CD n White Paper June

8/12/2019 CD n White Paper June

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The content delivery network (CDN): Delivering the

ultimate Web experience

White paper

June 2010

By Ari BlauVideo Solutions Portfolio Leader, Bell

and

Robert Kevork

Associate Director of Marketing. Bell Business Markets


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The content delivery network (CDN): Delivering the ultimate Web experience

2.

The content delivery network (CDN)

1.0 Delivering the ultimate Web experience

Just a few years ago, downloading files from the Web could be an exercise in frustration. Today,consumer and business audiences alike expect to download nearly all content, whether its a

document or a video game, in much the same way as they would launch an application from

their hard drives. But delivering rich media content and large files to the four corners of the

world puts enormous strain on network resources. In highly competitive business sectors such

as media, software, gaming, retail and finance, slow delivery is not an option, and organizations

are looking for ways to ensure that content reaches their audiences as quickly as possible,

every single time.

For many organizations, the solution is a content delivery network. CDNs are specialized server

overlays to the public Internet. By caching content on strategically placed servers networked

around the world, CDNs quickly and reliably deliver high-bandwidth digital content to large

numbers of widely distributed recipients.

CDN is not the only technology option available in the marketplace that can increase the speed

and reliability of content delivery to large, distributed audiences, but as a competitively priced,

mature technology, CDN is gaining widespread adoption in media and entertainment, software

and gaming, retail, financial and insurance industries, as well as in public-facing government

agencies and educational institutions.

The benefits that CDN offers include more effective storage, security and rights management of

content, but its primary advantages concern data delivery, including:

Improved reliability and performance in delivery of video, applications and other large

files

Enhanced global user experience

Reduced networking costs

No IT capital expenditures required

Potential to drive business growth with better delivery of richer Web content

This white paper will demonstrate how CDN can be an effective and time-saving means ofimproving Web site performance and delivering data both for B2B and B2C organizations. It will

also outline the advantages of network-based CDN architectures over Internet-based CDN

architectures. Most importantly, it will convey best practices in building a business case for

CDN, as well as selecting, roadmapping and implementing a CDN solution.


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2.0 CDN explained

In order to understand how CDN works, first consider how data is generally transmitted over the

Internet. Traditional data transmission over the Internet involves a request for information sent

to a hosted Web site and transmission of requested data back across the public Internet by the

route automatically calculated to be the most efficient. Content delivery networks, by contrast,

cache most frequently accessed information in servers located close to large numbers of end

users, thereby reducing demands on the hosted Web site. This increases speed and reliability

of delivery, as well as redundancy in the case of an outage.

2.1 Three categories of CDN

CDN is a service overlay that rides on top of Internet connectivity. Although an ISP may offer

CDN service, it is not considered an Internet service provider (ISP) solution per se because it

doesnt include Internet or wide-area network (WAN) access to end-users. There are three

categories of CDN delivery mechanisms, each with its advantages and disadvantages:

Peer-to-peer Peer-to-peer CDNs leverage the user base. Content is delivered torecipients from a central server, but once many copies have been distributed to user

PCs, these PCs become points of presence (POPs) in their own right and deliver data

directly to other PCs. This architecture is economical, but issues include security,

content refreshes and rights management

Cache-basedWith cache-based CDN, POPs are strategically placed close to high

concentrations of end-users. The POP most proximate to an end-user request is the one

that sends the data, minimizing distance. Ideal for high-demand content, cache-based

CDNs can be Internet-based or private network-based (the differences in each are

discussed in section 4.0 of this white paper)

Enterprise CDNThis is a private CDN that operates within a corporate WAN.

Multicast technology is employed to send identical content simultaneously to many users

by replicating data at the point closest upstream to a given user. In this way, many users

receive data although it is sent only once. Enterprise CDN saves on bandwidth and

network resources. It is especially useful for training purposes and for reaching a

distributed internal audience

By careful selection of the most appropriate delivery mechanism, CDN can address several

common challenges associated with delivering content over networks.

3.0 Why CDN?

The Internet has revolutionized communication, but it poses some unique challenges.

Transmitting information across large distances over the Internet entails multiple switches, each

of which causes some delay or latency. In the case of transmitting voice or streaming

applications, those delays can cause quality to degrade. At peak traffic times, transmissions

may also encounter blockages on some branch of the routing. And when demand on one

resource is high, enormous load can bog down servers and the local network, affecting speed

and performance. CDNs helps to overcome these obstacles.


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4.

