I¹d like to jump in here and address this point: ³While I agree that timing information is important, I don't think it's going to be so commonly used that we need to add convenience features for it. Adding a few event listeners at the top of the document does not seem like a big burden.²
I work for a company that sells a web performance monitoring service to Fortune 1000 companies. To give a quick bit of background to the monitoring space, there are two basic ways to provide website owners with reliable performance metrics for their web site/applications. The first is to do active/synthetic monitoring, where you test the site using an automated browser from various locations around the world, simulating a real user. The second approach is called passive or real user monitoring, which captures actual visits to your site and records the performance of those users. This second approach is accomplished with either a network tap appliance sitting in the customers datacenter that captures all of the traffic that comes to the site, or using the ³event listener² javascript trick which times the client side page performance and sends it back to a central server. Each of these approaches has pros and cons. The synthetic approach doesn¹t tell you what actual users are seeing, but it consistent and easy to setup/manage. The appliance approach is expensive and misses out on components that don¹t get served out of the one datacenter, but it sees real users performance. The client side javascript timing approach gives you very limited visibility, but is easy to setup and universally available. This limited nature of the this latter javascript approach is the crux of why this ³Web Timing² draft is so valuable. Website owners today have no way to accurately track the true performance of actual visitors to their website. With the proposed interface additions, companies would finally be able to not only see how long the page truly takes to load (including the pre-javascript execution time), but they¹d also now be able to know how much DNS and connect time affect actual visitors¹ performance, how much of an impact each image/objects makes (an increasing source of performance issues), and ideally how much JS parsing and SSL handshakes add to the load time. This would give website owners tremendously valuable data is currently impossible to reliably track. -- Lenny Rachitsky Neustar, Inc. / Software Architect/R&D 9444 Waples St., San Diego CA 92121 Office: +1.877.524.8299x434 / lenny.rachit...@webmetrics.com / www.neustar.biz
