TCP Hybla: a TCP enhancement for heterogeneous networks

TLDR

TCP connections over terrestrial or satellite links suffer from longer RTTs, making them less efficient than wired connections in heterogeneous networks. The paper proposes TCP Hybla to mitigate the RTT‑dependent performance loss in heterogeneous networks. TCP Hybla is derived from an analytical study of congestion window dynamics in TCP Tahoe, Reno, and NewReno, leading to modifications that eliminate RTT dependence; its performance is validated through simulations on ideal and realistic network topologies, comparing against standard TCP under congestion and loss. TCP Hybla consistently outperforms standard TCP, markedly reducing penalties for wireless and satellite links, while preserving end‑to‑end semantics and compatibility with other enhancements. © 2004 John Wiley & Sons, Ltd.

Abstract

Abstract In heterogeneous networks, TCP connections that incorporate a terrestrial or satellite radio link are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). To cope with this problem, a new TCP proposal, the TCP Hybla, is presented and discussed in the paper. It stems from an analytical evaluation of the congestion window dynamics in the TCP standard versions (Tahoe, Reno, NewReno), which suggests the necessary modifications to remove the performance dependence on RTT. TCP Hybla performance is firstly evaluated in the case of an ideal channel, with good correlation between analytical and simulation data. Then, more realistic situations, which require the adoption of a benchmark network topology and a careful ns‐2 simulation set‐up, are examined. In particular, TCP Hybla performance is compared with that achievable by TCP standard in the presence of congestion and link losses, either separately or jointly considered. In all the examined cases, the superiority of TCP Hybla is evident, as it greatly reduces the severe penalization suffered by wireless, and especially satellite, TCP connections. Finally, it is worth noting that TCP Hybla does not infringe the end to end semantics of TCP and is compatible with other promising enhancements. Copyright © 2004 John Wiley & Sons, Ltd.