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Windows 8 won't be a battery killer, Microsoft says


Despite its live tiles notifying a user of a new email, tweet or data from the Internet, Microsoft’s upcoming flagship operating system Windows 8 will be no battery killer. Ryan Haveson, a group program manager on the User Experience team, said power consumption was one of their top considerations in developing the Metro-style live tiles. "In Windows 8, we set out to design a notifications platform that would provide at-a-glance information, without all the performance and battery life concerns that face traditional plugin and gadget-based models. To that end, every design decision we made was viewed through the lens of performance and battery life efficiency," he said in a blog post. He said they built the Windows Push Notifications Service to make it easy for app developers to create live tiles without having to write complicated network connectivity code. Windows will also use standard web technologies such as HTTP POST, making it easy for developers to integrate notifications based on their existing web services. “The result is a notifications platform that delivers at-a-glance information while allowing you to install as many apps as you want without worrying about the impact on performance or battery life," he said. According to Haveson, the setup has a developer’s app sending XML tile data to the Windows Push Notification Service (WNS) via a simple HTTP POST, “and then we take care of the rest." Under Windows 8, he said all the code for connecting, retrying, authentication, caching, rendering, and error handling “is done in a uniform and power-efficient way." Haveson also said Windows 8 will use a push-based service instead of polling for data, which he said would consume battery life quickly. “(T)he value was clear: developers would get super-efficient real-time notifications to their customers for free, without having to build or maintain their own persistent connections to the client," he said. When there is an update, the app service sends a notification to WNS, which pushes the notification down to the client. Once it is time to show the tile update on the Start screen, the OS fetches that image from the app service based on the URL contained in the notification XML. Once the notification and the image are downloaded, the app renders the live tile based on the template specified in the XML, and presents it on the Start screen. “To ensure that developers did not have to write complex caching and retry mechanisms for when the PC is not connected (e.g. if it is a laptop that is sleeping), we cache one notification per app in the WNS cloud until the next time that PC is online," Haveson said. He also said they are separating the notification payload from the image payload as a typical notification XML is less than 1KB of data, but an image can be up to 150KB. “Separating these allowed us to save significant network bandwidth for scenarios where there is a lot of duplication of the images. For example, the image for a tile may be a profile picture of a friend, which your PC can download once and cache locally to be reused. Separating the notification from the image also allowed us to be smart about discarding unused notifications before we go through the expense of downloading the image," he said. “If my device screen is off and is sitting in my bedroom while I am at work, there is no point in downloading images for tiles that will just be replaced by subsequent updates before the next time I use the device," he added. Anonymous authentication system Haveson said Microsoft will use an “anonymous" authentication system to secure the communications channel between the app service and the tile on the Start screen. Apps and app services also authenticate when communicating with WNS. Authenticating both connections to WNS helps to protect against abuse of live tile updates, such as spoofing attacks. “The authentication mechanism used by WNS explicitly ties the application and service together in a way that keeps other applications (or nefarious individuals) from sending content to a tile that they do not own. And of course, all communication takes place over a secure channel," he said. Also, the anonymous authentication system prevents the developer of the app from using the notification pipeline to discover one’s Windows Live ID, system info, or location. Nearly 90M tile updates a day Haveson said Microsoft added metrics in the new Task Manager to allow one to keep track of how much bandwidth the tile platform is consuming for each application. At present, he noted Windows 8 was sending almost 90 million tile updates per day, “and we are not even at beta yet!" He said the notifications started at zero on Sept. 12, spiked to about 64 million on Sept. 16, and gradually climbed to the 80- to 85-million range in early October. — TJD, GMA News

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