Problem with random web pages failing to load?

A standard RJ45 Ethernet connector.
RJ45 - preferable to USB

Here’s one that’s bizarre but does make some sense eventually.

My boss had this issue originally and we never resolved it, I’m ashamed to say. We (erm… I) effectively blamed it on France Telecom / Orange and therefore not anything we could to something about. The problem was that some websites would pretty much always fail to load while others would pop up no problem at all. It just seemed less than coincidental that orange.fr worked fine every time whereas – fo instance plus.net failed. Tesco would work, but Boots wouldn’t. Every Google page (mail, documents, calendar) was fine, but forget getting into Hotmail. Outlook would receive, but not send when connecting to our own mailserver.

All the pages connected, but resulted in the browser just saying “Waiting for…” and never loading the pages, except for very rare flashes when one would work… but the same problem re-occuring if we refreshed or clicked on an internal link.

He was/is using a NetGear DG834G wireless router and the problem occurred via wi-fi and via direct cable connection. I took my laptop over, and had the same issue.

I left France, the problem remained unresolved but he had internet access in the office anyway.

I got back to France in January and two of the child care managers had the exact same problem in their flat. Again, they were using a DG834G. Again, we blamed France Telecom who checked the line and told us “C’est bon!” Then pretty much whatever French for “fuck off” is. Their customer service is actually worse than BT, which is impressive.

So I went over to prove that it was the line. Armed with another NetGear, a Thompson SpeedTouch 330 and a Sagem 800, plus a handful of microfilters and my laptop with XP and Ubuntu on it, my aim was to remove every common factor and leave the line as the only possible fault.

Laptop first. XP and Ubuntu both failed on the same websites wired up and wireless. I then updated the firmware in the router to the latest version. No joy.

Next step, I installed the drivers for the Sagem on Lydia’s machine, plugged it in, configured a “dial-up” connection and … blow me. Everything worked.

It was slower than the router connection, I assume because of the speed of the USB cable compared to CAT-5 (I think the modem uses USB1.1), but every site loaded.

Hum.

The problem was, this meant the line was fine. And the only equipment we had that would get it to work was a single-user USB router. Options started to flood in – get a router (not a router/modem) and a USB to RJ45 adaptor. Put the drivers on Lou and Lyd’s machines, give them a hub and share the connection on both PCs. That way whoever was home first would connect and the next one could share it.

What a lot of work.

But if the router’s faulty, then another one will solve the problem, surely?

So the next morning, Louise picked up a new DG834G (this one happened to be a v4 – the others were v3) and brought it up to where I was working. I configured it and, on a whim, tested the old one on someone else’s connection.

It worked. No problems.

So, more information. The issue was a result of some combination of that router and that line. Technically, the line was partially at fault. It had to be. Louise left with the new router and would call me once she got home and tested it.

Where it didn’t work. Same problem as the old one.

What. The. F…?

Armed with all the info to hand, I did a dig on Google. I can’t remember the terms I used, but after filtering through a lot of posts on various forums, a pattern developed. The issue isn’t ISP-dependant (I saw problems with AOL, PlusNet, Orange and several others) or with particular routers (a handful of Netgears, rebadged Thompsons, Linksys, etc.) but the solution was simple and it worked:

Reduce the MTU value on the router.

I can’t give you details for others, but on the NetGears just log on as the administrator to the web interface and locate the WAN settings down the left. In there, it defaults to 1500 or something. Reduce this to 1400. Click Apply. Wait a minute.

And the internet starts working again as if by magic.

Here comes the science:

An MTU is a Maximum Transmission Unit – the size of the largest packet of data that a communications protocol can forward. A higher MTU increases bandwidth efficiency, but large packets can block slower connections. It seems the 1500 default size (which, incidentally, is the largest allowed by Ethernet standards) was too much for the “fully working” France Telecom internet connection. By reducing this to smaller chunks, the blockages vanished and the connection started to work again.

I’m just glad we sorted it. Not as glad as Lou and Lyds, though. I believe I’m getting drinks out of this!

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