humiliating network problem

Randux · 09-14-2006, 01:23 PM

Guys, this is humiliating. I noticed poor network performance on my main desktop machine recently. It seemed like when I would refresh the DHCP lease it would be ok again for a while and then deteriorate. I had gotten in a pile of hardware so I tried everything including running with and without the router, running on another desktop on a different box, all possible combinations that I could think of. I tried running with and without arno on the Linux desktop.

Both desktops I'm trying this on are Slackware 10.2 machines that have been running like boiled monkeys forever. I cloned one to get the other so almost nothing is different except they have different NICs so I have some different stuff in rc.modules. I've never had any problems until recently and I was sure the ISP was strangling me for some reason.

I even tried slapping the MAC from my old bloze machine onto the router in case anyone was tracking it because I know if I change it more than a couple of times they disable the link.

I called my ISP and cable provider (two different companies

) and while the ISP threw up their hands the cable company checked the connection and gave me an ip address at their server to run a test from. From their server I can get the rated connection speed fine. When I ping my ISP I also get what I'm told is acceptable performance (by the guy at the cable company). But when I pull anything off my ISP's servers I'm getting about 50-100 kbps out of a 750kbps rated connection. The upload is almost as fast as the download now. I don't think it's a DNS problem because big downloads also go nowhere- except when I run from my cable company's server. Then they run at full speed.

Here's the horrible part, and it *is* horrible.

Windows screams. I mean I get the full rated performance and then some on bloze but Linux chokes.

How can this be happening? OMG somebody please help me!

I just thought of something: I tested the speed on my OpenBSD 3.9 desktop which is on the same physical box as the winbloze machine- it's also dead slow. This is really getting weird.

edit: it's not DNS because the bloze machine and my Slackware machines are using the same two DNS servers

macemoneta · 09-14-2006, 02:01 PM

If you are running a 2.6.17 or later kernel, try this:

Code:

echo 2500000 > /proc/sys/net/core/wmem_max
echo 2500000 > /proc/sys/net/core/rmem_max
echo "4096 5000000 5000000" > /proc/sys/net/ipv4/tcp_rmem
echo "4096 65536 5000000" > /proc/sys/net/ipv4/tcp_wmem
echo "0" > /proc/sys/net/ipv4/tcp_window_scaling

If it works, this explains it. If not, try disabling ipv6.

Randux · 09-14-2006, 02:07 PM

Hi macemoneta,

I'm running the default 2.4.31 kernel on the Slackware machines. I don't know if they even support ipv6 and if they do I'm not sure how to disable it. I'm checking the man pages now.

Thanks,
Rand

gilead · 09-14-2006, 02:08 PM

Warning - it's 5am and I'm guessing...

Have you used ifconfig (ipconfig on windows) to compare the settings on the network cards? For example, the default MTU is sometimes not set correctly.

Randux · 09-14-2006, 02:09 PM

Ok I see that arno blocks ivp6 by default. So it shouldn't be the problem on my Slackware machines.

Randux · 09-14-2006, 02:15 PM

Quote:

Originally Posted by gilead

Warning - it's 5am and I'm guessing...

Have you used ifconfig (ipconfig on windows) to compare the settings on the network cards? For example, the default MTU is sometimes not set correctly.

Hi gilead,

That's a good idea but remember this was working fine until recently. I'll check it now.

I don't see mtu on win ipconfig and I checked the tabs on network properties and I don't see it there either.
However my Linux MTU for eth0 and lo match the ones I've seen on posts here (1500, 16436) if memory serves...

Thanks,
Rand

Randux · 09-15-2006, 05:03 AM

Do certain ISPs throttle non-winbloze endpoints? Is that even possible?

mdarby · 09-15-2006, 06:06 AM

I'd check your DNS servers listed in /etc/resolv.conf

gilead · 09-15-2006, 06:20 AM

Yeah - I've never heard of a card spontaneously changing MTU settings

I've used drtcp from http://www.dslreports.com/drtcp to check settings under windows - I forgot about it until a little earlier.

ISPs here don't stop traffic based on OS, but they mostly refuse to support non-windows boxes.

Do you have the time to run a packet sniffer (ethereal/wireshark, tcpdump) to see if there are packets being lost or if it's slow throughput? If your ISP has changed the way that login/DHCP allocation happens it may be that your Linux/BSD boxes have more restrictive firewalls than the windows box.

Randux · 09-15-2006, 06:21 AM

Hi Matt,

Already checked as noted above: same two servers (and same order) for bloze, Slackware, and OpenBSD. And downloads are also dead-slow- no indication of DNS issue.

