Analysis of TCP and DTN Retransmission Algorithms in Presence of Channel Disruptions

“Challenged Networks” often violate the TCP design key assumption of continuous path availability from the source to the sink node. These networks are the preferred target of Delay/Disruption Tolerant Networking (DTN), which aims at providing a more robust network architecture. Against disruptions, however, even standard TCP offers a certain level of robustness, through its many retransmission algorithms. The aim of the paper is to present a comparative analysis of the TCP and DTN Bundle protocol retransmission algorithms triggered by channel disruptions. This analysis provides the reader with a comprehensive view of the many mechanisms involved and a first assessment of their impact on some performance metrics. Although DTN put on top of TCP clearly offers higher resilience against long disruptions, TCP itself can provide a certain level of robustness, provided that the many retransmission parameters are properly set. The analysis is completed by some numerical evaluations on a GEO satellite channel obtained by means of a Linux testbed.