FC2 - Strange Ethernet Behavior

[John Krische]

Hello everyone.

First, a big "thank you" to the Fedora team.  Hats off, no pun.  FC is 
impressing me more & more with each release.  But...

I have a rather strange behavior going on for _ALL_ FC2 machines my 
company operates, and I'm hoping you can help me figure it out.  This 
problem is **not** affecting any Windows-based hosts of any flavor, nor 
affecting other linux distros we run, such as Debian Woody and Sarge, 
all running on the same physical LAN, in the same physical segment. 
It's only affecting FC2 installations.  This behavior is occuring 
**regardless of the NIC installed** - tulip-based, e100, 3com cards, you 
name it, doesn't make a difference.  Because of this, I believe it's 
something deeper in the system, I figure, but I'll let you make that 
call.  If it is, I have no idea what to do about it.

The behavior is this:  our main connection is a T1.  Top download speed, 
ie when no heavy traffic is going on, should hover somehwere around 150 
K/sec, yes?  That's been my experience.  However, on **all** FC 2 
machines we have, regardless of hardware, and regardless of running the 
original 2.6.5 kernel or the updated 2.6.7 kernel (yum update), download 
speed does something odd.  It jumps up to about 180K/Sec, which causes 
alarms to go off at our ISP since that's above a T1's theo. limit, and 
then, shortly after 1.1 MB of file has downloaded, the connection speed 
plummets to less than old 28K dialup, ie, 2 K/Sec or less.  It's still 
downloading mind you, but barely.

Doesn't matter what you're DL'ing, where it is, or how large it is as 
long as it's above 1MB.  I guess that 1MB part is significant, as that's 
where the performance shift starts to happen.  To rule out traffic, I 
cancelled the FC2 download of a given thing, say, webmin's tgz, and told 
a windows client to DL it from the same mirror (UMN).  No problem.  Then 
I did it on a Debian system.  No problem.  Then on FC2 again.  Problem 
persists on FC2.  Did all three at the same time - FC2 fails, the others 
split the avail bandwidth 50/50.  Tried to do it via curl in the middle 
of the night; problem persists.  Argh.

Because this problem is not affecting anything but the FC2 machines, and 
because all our FC2 machines have different networking hardware, I have 
to conclude it's something about FC2 itself.  To strengthen this point, 
the machine from which I write this email, now running FC2 and having 
this problem, used to be running Mandrake 10 on the same hardware, just 
2 days ago, with no troubles in networking.

I have no idea how this affecting traffic in the other direction.  I 
hope it's not causing the same behavior for folks pulling stuff off of 
the FC2 machines.  I'll have to test that.

So, anybody got any relevant ideas?  Or am I destined to go hit Bugzilla 
for a fresh report?

Oh, btw... already played around with all the mii-tool options.  no effect.

John K., MCSE
(but rapidly converting to Linux!)