As part of UMTS protocol suite radio link control layer is indeed required in order to hide the errors caused by the imperfection of wireless links due to multipath propagation to higher layers. The persistent degree of retransmission in RLC has significant impact on Transmission Control Protocol(TCP) performance in mobile/wireless communication. We studied the performance of RLC by developing the analytical model of RLC retransmission mechanism. Our study showed that by limiting the maximum retransmission threshold the round trip time for a TCP segment in wireless link is bounded in a certain value but the TCP segment loss probability varies rapidly as wireless link condition changes. On the other hand without limiting the transmission threshold we got a certain TCP segment loss probability but the TCP round trip time varies as the wireless link condition changes. By well knowing the wireless link condition we can determine the optimal value of the retransmission threshold to maintain the TCP performance still high.