TCP developed for wired networks assumes congestion as the reason of packet loss. This assumption might not be true for infrastructure based wireless networks like CDMA2000 Packet Data Networks due to other reasons of packet loss like higher bit error rate, hard handoffs, limited bandwidth and multi-path fading. Hence knowing the reason of packet loss is important. We propose a TCP congestion window optimization mechanism for CDMA2000 Packet Data Networks that introduces new flags in TCP packet at PDSN to make both communicating entities aware of the reason of packet loss. Lossaware communicating ends initiate TCP slow start mechanism only if the reason of packet loss is congestion not data corruption.