Hello and welcome back. Let's take a look at some of CDNs use cases or scenarios. The most obvious use case for CDN is accelerating the delivery of static resources for a website or a web application that would include things like images, video, HTML, CSS, and JavaScript files. A typical architecture might have you storing these non-changing resources in Object Storage Service, whereas you'd have dynamically generated content being hosted and served up from a virtual machine, such as an ECS instance, that might be running a web server like NGINX or Apache.

Now the issue with delivering your static content directly from OSS would be that OSS is located in a specific Alibaba Cloud region. So if you're using an OSS bucket in Singapore, then what a user fetches an item from that bucket, their request has to travel to Singapore and then go back to the user, so if the user's far away from Singapore, there could be a significant delay. That's the problem CDN is trying to address. So what you can do is put Alibaba Cloud CDN in front of Object Storage Service, or if you want, directly in front of an ECS virtual machine, and then user requests will first hit the CDN.

The CDN, of course, is a distributed system, so there are CDN nodes all around the world. The user's request will go to the nearest or fastest CDN node relative to their location and requests will be served from there. Of course, each CDN node, as we discussed in the architecture section, has its own cache, so any content that has been recently requested from OSS will have been saved on the CDN node and can be served directly from there and passed on to the user. This is a common feature of all CDNs, the ability to store and accelerate static resources.

A common CDN use case is also on-demand audio and video delivery. This is for delivering large audio and video files on-demand, so this is actually very similar to the delivery of traditional static content like small images or CSS files with the exception that you may need to have the CDN node have the ability to deliver the content in multiple different formats or in multiple different resolutions for different devices, which is why our CDN supports fast download and distribution for MP4, FLV, and MPEG formats. We also support the acceleration of on-demand streams. That's for large files over 20 megabytes in size, such as MP4 and FLV video.

We recommend using CDN service with OSS for high-speed data transfer and to reduce bandwidth costs. Yet another area where Alibaba Cloud CDN can provide benefits is in media services. For instance, for live media streaming services, we provide an integrated solution including storage, slicing, and transcoding, as well as access authentication and acceleration. The solution can scale programmatically to handle sudden spikes in traffic using the Elastic Scaling Service. We also offer a standalone media transcoding service that can be used with or without the CDN that provides high-speed and stable transcoding service. Again, this service is a managed service which scales seamlessly to ensure smooth completion of media transcoding tasks.

Another area where we can offer an advantage is in live broadcast acceleration services. Although it's currently in the testing stage, we provide internal user testing and optimization to help you get the most out of any live broadcast you perform. Alibaba Cloud CDN can also be used to accelerate mobile application distribution. You can use Alibaba Cloud CDN for efficient and secure distribution of mobile apps in the form of APK files. You can take advantage of CDN to achieve the following, accelerate and optimize distribution of in-app images, pages, short videos, user generated content, and other content, prevent DNS attacks using the HTTP DNS service, retrieve DNS resolution results in near real time, and enhance the user experience with quick access to multiple resources including updates.

Our CDN also supports a full VOD solution, a video on demand solution as a service. You can see here a simple architecture in which Server Load Balancer, ECS, and CDN are being used together along with our VOD platform to provide video storage, transcoding, and acceleration. We have a similar video streaming solution aimed at streaming video. Again, this makes use of Load Balancer and ECS in concert with CDN and our video platform, which includes storage and transcoding features. A video stream can be directly passed from the recording source through the live video platform where it can be automatically stored and transcoded, and then it can be passed out to the CDN for delivery to end users. Next we'll have a brief demo in the Alibaba Cloud console.