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Old 11-28-2007, 09:46 AM
"Duncan Berriman"
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

If a TCP/IP connection is made to a certain public web server
then the transfer rate on Fedora Core 6 onwards is in the
region of 100B/S (bytes per second). On Fedora Core 2 and
Fedora Core 4 the speed is in the region of 300KB/s (Kbytes
per second).

wget http://www.xxxxxxxxxxxxx.com/
--20:57:23-- http://www.xxxxxxxxxxxxx.com/
=> `index.html.1'
Resolving www.xxxxxxxxxxxxxxxx.com...
Connecting to www.xxxxxxxxxxxxxxxxx.com:80... connected.
HTTP request sent, awaiting response... 200 OKLength:
unspecified [text/html]

[ <=> ] 11,042 149.60B/s

Again on any other FC4 it works fine.

wget http://www.xxxxxxxxxxxxx.com/
--20:57:23-- http://www.xxxxxxxxxxxxx.com/
=> `index.html.1'
Resolving www.xxxxxxxxxxxxxxxx.com...
Connecting to www.xxxxxxxxxxxxxxxxx.com:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]

[ <=> ] 38,085 231.38K/s

20:57:37 (230.42 KB/s) - `index.html.1' saved [38085]

Both these problems were encounted on a live server at a data
centre running Fedora Core 6. I then did a fresh install on
another machine at the office of FC6 and reproduced both
problems. I then did a fresh install of FC8 on the same
machine and again managed to reproduce them straight away.

I have since downgraded the live server (reinstall) to FC4 and
the problem is resolved. The problem does not exist in Redhat
Enterprise 3 or 4.

This is a bit of a show stopper as rehards using Fedora for us.

Anyone any ideas? Quite happy to send the server details for
Testing off list. If anyone can give me some ideas how to debug
It or provide more information (tcpdump?) I'll be happy to do
So.

PS. There is also a bug in wget that it shows the transfer
Rate as K/s rather than KB/s when doing the transfer as
Can be seen above. The summary figure is correct.

Thanks in advance
Duncan

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Old 11-28-2007, 10:05 AM
Tomasz Torcz
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

Dnia 28-11-2007, śro o godzinie 10:46 +0000, Duncan Berriman pisze:
> If a TCP/IP connection is made to a certain public web server
> then the transfer rate on Fedora Core 6 onwards is in the
> region of 100B/S (bytes per second). On Fedora Core 2 and
> Fedora Core 4 the speed is in the region of 300KB/s (Kbytes
> per second).

That sounds like TCP window scaling bug on remote server. Newer kernels
expose it. See http://lwn.net/Articles/92727/

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Old 11-28-2007, 11:14 AM
"Duncan Berriman"
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

You are quite correct.

Putting net.ipv4.tcp_window_scaling=0 into /etc/sysctl.conf and rebooting
works

I'll have to read more and understand the reasons and implications.

Thanks for your help.

Duncan

> -----Original Message-----
> From: fedora-list-bounces@redhat.com
> [mailto:fedora-list-bounces@redhat.com] On Behalf Of Tomasz Torcz
> Sent: 28 November 2007 11:05
> To: For users of Fedora
> Subject: Re: TCP/HTTP Bug Fedora Core 8 (and 6)
>
>
>
> Dnia 28-11-2007, śro o godzinie 10:46 +0000, Duncan Berriman pisze:
> > If a TCP/IP connection is made to a certain public web server
> > then the transfer rate on Fedora Core 6 onwards is in the
> > region of 100B/S (bytes per second). On Fedora Core 2 and
> > Fedora Core 4 the speed is in the region of 300KB/s (Kbytes
> > per second).
>
> That sounds like TCP window scaling bug on remote server.
> Newer kernels
> expose it. See http://lwn.net/Articles/92727/
>
> --
> Tomasz Torcz
>
> --
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>
> --
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> dangerous content by MailScanner, and is
> believed to be clean.
>

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Old 11-28-2007, 11:30 AM
"Duncan Berriman"
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

PS. Still a bug in wget


[ <=> ] 38,033 200K/s in 0.2s

14:16:40 (200 KB/s) - `index.1' saved [38033]

As you can see one says 200K/s and the other says 200KB/s (200KB/s is
correct). Its not major but it can cause concern when doing a download and
the speed reported is a factor of 8 out.

