Packet Path Diversity for TCP File Transfer and Media Transport on the Internet

We study the performance of TCP-based media transport when combined with packet path diversity (PPD) in the Internet. We present a simple PPD-TCP transmission scheme where the acknowledgments (ACKs) from the receiver are duplicated and sent across independent network paths. We also investigate a PPD-TCP scheme where in addition to path-diversified ACKs on the backward path, packet path diversity is also used on the forward path. In order to keep the additional network load small only small probe packets are sent across the alternative path that carries the same TCP header information but not the payload. From the time difference between the arrival of the probe packet and the corresponding data packet at the receiver we derive the superior path and, if advantageous, switch the path for the data packets. For comparison purposes we also implement a PPD-TCP transmission scheme where both, acknowledgment and data packets, are duplicated and sent over different network paths. This scheme provides us with an upper bound of the performance improvements that we can obtain for a single flow compared to a corresponding single-path TCP transmission. The performance of the different PPD-TCP schemes is verified and compared to standard single-path TCP transmission using simulations. It is shown that all investigated PPD-TCP schemes greatly outperform standard single-path TCP transmission for file transfer and real-time media transport. Keywords— packet path diversity, multi-path transmission, TCP-based media transport