TCP Non-Renegable Selective Acknowledgments (NR-SACKs) and benefits for space and satellite communications

Fan Yang (1) , Paul D. Amer (1) , Si Quoc Viet Trang (2, 3) , Emmanuel Lochin (2, 3)

1 CIS - Department of Computer and Information Sciences [Newark]
2 ISAE-SUPAERO - Institut Supérieur de l'Aéronautique et de l'Espace
3 DISC - Département d'Ingénierie des Systèmes Complexes

TCP is designed to tolerate reneging. This design has been challenged since (i) reneging rarely occurs in practice, and (ii) even when reneging does occur, it alone generally does not help the operating system resume normal operation when the system is starving for memory. We investigate how freeing received out-of-order PDUs from the send buffer by using Non-Renegable Selective Acknowledgments (NR-SACKs) can improve end-to-end performance. This improvement results when send buffer blocking occurs in TCP. Preliminary results for TCP NR-SACKs show that (i) TCP data transfers with NR-SACKs never perform worse than those without NR-SACKs, and (ii) NR-SACKs can improve end-to-end throughput when send buffer blocking occurs. Under certain circumstances, we observe throughput increasing by using TCP NR-SACKs as much as 15% and particularly over long-delay links such as GEO satellite links. The tradeoff for this potential gain is a change to the semantics of the TCP send buffer requiring the more complex management of non-contiguous PDUs. We investigate potential application performance gains when TCP receiver implements NR-SACKs and present empirical results on a real satellite link in the Centre National d'Études Spatiales (CNES) France's agency responsible for shaping and implementing its space policy in Europe.

Mots clés: Satellite communications; TCP; TCP Reneging; Selective Acknowledgment

Domaines: Réseaux et télécommunications [cs.NI]

Fan Yang, Paul D. Amer, Si Quoc Viet Trang, Emmanuel Lochin. TCP Non-Renegable Selective Acknowledgments (NR-SACKs) and benefits for space and satellite communications. Fifth Federated and Fractionated Satellite Systems Workshop, Nov 2017, Toulouse, France. ⟨hal-02549760⟩