3.1 Four primary challenges of content delivery

CDNs were designed to address four fundamental stumbling blocks of content delivery, each of

which continues to change rapidly:

Object size Files are increasing in size as applications, video and audio files increase

in quality all the way up to high-definition feature films and entire software applications Library size In order to satisfy users demands for choice and personalization,

organizations are managing and hosting an increasingly broad selection of audio, video,

images, text, software downloads and other content

Audience size and location Online audiences are global, interconnected, and

expanding, with users spending a growing amount of time on the Internet, and accessing

it on a wide variety of devices

Content popularity On the Internet, an audience of millions is really a million

audiences of one, and each requires the same rapid and consistent delivery of content

Given its potential to cope with these four factors, CDN solutions have become an attractive

option for organizations that share large amounts of information with great numbers of

geographically dispersed customers, business partners and internal users even if they are

only dispersed within one city.

3.2 Improving the customer experience

Users now expect lightning-fast access to all content, anytime, anywhere. The speed of online

delivery, quality of content and Web site performance are all major factors in improving the

overall customer experience and gaining a competitive advantage. It is a trend that is affecting

multiple sectors:

Media and entertainment video and audio content

Retail large libraries of high-resolution images for online shopping

Consumer electronics, software and gaming software updates, drivers and streaming

applications

Public-facing and international government agencies high-demand Web sites and file

downloads

Financial and insurance high-traffic, highly dynamic and custom Web site content to a

global audience

In order to satisfy users high expectations, major players in these industries are turning to CDN

for its ability to deliver content quickly, including live event streaming and HD content. Those

organizations have identified several principal benefits to CDN:

Richer Web content provided to the edge of the Internet

Improved delivery capability of large files


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5.

Improved user experience worldwide

Capital expenditures are not required

3.3 Additional value

But the benefits of content delivery networks go beyond simply increasing an organizations

ability to transfer large volumes of data. Other CDN functionality increases the attractiveness of

CDN to organizations for which security, storage and rights management are important. These

benefits include:

Security features such as security tokens, which increase user security and ability to

manage digital rights

Secure, redundant storage

Better access to reporting, including reporting of geographic usage of your content

Geo-blocking: preventing certain content from reaching given regions

As a competitively priced, mature technology, CDN is gaining widespread adoption and has

emerged as a leading approach to increasing the speed and reliability of content delivery to

large, distributed audiences.

4.0 CDN: Go private or go public?

There are two common varieties of CDN service commercially available today one delivers via

the public Internet; the other makes use of a private network. Both are cache-based services

that store copies of the original video, audio and data from centralized servers on geographicallydisparate POPs or cache servers.

4.1 Internet versus network-based CDN

The main differences between Internet-based and network-based CDN are the method of

distribution and the amount of visibility into data routing. The mechanics of each are as follows:

Internet-based CDN providers operate server overlays with widely distributed server

POPs that are interconnected via the Internet, with visibility into Internet layers four to

seven

Network-based CDN providers operate server overlays with widely distributed serverPOPs that are interconnected via a private, dedicated network, with visibility into Internet

layers one to seven

While both varieties are viable options, there are distinct advantages to network-based CDN

architectures. Chief among these is the advantage of network control. In addition to providing

CDN services, network-based providers are responsible for the basic routing, troubleshooting,

operations and management of network layers one to three. This gives them visibility into all

network layers and the ability to control delivery performance end-to-end.


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Like their network-based counterparts, Internet-based CDN providers offer server overlay

capabilities, managing POPs around the globe. But because they are limited to network layers

four to seven, they lack direct visibility into the network foundation that they rely upon. Internet-

based CDN providers are therefore relegated to interpreting application layer information

gathered with network probes in order to avoid the congestion and outages that plague the

public Internet. This information is not always accurate and never complete, which acts as a realimpediment to optimizing content delivery performance and results in occasional delays in

delivery.

Network-based advantages

Maintaining control of network infrastructure gives network-based CDN providers many

advantages, including the ability to:

Exert control over a wide set of resources used to deliver content to enterprises and

consumers

Collocate CDN equipment with network equipment so as to be physically close to end

users, reducing latency

Eliminate congestion from point of origin to POP

Maintain content security within the CDN from point of origin to POP

Provide a greater level of physical security, in the case of provider-owned data centres

Pass on end-user DNS query information to customers that are content providers. This

can be useful not only for performance measurement, but also for statistical analysis and

geotargeted marketing, sales and other efforts

Scale faster and provide quicker end user access to content, due to a greater ability to

manage capacity


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7.

