Introduction: This article is a continuation of the previous articles on Azure services. In this article we talk about content delivery network on Azure. This is a distributed network of servers that deliver web content to users typically resources for the web pages such as JavaScript, Stylesheet and HTML that are downloaded from content delivery network. CDNs that are closest to the application or clients are used so that there is little or no latency. Azure CDN can also accelerate dynamic content which cannot be cached, by leveraging networking optimizations such as the Point-of-Presence (POP) location and the route optimization via border gateway protocol benefits of using Azure CDN include better performance, large scaling and distribution of user requests.

The design of Azure CDN is very similar to that of object storage. Both perform geo-replication and automatic synchronization between virtual datacenters which is a term used to denote shared-nothing collection of servers or clusters. Both leverage some form of synchronization with the help of say, message-based consensus protocol. Azure storage is also a service that provides BLOB storage, but the CDN is hosted as its own service and comes with its arm resource that can be used to provision one or more CDNs. As with all Azure services the CDN service also provisions an Azure resource backed by an Azure resource manager template. When the resource is provisioned, it can be used to download content from the network.  ARM templates are infrastructure-as-a-code and policy-as-a-code so they can be used for achieving a desired state of the infrastructure and for orchestration.

Azure CDN is used for a variety of purposes suggest the following:

1)      delivering static resources for client applications as described earlier for websites

2)      delivering public static and shared content to devices

3)      serving entire websites that consist only of public static content

4)      streaming video files to clients on demand

5)      enabling faster access to public resources from Azure CDN POP locations

6)      Improving the experience for users who are further away from data centers

7)      supporting the Internet of Things by scaling to a huge number of devices that can access content

8)      handling traffic surges without requiring the application to scale

Some of the challenges involved when planning CDN involve deployment considerations about where to deploy CDN and a few others. For example, these include versioning and cache control of the content testing of the resources independent of the publications search engine optimizations and content security in addition CDN service must provide disaster recovery and backup options so that the data is not lost and is highly available system engineering design looks down upon CDN because of the costs involved if it is easier to scale the servers without requiring the planning of content delivery network which saves costs because the resources are co-located and there are easier options to scale. The customer would integrate the publication of their content which can be done with the help of the CDN