Wired Plain FTP Upload - Unexpected Throttling

If I try to upload a 4.48 MB executable file from my XP SP3 workstation (192.168.100.49) to a DMZ workstation (10.0.0.60) via a gateway (192.168.100.1) over 100 Mbit Ethernet using FlashFXP 4.2.5 (build 1813) or 4.3.0 RC (build 1910) then I see apparently throttled upload speeds averaging between 270–375 kB/s. If I download the same file afterwards I get around 3.86 MB/s. If I upload using FileZilla Client or a Windows FTP Web Folder then the speed is around 4 MB/s.

I cannot see any active throttling settings in FlashFXP. I have only Client for Microsoft Networks, Link-Layer Topology Discovery Responder and Internet Protocol (TCP/IP) items on my LAN connection. Anti-Virus is disabled (Kaspersky Endpoint 8). The firewall on the gateway has no explicit or dynamic throttling settings. The same outcome occurs if I use the portable FlashFXP client. If I upload with FlashFXP to an external site via FTPS then I can easily exceed 700 kB/s.

An example upload log follows:

FlashFXP 4.3.0 (build 1910)
Support Forums http://forum.flashfxp.com
[15:40:10] Winsock 2.2 -- OpenSSL 1.0.1c 10 May 2012
[15:40:21] [R] Connecting to Download Site -> IP=10.0.0.60 PORT=21
[15:40:21] [R] Connected to Download Site
[15:40:21] [R] 220 Sol Microsoft FTP Service (Version 5.0).
[15:40:21] [R] USER Administrator
[15:40:21] [R] 331 Password required for Administrator.
[15:40:21] [R] PASS (hidden)
[15:40:21] [R] 230-WARNING! Authorised Users Only
[15:40:21] [R] 230-
[15:40:21] [R] 230-LJ Create Ltd Download Server
[15:40:21] [R] 230 User Administrator logged in.
[15:40:21] [R] SYST
[15:40:21] [R] 215 Windows_NT version 5.0
[15:40:21] [R] FEAT
[15:40:21] [R] 500 'FEAT': command not understood
[15:40:21] [R] PWD
[15:40:21] [R] 257 "/" is current directory.
[15:40:21] [R] TYPE A
[15:40:21] [R] 200 Type set to A.
[15:40:21] [R] PASV
[15:40:21] [R] 227 Entering Passive Mode (10,0,0,60,11,163).
[15:40:21] [R] Opening data connection IP: 10.0.0.60 PORT: 2979
[15:40:21] [R] LIST -al
[15:40:21] [R] 125 Data connection already open; Transfer starting.
[15:40:22] [R] 226 Transfer complete.
[15:40:22] [R] List Complete: 3 KB in 0.20 second (3.9 KB/s)
[15:40:23] [R] CWD Damian
[15:40:23] [R] 250 CWD command successful.
[15:40:23] [R] PWD
[15:40:23] [R] 257 "/Damian" is current directory.
[15:40:23] [R] PASV
[15:40:23] [R] 227 Entering Passive Mode (10,0,0,60,11,164).
[15:40:23] [R] Opening data connection IP: 10.0.0.60 PORT: 2980
[15:40:23] [R] LIST -al
[15:40:23] [R] 125 Data connection already open; Transfer starting.
[15:40:23] [R] 226 Transfer complete.
[15:40:23] [R] List Complete: 556 bytes in 0.12 second (0.5 KB/s)
[15:40:25] [R] DELE FileZilla_3.6.0.2_win32-setup.exe
[15:40:25] [R] 250 DELE command successful.
[15:40:25] Deleted 1 File and 0 Folders (4.48 MB) in 0.01 second
[15:40:27] [R] TYPE I
[15:40:27] [R] 200 Type set to I.
[15:40:27] [R] SIZE FileZilla_3.6.0.2_win32-setup.exe
[15:40:27] [R] 550 FileZilla_3.6.0.2_win32-setup.exe: The system cannot find the file specified.
[15:40:27] [R] PASV
[15:40:27] [R] 227 Entering Passive Mode (10,0,0,60,11,165).
[15:40:27] [R] Opening data connection IP: 10.0.0.60 PORT: 2981
[15:40:27] [R] STOR FileZilla_3.6.0.2_win32-setup.exe
[15:40:27] [R] 125 Data connection already open; Transfer starting.
[15:40:42] [R] 226 Transfer complete.
[15:40:42] Upload: FileZilla_3.6.0.2_win32-setup.exe 4.48 MB in 14 seconds (322.9 KB/s)
[15:40:42] [R] SITE UTIME /Damian/FileZilla_3.6.0.2_win32-setup.exe 20130108150746 20130108150746 20130108150746 UTC
[15:40:42] [R] 500 'SITE UTIME /Damian/FileZilla_3.6.0.2_win32-setup.exe 20130108150746 20130108150746 20130108150746 UTC': command not understood
[15:40:42] [R] TYPE A
[15:40:42] [R] 200 Type set to A.
[15:40:42] [R] PASV
[15:40:42] [R] 227 Entering Passive Mode (10,0,0,60,11,166).
[15:40:42] [R] Opening data connection IP: 10.0.0.60 PORT: 2982
[15:40:42] [R] LIST -al
[15:40:42] [R] 125 Data connection already open; Transfer starting.
[15:40:42] [R] 226 Transfer complete.
[15:40:42] [R] List Complete: 556 bytes in 0.19 second (0.5 KB/s)
[15:40:42] Transfer queue completed
[15:40:42] Transferred 1 File (4.48 MB) in 15 seconds (313.4 KB/s)

