I've run out of ideas on this one and could use some suggestions.

First my network:
Zimbra mail server running on Ubuntu 8.04 - no network speed issues.
Apache server running on KVM on Debian (Proxmox kernel) - no network speed issues.
XP Home running on qemu on the same Debian server - no network speed issues.
Cisco SB107 DSL router.

The system with the problem:
Asus P5VD2-VMSE
Running a trial version of Windows 7 - no network speed issues.
Running Mint 8/Debian Lenny/Ubuntu 10.04 - Single file transfers across the router run a 1/3 as fast as they should. Streaming video, apt-get upgrade, speedtest.net and any single file downloads are affected.
Torrent's, however, run at full rated DSL speed.

As a workaround I am for the moment downloading files using the internal webserver and then downloading from the internal webserver to the problem child. I'll also be setting up apt-proxy on one of the others.

Here's what I've done/tested:

• IPV6 disabled.
• Used both the gnome network config tool and also manually set addresses via the /etc/network/interfaces file.
• Same DNS servers used throughout the network, also tested with ISP's DNS.
• Pulled the hard drive out and placed it in a HP 6010 somebody dropped off for virus removal. Boots and runs perfectly - same network problem.
• Switched from the onboard NIC (using a via rhine driver) to an add in card (using a realtek 8169 driver) - no change.
• Ran thru privoxy from one of the other systems.
• Dropped the MTU from 1500 to 1448.

My conclusions:
It is not a specific problem with any of the NIC's as I pull full wire speed internally.
It is not some kind of hard cap on external bandwidth as torrents can pull full DSL speed.
It is not an issue with the servers I'm downloading from as they work fine for the other systems.
It is not the well known IPV6 issue.
It is specific to these newer debian based distro's.
It may be kernel related as the debian lenny using the custom Proxmox kernel does not have this issue but a stock debian lenny does.

What I'm working on now:
I'll see about other kernel options or recompiling one by hand (cut my teeth and ran Gentoo for several years so this should'nt be too hard).


Any thoughts on where to look or what to test? I am at a complete loss to explain it.

I can suggest compare sysctl, and especially part about "net."

Very nice!

A quick diff between the modified Lenny and the troublesome Debian derivatives shows some minor value differences. I'm looking up their function and changing them to match Lenny one at a time and testing for change after each update.

Notably present in the slow Debian's are entries for net.ipv4.cipso*. I also see that the cisco ios commands have a command for ignoring the cipso field in packets. One of these two is going to go away and I'll report back the results.

Disabled cipso field checks on the Cisco router.

Modified the following to bring it inline with the good Lenny:
net.core.optmem_max = 20480
net.core.rmem_default = 131072
net.core.rmem_max = 131071
net.core.wmem_default = 131072
net.core.wmem_max = 131071
net.core.xfrm_larval_drop = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.eth0.rp_filter = 0
net.ipv4.icmp_ratelimit = 250
net.ipv4.route.gc_thresh = 65536
net.ipv4.route.max_size = 1048576
net.ipv4.tcp_allowed_congestion_control = reno
net.ipv4.tcp_available_congestion_control = reno
net.ipv4.tcp_congestion_control = reno
net.ipv4.tcp_ecn = 0
net.ipv4.tcp_max_orphans = 65536
net.ipv4.tcp_syncookies = 0

Still seeing faster uploads than downloads:
http://www.speedtest.net/result/771605682.png

Also please, check other fields. Because "net.*" was my thoughts also you may compare drivers version, and kernel modules from "lsmod".

May be this file also help you.

Also compare everything in /proc/sys/net/

Attached Files

ip-sysctl.txt (38.0 KB, 8 views)