Chart: comparison of Internet-based and network-based CDNs:

Function Business value Network-based CDN Internet-based CDN

Cache server

selection

Increased speed of

delivery

Routes to most

geographically proximate

cache server based on

request source location,

minimizing latency

Routes to cache servers

based on end users DNS

location

Avoiding

congestion

Reliable, fast delivery Congestion is avoided by

dynamically changing IP

routing within providers IP

backbone and peer IP

networks

Congestion is avoided

based on best alternate

routes detected

Avoiding

outages

Reliable, fast delivery Reroutes around detected

outages based upon actual,

dynamic network conditions

in addition to the relative

performance of alternates,

accelerating delivery

Probes gather application

layer information, which is

interpreted to determine

where outages exist. This

is not always accurate

Problem solving Reliable, fast delivery IP routing and link monitoring

detects congestion and

outages, speeding time to

resolution

Probes gather application

layer information, which is

interpreted to determine

the nature of problems.

Resolution can take

minutes

POP location Increased speed of

delivery

POPs are collocated in major

network provider routing

centers so user requests can

be handled locally

POPs are placed in third-

party data centers. User

requests are aggregated in

a local switching center,

then forwarded to a data

center, creating latency

Load balancing Reliable, fast delivery

Reduced strain on

network resources

Requests are filled based on

available resources in cache

servers, core routers, peering

links and access routers.

This gives good performance

and takes place in

milliseconds the time

routing updates take topropagate to the Layer 3

network

Requests are filled based

on the resources available

in cache servers. Load

balancing can be delayed

by minutes the time it

takes DNS changes to

propagate across the

Internet

End user

intelligence

Ability to provide

granular end-user data

to CDN customers

Visibility of end-user IP

addresses can help improve

network architecture, and is

useful for sales, marketing

and other purposes

Only DNS server

information is known, with

no direct knowledge of

end-user location


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5.0 The evolution of CDN and its future

Content delivery networks were first envisioned during the dotcom era as a way of meeting the

challenge of increasing speed of delivery to low-bandwidth connections an expensive niche

service provided by small, local, Internet-based networks. Since then, however, CDN solutions

have developed to become a global, high-capacity and inexpensive network-based technology

offering. ICT carriers are increasingly identifying CDN as a means to improve their service

offering to enterprise-level corporate, not-for-profit and public sector customers.

Now with more intelligence at the network edge, CDNs:

Deliver content to not just the personal computer but also to set-top boxes and

smartphones

Enable the delivery of different content to different users depending on the performance

of the end users network connection and on what kind of device is requesting the

content

Increasingly provide the fundamental delivery mechanism for cloud computing services

As networks continue to evolve, so will the role of CDNs. In the near future, fibre optic cabling

will be extended to the home, allowing high delivery speeds to be maintained from the edge all

the way to the end user, eliminating the current last-mile bottleneck, and providing faster file

downloads. Mobile cellular networks are quickly being upgraded as well, increasing wireless

speed and reliability, and delivering more rich media to mobile devices. These trends will put

growing demands on central servers, potentially affecting organizations abilities to compete

without a solution such as CDN.

6.0 Best practices for creating a CDN roadmap

In order to build an effective CDN architecture, you will need to develop a roadmap. Its

important to utilize best practices for implementing CDN because the technology has

implications for the rest of the network in terms of security, bandwidth, internal data transfer and

more. Your chosen solution also needs to take into account what your organization faces in

regards to the four primary challenges of content delivery: object size, library size, audience size

and location, and content popularity.

There are three overarching goals that inform CDN best practices:

Ensure sufficient storage and delivery capacity in the most strategic locations around the

world

Interconnect directly with the largest number of user access networks possible at

multiple locations worldwide

Bypass the Internet as much as possible, both by interconnecting with user access

networks and by moving content from location to location via a dedicated backbone


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6.1 Aligning CDN with your business

The first step in developing an implementation roadmap is to decide whether CDN is the best fit

your organization. CDN is not the only answer to business problems, although it is a viable

alternative to incurring significant capital expenses.

CDN delivers Web content faster and more efficiently regardless of whether it is video files,

images and graphics or Web pages. CDN makes best sense if you:

Are having issues with Web site performance

Have a need to scale your Web site while guaranteeing speed

Need to deliver efficient global access to your Web site

Have significantly variable or seasonal demand for Web site resources

6.1.1 Performance

To decide whether CDN makes sense for your organization, develop an understanding of the

impact that online performance has on your business. If your revenue model includes online

advertising, poor page-load times may result in fewer ad impressions. If you are an online

retailer, shopping-cart pages that perform poorly at times of peak demand will likely result in

customer drop-off and loss of sales.

6.1.2 Cacheability

Another consideration regarding fit is whether or not your content is highly cacheable. The

general rule is that static content is cacheable, while dynamic is not. In the case of a news Web

site where the majority of the content changes every few minutes, for instance, CDN may not be

the best choice. But when the bulk of pages are static but carry a dynamic componentin the

case of an online auction like eBay, for examplethe bulk of each page can be cached, with the

small dynamic portion pulled through from the origin server. A vendor Web site evaluation will

tell you how cacheable your content is.

