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

Transcription

1 The content delivery network (CDN): Delivering the ultimate Web experience White paper April 2010 By Ari Blau Video Solutions Portfolio Leader, Bell and Robert Kevork Associate Director of Marketing. Bell Business Markets

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 it s 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 of improving 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. 2.

3 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 doesn t 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 to recipients 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-based With 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 CDN This 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. 3.

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 Improved user experience worldwide Capital expenditures are not required 4.

5 3.3 Additional value But the benefits of content delivery networks go beyond simply increasing an organization s 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 geographically disparate 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 server POPs 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. 5.

6 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. Internetbased 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 real impediment 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 6.

7 Chart: comparison of Internet-based and network-based CDNs: Function Business value Network-based CDN Internet-based CDN Cache server Increased speed of selection delivery Avoiding congestion Avoiding outages Reliable, fast delivery Reliable, fast delivery Routes to most geographically proximate cache server based on request source location, minimizing latency Congestion is avoided by dynamically changing IP routing within provider s IP backbone and peer IP networks Reroutes around detected outages based upon actual, dynamic network conditions in addition to the relative performance of alternates, accelerating delivery Problem solving Reliable, fast delivery IP routing and link monitoring detects congestion and outages, speeding time to resolution POP location Load balancing End user intelligence Increased speed of delivery Reliable, fast delivery Reduced strain on network resources Ability to provide granular end-user data to CDN customers POPs are collocated in major network provider routing centers so user requests can be handled locally 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 to propagate to the Layer 3 network Visibility of end-user IP addresses can help improve network architecture, and is useful for sales, marketing and other purposes Routes to cache servers based on end user s DNS location Congestion is avoided based on best alternate routes detected Probes gather application layer information, which is interpreted to determine where outages exist. This is not always accurate Probes gather application layer information, which is interpreted to determine the nature of problems. Resolution can take minutes POPs are placed in thirdparty data centers. User requests are aggregated in a local switching center, then forwarded to a data center, creating latency 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 Only DNS server information is known, with no direct knowledge of end-user location 7.

8 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 user s 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. It s 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 8.

9 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 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 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 component in the case of an online auction like ebay, for example the 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 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? 9.

10 6.1.5 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 rapid delivery 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 site s 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. 10.

11 Business need Video delivery Content security Storage Mobile delivery Ad delivery and insertion CDN feature Streaming media services Geographically restricting content DRM, watermarking, and other ways to prevent content theft Preventing unscrupulous Web sites from deepl-linking to content Support for both customer and CDN-based origin Ability to detect device and delivery device-specific version of the content Ability to deliver advertising into video streams and in-page Take a test drive A demonstration will show you how well CDN works and how a potential vendor s 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 of delivery 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 SWIFT verification for financial transactions Using real-time messaging protocol to encrypt streams 11.

12 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 specialist to 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 connectivity Are 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 Internet exchanges where telecommunications companies, Internet service providers (ISPs) and major access networks come together and connect Features and options What 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 agreement What are the particulars of the SLA? Can the provider guarantee 100 percent uptime and 100 percent content availability? Pricing Are data volume rates fixed, or is there a variable rate based on volume? 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. 12.

13 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 Internetbased, 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 being delivered 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 Bell s CDN offering, CDN consulting services or to gain a deeper understanding of how a CDN fits in with other Web-centric offerings, contact for Bell account representative or request 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 Video Solutions in Bell Business Markets, including Telepresence, Video Conferencing, Broadcast Video Network, Content Delivery Network and Digital Media Solutions. Robert Kevork is Associate Director of Marketing with Bell Business Markets. Currently responsible for product management of Bell s Content Delivery Network service, Robert has more than 20 years of experience in the development and marketing of information and communication technologies and services in a variety of industry sectors, including manufacturing, distribution, retail, government and telecommunications. 13.