I have a Windows FTP Server running on a 15 Mb/s DS3. When I connect to the server from a faster connection (40 Mb/s) and download from the server with 1 conenction I get roughly 50% of the 15 MB/s connection Speed (8 Mb/s) and when I run 2 connections at the same time I can max the conenction speed out. When I run a speed test from a speed test site I recieve roughly 15 MB/s up and down. The same goes for upload speeds internally I can upoload at about 50% of the server's connection speed. I uploaded a 50 meg file at 58.24 Mb/s.

The problem is when I upload from the internet I am getting much slower speeds. Mostly around .2 Mb/s from a 40 Mb/s internet connection. There are no proxy servers between any of the connections.

How can I increase/troubleshoot the upload connection speed?


  • To clarify, when you upload from another internet connection to your DS3, you're only seeing .2Mb/s? – Matt Simmons Sep 27 '09 at 4:32
  • I did some bad math and when I recalculated after some sleep my upload speed from the fast internet connection was 1.56 Mb/s. I also tested from my home internet connection and my upload speed was .5 Mb/s (ISP limit = .5Mb/s) – Joe Sep 27 '09 at 13:17

I'm not too certain about how you're interpreting some things, but first off, the max speed you'll ever get from the internet here is 15 mbps, as the chain is only ever going to be as strong as it's weakest link.

There may be no proxy servers, but there will be routers between the 2 boxes, which will all give accumulated latency. Depending on the path that traffic takes from your upload machine, through the internet, to the FTP server, this could potentially be quite high. Also, if one of the intermediate routers is bandwidth throttled, this will contribute further.

A troubleshooting step here might be to try some traceroute/tracert commands from one to the other. You'll need to run a few tests to rule out transient conditions, but overall you should get a reasonably good picture of how many hops the connection requires, as well as if any of the intermediate points are inordinately slow.

Regarding your 40 mbps connection, that might not be all it seems. If it's ADSL or similar, you're going to have slower upload speeds as a consequence of the technology. Your ISP (or even one of the intermediate points) may be implementing some form of bandwidth shaping. All manner of evil could be going on.

Your NIC may also be at fault. I have found in the past that certain NICs from certain manufacturers do not behave themselves well in sustained upload scenarios, so that's another one to add to the list of things that might be going wrong.

  • The 40 Mb/s is ethernet and the speed test run from a website both before and after the upload test shows about 40. As far as latency goes would that effect upload and download differently? We recieved a complaint from a customer stating this issue and when we tested from an outside source we found it to be true. When testing from a local server on a seperate subnet passing through the same firewall we had a sustained connection at 58 Mb/s. My ideal scenerio would be recieving at about 8 Mb/s and not the 1.5 Mb/s I am currently getting. – Joe Sep 28 '09 at 0:40

FTP uses TCP for the communication. Have you considered that perhaps it's the latency that is affecting your FTP speed?

TCP was designed to slow down as latency increases. So the higher the latency the slower the throughput.

Do a ping test to check the latency between your 2 end points.

For example: at 10ms latency, you will only be able to achieve 10Mbps out of your 40Mbps link.

At 50ms the maximum throughput drops to 5Mbps.

There are many commercial products dealing with this problem, FileCatalyst is one of them: http://www.filecatalyst.com/starting-points/fast-file-transfer

There are also some opens source solutions, http://www.filecatalyst.com/open-source-fast-file-transfers

Full Disclosure: This user is an employee of FileCatalyst.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy