Bandwidth issues in the Sprint network

Robert D. Scott robert at
Mon Apr 7 22:58:25 UTC 2008

See if you can find a nother connector that can help with using iperf. Also,
make sure any system testing systems have tuned IP stacks. That info is also
linked from the iperf web page.

Robert D. Scott                 Robert at
Senior Network Engineer         352-273-0113 Phone
CNS - Network Services          352-392-2061 CNS Receptionist
University of Florida           352-392-9440 FAX
Florida Lambda Rail             352-294-3571 FLR NOC
Gainesville, FL  32611

-----Original Message-----
From: owner-nanog at [mailto:owner-nanog at] On Behalf Of
Scott Weeks
Sent: Monday, April 07, 2008 5:24 PM
To: nanog at
Subject: Re: Bandwidth issues in the Sprint network

--- braaen at wrote:

I am currently having problems get upload bandwidth on a Sprint circuit. I
am using a full OC3 circuit.  I am doing fine on downloading data, but
uploading data I can only get about 5Mbps with ftp or a speedtest.  I have
tested against multiple networks and this has stayed the same.  Monitoring
Cacti graphs and the router I do get about 30Mbps total traffic outbound,
but individual (flows/ip?) test always seem limited.  I would like to know
if anyone else sees anything similar, or where I can get help.  The
assistance I have gotten from Sprint up to this point is that they find no
problems.  Due to the consistency of 5Mbps I am suspecting rate limiting,
but wanted to know if I was overlooking something else.

I would not use one FTP session to test bandwidth.  The rate limiting may be
in the FTP software or other area of the computer.  Likewise, Speedtest
servers (in my opinion) are more marketing tools than testing tools.  Try
several similarly configured (but separate boxes) FTP servers
simultaneously.  If you see it go up by a factor of three you've found the

I have had to push my four OC-12s to Sprint to the max at times and get full
BW.  That's in Hawaii, but I imagine it's the same as other areas.


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