Route-over vs mesh-under routing in 6LoWPAN

Transmission of IPv6 packets over Low-power Wireless Personal Area Networks (6LoWPAN) was considered nearly impractical once. The size of IPv6 packets is much larger than the packet size of the IEEE 802.15.4 data link layer. 6LoWPAN implements an adaptation layer between network and data link layers. Main purpose of the adaptation layer is to fragment and reassemble IPv6 packets. Implementation of the adaptation layer enhances the routing/forwarding decision of packets both network and adaptation layers. We can divide the routing scheme in 6LoWPAN into two categories: the mesh-under and the route-over, based on the routing decision taken on adaptation layer or network layer respectively. In this paper we perform an analytical comparison between these two schemes in terms of the packet/fragment arrival probability, the total number of transmissions and the total delay between source and destination. We also compare the selective fragment retransmission mechanism between mesh-under and route-over schemes.