Cable Modem slow Speeds

I have an IBM Netvista with a 633mhz Celeron Processor serving as an
Internet Router and firewall box for a Small Businees network (10
pcs)Runing either Win95, Win98, Win2k, or WinXP They are connected to an
RCA Cable Modem supplied by Roadrunner.

Roadrunner says the problem is not on their end.

The OS on the server is Redhat 7.2, and I am using IPtables for the
firewall and NAT. I used gSheild to configure the firewall. I had
previously been using a scripted ipchains firewall script.

My problem appears to be upload speed. I have been testing on the
www.bos.speakeasy.net website.

My Download speeds have been pretty consistant betweent 930kbs and
980kbs, but my upload speeds have be slow and much more inconsistant.
Maxing on average at 130kbs, and going as low as 21kbp.

I am using a PCI 3com59x card for my connection to the Cable modem. I
have tried turning off full duplex mode in my modules.conf settings, and
also tried addjusting the values in the following files in
/proc/sys/net/core
rmem_default wmem_max
wmem_default rmem_max

The default setting for each was 65535, I have tried lowering that and
increasing it with little effect.


Any suggestions would be greatly appreciated.