Thanks a lot "yairi" and "ingvar_j" for your response. Finally I was able to achieve ~20 Gbs on FDR.
with
OFED : MLNX_OFED_LINUX-2.0-3.0.0 (OFED-2.0-3.0.0)
Firmaware: 2.30.3000
Infiniband card type: x4 FDR, Rate: 56Gbps
CDM: netperf -H 192.168.180.101 -t TCP_STREAM