Content Delivery Networks

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Content Delivery Networks

by James G. Barr

Docid: 00018998

Publication Date: 2105

Report Type: TUTORIAL


Content delivery networks (CDNs) distribute bandwidth-intensive files and
media streams more rapidly and reliably than ordinary Internet hosting
services. Many CDNs are operated by providers who charge customers
monthly hosting and usage fees, freeing them from the responsibilities of
managing their underlying web servers and routers. The use of CDNs has
grown as streaming media and cloud computing have become commonplace.

Report Contents:

Executive Summary

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In the early days of the Internet, it was hard to deliver
high-performance streaming media and perform other
bandwidth-intensive activities.

Related Faulkner Reports
Streaming Media Market Trends
Akamai CDN Services Product
Amazon CloudFront Services Product
Level 3 Communications CDN Services Product
Limelight Networks CDN Services Product

The Internet’s architecture did not afford the speed or reliability
that many enterprises needed for their Web-based services. To address
this problem, content delivery networks (CDNs) were created. CDNs are
specialized hosting services that use high-performance equipment and
specialized architectures to optimize the distribution of online content.

CDNs typically mark media assets like images and streaming video with
special URLs in HTML tags. These tags refer to a special DNS server that
determines the user’s location and redirects the request to a cache server
located near her. If that cache server does not have a copy of the
requested file, it will retrieve it automatically from the central site
and cache it until it is set to expire.

Many CDNs are operated as commercial services, a model in which the
provider manages the underlying servers, routers, and other infrastructure
so that the customer’s only investments are the monthly hosting and
usage fees. Some of the leading CDN providers are

  • Akamai
  • Amazon Web Services
  • Google
  • IBM
  • Microsoft

Telecommunications carriers are also involved in the market: agreeing to
share network capacity and push content closer to end users.

Lastly, it is possible to build a custom CDN using open source tools in
order to save on the costs involved.


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As defined by analyst Rahul Nanwani, a content delivery network (CDN),
also known as content distribution network, is “a globally distributed
network of servers that store… and deliver some or all of [a] website’s

“Each of these servers in [a] CDN’s network is called a Point of Presence
(PoP) or an edge server.”1

Increasing their utility, CDNs offer products that take advantage of ESI
(edge side includes) to dynamically create content at the edge of the
network. This enables enterprises to offload the processing of dynamic pages
to the edge servers which are closest to the users.

Importantly, CDN use is not exclusive to large enterprises.
Small-to-medium-sized enterprises (SMEs) can take advantage of CDNs’
worldwide distribution capabilities, a key feature since virtually all
business today has an international component.2

CDN Benefits

According to CDN provider Cloudflare, content delivery networks are
designed to

the following four benefits:

  1. Faster load times – “By distributing content closer
    to website visitors by using a nearby CDN server (among other
    optimizations), visitors experience faster page loading times.”
  2. Lower bandwidth costs – “Through caching and other
    optimizations, CDNs are able to reduce the amount of data an origin
    server must provide, thus reducing hosting costs for website owners.”
  3. Improved content availability – “Large amounts of
    traffic or hardware failures can interrupt normal website function. A
    CDN can handle more traffic and withstand hardware failure better than
    many origin servers.”
  4. Enhanced website security – “A CDN may improve
    security by providing [distributed denial of service (DDoS)] mitigation,
    improvements to security certificates, and other optimizations.”3

Business Continuity

As outsourced infrastructure and services elements, CDNs are instrumental
in supporting enterprise sustainability, limiting any fallout from local
or on-premises disasters. On the negative side, however, enterprise users
must be prepared to compensate for any wholesale CDN failures, perhaps by
enlisting the services of backup providers, or by splitting their CDN load
across multiple providers. This is a universal issue associated with the
utilization of public cloud or cloud-like services.

CDN System Architecture

Figure 1 shows a typical CDN in action. In this example, two users are
requesting the same movie file from a website.

