[103913] in North American Network Operators' Group
Re: Bandwidth issues in the Sprint network
daemon@ATHENA.MIT.EDU (Mike Gonnason)
Thu Apr 17 18:46:06 2008
Date: Thu, 17 Apr 2008 14:31:42 -0800
From: "Mike Gonnason" <gonnason@gmail.com>
To: "Brian Raaen" <braaen@zcorum.com>
Cc: nanog@merit.edu
In-Reply-To: <200804171700.27066.braaen@zcorum.com>
Errors-To: owner-nanog@merit.edu
On Thu, Apr 17, 2008 at 1:00 PM, Brian Raaen <braaen@zcorum.com> wrote:
> Some people wanted to know what I found the problem to be. I have discovered.
> the problem for a fact is the TCP window size on uploads. I have a Linux box
> that I changed the Window sizes to match and I still get 32k on a upload
> window and 64k on a download window. With a ping time of 50ms I have a max
> theoretical throughput of 5.2Mbps Which is about what I was getting. The
> formula to calculate this is the following.
>
> (((Ts/Tw)*Rtd)/1000)+((Ts*8)/(Lr*1000)))
>
> Where the following are
>
> Ts = Transfer size in Bytes
> Tw = Tcp Window size in Bytes
> Rtd = Round trip Delay in milliseconds
> Lr = Line rate in bps
>
> At this point I am still trying to locate the offending device that is
> changing the window size. After I determine for sure whether the problem is
> with my router, the sprint network, or another upstream system I will let
> everybody know what I find.
>
>
> --
> Brian Raaen
> Network Engineer
> braaen@zcorum.com
>
>
>
>
> On Monday 07 April 2008, Brian Raaen 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.
> >
> > --
> > Brian Raaen
> > Network Engineer
> > braaen@zcorum.com
> >
>
Thanks for reporting back to curious minds.
Mike Gonnason
