How to measure network transmit speed?

FTP speed restricted by its limitation. You cannot rely on the result made by FTP, especially when you transmit data with using high speed network.
Secondly, to avoid disk I/O bottlenet when performing network speed measurement, you should use dd from /dev/zero to /dev/null
In this case, I use a pipe file as source data and used ssh to read the file. The result likely consistent.

Data size 1024 MB

Case A 100/NIC to 100/NICĀ  = 94 sec
Case B 1000/NIC to 1000/NIC = 27 sec
Source Machine – machine1 (data)

1. Make a pipe file in /tmp
mknod /tmp/applepipe p

2. dd 1GB data into the pipe file
dd if=/dev/zero bs=8k count=128000 of=/tmp/applepipe

Client Machine ( Read )
timex ssh machine1 “dd if=/tmp/applepipe bs=8k”|dd of=/dev/null bs=8k