Size limit of ca 1kB on upload

I've been using adsl for about 7 years now with the same ethernet router with few problems. Over the last week or so, tho, I've been having a bizarre problem where any content posted of more than ca 1kB hangs and eventually times out. It looks like the connection is dropping after the 1kB. This applies to all protocols - ftp, smtp, http post - and is not restricted to any software or pc. So I can send short emails, but not long ones. Downloading, however, works without problem. There are no problems with logging in, and the router shows no obvious problems with errors.

My ISP (Pipex) tells me it's a problem with my router, but I have no great confidence in their diagnosis.

Anyone like to hazard a guess what might be causing this? I use Linux; is there a program I can install to check out the connection and try and locate the problem? It's making many apps pretty much unusable.

Hi

Typicallly this is a problem with the MTU setting on your computer or your router or both.

What operating system are you using?

What does it say about MTU if you visit this web page http://www.speedguide.net/analyzer.php

Regards

Phil

thanks for the reply, Philip, and your informative analyzer page. It gives MTU as 1480, and also says "RWIN seems to be set to a very small number". I can certainly play around and change these numbers, and see if that fixes the problem. But I don't understand why it should suddenly start occurring now, after 7 years w/o problem!

I last installed a (Linux) kernel some 6 weeks ago, and it was working ok up till about a week ago. Nothing has changed on my m/c since then. Might it be that these settings combined with some settings change at the ISP a week ago combined to create the problem?

Hi

Who is your internet provider? Normally you should have an MTU of 1500 so something has changed for that to be less. This could be your internet provider or something on your router or computer. If your Linux system is trying to send out larger packets of data and isn't allowing them to be fragmented you get the problem you are having.

I'm not familar enough with Linux to offer much more help.

Regards

Phil

"ifconfig eth0" shows mtu is set to 1500 on my box. According to http://www.speedguide.net/faq_in_q.php?category=98&q... "The most likely cause of different MTU than what you have set for your Registry (using the Optimizer or manually) is that a NAT router on the path is limiting the MTU to a lower value."

I can't find any setting for mtu on my router - and in any case the config there hasn't changed for 7 years. So, if mtu is the problem, then the finger seems to point, as I've assumed all along, to something at my isp (pipex).

I suppose I could try bothering one of my neighbours, installing my router/pc on their line, and see if it works.

Thanks for your help, anyway.

as an afterthought, is there a way to find out where on the network this lower mtu setting is being set?

Probably by the router. What router is it?

Not that I know of, try a lower value of 1458 first or 1430, or 1400.

Pipex is Tiscali now Carphone Warehouse, and its not unusual for odd network configs to appear and then magically vanish later.

In reply to a post by MrSaffron:

Not that I know of, try a lower value of 1458 first or 1430, or 1400.

yup, that seems to have done the trick. In case anyone else has a similar problem:
"ifconfig eth0 mtu 1458"
fixes it. I am now back to normal

In reply to a post by MrSaffron:

Pipex is Tiscali now Carphone Warehouse, and its not unusual for odd network configs to appear and then magically vanish later.

yes, that's always been my experience too. There are odd glitches which disappear after a while. This one was more serious as it was going on for a week or more. It is of course entirely possible that Windows was able to handle whatever change was made on the router, so most of Pipex's customers were unaffected.

Thanks for your help

In reply to a post by pwr:

yup, that seems to have done the trick. In case anyone else has a similar problem:
"ifconfig eth0 mtu 1458"
fixes it. I am now back to normal

Is this a command to your operating system or your router?