features fast integration and easy management, supporting self owned origin servers, Cloud object storage bucket origin servers, and a variety of other origin servers. It also features comprehensive configuration options and rich reports, providing various configuration option, real time alerts, troubleshooting tools, statistical analysis reports, and logs. Lastly, it features flexible billing and project management support, providing multiple billing methods and project management support. With Tencent Cloud CDN's origin servers, access latency can be reduced fivefold from when non CDN origin servers are used, and availability can be increased to 99.5 percent from the 94.8 percent provided by non CDN origin servers. Tencent Cloud CDN also outperforms the CDNs of other Cloud service providers. The average latency of Tencent Cloud CDN is 0.26 seconds, which is twice as fast as CDNs from other Cloud service providers.
