Modeling Network Coded TCP Throughput: A Simple Model and its Validation

We analyze the performance of TCP and TCP with network coding (TCP/NC) in lossy wireless networks. We build upon the simple framework introduced by Padhye et al. and characterize the throughput behavior of classical TCP as well as TCP/NC as a function of erasure rate, round-trip time, maximum window size, and duration of the connection. Our analytical results show that network coding masks random erasures from TCP, thus preventing TCP's performance degradation in lossy networks (e.g. wireless networks). It is further seen that TCP/NC has significant throughput gains over TCP. Our analysis and simulation results show very close concordance and support that TCP/NC is robust against erasures. TCP/NC is not only able to increase its window size faster but also to maintain a large window size despite the random losses, whereas TCP experiences window closing because losses are mistakenly attributed to congestion. Note that network coding only masks random erasures, and allows TCP to react to congestion; thus, when there are correlated losses, TCP/NC also closes its window.