Guy Kewney

Technically, if I showed up in a restaurant that advertised ‘all you can eat’ it would be right to say that if they only sold hash browns and only had one pan to fry them in, I might not eat very much.

The chef could also argue that if he made one hash brown every half an hour, I couldn’t eat any more than that.

So I was extremely vexed to find that the world’s ISPs are sneakily rationing what we get from broadband.

‘Unlimited’ doesn’t mean what it should. In particular, if you use Bit Torrent or Edonkey for downloading big files, your ISP is quite likely to strangle the bit pipe.

I learned this from Sandvine, a company that makes the equipment the ISP uses to do this.

The technology is quite simple: a device sits in the network and looks at the data coming in. If it’s peer-to-peer traffic – like Skype or Bit Torrent – it puts a lower priority on those packets and in some cases can prevent connections.

They spot an attempt to connect to a Bit Torrent node – either to download or to upload and they limit the number of connections that are successful.

The sneaky thing about this is that you, the user, will just see a failure to connect or, even worse, you won’t. Someone else will.

They’ll ask their Bit Torrent client to find a host (you) and the client will try and fail. So you won’t be able to upload the file and the ISP will have more capacity, without buying more equipment.

Even nastier: if they have their own Internet voice service, they can give that priority. So if you use their VoIP phone service, you can find that it works really well, but if a Skype call comes in, it will buzz, blip and hiccup.

Is that unlimited broadband? In one sense, yes. If you accept that they aren’t setting a cap on the number of bytes you can download, it’s unlimited.

And, if you think that limited broadband means 200 minutes a month and they let you surf the web 24 hours a day, then anything else really is unlimited. But in a very real sense they are limiting what you can do.

Apparently this is very common. Exactly how many ISPs are using this equipment is hard to find out, because the ISPs aren’t boasting about it and Sandvine isn’t saying who its customers are.

But Sandvine did boast that peer-to-peer traffic was accounting for 70 per cent of all bits carried on networks before their equipment was installed and afterwards it was down to 20 per cent. The missing 50 per cent were ‘failed’ invisibly.

Of course in the real world it isn’t possible to offer everybody a service that runs at full speed for all subscribers all the time.

The economics of being an ISP mean it assumes that most of the time most customers are offline or only sending a few web page requests every few minutes.

Uploading pictures to Flickr isn’t too bad. You’re looking at about 1MB per photo and Flickr limits you to so many pictures per month. But with Bit Torrent, things get hairy, as we’re in the age of digital video.

A new episode of Desperate Housewives airs in the US and fans in Europe want it now – so they start downloading files around 600MB or more. And when they’ve got it, they forward it to other fans, which is a serious problem.

Speed isn’t the issue here. The system will only improve if the ISPs create a bigger data pipe, which costs serious money. So you can have the pipe, if you’re prepared to pay, but a standard £15 per month subscription won’t buy it.

When you’re the first customer, you’ll get it; when 50 other customers are sharing your connection in the local exchange, you certainly won’t.

What will happen is that technology will find a way around Sandvine. It can spot the digital signature of a VoIP call today; so if you encrypt it first, it will look like raw data.

But the big switch makers still reckon they have ways of detecting traffic patterns and will spot ‘unwelcome’ traffic, offering customers the option of switching it off. Some corporations prohibit Skype and there’s nothing illegal or immoral about their doing so.

What is immoral though, is pretending that a service is unlimited, when it isn’t. I intend to approach the Advertising Standards Authority, and complain that ISPs who offer an unlimited service should either stop limiting what you can do or stop making unwarranted claims. I suggest you do so, as well.

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