Duncan

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Old 11-28-2007, 12:46 PM
Dario Lesca
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

Il giorno mer, 28/11/2007 alle 12.14 +0000, Duncan Berriman ha scritto:

> Putting net.ipv4.tcp_window_scaling=0 into /etc/sysctl.conf and rebooting
> works

But this operation is better do it on all f[8-6]?

Or is sufficient remove ipv6 support?

Thanks

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Old 11-28-2007, 02:54 PM
"Duncan Berriman"
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

Its nothing wrong with Fedora (or for that matter it seems Vista which also
has this on by default now).

Its an out of date or wrongly configured router at the customer end causing
the problem as it does not support tcp window scaling and thus causes
performance issues.

Nothing to do with ipv6.

Duncan


> -----Original Message-----
> From: fedora-list-bounces@redhat.com
> [mailto:fedora-list-bounces@redhat.com] On Behalf Of Dario Lesca
> Sent: 28 November 2007 13:46
> To: For users of Fedora
> Subject: RE: TCP/HTTP Bug Fedora Core 8 (and 6)
>
>
> Il giorno mer, 28/11/2007 alle 12.14 +0000, Duncan Berriman
> ha scritto:
>
> > Putting net.ipv4.tcp_window_scaling=0 into /etc/sysctl.conf
> and rebooting
> > works
>
> But this operation is better do it on all f[8-6]?
>
> Or is sufficient remove ipv6 support?
>
> Thanks
>
> --
> Dario Lesca <d.lesca@solinos.it>
>
> --
> fedora-list mailing list
> fedora-list@redhat.com
> To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>
> --
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
>

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Old 11-28-2007, 04:31 PM
Tim
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

On Wed, 2007-11-28 at 15:54 +0000, Duncan Berriman wrote:
> Its nothing wrong with Fedora (or for that matter it seems Vista which
> also has this on by default now).
>
> Its an out of date or wrongly configured router at the customer end
> causing the problem as it does not support tcp window scaling and thus
> causes performance issues.

I'm yet to encounter this error, oddly enough. Has anybody got some
known problem server addresses I can try out?

--
(This computer runs FC7, my others run FC4, FC5 & FC6, in case that's
important to the thread.)

Don't send private replies to my address, the mailbox is ignored.
I read messages from the public lists.

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Old 11-28-2007, 08:15 PM
"Duncan Berriman"
 
Default TCP/HTTP Bug Fedora Core 8 (and 6)

Unfortunately the server I discovered the problem with is not mine so I'm
not keen to give out its address and now that I have identified a problem
with it I'm sure the owner will quickly sort it out as any visitor using a
recent version of Linux or using Windows Vista will have problems accessing
their web site.

It shouldn't really happen if your router is a recent model or has up to
date rom and has been configured correctly.

>From the information on http://lwn.net/Articles/92727/ the rfc for this
change was published in 1992! From the looks of things people started
noticing issues in 2004 when it appears to have become a default in Linux
kernels. It also appears to be turned on in Windows Vista by default.

If you find it means someone is probably running a very old router or
firewall or has mis configured it.

Duncan

> -----Original Message-----
> From: fedora-list-bounces@redhat.com
> [mailto:fedora-list-bounces@redhat.com] On Behalf Of Tim
> Sent: 28 November 2007 17:31
> To: For users of Fedora
> Subject: RE: TCP/HTTP Bug Fedora Core 8 (and 6)
>
>
> On Wed, 2007-11-28 at 15:54 +0000, Duncan Berriman wrote:
> > Its nothing wrong with Fedora (or for that matter it seems
> Vista which
> > also has this on by default now).
> >
> > Its an out of date or wrongly configured router at the customer end
> > causing the problem as it does not support tcp window
> scaling and thus
> > causes performance issues.
>
> I'm yet to encounter this error, oddly enough. Has anybody got some
> known problem server addresses I can try out?
>
> --
> (This computer runs FC7, my others run FC4, FC5 & FC6, in case that's
> important to the thread.)
>
> Don't send private replies to my address, the mailbox is ignored.
> I read messages from the public lists.
>
> --
> fedora-list mailing list
> fedora-list@redhat.com
> To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list
>
> --
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
>

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