Connection-oriented communication devices are provided with round trip time estimation. An exemplary method is provided for communicating between first and second communication devices over a wide area communication network. The first communication device sends a Round Trip Time (RTT) packet comprising a timestamp to the second communication device. The second communication device receives the RTT packet, copies the timestamp into a reply RTT packet and sends the reply RTT packet to the first communication device. The first communication device receives the reply RTT packet and determines a current Round Trip Time based on a difference between the timestamp and a current time. The current Round Trip Time is optionally processed by a congestion avoidance and control algorithm. An application can control a size of a queue based on conditions of the wide area communication network.