6.1.3 Planning for growth

The next step in determining whether CDN is the right solution is to evaluate your current ability

to handle content delivery with respect to future needs, and how much it will cost to deliver it

effectively. Ask yourself:

How many requests per minute can your Web application handle on a single server? How much bandwidth do you have available to handle requests?

What is the cost for increasing bandwidth?

What are the operational costs associated with serving content to your end-users?

How will costs increase as server load climbs?


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10.

6.1.4 The right fit

There are many ways to provision content, but in general CDN is a good choice when:

The bulk of content that you are delivering over the Internet is more static than dynamic

Your audience is national or global rather than local

You have a large audience and/or transmit large amounts of data

6.2 Perform a Web site evaluation

The best way to decide whether CDN is a viable solution is to have a potential vendor perform a

Web site evaluation. They will determine which elements of your pages are cacheable, which

are not, and how to optimally configure your Web site footprint to make best use of CDN, with

an eye to offloading as much transmission as possible while maintaining control.

Keep in mind that CDN provides a way to increase and expand your business. Thanks to rapiddelivery of large file sizes to enormous audiences, CDN can allow you to put richer, more

interactive content on your Web site or send larger, custom files to the four corners of the world

with great speed. It can also constitute a strategic advantage in a crowded marketplace.

6.3 Assess your current environment

If you have decided that CDN is a good fit for your business, you will need to benchmark your

environment in order to build the business case for implementation. Things to measure include

user demand now and in the future, as well as audience metrics. Consider:

What pages or files are being requested most often and with what frequency?

Where are end users located?

What are end users patterns of use in terms of time of day, type and size of files

accessed and user location?

What is your projected user demand over the next five years? Take into account how file

sizes and quantities are likely to change?

6.4 Build for the future state

An assessment of your current environment will show you where you stand and paint a clearer

picture of where you want to be. Even if your Web sites performance is sufficient right now, it

may not be adequate for what you would like to do. What are your future state ambitions? With

CDN you might easily be able to add a video library, include higher quality photos, send richer

files and more. The following table shows some how some common business needs are

answered with CDN.


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Business need CDN feature

Video delivery Streaming media services

Content security Geographically restricting content

DRM, watermarking, and other ways to prevent content theft

Preventing unscrupulous Web sites from deep-linking to content

Storage Support for both customer and CDN-based originMobile delivery Ability to detect device and delivery device-specific version of the

content

Ad delivery and insertion Ability to deliver advertising into video streams and in-page

6.4.1 Take a test drive

A demonstration will show you how well CDN works and how a potential vendors offering fits.

Have a vendor set up CDN in beta for you without affecting actual Web site traffic. A proof of

concept will also show you the technical adjustments that will need to be made. These can

include:

Changing content management system naming conventions

Protecting content from the edge

Changing streaming media player requests in order to point to CDN servers

6.5 Tailor the experience

Content delivery systems are tailored to meet organizations specific needs. These are the

adjustments and decisions that will provide maximum economies, optimize content distribution

and freshness and minimize load on origin servers in a secure environment. Points to consider

in tailoring your CDN set-up include:

Time to live policies These optimally balance content freshness as well as

cacheability, based on business operations. They take into account the frequency with

which content at the edge is purged or updated, and the process that is followed

Handling the long tail If you need to transmit very large files or you have a large

library consisting of popular and not-so-popular content, how do you efficiently deliver

everything quickly? In cases like these, it can make sense to synchronize a duplicate

CDN storage server with your origin server. Then when files are requested from the

edge of the network, your origin server is not carrying the load of pulling the files through

Integrated security There are a number of different solutions to ensuring security ofdelivery with CDN:

Using secure socket layer (SSL) for delivery of encrypted content over an http

connection

Authorizing only certain users, Web sites and media players (in the case of

streaming content) to access content

Using real-time messaging protocol to encrypt streams


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Accessibility of content Are there certain locations or regions that should not be able

to access some kinds of content? Geo-blocking can deny access to any part of the world

Once these adjustments have been made and tested, you will be in a position to go live and

ramp up your speed, volume and security of content delivery. Keep in mind that if implementing

a CDN solution is unfamiliar territory, it may make sense to engage the services of a specialistto create the optimal scenario.

