The peak-hopper: a new end-to-end retransmission timer for reliable unicast transport

We analyze the RTO algorithm standardized for TCP and SCTP (V. Paxon et al., 2000) that is widely deployed in the Internet, referred to as the RFC2988-RTO in this paper. We briefly demonstrate three well-known problems of the RFC2988-RTO. We then develop a new RTO algorithm called the peak-hopper-RTO (PH-RTO) that eliminates the mentioned problems. Through extensive simulations in ns2, we evaluate the effectiveness of both RTO algorithms. The key advantage of the PH-RTO over the RFC2988-RTO is its predictability. Although the RFC2988-RTO often exhibits low loss detection times, it also exhibits frequent "RTO outliers" that can lead to exceptionally long loss detection times. The loss detection times of the PH-RTO are much more closely spread around the mean. Finally, our results show that the PH-RTO is much more robust to sudden delay spikes that are particularly common in wireless networks.