Efficient Transport in 2.5G3G Wireless Wide Area Networks

This paper has several contributions. First, we report that long sudden delays during data transfers are not uncommon in the GPRS wireless WAN. Long sudden delays can lead to spurious TCP timeouts and unnecessary retransmissions. Second, we show that the New Reno algorithm increases the penalty of spurious TCP timeouts and that an aggressive TCP retransmission timer may trigger a chain of spurious retransmissions. Third, we test how four widely deployed TCP implementations recover from a spurious timeout and notice that two of them have severe problems to recover. Finally, we discuss several existing ways to alleviate the problems.