Multiple Layer Error Control over Wireless Links
George Xylomenos · 2007
In this paper we compare the wireless performance of TCP with or without selective acknowledgments and in the presence or absence of a reliable link layer protocol, in order to determine whether link layer error control remains beneficial for TCP variants with improved error recovery capabilities, such as TCP SACK. We also examine whether there are adverse interactions between the two protocol layers, that is, whether link layer error control degrades the congestion control performance of the transport layer, and whether transport layer error recovery degrades the error control performance of the link layer. Our results show that, even with TCP SACK, link layer error control remains critical for TCP performance over wireless links. Furthermore, our results show that with a TCP unaware link layer protocol we have a clear separation of concerns, whereby the link layer handles wireless losses and the transport layer handles congestion.