Content Delivery Networks (CDNs) allow sites and applications to draw files from common servers. This allows far more efficient caching, reduces bandwidth and disk space requirements on both the server and client sides.

The next logical step are Application Delivery Networks (ADNs). These are hosted application services like WordPress’ blogs (http://wordpress.com/), Ning social network (http://www.ning.com/), Shopify ecommerce (http://www.shopify.com/), LivePerson live support (http://solutions.liveperson.com/index.asp), Kayako Support (http://www.kayako.com/solutions/hosted-support-desk/), News Letter or Paper Hosting (http://www.our-hometown.com/). The challenge is to develop an architecture that allows you to take advantage of the hosted services while integrating them seamlessly into a site.

Advantages

• Security is the responsibility of the hosting company and application provider. They know the server and the application, they can prevent and recover from problems quickly and in all likelihood, without disrupting service.
• Server administration is virtually eliminated. Application installation and maintenance is not necessary.
• Reduction of support requirements.
• Scalability is less of an issue. It is assumed that the application providers have the infrastructure to support busy sites if necessary

• Distributing the applications to other companies increases the fault tolerance of the systme. If one application crashes, the others can still run.

• A CDN can be used to deliver the design files, as well as a the home page or portal into the system. This also increases the fault tolerance of the system.

• Engineering tends to be the most expensive part of site development. Purchasing the logic allows more money to be spent on sophisiticated design interfaces, or - amazing application integration.

• Rapid deployment of extremely complex sites.

Disadvantages

• Customization may be difficult, expensive, or impossible. This includes design and functionality. WYSIWYG.
• A layer is added into the support path. The application provider must perform requested support, the site provider is dependent on them.
• Induces recurring hosting costs, which may be significant.

Supporting Trends

• The increased use of open source applications and toolkits is definitely making this vision more possible.
• The skills of web professionals are increasing exponentially
• Bandwidth is becoming a valuable commodity
• Security has become extremely important, even for ’simple’ blogs
• Cooperation within the open source community, across all boundaries
• The ability to use CSS to control the pagelayout and design allows the application to deliver well-formed XHTML that can be presented as defined by CSS. This is the key to a successful integration. Furthermore, the CSS must be assembled in such a way that it is hierarchical and observes site, application, and possibly page specific requirements.

Opportunities

• Architecture definitions
• Multiskin/multitoolkit applications
• Education
• Innovative connections