Figure 1. Typical CDN Architecture

Figure 1. Typical CDN Architecture

Source: Akamai

One of the users is located in the US, the other in the UK. The HTML
page that both users have requested has had all the media links changed to
point to a specialized location-aware DNS server. The DNS server
determines where the user is located and redirects the user to the proper
content cache. The user’s browser or media player requests the file from
the nearest cache and, if the file is not present on that cache, it is
downloaded by the content cache directly from the source server. The
content can usually be cached based on user demand or pre-cached with all
the other content. Both users end up having content efficiently streamed
to them by a local server with minimal requests back to the main server.
The US user gets content from the US caching server, and the UK user gets
content from the UK caching server.

Enabling Content for CDN Hosting

Typically, customers host only resource-intensive files on a CDN. These
include images, movies, and streaming video. HTML files are usually small
and can be delivered from an ordinary Web server. In most cases, it is
simply necessary to modify links to these resources to take advantage of
the CDN. Some vendors offer more advanced options that host Web
applications at the edge of the network rather than from centrally managed
servers. The vendor will supply the packaging format for the application
and management tools to monitor the application’s performance.

Building a CDN with Open Source Tools

If the budget is not available to work with one of the big CDN
providers, a simpler version of a CDN can be built using open source
software and some custom software development.

The hardest part of building a CDN comes with creating the code to
determine the closest network cache. Simple redirection based on host
information can be accomplished easily, but more complex algorithms are
extremely difficult and expensive to implement.


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The Need for Speed

Content delivery networks are deigned to deliver content expeditiously.
Analyst Brenda Barron reminds us while speed is a vital, virtually
indispensable, feature.

  • “Google made site speed a ranking factor in as early as 2010. [Source:
    Search Engine Land].
  • “47 percent of consumers expect a web page to load in 2 seconds or
    less. [Source: Kissmetrics via Akamai and]
  • “40 percent of consumers abandon a website that takes more than 3
    seconds to load. [Source: Kissmetrics via Akamai and]
  • “79 percent of shoppers who are dissatisfied with website performance
    are less likely to buy from the same site again. [Source:
    Kissmetrics via Akamai and]
  • “52 percent of online shoppers state quick page loading is important
    to their site loyalty. [Source: Kissmetrics via Akamai and]
  • “A 1-second delay in page response can result in a 7 percent
    reduction in conversions. [Source: Kissmetrics via Akamai and]”

Cloud Impact

Providers are increasingly offering content delivery as a cloud service.
Enterprises pay for the service and then use it to deliver streaming media
and other services to their employees or customers.

The advent of cloud-based models of content delivery is a natural
progression. Cloud computing is largely about hiding technology from
users, making IT more about services than about hardware and software.
Cloud-based models focus on getting customers up and running quickly and
on allowing them to easily manage what they deliver to their employees and

Telco CDNs

The growth of streaming video traffic requires extensive resources from
broadband providers to meet demand. To deal with this need,
telecommunication services have started their own CDNs to reduce the
demand on their network infrastructures. Because telecommunication
companies own the networks over which video content is transmitted, telco
CDNs can deliver content faster to their subscribers because it can be
cached in their own networks. This deep caching minimizes the
distance the data needs to travel. Telco CDNs also have a cost
advantage due to owning their equipment instead of needing to lease it
from other providers. Some of the largest telecommunications carriers
in the world have agreements through which they share their networks to
act as CDNs for each other.

CDN Market

According to MarketsandMarkets, the global Content Delivery Network
market is expected to grow from $14.4 billion in 2020 to $27.9 billion in
2025, a compound annual growth rate (CAGR) of 14.1 percent during the
forecast period.

The major factors driving CDN growth include:

  • “The rising need for effective solutions to enable live and
    uninterrupted content delivery over a high-speed data network,
  • “Increasing demand for enhanced QoE (Quality of Experience) and QoS
    (Quality of Service),
  • “A proliferation of video and rich media over websites,
  • “Increasing demand for enhanced video content and [a] latency-free
    online gaming experience, and
  • “Increasing Internet penetration and adoption of mobile devices
    leading to rising opportunities for mobile CDN.”5

Market Segmentation

The CDN market is generally segmented into several categories:

  • Media and entertainment
  • Online gaming
  • Retail and e-commerce
  • e-Learning
  • Healthcare
  • Enterprise

Of these, e-Learning and healthcare are exhibiting perhaps the greatest
growth as the COVID-19 pandemic produced vast and immediate requirements

