problems with large files

I have two computers under my care, just down the street from each
other. They both run Slackware-current with a 2.6.12.3 kernel,
althought my problem was there with 2.6.11.11 kernel as well.

Machine A is connected to the Internet via fibre while Machine B is
connected via DSL.

File transfers (email and scp) from A to B are fine, no matter what the
file size. Large files from B to A bog down and usually time out. As a
test I've sent myself an email from A to B which redirects back to me at
A and it only took a few seconds to make the first leg, but still didn't
get delivered almost three hours later.

This behaviour is consistent. Frankly, I'm at a loss as to where to
look. Any suggestions?

Mike

On Thu, 28 Jul 2005 17:59:11 GMT, Michael Surette <(E-Mail Removed)> wrote:
> I have two computers under my care, just down the street from each
> other. They both run Slackware-current with a 2.6.12.3 kernel,
> althought my problem was there with 2.6.11.11 kernel as well.

> Machine A is connected to the Internet via fibre while Machine B is
> connected via DSL.

> File transfers (email and scp) from A to B are fine, no matter what the
> file size. Large files from B to A bog down and usually time out. As a
> test I've sent myself an email from A to B which redirects back to me at
> A and it only took a few seconds to make the first leg, but still didn't
> get delivered almost three hours later.

> This behaviour is consistent. Frankly, I'm at a loss as to where to
> look. Any suggestions?

Is the slowness/timeout only with B->A, or does it also happen with
<some other machine>->A? If it also happens with some other machine,
then it's specific to A incoming, not B->A.

Do they have the same firewalls? Is either machine's incoming or
outgoing firewall slowing the connection?

Do their internet connections have different upload/download speeds or
qualities? For example A->B uses A's upload speed and B's download
speed, whereas B->A uses A's download and B's upload.

I assume by A->B you mean A->internet->B, right?

--
Dale Dellutri <(E-Mail Removed)> (lose the Q's)

Dale Dellutri wrote:
> On Thu, 28 Jul 2005 17:59:11 GMT, Michael Surette <(E-Mail Removed)> wrote:
>
>>I have two computers under my care, just down the street from each
>>other. They both run Slackware-current with a 2.6.12.3 kernel,
>>althought my problem was there with 2.6.11.11 kernel as well.
>
>
>>Machine A is connected to the Internet via fibre while Machine B is
>>connected via DSL.
>
>
>>File transfers (email and scp) from A to B are fine, no matter what the
>>file size. Large files from B to A bog down and usually time out. As a
>>test I've sent myself an email from A to B which redirects back to me at
>>A and it only took a few seconds to make the first leg, but still didn't
>>get delivered almost three hours later.
>
>
>>This behaviour is consistent. Frankly, I'm at a loss as to where to
>>look. Any suggestions?
>
>
> Is the slowness/timeout only with B->A, or does it also happen with
> <some other machine>->A? If it also happens with some other machine,
> then it's specific to A incoming, not B->A.
>
> Do they have the same firewalls? Is either machine's incoming or
> outgoing firewall slowing the connection?
>
> Do their internet connections have different upload/download speeds or
> qualities? For example A->B uses A's upload speed and B's download
> speed, whereas B->A uses A's download and B's upload.
>
> I assume by A->B you mean A->internet->B, right?
>

Could be B does not have enough RAM. Last time I saw this problem
however it was a hardware problem with the network card.

--
Respectfully,


CL Gilbert

Dale Dellutri wrote:
> On Thu, 28 Jul 2005 17:59:11 GMT, Michael Surette <(E-Mail Removed)> wrote:
>
> Is the slowness/timeout only with B->A, or does it also happen with
> <some other machine>->A? If it also happens with some other machine,
> then it's specific to A incoming, not B->A.
>
I haven't noticed any problems from anywhere else. My test files are
just over 1MB. I see emails coming in over 10MB from elsewhere with no
problems

> Do they have the same firewalls? Is either machine's incoming or
> outgoing firewall slowing the connection?
>
They both have iptables firewalls, but the rules are diffenent, I'll
check into that.

> Do their internet connections have different upload/download speeds or
> qualities? For example A->B uses A's upload speed and B's download
> speed, whereas B->A uses A's download and B's upload.
>
Good point. The fibre connection is almost as fast as my internal LAN.
The 3MB DSL is slower and asymetrical. That would make B's DSL speed
the controlling factor. However we have no problems with our other DSL
sites.

> I assume by A->B you mean A->internet->B, right?
>
Right.

Thanks for the ideas. I'm off to check my firewall rules. More
thoughts are welcome.

