The Design, Implementation and Performance Evaluation of Xylophone: A Scalable QoS-enabled Wifi Locator Service
Xinyu Xing, Jianxun Dang, Shivakant Mishra, Xue Liu · 2010
WiFi access points that provide Internet access to users have been steadily increasing in urban areas. Different access points differ from one another in terms of services that they provide, including available upstream and downstream bandwidths, overall network capacity, open/blocked ports, security features, and so on. However, there is no reliable service available at present that can aid a user in selecting an access point from the many that are available. This paper presents xylophone, a WiFi locator service that enables users to select commercial hotspots in accordance with the current quality of service of hotspot access points. The primary research challenge in xylophone is how to accurately estimate current quality of service of various access points in an efficient manner without requiring any installation of special software on the access points, and not burdening the WiFi subscribers to perform any communication or computation intensive task. Xylophone has been extensively evaluated via a prototype implementation in an indoor testbed and in the Amazon’s EC2 platform. The evaluation demonstrates low latencies experienced by WiFi subscribers to measure DHCP connectivity, authentication and association process, and discover open/blocked ports. Also, the bandwidth measurement component of xylophone exhibits high measurement accuracy, low latency, high scalability, and minimal intrusiveness.