FTP performance issue

Posted on 2009-12-21
Last Modified: 2013-12-02
Hi guys,

I have a head scratcher here.  One of my users is getting REALLY slow download speeds to my data center.

I have tested from here and 6 other locations and I consistently get speeds 12 times faster.

That customer can connect to our backup data center 30 miles away just fine.

The customer has brought in a second ISP service and still has the same issue, even though the new line is significantly faster.

Here's the catch.  The customer is in Panama.  My suspicion is that the two carriers use the same trunk and there is some sort of routing problem, but that thought has not sat well with the customer.

Here are my assumptions:
1.  Since my testing has consistently resulted in much better speeds than the customer is seeing, I'm assuming my firewall and network are ok.
2.  Since I tested directly to their server I assume that everything is ok with that system.
3.  I also assume that there isn't anything wrong with the data center since every other test I've run works fine.  I don't think they would filter out foreign traffic.

My question boils down to this:

Are there any further tests that I can run to try to isolate the issue?

So far, the thing that comes to mind is to run a tracert and compare the results between the two data centers and Panama.  

Thanks for your help!
Question by:jl542uop
    LVL 1

    Accepted Solution

    Has your customer tried downloading/uploading to/from a different workstation behind the same internet connection? From what I can gather the problem is isolated to a single machine rather than their environment. If it's a single machine and it works from another machine then the problem lies with the individual's machine. If everybody behind the same environment has the problem, then you'd have to start looking at their Router/Firewall blocking or throttling certain types of traffic (seeing you've already tried two seperate ISPs).

    You could always create an FTP Service on a different port (if your FTP software allows) and have the user connect to the new port instead of the default.

    Author Comment

    Good idea!  I'll try that.

    The other idea I had was to try to use a different FTP software, so I'm having him download and use CoreFTP to test with.

    On the different ports, could I just map that through our firewall using a port NAT?
    LVL 1

    Assisted Solution

    I am unsure what FTP Server you are using, but if it's IIS just setup another IIS FTP instance and change it away from the default port 21.

    The potential problem you might be facing then is that the Clients Firewall and your hosting centre Firewall might need additional ports opened which might not be as easy (depending on who maintains the firewalls).

    Anyway... post your findings. It would be good to know :)
    LVL 6

    Expert Comment

    Go download and run PingPlotter Pro from  for a few weeks it is free.  A very useful tool for this.  have the customer do the same.  It will help pinpoint any latency issues along the route and really show you what is up with the routers and paths to the sites.  it can do multiple paths and multiple targets in parallel and shows graphs in real time.

    It can run a much more robust traceroute that the CLI.

    A packet trace/capture from the FTP stream can show what TCP/IP is seeing and what the average RTT are during the transfer.  That will help as well...
    LVL 1

    Expert Comment

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