Bandwidth issues in the Sprint network
Brian Raaen
braaen at zcorum.com
Thu Apr 17 21:00:12 UTC 2008
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 at 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 at zcorum.com
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 189 bytes
Desc: This is a digitally signed message part.
URL: <http://mailman.nanog.org/pipermail/nanog/attachments/20080417/9d92d251/attachment.sig>
More information about the NANOG
mailing list