A method for determining a route for communication across a network in real-time, said method including: collecting a set of network delay information at a caller device; storing the set of network delay information at the caller device; based on a stored set of network delay information at the caller device and the callee device, determining, by the caller device, in cooperation with the callee device, a set of relay server candidates to be used to relay data packets between the caller device and the callee device; and based on calculated round trip times for probing data packets set out and sent back, selecting, by the caller device in cooperation with the callee device, a shortest routing path as an active routing path for use for transporting a first data packet between the caller device and the callee device.