A Content Delivery Network, or CDN, is a global network of caching servers used for high-speed delivery of multimedia content to users. The CDN brings content closer to the user, improving overall network efficiency.

What Benefits does a Content Delivery Network offer?

A CDN offers numerous benefits to both consumers and content providers such as increased Web site performance, faster download speeds, load balancing and security, among others.

How Does a CDN Work?

Under the typical Web server model, when a user visits a Web site on the Internet, the user's Web browser sends a request to that site's main server. That server is known as the origin server, and when a request is received, the server processes that request and delivers the appropriate content to the user. The majority of Web sites on the Internet work this way. A CDN does things a little differently.

A Content Delivery Network is comprised of caching servers, also known as CDN nodes, which are strategically located in every region of the world. The idea behind these servers is to bring the content closer to the user, and the CDN accomplishes this by working in conjunction with the Web site's origin server to store cached content on the CDN nodes. Using a CDN model, when a user requests content from a Web site, the following sequence takes place:

First, the user visits the site and the browser sends the request to the origin server. That request is actually redirected to the nearest CDN node to see if that node has already cached the content. If the node has the content, it will be returned to the user. If the node does not have the requested content, the node itself will request content directly from the origin server, cache it, and return it to the user. Now that the CDN node has that content cached, any users within that node's region can get the content straight from the CDN. Because the content has now been moved closer to the user, download times are much quicker for all users in that region requesting the same content.

What Are the Other Advantages of a CDN?

In addition to performance increases gained by use of the caching servers, a CDN will also grant the following benefits:

• Reliability of Content: Should a Web site's origin server go down, it is still possible for content to be served. The network can be configured so that if a CDN node requests content from the origin server and the server is unavailable, that node will then request that content from the next nearest node; if the content is present, it will be delivered to the user. Content can also be set to expire from the CDN at a certain time, so that if a site is purposefully taken down for maintenance or other reasons, content will not be served inadvertently.
• Flash Crowd Protection: Unexpected surges in traffic, known as flash crowds, can happen at any time. This can put considerable strain on a single server. A Content Delivery Network uses load balancing technology to help manage bandwidth and keep the site running when traffic spikes. Each CDN node uses several servers clustered together acting as a single server, so the load is balanced equally among them to ensure no one particular server is overloaded.
• Security: Depending on how the network is set up, a CDN can 'hide' the origin server from the outside world. This way, only requests coming from a CDN node will actually make it to the origin server; any Internet requests will be discarded, helping to protect your content from attack or theft.
• Scalability: Because a CDN uses pre-existing lines and nearly unlimited bandwidth, there is no need for internal network expansion. The CDN scales on demand, so when the need for more bandwidth arises, the CDN has it immediately available.
• Extended Server Life: Because the only requests hitting the origin server are those coming directly from CDN nodes, the load on the server is greatly reduced, allowing the potential for extended hardware life.

How Do I Know if I Need a CDN?

A Content Delivery Network is best suited for Web sites that serve large amounts of static content. Music, video and application downloads are most efficiently served from as CDN, as well as image galleries and Flash objects. The caching technology of a CDN would enable fast delivery of these objects to the user.

For highly dynamic content, a CDN might not be as useful. A stock ticker, for example, updates in real-time, so there is nothing to cache. Static content does not need to always stay static, however; a Time-To-Live (TTL) option can be set on each piece of content, so that when the time period of the TTL expires, the content will be refreshed on the caching server. In such cases, a CDN will improve performance through caching as well as keep content up to date.

Sites that have both static and dynamic content can experience the best of both worlds from a Content Delivery Network by placing static content on the CDN, and serving dynamic content directly from the origin server.

How Do I Get Set Up?

The first step in getting set up on the CDN is to speak with a NationalNet Sales Representative. (Contact information is provided at the end of this document.) Once a deal has been reached, a conference call will be scheduled between you (the client), the NationalNet Sales Representative, and a representative from Level 3, the CDN provider. During this conference call, it will be discussed which files will go on the CDN, how to get them onto the CDN, how to log into the administration system, what DNS information needs to be modified, and any other pertinent details. Once this call is complete, the rest of the CDN setup will be handled by Level 3.

How Do I View Reports?

Reports are available using the CDN Portal, a Web-based administration and reporting tool. The location of the portal as well as login information will be given to you when the CDN setup is complete.

How Do I Use the Portal?

When you first log into the Portal, the Home page will give you a brief overview of the CDN and links to the various reporting tools. The Library tab links to technical documentation regarding how various facets of the CDN operate. The CDN tab contains the reporting tools, and Home takes you back to the Portal's Home page.

What Reports are Available?

Under the CDN tab, follow the Caching link, where the following reports can be viewed:

• Dashboard: This is an overview of all usage statistics for the current month. Listed are the 95th Mb/sec, the total number of Megabytes served by the CDN for all assets, the total number of hits, and overall Cache Efficiency. Cache Efficiency shows what percentage of total content served comes directly from the CDN cache without accessing the origin server. The data is shown in table form at the top of the page and in graphical form directly beneath the table. This data can be further broken down by date, region, and property (domain/subdomain).
• Custom Reports: You can create custom reports by selecting from the options on this page. Available options include starting and ending dates and times, breakdown by region or property, and whether to display as a graph or table.
• Usage Summaries ? This report shows CDN usage broken down by month and either region or property for all files currently served by the CDN. The fields included in this report are 95th Mb/sec, Peak Mb/sec, total number of megabytes of data served by the CDN, total number of hits, and Cache Efficiency. The data can be output as an HTML table or delimited CSV flat text file.
• URL Reports: This report displays data for the most commonly requested URLs of each property. You will be able to select a date and property, and view Top URLs by Megabytes, Top URLs by Hits, and Error URLs. The information can be output as an HTML table or CSV file.
• Filtered URL Reports: Reports can be filtered according to any criteria, such as file type. Filters are set up using the URL Filters link below the report link and can be applied to the Filtered URL Reports.

What Other Options are Available?

Other reporting and administration options are available:

• Real-Time Monitoring: This allows you to monitor CDN usage in real time as the data is transferred across the CDN. This data is viewable as a chart, world map, or table. You must have the Java Runtime Environment installed to view real-time statistics.
• Invalidation: This tool can be used to invalidate certain resources; for example, disabling port 80 on a particular property. Invalidations can be set using the Submit from Form link as well as managed and customized using the Manage link.
• Property Nicknames: This page displays a table containing a list of all properties, their respective origin servers, and their current nicknames. A link will be provided at the end of each line to change the nickname of that property; the nickname will then be used in place of that property's domain name for all reports.

Why NationalNet?

NationalNet has built a solid reputation by providing full-service hosting for its clients. Reliability, integrity, performance, and 24/7 support make NationalNet the ideal choice for your Content Delivery Network. To get started, contact NationalNet Sales today at 1-888-462-8628

For more information, contact us at sales@nationalnet.com