Bottleneck Diagnosis And Overcoming Of Offline Downloading

File downloading is one of the fundamental functions of the Internet.Most users in China suffer from low-quality connections,especially when downloading large files.To address this issue,hundreds of millions of China’s users have resorted to technologies that allow for “offline downloading”,where a proxy is employed to pre-download the user’s requested file and then deliver the file at her convenience.There are two typical implementations of offline downloading: the cloud-based approach and the smart AP(access point)based approach.Currently,there is a dispute over which approach better suits the best-effort Internet.This selection dilemma confuses the users of offline downloading services,especially those who have little expertise in Internet content delivery.A wrong choice may not only degrade the downloading user experience,but also reduce the offline downloading system’s usability.In order to solve the selection dilemma and improve the usability of offline downloading systems,this paper examines two typical implementations of offline downloading:(1)Using a large-scale dataset collected from a major cloud-based system and comprehensive benchmarks of popular smart APs,we find that the two approaches are complementary while also being subject to distinct performance bottlenecksin this paper.(2)Driven by these results,we design a solution for offline downloading redirection.The solution can resolve the performance bottlenecks found before.(3)According to the solution for offline downloading redirection,we implement a middleware called ODR(Offline Downloading Redirector,Site URL is http://odr.thucloud.com)to help users get rid of performance bottlenecks.ODR makes redirection decisions based on two types of information.First,after receiving an offline downloading request,ODR queries the content database of Xuanfeng to obtain the popularity information of the requested file.Then,ODR examines whether there is a potential bandwidth bottleneck by analyzing the user’s IP address,access bandwidth,storage device,and so forth.Finally,ODR makes redirection decisions based on two types of information.The evaluation results indicate that ODR is able to effectively overcome the performance bottlenecks.