Bandwidth issues in the Sprint network

Frank Bulk frnkblk at
Wed Apr 9 14:28:40 UTC 2008

Does anyone know of bootable Linux CD with iperf on it?


-----Original Message-----
From: owner-nanog at [mailto:owner-nanog at] On Behalf Of Mike
Sent: Wednesday, April 09, 2008 9:05 AM
To: nanog at
Subject: Re: Bandwidth issues in the Sprint network

On Tue, Apr 8, 2008 at 9:19 AM, Brian Raaen <braaen at> wrote:
> I have been using the Java based versions of the speed test.  At this
point I
>  have had some Sprint people get in contact with me so I will see what
>  find.  Thank you for all your help to everyone.
>  --
>  Brian Raaen
>  Network Engineer
>  braaen at
> > On Monday 07 April 2008, you 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
>  tested against multiple networks and this has stayed the same.
>  Cacti graphs and the router I do get about 30Mbps total traffic outbound,
>  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.
>  to the consistency of 5Mbps I am suspecting rate limiting, but wanted to
>  > know if I was overlooking something else.
>  >
>  > --
>  > Brian Raaen
>  > Network Engineer
>  > braaen at
>  >

Most of the speed test sites on the Internet basically issue a HTTP
GET request to a server and time the download. For upload they utilize
a HTTP POST via a CGI script and time that. The main issue I have with
these speed tests is that they only use a single TCP session for data
transfer, which is fine if you have a large or self adjusting TCP
window size and a relatively low latency link.

However for high capacity links, it is unlikely (but possible) that
you are planning to use a single TCP session and consume all the
available capacity. Realistically you will have a few dozen
server/applications/users and produce hundreds/thousands of TCP
sessions which will fully utilize the link.

For our PtP customers that have concerns regarding capacity, I
generally they suggest setup iperf at both ends and run a few tests
with multiple TCP sessions so they can independently verify. Hopefully
Sprint will take your concerns to heart and assist you with testing.

-Mike Gonnason

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