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Community Blog What is CDN (Content Delivery Network)? Why Use It?

What is CDN (Content Delivery Network)? Why Use It?

CDN (Content Distribution Network) refers to use the server closest to each user to send music, pictures, videos, applications and other files to users faster and more reliably .

Your website should be able to run in a complex network environment in order to ensure good access experience for users from across the globe.

If you are running a website, you should know some of the factors that are key to your success:

• Relevant content
• Fast access
• Highly interactive interface
• Easily accessible from everywhere

Furthermore, your website should be able to run in a complex network environment in order to ensure good access experience for users from across the globe. With the increasing use of objects (such as images, frames, CSS, and APIs) and various actions (such as sharing and tracking), your website will also become larger in scale. Eventually, the system will get increasingly slower and it will lead to potential loss of customers.

Multiple studies from Google and other popular sites show that delays in access speeds, even as little as one second, will lead to a huge loss in terms of user numbers. To make matters worse, some of the users will never again attempt to access the website. As you can imagine, if the website is your main profit channel or brand window, delayed access speeds can be devastating to your business.

This is a major consideration when deciding whether you should be using a CDN – to accelerate website access.

In addition to content acceleration, CDN has other beneficial effects, such as:

  1. Achieving Cross-Carrier, Cross-Region, Network-Wide Coverage
    Networks that are not interconnected, regional ISP limitations, outbound bandwidth limitations, or other factors can make websites inaccessible on a regional basis. CDN acceleration can make full use of bandwidth resources, balance source station traffic, cover global lines, and deploy IDC resources locally. Furthermore, CDN provides edge distribution and storage nodes at backbone nodes across the country through cooperation with carriers. Alibaba Cloud has over 1000 nodes inside China and an additional 200+ nodes outside of China, covering most countries and regions. This ensures the stability and speed of CDN services.
  2. Ensuring the Security of Your Website
    Server Load Balancer and Distributed Storage technologies in CDN can improve your website's reliability, and provide protection for your website to deal with most Internet attacks. The anti-attack system also protects websites from malicious attacks. Alibaba Cloud CDN can be easily paired with Anti-DDoS and WAF products for enhanced security.
  3. Achieving Remote Backup
    When a server failure occurs, the system will invoke other nearby non-failed server nodes for service, to provide nearly 100% reliability. This will keep your website up and running 24/7.
  4. Reducing Costs
    When using CDN acceleration to establish websites throughout China, you do not have to purchase servers and follow-up hosting O&M, or mirror synchronization between servers. You also do not have to manage or maintain a team of technical experts to maintain these servers. By cutting down on CapEx and OpEx, you can focus your resources on more relevant matters.
  5. Allowing You to Focus More on Business
    CDN acceleration providers generally provide a one-stop service that are not limited to just CDN. They also provide corresponding cloud storage, big data services, and video cloud services. Most providers also provide 24/7 O&M monitoring support to ensure the network is available for use at any time. This frees you up from unnecessary tasks, helping you focus on the development of your core business.

These are some of the reasons you should use CDN. If there are any other benefits that you have experience from using CDN, please share in the comments below!

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Best Practices of Global CDN QoS Optimization

Alibaba Cloud Content Delivery Network (CDN) serves more than 300,000 customers through its 1,500+ nodes deployed across over 70 countries and regions on six continents with a bandwidth capacity greater than 120 Tbit/s, making Alibaba Cloud the only CDN provider in China that has been rated as "Global" by Gartner. As the business and node bandwidth grow, quality of service (QoS) optimization has become a topic that is worth discussing. In the Apsara User Group—CDN and Edge Computing Session at the Computing Conference 2018 in Hangzhou, Liu Tingwei, Senior Technical Expert at Alibaba Cloud, shared with the audience the technical practices of CDN QoS optimization.

Global Development Process of Alibaba Cloud CDN

Alibaba Cloud CDN originated from Taobao's self-built CDN in 2006. It originally provided Taobao with acceleration services for small files such as images and web pages, and gradually began to serve the entire internal business of Alibaba Group. In March 2014, Alibaba Cloud CDN was officially put into commercial use. Since its commercialization, we had paid great attention to product standardization. Alibaba Cloud CDN provided a powerful console and a complete set of application programming interfaces (APIs), which could be used by users immediately after purchase, just like other cloud resources.

In the next few years, Alibaba Cloud CDN released the high-speed CDN 6.0, P2P CDN (PCDN), Secure CDN (SCDN), Dynamic Route for CDN (DCDN), and other related products in succession. In March 2018, Alibaba Cloud was rated as "Global" by Gartner in its latest Market Guide for CDN Services. In this summer, Alibaba Cloud CDN carried 70% of the live traffic for the 2018 FIFA World Cup.

