Assymetric results from iperf across gigabit link (long)

[Eli Dart]

In reply to Mike Hunter <mhunter at ack.Berkeley.EDU> :

> On Jan 30, "To freebsd-net at freebsd.org" wrote:
> 
> > Hi,
> 
> [snip]
> 
> I switched the two pieces of hardware, and the photons still prefer going
> uphill, so maybe there's a problem with the fiber after all.  I'd still
> appreciate any hints on what to ask freebsd to help me figure it out.
> (Yes, we have real fiber test gear, this is more of an experiment.)

Have you looked at interface error counts?  (netstat -inbd)  If you 
have dirty fiber, you could just be missing/corrupting the odd packet 
here and there, which would be enough to impact a high-bandwidth TCP 
flow.

the other thing to check is if a UDP cannon has the same bandwidth 
asymmetry, since the UDP iperf tests don't have TCP's timidity (if 
memory serves me)....

		--eli

> 
> Thanks,
> 
> Mike
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