Mike

Michael Surette wrote:
> I have two computers under my care, just down the street from each
> other. They both run Slackware-current with a 2.6.12.3 kernel,
> althought my problem was there with 2.6.11.11 kernel as well.
>
> Machine A is connected to the Internet via fibre while Machine B is
> connected via DSL.
>
> File transfers (email and scp) from A to B are fine, no matter what the
> file size. Large files from B to A bog down and usually time out. As a
> test I've sent myself an email from A to B which redirects back to me at
> A and it only took a few seconds to make the first leg, but still didn't
> get delivered almost three hours later.

Email What?? Email How ?? ReDirected how?? Each machine running
sendmail ?? Same version email programs?? Details Man we're not mind
readers.

>
> This behaviour is consistent. Frankly, I'm at a loss as to where to
> look. Any suggestions?
>
> Mike

How do A and B work to you C ?
First thought is isp problem with DSL provider.

CL (dnoyeB) Gilbert wrote:
> Dale Dellutri wrote:
>
>> On Thu, 28 Jul 2005 17:59:11 GMT, Michael Surette
>> <(E-Mail Removed)> wrote:
>>

>
> Could be B does not have enough RAM. Last time I saw this problem
> however it was a hardware problem with the network card.
>

B has 512 MB of ram. I'll have to try another network card.

Thanks for the input.

Mike

SEND NO SPAM wrote:
> Michael Surette wrote:
>
>> File transfers (email and scp) from A to B are fine, no matter what
>> the file size. Large files from B to A bog down and usually time
>> out. As a test I've sent myself an email from A to B which redirects
>> back to me at A and it only took a few seconds to make the first leg,
>> but still didn't get delivered almost three hours later.
>
>
> Email What?? Email How ?? ReDirected how?? Each machine running
> sendmail ?? Same version email programs?? Details Man we're not mind
> readers.

Both are running the latest version of sendmail (8.13.4).
I am postmaster at B so I sent an email with an attachment to
postmaster@b which gets aliased to my email address here.

> How do A and B work to you C ?
> First thought is isp problem with DSL provider.

My workstation is on the same network as A and has no problems with
transfers in either direction to A. I am unreachable from B, although I
have no problems transfering to B.

I have since tried to transfer via scp to A from each of our sites as a
test. One other site gave me the same problem. It's an older 400MHz
Pentium with 128MB of ram. All our other sites are at least 1GHz Athlon
with 512 MB of ram.

I'm definitley leaning on the side of a hardware problem at this point.

Mike

Hi! Your question seems a little bit strange because:

When you copy like A -> Internet -> B

B copy the file from A with fibre upload speed (3MB Adsl line is like
you download at 300kb/s)

BUT when you try to copy like B -> Internet -> A

A copy the file from B with ADLS UPLOAD SPEED

And as adsl is asymetrical, usually the upload speed is far lower than
download speed. For exemple, here in Belgium, I have an ADSL line 4Mb
down speed / 384kb upload speed.

So it's normal it takes more time. But it should transfer anyway, here
is a problem with your ISP maybe who doesn't allow outbound SMTP
connection.



Hope it helps!



Ad

Michael Surette <(E-Mail Removed)> wrote:
> I have two computers under my care, just down the street from each
> other. They both run Slackware-current with a 2.6.12.3 kernel,
> althought my problem was there with 2.6.11.11 kernel as well.

> Machine A is connected to the Internet via fibre while Machine B is
> connected via DSL.

> File transfers (email and scp) from A to B are fine, no matter what the
> file size. Large files from B to A bog down and usually time out. As a
> test I've sent myself an email from A to B which redirects back to me at
> A and it only took a few seconds to make the first leg, but still didn't
> get delivered almost three hours later.

> This behaviour is consistent. Frankly, I'm at a loss as to where to
> look. Any suggestions?

Perhaps it's PPPoE DSL and you just need to configure the firewall
on B to use the --clamp-mss-to-pmtu option; see man iptables for how
to do that.

--
Clifford Kite Email: "echo xvgr_yvahk-(E-Mail Removed)|rot13"

On Thu, 28 Jul 2005 18:25:49 -0500, Clifford Kite <(E-Mail Removed)> wrote:
>
> > This behaviour is consistent. Frankly, I'm at a loss as to where to
> > look. Any suggestions?

Large file attachments are being dropped by ISPs routinely, without
notice. Best option from my POV was to setup anonymous FTP server
with speed / connection limited write only upload directory

> Perhaps it's PPPoE DSL and you just need to configure the firewall
> on B to use the --clamp-mss-to-pmtu option; see man iptables for how
> to do that.

This addresses a different issue, where packets of a certain size
range are dropped, different symptoms, use the ping with packet
size option to discover.

Related is ISPs dropping all ICMPs, then you must clamp to a set
value, I set the Cisco minimum MSS of 1360:

http://www.cisco.com/warp/public/794/router_mtu.html

As path MTU discovery not useful in this case.

Cheers,
Grant.