Edge Side Includes (ESI) could be making a comeback, thanks to supplier Akami, which is offering edge computing using ESI as part of its Edge Platform service for accelerating delivery of web pages.
ESI is a technique that can be applied to offload the work required to render web content onto servers that reside on the edge of a network. Although it was seen as a breakthrough technology when it appeared in 2001-2002, until now, interest among users has been muted.
Last month Akami extended its Edge Platform service to support Macromedia Flash, allowing users to increase the scalability of their websites by offloading streaming Macromedia content onto the Akami network.
Media firm Cantos is one example of a company using ESI to make better use of its web servers. It is using the technique to split the user interface (HTML) aspect of its web application, which needs to be created on-the-fly, from the business of uploading web content.
Usually, a web application, comprising a user interface and business logic, is deployed such that the application uses a single logical connection, or endpoint, to communicate across a network.
The idea of edge computing involves offloading the processing required to present the application's user interface onto a network of servers run by a third-party service provider across the network.
At Cantos, components of dynamic web pages are identified using ESI and cached on the Akami network. When a page is requested, it is rendered via the Akami servers, rather than from Cantos' web server infrastructure, reducing its workload.
Tim Jennings, research director at analyst firm Butler Group, said edge computing allows the user to retain control of the website, but the large-scale server infrastructure required to provide scalability is offloaded to a service provider.
"It is easy to scale up and down," he said, allowing a business to support peaks and troughs in demand. Such variations can occur on e-commerce sites during seasonal peaks or when there is a special offer.
However, edge computing is not a panacea for overworked servers. Jennings warned that only certain types of website are suitable for ESI.
Akami is one of the main proponents of edge computing, but Jennings said he expected other service providers to offer edge computing services to support users building applications engineered around a service-oriented architecture. SOAs fit particularly well in an edge computing environment, he said.
Thomas Mendel, principal analyst at Forrester Research, warned that ESI has drawbacks that could limit its use - the main one being that sites need to be redeveloped to support ESI.
He said most users were looking to develop websites to support more transactional activities, rather than simply speeding up presentation of information. These require application-specific accelerators to speed-up database requests, rather than speeding up the user interface, which is where ESI is focused.
However, he added, "ESI still has a use if you are looking to redesign your website."
What is ESI?
IBM, which has been working with Akami on edge computing services around its Websphere application server, said the basic concept of edge side includes involves the user interface being deployed "on the edge" and communicating back to the "enterprise" via web service calls.
By serving the user interface from an edge server, IBM said the user interface would no longer compete with back-end operations for server resources.
This was first published in March 2005