Summary
FTP uploads using Windows Explorer and Internet Explorer are slower than FTP uploads with the command prompt. This is because Windows Explorer and Internet Explorer have a default send buffer size of 4096 bytes. Due to this default size, FTP uploads initiated from Windows Explorer and Internet Explorer will be slower when compared with command prompt.
Note: This buffer size is not configurable in current versions of Windows.
More Information
ftp.exe with command prompt does have a configurable send buffer size. To specify a custom buffer size in the command prompt, type in:
ftp.exe -x:buffersize in bytes (for example: 8192)
You will then see the following message:
SendSocketBuffer: 8192 Bytes
The send buffer size is now set for this session and you can then proceed with the FTP connection.
