Design and performance evaluation of a mechanism to share contents over broadcast channels

In this paper, we present a novel mechanism (Wireless Data Sharing, WDS) to share popular contents between a set of second-level (children) proxies connected to a parent proxy by means of a bandwidth limited, wireless, broadcast channel. The idea is as follows: when one of the children proxies requests a content from the parent proxy, the parent publishes the transmission of this content over a specific TCP connection between itself and the requesting child, so as to enable all the other children to capture it. Finally, the parent starts transmitting the content and the children may listen to the broadcast channel and sniff the content from the TCP connection. This allows users served by these proxies to decrease the time to access contents, without any additional bandwidth consumption. Furthermore, such a mechanism is able to decrease the load of the parent proxy. This work provides a detailed description of the architecture and functions of the WDS system, with explicit reference to the prototype we implemented. This prototype enabled us to evaluate the performance of the data sharing mechanism from both user and network viewpoints. In this regard, we carried out a measurement campaign in an IEEE 802.11 environment to evaluate the performance of the mechanism quantitatively. The results show that the WDS system guarantees not only bandwidth saving, but also lower content access latency with respect to the legacy proxy hierarchy system. In addition, the signalling overhead associated with the publishing mechanism proves to be very low.