So what is a Content Delivery Network (CDN) and what advantages can it bring to established web businesses? Presented below are general details and views on CDN in the public domain:
A Content Delivery Network (CDN) is a geographically dispersed system of interconnected servers connected to the Internet that serve web content to end users.
Customer's content is retrieved by the CDN from the customer’s own origin server and duplicated and stored or streamed across the dispersed server network, effectively re-distributing the content from the core to the edge of the Internet.
When an end user makes a request for CDN-enabled content, complex routing and DNS algorithms intelligently establish the location of the end user and directs the request to the optimal CDN server node. The optimal serving CDN node is typically one that is nearest to the end user in network terms(*), has the most bandwidth and capacity available, or maybe the least expensive serving location, or a combination.
(* network proximity is not necessarily geographically nearest)
Where engineered for performance gain, the assigned serving node of the CDN will deliver content to the end user quicker and more efficiently than the customer's own origin server - as a result of having lower network latency and higher network throughput available.
top
Use of a CDN can bring a host of benefits to any Internet-orientated business.
The inherent characteristics of a geographically dispersed, carrier-grade, highly connected, highly scalable, and resilient CDN infrastructure allows customers to mitigate the risks and counter the unpredictability of operating a business or service on the Internet.
Key customer advantages are as follows:
- Improved End-user experience
The CDN ensures that users requested content reaches the end-user as quickly as possible having traversed the network route of least latency, lowest packet loss and least congestion.
Customer has dependable use of a network that is significantly scaled and effectively over-provisioned, capable of comfortably handling traffic surges and unpredictable rapid traffic growth that the customer may experience for their content and services.
The international geographic distribution of the CDN gives customers an active serving local presence in, or near to, every major end-user target market in the world.
Multiple active CDN nodes carrying and serving customer content minimises site timeouts and maximises site response times, mitigating the risk of server overload, server or node failure, Internet congestion or cable system failure.
The CDN represents a ready-made on-demand distribution network for its customers. There is no need for downtime or build-out time in order to deploy an infrastructure capable of supporting new products or services.
- Customer-own Infrastructure requirement and TCO
CDN offers built-in redundancy and resilience to a customer's web operations and as such the customer only has to maintain a single or dual origin server and Internet connection(s) in a single territory. This results in significant cost savings, lower total cost of ownership (TCO) and reduced complexity across the following areas:
- Systems Management, man power and in-house expertise
- Hardware and software capital and operational expense
- Network infrastructure capital and operational expense
- Data Centre / Co-location infrastructure capital and operational expense
- Network Security policies and procedures
In addition, use of a CDN can significantly simplify and off-set the need for customers to retain in-house expertise and an operating infrastructure designed to support non-core IT activities such a load balancing, domain name services (DNS), and gateway routing protocols (eBGP, OSPF etc).
CDN replaces all these with a utility-based, on-demand, highly flexible, highly reliable and cost-efficient content delivery infrastructure.
The CDN acts as a buffer absorbing and neutralising internet-based threats that can potentially bring down a customer's Internet services. The effects of domain squatting, distributed denial-of-service (DDoS) attacks can be mitigated by the scale and expanse of the CDN hiding and protecting the customer's origin servers.
top
Edge-caching was initially a technology utilised by Internet Service providers (ISPs) and Content Delivery Providers to improve their end-users experience of frequently visited web pages and content, as well as reduce their traffic demands on upstream providers.
Early CDNs correctly identified the value that this technology represented to the content owner by improving end-users experience of their services, and deployed their own caching servers within popular ISP' infrastructures. Significant investment and advancement in optimal path routing techniques, application development and in the CDN's own upstream infrastructure were made during the 1990s, by early CDNs such as Sandpiper, Mirror Image, Skycache,Akamai and Digital Island.
CDNs optimised to meet today's rich media demands tend to see fewer, but larger, server node deployments. By leveraging the power of modular computing and virtualisation, today's CDN server nodes are highly scalable, more manageable, and better placed to secure the very high and guaranteed network bandwidth appropriate to serving larger file sizes and more complex applications. By locating nodes at major Internet peering locations (private and public), the fractional latency benefits of locating within an actual ISPs network are far outweighed by the all-round benefits of greater bandwidth availability, more concentrated computing power, more storage capacity, scope for greater built-in redundancy, lower management requirements, more predictable costs, and advantageous economies of scale.
top
Below are some of the more common applications for CDN:
- Large File Downloads and Object Delivery
- Video (live and on-demand, HD)
- Music (live and on-demand)
- IPTV, Set-top TV
- Software (including live online gaming)
- Images
- Flash files
- Social Media
- High-Traffic Large Library Web Sites
- Online Advertising
top
Improved End-user experience... Increased content delivery speeds
Scalability... scalable delivery and storage
Geographic Reach... established presence in or near major customer markets
Availability... redundant and resilient networks
Time to Market... quick implementation, reduced time to market
Reduce Customer-own Infrastructure requirement and Lower TCO / Investment... minimised cost of delivery versus a self-hosting infrastructure build
Security... additional layer of capacity and routing aiding security of the origin server ensuring availability of content
top
Wikipedia: http://en.wikipedia.org/wiki/Content_Delivery_Network
Techtarget: http://whatis.techtarget.com/definition/0,,sid9_gci1187046,00.html
Level 3 Communications: http://www.level3.com/content/index.html
top