On Fri, 9 Apr 1999, Paul H. Anderson wrote:

> 
> TCP streams via FTP seem FUBAR.  In pretty much any combination that we've
> tried, an alpha talking to an alpha gives about 50-100KBytes/second
> throughput - about 1/100 of what it should.  Same HW ifconfig'd to 10baseT
> gives 1MB/sec, i.e. full 10baseT throughput.
...
> We've switched cables, hubs, etc.  No change.  Hook two machines up via
> crossover cable, same result.  Adding a etherexpress card causes the
> machine to hang hard, so I'm guessing other drivers are out.

We now believe that there is a condition exploited by the ftp program
which causes low throughput between two netbsd 1.3 Alphas.

We've effectively eliminated any possibility of hardware being the problem
by swapping hubs, cables, switches, NICs, and processors.  We switch
between full duplex, half duplex, no change.  We have 11 alphas, and they
all show the same problem.  If we switch the interface to 10baseT, it
works 'fine' in the sense that it gives 10Mb/s throughput.

We tried different ethernet brands (etherexpress pro 100 +) cards, which
also showed the problem.

I updated the de0 driver to the latest snapshot (there are a few small
changes) - no difference.

It should be easy to reproduce if anyone has high speed alphas.  Just use
ftp both to get and put a large file between two directly connected 533MHz
164LX alpha boxes. I'm guessing that anyone using the same hardware as I
have will be able to reproduce the problem.

The problem appears to be related only to the FTP program, not to either
NFS, UDP, or other TCP based test programs.

I don't have any more time to screw with it, and if no one else can
reproduce it now, then I guess that's a shame, but I'm not going to worry
about it.

Paul