Wireless multi-hop networks are scalable in that devices can easily connect to the network. Such scalability is also required in IoT. However, wireless multi-hop network mostly suffers from high probability of transmission failure due to interference, and nodes connected to the network often experience connection loss and subsequent segment loss which node mobility and routing update incur. Due to the fact that the congestion is not a sole reason for segment loss in wireless multi-hop network, the congestion control of TCP should consider momentary link instability, which unnecessarily reduces transmission speed. For this reason, this paper suggests adjustment of slow-start threshold (ssthresh) value which is used for congestion control algorithm. The adjustment algorithm is called adaptive ssthresh decision ASD algorithm that is to reduce unnecessary decrease of transmission speed in wireless multi-hop network.