windows - Slow CIFS file copy over routed network with different bandwidths

We have a long distance 100 Mbit/s link between sites over internet
Ping over vpn:
Reply from : bytes=32 time=38ms TTL=60
Reply from : bytes=32 time=38ms TTL=60

Speed of intersite file copy is near 1mb/sec if Server(w2k8) and client(W7) both have 1Gb Full Duplex LAN connections

If we change one or another host's NIC mode to 100Mb Full Duplex then speed of file copy grows up to 5mb/sec

Problem is same with differrent drivers, hardware, OS versions, tcp/NIC/ethernet settings (flow control, offloading, chimney, ECN, MTU, RSS, tcp windowsize autotuning)

Certainly we cannot accept slowing down one-side link as workaround
Can we have fast intersite file copy and fast LAN connection simultaneously?

Jumbo is disabled on both ends

ping -f -l 1200 server
Reply from 192.168.1.2: bytes=1200 time=39ms TTL=123
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 38ms, Maximum = 39ms, Average = 38ms

ping -f -l 8000 server
Packet needs to be fragmented but DF set.
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

ping -l 8000 server
Reply from 192.168.1.2: bytes=8000 time=42ms TTL=124
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 42ms, Maximum = 42ms, Average = 42ms