Re: Network Performance?

[Tim Sailer <sailer@bnl.gov>]

On Mon, Jan 08, 2001 at 01:40:57PM -0500, Craig I. Hagan wrote:
> > 101 packets transmitted, 101 packets received, 0% packet loss
> > round-trip min/avg/max = 109.6/110.3/112.2 ms
> > 
> > > Does the problem occur in both directions?
> > 
> > Good question. I'll find out.
> > 
> > > Are you _sure_ the window size is being set correctly? How
> > > is it being set?
> > 
> > I'm fairly sure. We echo the value to the file. catting it back
> > shows the correct value. If we go lower than default, it slows
> > down even more.
> 
> what are you setting it to on the solaris machine? what window
> sizes have you tried?
> 
> Your pipe looks like it will have quite a few bits in flight due to its

Yup. That's why the tuning. WAN performance here is very important.

> latency. From my quick guess math, which sucks, it appears that you can fit 1.2
> to 1.5 megabytes on the wire (100mbit machine<-> machine) times 100-120ms wire

Hmm. 100/8 is about 12, no? 

> time. This is a rather large number, so you may want to see what hosts really
> support, perhaps starting with 64k or 128k and work up. Make sure that you have
> window scaling turned on if you go with very large windows.

Yes, we have that enabled too.

> Also, have you upped your socket buffers to match your window sizes?

We are using straight ftp for the testing.

> Last, solaris tends to have poorly tuned tcp values out of the box, look at
> this link and tune the solaris stack to better reflect reality.
> http://www.google.com/search?q=cache:www.rvs.uni-hannover.de/people/voeckler/tune/EN/tune.html+%2Bwan+%2Bwindow+%2Bscale+%2Bsize+%2Bnetwork&hl=en
> 
> linux tuning has a decent amount of data in the docs section of the kernel
> sources.

I'll take a look. THanks.

Tim

-- 
Tim Sailer <sailer@bnl.gov> Cyber Security Operations
Brookhaven National Laboratory  (631) 344-3001
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