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: nanog@merit.edu > 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.