We study, using queuing, control and bifurcation theory, nonlinear fluid models of TCP Reno with Drop-Tail. In an intermediate buffer regime, we show that the system loses stability as link capacity or the feedback delay increases. With small buffers, a simple model for bursty traffic highlights the loss of local stability via a Hopf bifurcation when the buffer sizes, or thresholds for dropping packets in queue policies, increase. Finally we offer some guidelines, for a threshold-based queue policy to ensure stability of the queues and low-latency in the network. Packet-level simulations serve to corroborate the analysis and the proposed guidelines. © 2012 IEEE.