For the last few days, I haven't been able to use the Internet on my Linux install. The wlan is seen and connected to, but internet is marginal - pages take a long time to load, I get errors when I try to send replies in forums, MSN clients refuse to connect and pings to google take 4/5 as long (125ms or so, when I usually get 30 - indeed what I just got now from Windows). After a few minutes, browsing becomes impossible - even pages that loaded slowly when the system started refuse to come up altogether (but pinging still works at the same slow speed). Using OpenDNS doesn't improve the situation.

The weirdest thing is that I can't think of anything I might have done to cause this (short of switching the USB port of the wifi dongle, but I've done that in the past and never had any trouble).

Distro is Debian Squeeze, Network manager is wicd.

How do I fix this?

Thanks.

Maybe disable iPv6?
Append to "kernel" line -- iPv6.disable=1

I'll try, but how can this have happened out of the blue? Whatever options are enabled now surely were enabled before, too.

Disabled IPV6. No change. *sigh*

Edit: if it can help, netstat -i reports 55 RX errors and 58 TX errors on wlan0. Not sure if this is relevant, I'm googling about slow connections and posting results as I go.

Try to use a different DNS server
EDIT
Sorry, didn't see you tried this already.

Actually, I've just removed the OpenDNS IPs from wicd, and things are working a lot faster. Possibly trouble-free (except not, see edit).

I tried removing OpenDNS IPs before, but it didn't work, so I put them back in. Only thing I did differently this time was to delete /etc/resolv.conf beforehand. Apparently that fixed it, for some reason I can't see.

Now, the only question that remains is: why the heck can I use openDNS with no trouble under Windows, but if I try under Linux everything slows to a crawl?

Edit: I've spoken too soon. The internet is now generally useable, but it's still a lot slower opening pages than, say, my netbook - which is running the same OS. *sigh*

Edit2: while experimenting, I tried running links in terminal and pointing it to linuxquestions (for some reasons, one of the sites it's slowest to open in this weird half-working state). It said "request sent" and stayed there for a while until I quit.

Then I stopped X (/etc/init.d/gdm stop) and tried links again from commandline, and it seems to work just fine.

Based on this, I think whatever's causing this problem is a part of X, as when X isn't running the connection works fine.

What happens if you use the wired connection?
Try to disable wep/wpa to see if the problem persist.
Do you have a firewall?

Try running strace (or equivalent) on a ping and see if that shows you anything you can use to pinpoint a DNS issue. I had similar issues on a Kubuntu laptop that turned out be it was using something called avahi-daemon instead of just /etc/resolv.conf.

Too far away, and computer is not portable. If worse comes to worst I can always unplug everything and move it on the other side of my home to try, but I'd rather try everything else first - conservation of energy, y'know. :P
Edit: well, I'm dumb and forgot I have phone plugs closer to my room too. I'll move the router instead and see what happens.

Can't do that either. My connection comes with a custom non-configurable router, with a fixed WPA key that can't be disabled. Stupid, I know, but if you want a fast connection in this deityforsaken country it's the only one that won't make you poor.

Nope.

Avahi-daemon gets loaded on *buntu by default, I think. At least, I've seen it on any *buntu system I've set up. Can't remember if it happens on Debian too, I'll see. I actually had no idea it had anything to do with the connection.

I'll also try running the trace and report the results.

Edit: well, I disabled avahi-deamon, and things seem to be back to normal. At least, I've been using it for a few minutes and it has yet to slow down. I wonder how is it that it used to work fine with avahi, then out of the blue got screwed up...

Well, it's working a lot better now, but it still isn't good. I have to wait less on websites to load, but the same websites load almost instantly in Windows. I also noticed that the wifi "power" indicator is always at half or less, which is suspicious because Windows always says it's a lot higher, on the same machine and using the same dongle. The netbook agrees with Windows.

The wireless device driver may or may not be equal in quality and performance to the commercial one, you know how vendors looove disclosuring their stuff to the Horsemen of The Linupocalypse ;-p Other than that there's mo mention of a specific troubleshooting data like kernel in use, wireless software, device drivers, configuration, debug output and objective statistics for comparison. Lacking that I wonder what end result one may expect...

Post deleted - everything I said proved to be false. Long story short, I wiped and installed Linux Mint Debian edition, and the problems seem to still be there. I guess it's a hardware or driver problem, I dunno. I'll try seeing if I can scavenge another dongle from somewhere and try with that - this one is a dodgy off-brand cheapie with what seems a fairly weak antenna.

*sigh*

Well, I unplugged the wifi dongle from the USB port on the case, put it at the end of an extension cord and dangled it on my screen, and all problems seem to have magically gone away - despite the connection strength still being reported as 50% or lower.

Weeks of agony and this was all I needed to do. *sigh*

Maybe my case has a grounding problem, or something, I dunno...but hey, at least this misadventure has made me try Mint Debian, which I like a lot so far.