TCP/IP Send-Q fills up

I have a QNX box talking to a Windows XP box through TCP/IP over Ethernet link. The connection is noisy and I see some packet losts, retransmissions happening on the link. After a while QNX box stops sending any packets and Send-Q buffer start increasing in size. QNX box still responds with ACKs to received packets from the Windows XP box.

Could anyone tell me what could be the reason for this?


The other end isn’t reading (it’s recv Q has filled) and therefore
the window it’s advertising on the wire is 0.