Integration of QoS Parameters from IEEE 802.11s WLAN Mesh Networks into Logical P2P Overlays

Adopted in late 2011, IEEE 802.11s comes as the first industry standard to enable vendor-independent and inter-operable WLAN mesh networks. Featuring automatic device interconnection and routing, they provide a higher scalability, flexibility, and robustness compared to common centralized WLAN infrastructures. The 802.11s standard defines mandatory support of the Hybrid Wireless Mesh Protocol (HWMP) and Airtime Link Metric (ALM) for MAC-layer routing. While 802.11s covers the physical network underlay, Peer-to-Peer (P2P) protocols are an equivalent on the application level. In contrast to centralized client/server communication, they establish a fail-safe and scalable logical network overlay for, e.g., distributed content sharing, streaming, search, or synchronization. Thus, P2P networks exhibit many of the characteristics of physical WLAN mesh networks. It is obvious to consider joint solutions, where both technologies are combined to leverage future distributed local area wireless applications. Nevertheless, common P2P protocols, such as BitTorrent, do not consider the structure of the physical underlay while performing topology management. Furthermore, they are primarily designed to be used over wired communication networks such as large parts of the Internet. When deployed over WLAN mesh networks with their quickly varying channel conditions, BitTorrent shows severe performance drawbacks. We present a cross-layer approach based on 802.11s and BitTorrent, that optimizes application layer peer selection by considering the mesh standard's routing metric ALM. Our solution was implemented and evaluated in a real-world testbed. Results show that average download time can be reduced by up to 20% already in small network setups.