Hello,

If you transfer the same exact file twice in a row is the second transfer faster, if so by how much?

What version of Windows are you using?

Is the file you're uploading located on a local hard drive, removable (flash/usb) drive, or network share?

In FlashFXP, in the Preferences dialog / Connection section (or per site if configured) what are the TCP/IP buffer sizes for Send and Receive?

If you turn on the transfer graph (under the View menu > Graph) is the transfer speed consistent?

Every transfer attempt is around the same speed, independent of whether it is the first time of uploading after program start or a follow-up attempt.

The OS is Windows XP Professional SP3 on x86 with 3 GB RAM and 2.26 GHz Intel Core Duo

The file was being uploaded from My Documents on local drive C:\

The TCP/IP buffer sizes started out at 32 kB/s Send and 64 kB/s Receive and I have already tried the default and auto options for both settings without seeing the transfer rate improve.

The transfer speed gets to the range stated within a second or so and then hovers consistently within that range until transfer completion. Typically averaging 320 kB/s.

What about uploading not-executable file? like a movie file or a zip.

The original file I experienced the problem on was a 3.64 GB .ISO. The reduced upload speed also happens for a 6.45 MB .TXT file. Both download at full speed. A similar throttled upload is experienced with other workstations in the DMZ group. I can upload at full speed to other workstations on the same subnet, just not via the gateway with FlashFXP.

If you were connected to the FTP server while changing the TCP/IP buffer size did you reconnect? This setting can't be changed for active connections and only applies to the next connection attempt.

The network stack in Windows XP is quite iffy. This can boil down to everything from the network card drivers, bad ethernet cables, corrupted network protocol stacks, network protocol registry tweaks, etc.

Now you're probably wondering how this could be that only FlashFXP is slow while all the other applications you tested were full speed. A lot of this has to do with the underlying framework of how these applications were written.

I would try playing with the TCP/IP buffer sizes again, try 8, 64, 128, 256.

There should be a noticeable difference between the optimal and non-optimal buffer sizes.

You might also want to checkout SG TCP Optimizer, not so much to change your settings but just to review them and perhaps find any that don't look right, sometimes these settings can get changed from the windows default. The windows default works best 90% of the time.

I just tried various Send TCP/IP Buffer Sizes with disconnects between and discovered that for all under 64 kB/s the slow transfer happened. As soon as I used 64 kB/s or above the transfer speed jumped to 6.45 MB/s. It doesn't matter what setting I use for Receive, that seems to always download at full rate. I start to wonder if this is a combination issue with the hardware firewall. However, I now have a means of getting the expected upload rate over the local network.

I tried SG TCP Optimizer, which showed that the majority of my current settings are undefined and so presumably OS defaults. I gave it a go on the optimal settings for 100+ Mbit with a reboot but still needed to set at least 64 kB/s in FlashFXP's Send TCP/IP Buffer setting to avoid limited FTP upload.

Thanks for the update and that is great news, I am so glad that solved your problem.