Thanks,
Rand

Randux · 09-15-2006, 06:25 AM

Quote:

Originally Posted by gilead

Yeah - I've never heard of a card spontaneously changing MTU settings

I've used drtcp from http://www.dslreports.com/drtcp to check settings under windows - I forgot about it until a little earlier.

ISPs here don't stop traffic based on OS, but they mostly refuse to support non-windows boxes.

Do you have the time to run a packet sniffer (ethereal/wireshark, tcpdump) to see if there are packets being lost or if it's slow throughput? If your ISP has changed the way that login/DHCP allocation happens it may be that your Linux/BSD boxes have more restrictive firewalls than the windows box.

I'm not sure how to check that. Remember, the problem appears to be between the ISP and the cable provider. Between me and the cable provider we proved I get full speed on my Linux machines. There is no login at the ISP and the dhcp lease is between me and the cable company- they gateway me to the ISP directly. And this connection is the same connection I get no matter which desktop machine I'm using because everything is behind the same router. Even without the router, the exact same problem occurs.

If I missed something in your comments it's because I'm network-stupid

Thanks,
Rand

Old_Fogie · 09-15-2006, 08:26 AM

I had cable for years, and moved over to DSL because of issues like this.

One thing I did learn from being on the phone with tech support of my cable ISP was a thing called "signal noise ratio".

Think of it as 'noise in your line' ok.

For my ISP they allowed up to 45 db noise, which was, well, good enough to surf with windows (remember I'm new to linux so back then I was windows on cable). However something simple as typing in a web-site address, had a pause, then bang, the page loaded.

You see, cable is analog. They have repeaters out there on the street and amplifiers that boost the signal to you.

However, you are limited by your modem back to the street.

The technicians came to my home and told me, "yeah the office says you can go to 45 db noise upload, but that's brutally slow. we the tech's try and get everyone down to 38 db (better is lower)to give them some overhead."

They also told me that those speed tests will show fine even tho you have a lot of noise going up.

I know you said you think this is on linux side only.

But being that these technicians insisted that I changed all of the wires in my house, yes I even paid for it, but it did work.

I recommend that for kicks and giggles, just remove the splitter's if any, turn off/unplug digital tv boxe's and get your modem as the only thing between your pc and the street as best possible.

See if this makes a difference.

These technicians many times find one connector on the end of a cable wire, and it add's to much resistance for the low wattage singal upload of your modem.

You can usually get this reading of your cable company from 'level 2' tech support. You have to insist to be moved up to a level 2. All those companies have them. Don't let them bully you by saying that you're using an alternate OS, or that you have spyware or need to defrag,,as that is what they all say and it's just plain ridiculous.

Just a thought, I hope you get this solved

bonowax · 09-15-2006, 10:18 AM

Hi there...

Could you be using your ISP's proxy server under windows but not under linux?...
Just an idea...

Edit: And btw, about throttling down non-bloze machines... http://www.onlamp.com/pub/a/bsd/2006...filtering.html

Cheers

Randux · 09-16-2006, 02:48 PM

Quote:

Originally Posted by Old_Fogie

I had cable for years, and moved over to DSL because of issues like this.

Just a thought, I hope you get this solved

Hi Old_Fogie,

Thanks for your comments.

Unfortunately this can't be the issue here since bloze is running fine and everything else is not. It's all the same hardware, cabling, etc. The only variable is bloze/not bloze. I don't know how to check bloze MTU values but everything I've read says that it uses 1500 which is the same as Slackware.

And when I go to the cable company's server I get the same performance on bloze and everything else. It's only from my ISP that the problem happens- and I'm 99% sure they're throttling non-bloze endpoints.

Rand

Randux · 09-16-2006, 02:51 PM

Quote:

Originally Posted by bonowax

Hi there...

Could you be using your ISP's proxy server under windows but not under linux?...
Just an idea...

Edit: And btw, about throttling down non-bloze machines... http://www.onlamp.com/pub/a/bsd/2006...filtering.html

Cheers

Hi Bono,

There should be no proxy server involved- but I am not sure how to check on winbloze.

Thank you for your link. I am now almost 99% that they are doing this, even though many people say it's not possible. It's obviously possible.

One person on bsdforums had a really good idea to run my Slackware or OpenBSD machine behind my bloze machine using winbloze ICS (internet connection sharing). This could prove it, but I only have one NIC in that machine so I can't test it.