  In this paper, we focus on the experimental evaluation of TCP over the High
Speed Downlink Packet Access (HSDPA), an upgrade of UMTS that is getting
worldwide deployment. Today, this is particularly important in view of the
"liberalization" brought in by the Linux OS which offers several variants of
TCP congestion control. In particular, we consider four TCP variants: 1) TCP
NewReno, which is the only congestion control standardized by the IETF; 2) TCP
BIC, that was, and 3) TCP Cubic that is the default algorithm in the Linux OS;
4) Westwood+ TCP that has been shown to be particularly effective over wireless
links. Main results are that all the TCP variants provide comparable goodputs
but with significant larger round trip times and number of retransmissions and
timeouts in the case of TCP BIC/Cubic, which is a consequence of their more
aggressive probing phases. On the other hand, TCP Westwood+ provides the
shortest round trip delays, which is an effect of its unique way of setting
control windows after congestion episode based on bandwidth measurements.
