Re: Only some websites will open - Ubuntu

kubismo@xxxxxxxxx wrote:
I'm having exactly the same problem as Big Dave at the start of this
thread. I recently put together a new computer and installed Kubuntu
7.04. When I surf the web only Google and the Mozilla site are
available (they work perfectly) and pretty much nothing else. I
haven't quite figured out what is happening but I think I can add some
information to the discussion.

* It has absolutely nothing to do with the router. I tried a brand new
router (different make) and also tried without a router and the
problem was still there.
* It has absolutely nothing to do with the computer hardware. I tried
using a LiveCD on another computer which normally has no problem
connecting to the net with Windows and had the same problem.
* It has absolutely nothing to do with the MTU setting. I tried
adjusting it from 1500 down to 500 and it made no difference.

What's really interesting is that I took the Kubuntu computer to my
wife's office and it surfed the web perfectly there.


Intersting..

The difference between my wife's office and home is that at home we
have a static IP and at the office it's dynamic. The ISP is the same
for both locations except that at home we also have a community-built
wireless network (we're in the country) between the house and the ISP
(hence the static IP at that location).

Thats a pretty BIG difference. Its not just static/dynamic stuff, its a whole slew of other issues as well.


My theory about why it's only Google that's delivering pages is that
normal webservers (I believe) feed a small chunk of data and then wait
for an acknowledgment. I'd speculate that Google sees this as a waste
of bandwidth and processing time and just shoots the whole page down
the line in one shot.

Nope. Can't be done that way. However it MAY be to do with window sizes..in addition to the MTU - which is the MAX size of each data packet - there is a window size that is negotiated for a TCP connection..that specifies how much data can be sent without waiting for an ACK. On high latency reliable connections (satellite is a prme example) many data packets will be sent before an ack is expected, and several ACKS may go back in a single packet.

I have no idea how t tune a Linux kernel for windows size tho. Its typically a multiple number of kilobytes ..

Nor indeed am I sure that this is the problem, though we may be getting closer.




If this theory is correct, Kubuntu is, for some reason, not able to
get the acknowledgment back to the regular webservers and that's why,
for most pages, we get just a tiny chunk of the HTML before it dies.

Well that may be what is happening, but why? If you can contact the server in the first place you can send packets.. OK if the overall link is suffering packet loss, all bets are odd. Again in the bad old days we used to pull windows sizes down to avoid stalling connections..


I don't know why this would be a problem with Kubuntu and not with
Windows. It could be a bug in Kubuntu or it might be that some kind
of security setting is getting in the way. This is all based on a
fuzzy understanding of how the Internet works but it's all I have to
go on at the moment.


Well you got me thinking, and I found this page.

http://dsd.lbl.gov/TCP-tuning/linux.html

Maybe something in there will work for you.

Some of the issues describe sound rather like what you are exeperiencing.

Remember its not you who does packet fragging - its the routers between you and the target..a local wireless network may be doing a load of stuff you don;t even see or know about..but it may be that upgrading kernels to the latest and playing around with the tuning as described will do something.

I have to say that I started out my networking existence with PC-TCP and SUN NFS on DOS PC's way back.. anyone remember the Novell NE100 and 3COM 501 networking cards? Yuk. What a joy when 3com and western digital got cards that had BUFFERS on them!! and these issues are all what we had then..I thought everyone had sorted them all out by now..

Ok..one thing I found by looking at that page is that you should use "netstat -s" to assess whether there are a high level of retransmits going on.

Not that doing this on my system produced anything that I could interpret, it has to be said ;-)

However it may be useful to dump that in a post here., as others who are more up to date than I may be able to pick over the carrion and find some useful tidbits to digest.

Now I don;t know a lot about Ubuntu upgrading processes, but my first instinct would be to upgrade the kernel to the latest one.

Another thing occurs to me.. is FTP working ok to large FTP sites?


.

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