Segment losses due to intermittent connectivity and mobility lead to sub optimal performance of the Transmission Control Protocol (TCP). This is due to the fact that segment loss is considered as a binary signal for triggering congestion control and retransmission mechanisms at the TCP sender. In wired networks, segments are dropped due to congestion at the routers and the strategy of taking missed acknowledgment as an implicit signal for congestion control performs well. However, in wireless networks, segment losses are primarily due to mobility and transmission errors. Unlike many previous efforts, this paper proposes the design and implementation of Software Defined Network (SDN) assisted TCP which does not require the wireless Access Points (APs) to be TCP-aware and preserves end to end semantics. Further, no changes are required to be done in TCP protocol implementation at the end-hosts. The proposed approach utilizes the programmability provided by the SDN paradigm to intelligently trigger the spurious timeout detection and response algorithms, already implemented in standard TCP. The proposed approach is compared with the standard TCP and SDN assisted Zero Window based approach on Linux kernels using virtual data-plane switches and APs provided by the Mininet-WiFi platform. The implementation results establish the applicability of the proposed approach.

由于间歇性的连接性和移动性而造成的网段损耗导致传输控制协议（TCP）的性能欠佳。这是由于以下事实：段丢失被视为在TCP发送方触发拥塞控制和重传机制的二进制信号。在有线网络中，由于路由器的拥塞而导致网段丢失，并且将错过的确认作为拥塞控制的隐式信号的策略效果很好。但是，在无线网络中，网段丢失主要是由于移动性和传输错误。与以前的许多努力不同，本文提出了软件定义网络（SDN）辅助的TCP的设计和实现，该技术不需要无线接入点（AP）感知TCP，并保留端到端语义。进一步，在终端主机的TCP协议实现中无需进行任何更改。所提出的方法利用SDN范例提供的可编程性来智能地触发已经在标准TCP中实现的虚假超时检测和响应算法。使用Mininet-WiFi平台提供的虚拟数据平面交换机和AP，将该提议的方法与基于Linux内核的标准TCP和SDN辅助基于零窗口的方法进行了比较。实施结果确定了所提出方法的适用性。使用Mininet-WiFi平台提供的虚拟数据平面交换机和AP，将该提议的方法与基于Linux内核的标准TCP和SDN辅助基于零窗口的方法进行了比较。实施结果确定了所提出方法的适用性。使用Mininet-WiFi平台提供的虚拟数据平面交换机和AP，将该提议的方法与基于Linux内核的标准TCP和SDN辅助基于零窗口的方法进行了比较。实施结果确定了所提出方法的适用性。