Loss-Tolerant TCP (LT-TCP): Implementation and experimental evaluation

TCP is the ubiquitous transport protocol in the Internet. However, in a wireless ad-hoc environment where links are unreliable, TCP causes a number of performance issues. The key reason behind this is that TCP considers all packet losses to be due to congestion and reduces its send rate, which is not necessarily appropriate in a lossy ad-hoc environment. In prior work, we have designed Loss Tolerant TCP (LT-TCP) [1], [2], which extends TCP towards making it more efficient and robust in a wireless ad-hoc environment. LT-TCP uses Explicit Congestion Notification (ECN) and forward error correction (FEC) to mitigate the effects of random packet losses. The protocol uses these mechanisms to both distinguish between congestion and other losses, and recover from losses due to lossy wireless links. In this paper, we describe the implementation of LT-TCP in the Linux operating system kernel, and present and analyze initial performance results for the protocol on lossy links. Results show that LT-TCP provides much improved performance over TCP over lossy connections that model ad-hoc networks. In addition, it shows that performance of LT-TCP is nearly linear with loss rate, whereas TCP suffers disproportionately as loss rate increases. These promising implementation results point to further experimentation for LT-TCP, including a push towards Internet standards bodies.