  • At-home education – K-12 through college; and
  • “Telemedicine” – where physicians can diagnose their patients via
    “Zoom”-like computer sessions.6

Prominent Providers

Leading in a crowded CDN space are vendors like:

  • Akamai
  • Amazon Web Services (AWS)
  • Google
  • IBM
  • Microsoft

Security & Privacy

As revealed by MarketsandMarkets, certain CDN activity, like video
streaming, has raised security and privacy issues. “Security and privacy of
the video content shared across various platforms is one of the major
concerns. At the same time, there are also concerns related to copyrights
and digital rights mismanagement, which can arise due to the misuse of data
and information leakage.”7


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CDNs are a tremendous asset to content-rich websites with large
followings. Without using a CDN, a site can easily get swamped with hits,
effectively shutting it down. Another benefit of hosting applications and
content on a CDN is that it is much harder to be shut down by
a distributed denial of service (DDoS) attack. If someone tries to
attack the site, the CDN will just shift resources to other nodes in the
network while working to block access from the offending sources.

The big decision in adopting CDN technology is determining when a
website’s demands are large enough to make the switch beneficial. The
costs involved must be evaluated carefully. It is not easy to quantify all
benefits that a CDN can offer in the short run. In the long run, increased
satisfaction by users can lead to higher hit numbers and eventually higher
sales. Unless an organization has the resources and expertise, it
would be better off using a service provider rather than building a
CDN internally.

For a simpler go/no-go calculus, analyst Brenda Barron asserts that:

“You should consider implementing a CDN if…

  • “You have a traffic-heavy site.
  • “You expect your business to grow and cause huge spikes in traffic.
  • “You use a lot of media items, especially images.
  • “You attract visitors from all around the world.
  • “You experience issues with site performance.

“You should not consider implementing a CDN if…

  • “You have a local website.
  • “You have a small website.
  • “You don’t have a lot of traffic.
  • “You don’t use a lot of media items.”8

Choosing a CDN Service Provider

In choosing a CDN service provider, analyst Max Wilbert suggests adhering
to three “golden rules:”

  1. Select a provider, like Akamai, that offers a large network and wide
    distribution. “We live in an increasingly globalized, interconnected
    world. If you value reaching a global audience, look for a global CDN
    service provider.”
  2. Select a provider that offers responsive, knowledgeable customer
    support. “Look for a CDN option that offers 24/7, in-house tech support
    to prevent unnecessary issues while streaming live.”
  3. Select a provider that offers affordable and transparent pricing.
    “Choose a CDN service provider with the right pricing model for your


1 Rahul Nanwani. “What is a Content Delivery Network (CDN) – A
Beginner’s Guide.” ImageKit Private Limited. July 2, 2020.

2 Mike Williams. “Best CDN providers of 2021 to speed up any
website.” Techradar | Future US, Inc. April 16, 2021.

3 “What Is a CDN?” Cloudflare Inc. 2018.

4 Brenda Barron. “What Is A CDN? A Beginner’s Guide to Content
Delivery Networks.” WP Superstars. February 6, 2018.

5 “Content Delivery Network Market by Component (Solutions
and Services), Content Type (Static and Dynamic), Provider Type
(Traditional CDN, Telco CDN), Application (Media and Entertainment, Online
Gaming, Healthcare), and Region – Global Forecast to 2025.”
MarketsandMarkets. January 2021.

6 Ibid.

7 Ibid.

8 Brenda Barron. “What Is a CDN? A Beginner’s Guide to Content
Delivery Networks.” WP Superstars. February 6, 2018.

9 Max Wilbert. “Three Golden Rules for Choosing a CDN Service
Provider in 2019.” DACAST. October 4, 2018.

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About the Author

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James G. Barr is a leading business continuity analyst
and business writer with more than 30 years’ IT experience. A member of
“Who’s Who in Finance and Industry,” Mr. Barr has designed, developed, and
deployed business continuity plans for a number of Fortune 500 firms. He
is the author of several books, including How to Succeed in Business
BY Really Trying
, a member of Faulkner’s Advisory Panel, and a
senior editor for Faulkner’s Security Management Practices.
Mr. Barr can be reached via e-mail at

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