[UCI-Linux] network probs with fedora core 2 kernels

Jeff Stern jas at uci.edu
Fri Aug 20 10:20:47 PDT 2004


hi, all uci-penguins :P,

this is just a notice to recommend that everyone running fc2
(fedora core 2) update to the newest kernel rpm
(kernel-2.6.8-1.521) if they are having slow or erratic network
performance.

the problem is with some recent kernels, and would lead to
slowdowns in data transfer rates on some protocols (like nfs,
smb, http, and scp) but not on others (like ftp).. data transfer
rates would slow to as little as 30kB/sec. i think this is
because some network parameters were tweaked in recent kernel
versions, and packets get lost..

the last bad kernel i had the problem with, the fedora rpm was:

   kernel-2.6.7-1.494.2.2

but today redhat released an rpm:

   kernel-2.6.8-1.521

which fixes the problem.

i am not strong in networking but it had something to do with 
tcp window-sizes or something like that.. there are discussion 
threads at :

http://readlist.com/lists/redhat.com/fedora-list/0/1363.html

  and

http://www.linuxarkivet.se/mlists/linux-net/0406/msg00230.html

about it.. i searched bugzilla at redhat but couldn't find an 
exact addressing of the problem, though there are several open 
bugs relating to network slow-downs.

in any case, the kernel developers seem to have gotten this fixed 
in later versions of the kernel, and redhat has passed on their 
rpm for it.

this thing gave me all sorts of problems and i was trying to 
isolate whether it was a bad ethernet card, hub, port repeater, 
or software. it lead to totally erratic behavior depending 
on how each application (or service) was programmed (or 
not) to deal with buggy data it received over a network 
connection, so i just wanted to save others the problems..

(also, if you *do* have automatic updating /up2date running on 
your machine(s), remember to reboot so you can run the newest 
kernel. updating itself will of course not start running the 
newer kernel :)

if anyone else has a more precise description of the exact cause
of what the problem was (or URL for same), i'd be curious to know
so please post or write me, thanks..

-- 
  Jeff Stern
  Social Sciences Computing Services
  sst 629 / 949-824-2326 / jas at uci.edu
  via post:
    Jeff Stern
    3151 Social Science Plz
    Irvine CA 92697-5100


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