However, as the business and node bandwidth grow, QoS problems have become more and more prominent. Liu said, "When discussing QoS optimization, we need to consider the entire ecosystem to combine technical and industry backgrounds and search for all possible directions to which optimization can be made. This figure best describes how we felt at the beginning: We could see our goals ahead, but we had no way out. Then, our team tried to calm down and make up our minds to completely solve QoS problems."

The following figure is a simplified CDN logical architectural diagram, which shows that CDN is a complete ecosystem. From the perspective of a user's access path, we can see what subsystems are involved in each phase of the ecosystem. First, the user's access request is sent to a scheduling subsystem, in which the carrier's local Domain Name System (LDNS) and the CDN's scheduling system jointly assign a nearest edge node to the user. Then, when the access request arrives at the edge node, the user obtains the corresponding live, on-demand, download, trend, or real-time audio and video content from the edge node. This part is implemented by the cache system. Next, the link quality system takes charge of data transmission between cache nodes, between cache nodes and the user, and between cache nodes and the origin. Finally, there is a business support system for configuration, data, and monitoring.

Connect Function Compute and CDN with the CDN Trigger and Fun

In this tutorial, you will learn how to use Function Compute and Fun to configure and deploy the CDN trigger. But before we dive into anything in this tutorial, let's first take a look at several of the important concepts mentioned in this article and also discuss some things you'll need to complete before starting this tutorial.

Background Information

First, there's Function Compute, which is an event-driven service that allows users to write and upload code without needing to manage server health along with other factors. Function Compute prepares and auto-scales to the correct amount of computing resources to run user code. The user only pays for the resources required to run their code.

Next, there's Fun, which is a tool that supports serverless application deployment and allows easy management of resources such as Function Compute, API Gateway, and Log Service. You can use Fun to develop, build, and deploy resources by describing specified resources in the template.yml file.

Last, there's also the concept of a Content Delivery Network. In this article, we will be specifically concerned with the Alibaba Cloud Content Delivery Network (CDN), which is Alibaba Cloud's version of this service - which most cloud provider provide nowadays. This service can be understood as providing a distributed network that is built on and overlays with the bearer network, and which also is composed of edge node server clusters distributed across different regions. CDN replaces the traditional data transmission model based on Web Servers, and rather, specifically in our case, it stores resources on the source stations to Alibaba Cloud edge servers closer to your specific region to allow users quickly obtain resources nearby. This improves the user experience and reduces the burden on the source stations.

Before You Begin

Before you begin this tutorial, make sure that you have completed the following:

  1. Activate Alibaba Cloud Function Compute and Alibaba Cloud Content Delivery Network.
  2. Understand the associated terms, including things like source stations and canonical domain names.
  3. Add a CDN accelerating domain, and then go to the DNS server provider to add the CNAME record.

begin this tutorial

Deploying Static Websites Using OSS and CDN on Alibaba Cloud

This guide aims to introduce an approach to deploying static websites and frontend applications onto Alibaba Cloud in a simple and reliable manner.

Being a collection of static files – a static website and a frontend application have virtually no difference when it comes to deployments. They both come with static files such as HTML, CSS, JS, JPEG, and PNG.

A common approach for hosting static websites on Alibaba Cloud is to use the "static hosting" feature of Object Storage Service (OSS) and Content Delivery Network (CDN):

  1. No server is required to host the assets
  2. OSS stores redundant copies of the assets across multiple zones within a region; thus, region-level high availability is provided for the origin of the assets without the need to do anything additionally
  3. CDN is used to improve delivery and, thus, the user experience
  4. CDN is a massive global network of interconnected servers so high availability is provided at global level for the user facing servers
  5. OSS is very cheap

This guide aims to introduce an approach to deploying static websites/frontend applications onto Alibaba Cloud in a simple and reliable manner. It serves as a good reference for a company's engineering team wishing to automate deployments. It should be noted that even though this practice can be used with video, audio and large files, Alibaba Cloud CDN provides a CDN type optimized for each of those use cases (thus, even a better user experience can be delivered by separating these assets and using a dedicated CDN type for each one of them).

Prerequisites

The following things will be required to follow this guide:

  1. Aliyuncli and ossutil installed and configured. If you have Docker installed, a quicker alternative is to use the "python-toolbox" which includes both
  2. curl installed (alternatively, you can use a browser with the inspection functionality in sections where we inspect headers)
  3. Firm understanding of Object Storage Service (OSS) and Content Delivery Network (CDN)
  4. Essential Linux skills on a Linux box

Architecture

The diagrams below show the simplified flow of what we will be implementing:

implementing

So what's happening here? The machine with the source assets ("Source") pushes them up to OSS. OSS serves as the "Origin" for the CDN which will fetch assets from it whenever it can't find a copy of the asset in its cache; the CDN accepts all requests for static files.

