A novel approach to WLAN mesh interworking with multiple mesh portals

In this paper we study IEEE 802.11s-based wireless local area network(WLAN) mesh interworking with external LANs. Interworking with multiple mesh portals is necessary not only for network reliability but also for load balancing and increased throughput. In case, however, two or more mesh portals connect the mesh to one external LAN segment, broadcast loops may occur and the IEEE 802.1D bridging protocol may cause the LAN ports of mesh portals to be closed, which results in interworking with the LAN through only one mesh portal. To enable multiple portals in WLAN mesh interworking, we propose a new architecture for mesh portals to implement all but the port blocking function of IEEE 802.1D bridge; thus allowing bridge protocol data units (BPDUs) to be transparently forwarded inside the mesh network. Our proposal is to eliminate the formation of broadcast loops while enabling multiple mesh portals to interwork with the same external LAN segment. This can be achieved by filtering frames at mesh portals making use of new fields we introduce in the portal announcement information element and mesh header so that no frame can be transmitted from a mesh portal to another portal more than once when both mesh portals are connected to the same LAN segment.