A TCP Decoupling Based SDN Architecture for Asymmetric Networks

In traditional TCP (Transmission Control Protocol), we commonly acquiesce in that the uplink and downlink paths of TCP sessions are symmetric. But in practice, in wireless communication systems, such as VLC (Visible Light Communication), mmWave, WiFi, or LTE systems, and even in wired systems due to asymmetric routing problems or other reasons, paths for uplink and downlink transmission in TCP sessions are asymmetric. The asymmetry can be reflected in bandwidth, delay, packet loss differences between uplink and downlink paths, and the mismatch between uplink and downlink paths may cause performance degradation on the performance of TCP. Decoupled TCP breaks through TCP's limitation to a unidirectional link, and allows users to fully utilize network resources. In this paper, we analyze the necessity and benefit of TCP decoupling. Then we propose a TCP decoupling based SDN (Software Defined Network) architecture for asymmetric networks and apply a modified Dijkstra's shortest path algorithm to determine the optimal uplink and downlink. Last, we prove that Decoupled TCP and the TCP decoupling based SDN architecture can improve the performance of TCP sessions in different asymmetric scenarios by simulation.