FC3 with BEFSR11 Linksys router slow connection

[Shawn Iverson]

Greetings,
I am experiencing a problem with FC3 that has basically stumped me.
Network access through a Linksys router model BEFSR11, default settings
with the latest firmware (in an attempt to resolve the problem), is
extremely slow at about <=1.0KB/s using an Intel Pro adapter as the NIC.
If I unplug the exact same wire going to the FC3 box and into an XP Pro
machine, I experience no problems with the connection.  If I bypass the
Linksys router altogether and plug the FC3 box directly into the cable
modem, firewalled of course, no problems.  I have certified all wiring
between the cable modem and Linksys and Linksys and FC3 box using an
Agilent Wirescope 350.  The cable company dispatched a person to certify
the cable coming into the building as well. Some incompatibility seems
to exist between the Linksys and FC3.

ipconfig -a shows a lot of tx packet errors:

TX packets:55054 errors:41 dropped:0 overruns:0 carrier:41

I also ran Ethereal, initiated an ftp download (firewall disabled, but I
use ip_conntrack_ftp anyway), and monitored it.  I am getting a lot of
TCP Out of Order packets inbound and TCP Duplicate ACKs outbound,
suggesting some kind of packet loss and delay to me.  Eventually, the
ftp download times out.

I have an FC3 box that is multihomed.  Here are the specs:

FC3 running kernel version 2.6.10-1.766_FC3, patched as of 3/17/2005.
Motherboard is a Gigabyte GA7VM400M-RZ with 2.6 GHz Athlon. Onboard NIC
connected to the internal network (VIA Rhine II) Second NIC connected to
the Linksys router (Intel Pro 100+ Management PCI Adapter)

Please note that during troubleshooting, I did unplug the onboard
interface from the network.  The Intel Pro was set to use DHCP and
obtain DNS information, and it was fetching the DHCP information from
the Linksys properly.  My tests consisted of downloading files with
Mozilla Firefox from a known good remote connection and downloading
files with wget from the commandline.  On the XP machine, downloads were
performed from the same location using Internet Explorer
(http://ftp.ussg.iu.edu and ftp://ftp.ussg.iu.edu).

Has anyone else had this problem, or does anyone have some suggestions? 

I am highly suspicious about the kernel settings.  Surfing the net I
found this option in the kernel that controls TCP Explicit Congestion
Notification.  Would this option be related to my problem
(CONFIG_INET_ECN=y)?  I guess that it won't hurt to try recompiling the
kernel with this option turned off, if it exists in the 2.6 kernel.
Something in the back of my mind tells me that the Linksys is breaking
some tiny, little TCP/IP standard on which FC3 depends.

--

Shawn Iverson
Technology Associate
MCP W2K3S and W2KP, Linux+, Network+, A+
New Castle Community School Corporation
shawn at nccsc.k12.in.us

                __ (.)(.) __            
***************(||)**()**(||)***************
  Please leave the subject line blank when 
    sending me new emails that originate  
   outside of nccsc.k12.in.us (to prevent 
     dropped messages during delivery).
********************************************