Performance By Design

This is a continuation of a series of blog entries on this topic. The series starts  here . The YSlow model of web application performance, depicted back in Equations 3 & 4 in the previous post , leads directly to an optimization strategy to minimize the number of round trips, decrease round trip time, or both. Several of the YSlow performance rules reflect tactics for minimizing the number of round trips to the web server and back that are required to render the page. These include designing the Page so there are fewer objects to Request,  using compression to make objects smaller so they require fewer packets to be transmitted, and  techniques for packing multiple objects into a single request.  For example, the recommendation to make fewer HTTP requests is in the category of minimizing round trips. YSlow rules regarding image compression or the use of “minified” external files containing JavaScript and CSS are designed to reduce the size of Response me...

This is a continuation of a series of blog entries on this topic. The series starts here . In this blog entry, I start to dive a little deeper into the model of web page response time that is implicit in the YSlow approach to web application performance. As depicted in Figure 3, the HTTP protocol defines a simple Request:Response sequence for accessing a document, identified by its Universal Resource Identifier (URI). The web browser issues a GET Request for the resource, receives a Response message in reply, and then composes and renders the document it received inside the web browser. Figure 3. A GET Request issued from the web browser triggers a Response message from the server, which is received by the web client where it is rendered into a web page. This simple picture leaves out many of the important details of the web protocols, including the manner in which the web server that can respond to the GET Request is located using DNS, the Internet Protocol’s (IP) Domain...