North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical RE: Bandwidth issues in the Sprint network
even with tuned TCP window sizes, make sure you don't have TCP syncookies enabled on either endpoint. many syncookie implementations have implications on supporting RFC1323 options. cheers, lincoln. > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf Of Brian > Raaen > Sent: Friday, 18 April 2008 7:00 AM > To: [email protected] > Subject: Re: Bandwidth issues in the Sprint network > > 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 > [email protected] > > > 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.
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