7.0 Best practices in choosing a partner for CDN

When choosing a CDN provider, there are many things to consider above and beyond simple

access to content. Because initial planning is so crucial, it is important to choose a partner that

understands the entire Web value chain, from Web site architecture to CDN delivery. This depth

of knowledge, coupled with experience, will help contribute to strategic planning and ongoing

provision of services, including configuration optimization, content management expertise and

private CDN services.

Important partner considerations include:

Regional connectivityAre points of presence geographically near to your greatest user

bases? In Canada specifically, POP location is important. Most CDN providers

concentrate POPs in the U.S. not at all close to Canadian user bases. But POP

location alone is not the only consideration. You should ascertain:

Server density in each location

If servers are directly peered with all regional carriers for direct connectivity

If POPs are directly connected with TorIX, BCIX and other major Canadian Internetexchanges where telecommunications companies, Internet service providers (ISPs)

and major access networks come together and connect

Features and optionsWhat features and options are available and how are they

delivered? Features can include geo-specific reporting and blocking; redundant storage;

and increased security features

Last mile ownership Who owns the last mile? If the vendor is also an ISP, they will

have direct access to customers and direct access to the Internet exchanges for other

ISPs. By owning the connection from POPs to many end users, a vendor has an

increased ability to maximize the speed of content delivery

Service level agreementWhat are the particulars of the SLA? Can the providerguarantee 100 percent uptime and 100 percent content availability?

PricingAre data volume rates fixed, or is there a variable rate based on volume?


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8.0 The bright future of online delivery

As data volumes and files sizes increase, the means of transportation from origin server to end

user continues to change. Content delivery networks have evolved from small, Internet-based

networks to global, dedicated fibre optic networks with massively provisioned and highly

connected points of presence. At the same time, the cost of CDN has dropped, making it a

viable choice for organizations large and small in a wide variety of business sectors.

Content delivery networks are especially effective in Canada, where large distances and

relatively few Internet exchanges combine to form challenging conditions for rapid delivery of

rich media and large files to a broadly online population. There are many benefits to CDN,

including:

Ability to drive business growth through richer, better Web content

Improved reliability and performance of delivery

Enhanced global access and user experience

Lower networking costs

Reduction in the need for IT capital expenditures

The extent to which you can realize these benefits depends on the CDN provider that you

choose. There are significant advantages to choosing a network-based CDN over Internet-

based, chief of which are visibility into traffic routing and ability to instantaneously avoid outages

and congestion, guaranteeing speed of delivery to the point of presence nearest the end user.

In the case of telecommunications providers, the last mile connectivity from POP to end user

can also be optimized for telecommunications clients.

The future of online data delivery is bright. Richer, more highly customized content is beingdelivered to customers across the world with very little delay, thanks in great part to robust CDN

networks. As CDN continues to proliferate and more organizations adopt the technology, we will

see a great increase in the richness and variety of content available online to consumers and

business audiences alike.

Bell can help

Bell provides access to the largest, most robust CDN network in Canada thanks to an exclusive

partnership with Limelight Networks, a leading worldwide provider of network-based CDN

services. For more information about Bells CDN offering, CDN consulting services or to gain adeeper understanding of how a CDN fits in with other Web-centric offerings, contact for Bell

account representative orrequest that a Bell representative contact you.

About the authors

Ari Blau, the Video Solutions Portfolio Leader with Bell Business Markets, has more than 10

years experience in video, content and digital media technologies and applications. In his

current role, he is responsible for leading product development and life-cycle management for
http://bell.ca/enterprise/portlets/enterprise/documentform/core_content_downloads.jsp?FormId=rep_request_form&language=en&ETCID=pdf_060210_en_CDN_WhitePaper_emkhttp://bell.ca/enterprise/portlets/enterprise/documentform/core_content_downloads.jsp?FormId=rep_request_form&language=en&ETCID=pdf_060210_en_CDN_WhitePaper_emkhttp://bell.ca/enterprise/portlets/enterprise/documentform/core_content_downloads.jsp?FormId=rep_request_form&language=en&ETCID=pdf_060210_en_CDN_WhitePaper_emkhttp://bell.ca/enterprise/portlets/enterprise/documentform/core_content_downloads.jsp?FormId=rep_request_form&language=en&ETCID=pdf_060210_en_CDN_WhitePaper_emk


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Video Solutions in Bell Business Markets, including Telepresence, Video Conferencing,

Broadcast Video Network, Content Delivery Network and Digital Media Solutions.

Robert Kevorkis Associate Director of Marketing with Bell Business Markets. Currently

responsible for product management of Bells Content Delivery Network service, Robert has

more than 20 years of experience in the development and marketing of information andcommunication technologies and services in a variety of industry sectors, including

manufacturing, distribution, retail, government and telecommunications.

Documents

CD n White Paper June