[tech] Something is up with uccrouter..

[Simon Fryer]

Bingle

> A while ago Grahame Bowland tapped:

> Typhaon -> uccrouter gets reasonable transfer rates
> Typhaon -> morwong gets abysmal transfer rates (32:00 for 7Mb)
> morwong->uccrouter is fine
> 
> Conclusion: packet forwarding on uccrouter is broken.
> I don't see anything suspicious in the syslog and the cpu 
> load isn't looking bad, anyone have an idea what's up 
> with it?

I doubt that this is related but it may be due to TCP/IP fragmentation/
acknowldgement stuff. I get really poor transfer rates between my DU4.0d
and the Debian Linux (Nick, what kernel revision?) over NFS, 100Mb switched. 
I get better rates when both source and destination directorys are NFS mounted 
on my OpenBSD PC which is on a shared (ok, not by very much) 10Mb ether. 

>From looking at the lights on the switch, it feels as though ack packets are 
not being recieved/processed/sent correctly. It is almost as if the TCP settings
for both machines (in terms of No. of packets recieved before timeout/sending 
ack packets and resending packets again) are different. 

This is just my guess and my problems may also be due to the fact that the DU
box thinks the ethernet link is 100Mb/s Full duplex and the switch only thinks
it is half duplex. And for the record, the card is a DE500, rev (too slack to
check). The switch is a cheap mostly unknown brand. 

See Ya
Simon

-- 
------------------------------------------------------------------------
"Well, an engineer is not concerned with the truth; that is left to 
philosophers and theologians: the prime concern of an engineer is 
the utility of the final product."  
Lectures on the Electrical Properties of Materials, L.Solymar, D.Walsh