This paper presents a dynamic buffer aided medium access control protocol for asymmetric traffic conditions in an IoT network, where the IoT devices send data to a wireless access point (WAP) which then forwards the data to the network fusion center. Specifically, the control frame structures of conventional carrier sense multiple access with collision detection (CSMA/CD) protocol are modified for incorporating the traffic asymmetry of the network. The devices and WAP are assumed to have full duplex abilities to support continuous sensing of the channel. The sensing performance of the considered system is derived for arbitrary number of devices in terms of probabilities of false alarm and miss detection. Moreover, the throughput of the network is also obtained. Simulation results show that the proposed cross-layer design achieves significant throughput improvement while incorporating traffic asymmetry of the network.