Phase 3
Figure 16 shows the third phase of the evolution of a business-to-consumer network, with the static Web adopting a dynamic presentation method. The proxy server cluster has been enhanced to support the caching of dynamic Web content and assembly of page fragments written to comply with the Edge Side Includes (ESI) protocol. Rather than using server-side include mechanisms to build Web pages on the content servers and then propagating these client-specific, noncacheable, pages through the entire network, ESI mechanisms permit pages to be assembled from cached content at the edge of the network, thereby reducing bandwidth consumption and decreasing response time.
ESI mechanisms are crucial in this third-phase scenario, where each client receives a personalized home page from the Web site. The building blocks of these pages are retrieved from a series of WebSphere® Application Servers. Application servers containing sensitive business logic and ties to secure databases are isolated behind a firewall.