[geeks] Network Slowness

[Sridhar Ayengar]

Mike Meredith wrote:
>> The speed LED for all three ports on the switch reads as gigabit, and 
>> ifconfig (on UNIX) and Network Connections (on Windows) report that
>> I'm connected at 1000Mbps.
> 
> Also check (if possible) if both ends are autonegotiating full duplex;
> if you've got a mismatch there, you will get terrible performance.
> Gigabit (I think) is supposed to be full duplex only, but it's still
> worth checking.

If memory serves, when I checked this out yesterday, everything seemed 
to look normal, but I'll double check just to be sure.

>>> * PA-FE-TX? Is that 100BaseFX ? Might be worth disconnecting that
>> No, that's 100BASE-TX.  And the indicator LED for that port on the 
> 
> I meant 100BaseTX; brain fart got in the way :)
> 
> Still worth trying without it connected just in case.

I'll try that.  But in any case, I won't be able to operate without it 
for long, since that's the connection to the rest of the network in my 
house, as well as the outside world.  And gigabit interfaces for the 
Cisco 7500-series are not reasonably priced.  ($500+ used, tested)

>>> 890Mbps. It may just be the Procurve just isn't up to the job.
>> I had a little trouble parsing the next-to-last sentence there.  What 
>> did you mean?
> 
> Well I can't see what's wrong with the sentence right now (brain is a
> little frazzled from staring all day at php code), but it's obviously
> bad English if you can't understand it!
> 
> I just meant that not all switches will do gigabit very well, and
> perhaps your Procurve is one of the switches that choke when pushing
> packets that fast.

Ah.  I certainly hope it's not that.  The switch wasn't particularly 
inexpensive, and Procurve networking products seem to have a pretty good 
reputation.  Maybe I've just got a bum switch.

> Other things to try :-
> 
> * Switch to using nc (as others have said) to benchmark the network ...
>   it may not be what you want to use, but it eliminates an unnecessary 
>   variable. And you should  get some nice big numbers out of it once
>   you have fixed this problem :)
> 
> * Check the stats that ifconfig gives you to see if you are getting
>   any errors there.
 >
> * Do a tcpdump (or similar) on the network transfer to see if you're
>   getting lots of tcp retransmits. You should probably see some, but
>   not *too* many. 

Will do the above.

> * Swap out the cable(s) 

I guess the first thing I'll try is to do it with just a crossover 
cable, as was suggested earlier.  I'll whip up a new crossover cable 
just for this.

> (some bastard spammer is joe-jobbing my redhairy1.demon.co.uk domain 
>  at a rate of 50 backsplatters every 10 minutes :( )

I feel your pain.

Peace...  Sridhar