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Use Alibaba Cloud CDN to Accelerate Your Content Globally

In the era of big data with explosive growth of network resources, improving the response speed and success rate of user access and solving the problem of access delay caused by distribution, bandwidth and server performance are of great significance for enterprise websites and applications. This clouder online course and certification is designed to help students learn about CDN related knowledge and skills, and master the specific operations of Alibaba Cloud CDN's multiple functional modules to accelerate website access.

Introduction to Network Attached Storage

The File Storage in the Cloud course is designed to provide you with the fundamental knowledge to plan, configure and administer Network Attached Storage (NAS) in Enterprise enviroment. In this course we will discuss deployment best practices and use cases of Network Attached Storage (NAS).

Distributed Storage Introduction

The current approach to storage does not work anymore: it is not flexible enough, fast enough or the cost is prohibitively high. By design a distributed storage system solves all of these issues at once. Through this course, you will learn, you can learn about the concepts and features of distributed storage system and its benefits compared to traditional storage.

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Interconnecting VPC Using Cloud Enterprise Network

By the end of this course, you will be able to plan, configure and administer Alibaba Cloud VPC connection using Cloud Enterprise Network (CEN) and establish global connectivity.

Introduction to Network Attached Storage

By the end of this course, you will be able to plan, configure and administer file storage using Alibaba Cloud Network Attached Storage (NAS).

Related Documentation

Content Delivery Network (CDN) Service Level Agreement

This Alibaba Cloud International Website CDN Service Level Agreement (“SLA”) applies to your purchase and use of the Alibaba Cloud International Website CDN (“Service”) and your use of the Service is subjected to the terms and conditions of the Alibaba Cloud International Website Product Terms of Service (“Product Terms”) between the relevant Alibaba Cloud entity described in the Product Terms (“Alibaba Cloud”, “us”, or “we”) and you. This SLA only applies to your purchase and use of the Services for a fee, and shall not apply to any free Services or trial Services provided by us.

  1. SCOPE AND DEFINITIONS
    1.1 “Downtime” means the total number of minutes during which the Error Rate is greater than 0.05% for at least two (2) consecutive Time Intervals

1.2 “Error Rate” means the total number of Failed Transactions divided by the Total Transactions during each Time Interval.

1.3 “Exclusions” means any unavailability, suspension, or termination of the Service that is due to any of the following:

(a) suspension or termination described in Clause 8.2 of the Membership Agreement;

(b) events that are outside of our reasonable control, including any events of force majeure, such as earthquakes, epidemic, downtime of the relevant submarine communication cables, failure of telecommunications infrastructure or systems, hacking, cyberattacks, riots, Acts of God, etc.;

(c) events that result from any actions or inactions on your part in connection with your use of the Service;

(d) events that arise out of your or any third parties’ (not under our direct control) equipment, software, and/or technology;

Why choose Alibaba Cloud CDN?

This topic describes the major performance indicators that are used to evaluate the performance of content delivery before and after a website is connected to Alibaba Cloud CDN. This topic also describes the benefits of Alibaba Cloud CDN.

Using Alibaba Cloud CDN can offload the workloads on origins and accelerate content delivery. The performance indicators that are used to evaluate the performance of content delivery include common indicators and scenario-specific indicators. By referencing these indicators, you can learn how Alibaba Cloud CDN accelerates content delivery and how Alibaba Cloud CDN is applied to your services. This helps you make adjustments and business decisions.

Common performance indicators

You can use the following indicators to measure the performance of your website before and after the website is connected to Alibaba Cloud CDN. The indicators include but are not limited to the following:

  1. Latency: shows the total amount of time it takes for a server to receive a request from a client and then return a response to the client. The lower the latency, the higher the performance.
  2. Downloading speed: data transmission rate, which shows how quickly a client can download data from a server. The higher the downloading speed, the higher the performance.
  3. Website content loading speed: shows how quickly a Web page can be loaded. The faster the loading speed, the higher the performance.
  4. Packet loss rate: shows the number of packets lost during data transmission to the total number of packets.
  5. Back-to-origin rate: includes the back-to-origin request rate and back-to-origin data transfer rate.

Related Products

CDN

A scalable and high-performance content delivery service for accelerated distribution of content to users across the globe

Dynamic Content Delivery Network (DCDN)

A content delivery acceleration service, which has been designed based on Alibaba Cloud CDN to accelerate content delivery for hybrid sites, dynamic sites, and applications.

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