Category Archives: Technology

The limits of Skype

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Bob Cringeley has an interesting analysis of how Skype works. Extract:

If you are a Skype user then you are used to seeing on your Skype client interface a real-time read-out of how many people are using the system at that very moment. I just looked and as I write this that number is just over 6.1 million. But what does this number actually mean? It means 6.1 million clients were registered with the system just then, NOT that 6.1 million people were talking. If all 6.1 million Skype users tried to talk at the same time, it would probably bring down the system.

Hey, it isn’t supposed to work that way! Skype is a peer-to-peer (P2P) network, right? And that means its capacity will expand to handle any number of users. No. Skype uses a technology called “Skype peer-to-peer,” which has some definite server involvement and therefore finite scalability. In fact, the number of people who can use — really, actively use — Skype at any moment is probably back to that 10-15 percent, which in this case would be 10-15 percent of 6.1 million or a maximum of 900,000 users. That’s a LOT less than the nearly 200 million registered Skype users and gives us a sense of what eBay got for its $2.6 billion.

Skype’s server involvement works two ways. First there is the registration server that helps you log-in, tells the world you are available, and facilitates connections, some of which are true peer-to-peer. But a lot of Skype connections aren’t P2P at all. These connections require some server assist because one side of the conversation or another is hidden behind a Network Address Translation (NAT) firewall. NAT was invented a dozen years ago to help preserve IPv4 addressing and has thrived as a poor man’s firewall for home networks, but NAT is the bane of P2P systems like Skype that often can’t see nodes hidden behind NAT firewalls.

The way Skype handles this so-called “NAT traversal” problem is by inserting a server in the middle that can be seen by connections at both ends. This server for Skype is called a “super node” and may well be inside your computer without your knowledge, because Skype super nodes use borrowed bandwidth and processing power. Lucky us.

Skype users who are operating in true peer-to-peer fashion are those whose IP addresses, whether static or dynamic, are readily viewable from anywhere on the Internet. That means no firewall, no Zone Alarm, no Gibson Shields Up!, which is a condition increasingly rare among Internet users. For those Skype users who do sit behind firewalls or use Zone Alarm, they connect through a super node that is visible from both ends of the conversation. Again, the super node has to be unprotected, and it has to have a surplus of bandwidth to handle the conversation relay. This kind of wide open connection is even rarer and there are right now only about 20,000 such super nodes on the Skype system.

Each super node can handle about 10 simultaneous connections for a total of 200,000 connections or 400,000 users. If half of Skype calls have to go through super nodes, that means the actual maximum capacity of the system is less than one million callers…

The memory man

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Following a link about something else, I came on this piece about Gordon Bell’s MyLifeBits project…

Gordon Bell doesn’t need to remember, but has no chance of forgetting. At the age of 71, he is recording as much of his life as modern technology will allow, storing it all on a vast database: a digital facsimile of a life lived.

If he goes for a walk, a miniature camera that dangles from his neck snaps pictures every minute or so, immediately committing the scene to a memory built not of neurons but ones and noughts. If he wanders into a cafe, sensors note the change in light, the shift of temperature and squirrel the information away. Conversations are recorded and steps logged thanks to a GPS receiver carried with him.

Dr Bell has now stored so much of his life on computer that he is in danger of forgetting how to remember. “I look at it as a surrogate memory,” he says. If he wants to recall something, he switches on and picks his way through days and months of information until he finds what he is after. It was all dreamt up at Microsoft’s Bay Area Research Centre in San Francisco, where Dr Bell works…

Thanks to Wesley Bradley of Activate Design for spotting the broken link to Gordon Bell.

Websites that changed the world

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The Observer had the nice idea of celebrating the 15th birthday of the Web by compiling a list of the sites that have had had a big influence on our lives. I wrote the introduction. Sample:

By any standards, the web represents a colossal change in our information environment. And the strange thing is that it has come about in just 15 years. Actually, most of it has happened in less than that, because the web only went mainstream in 1993, when the first graphical browsers – the computer programs we use to access the web – were released. So these are early days. We can no more envisage the long-term implications of what has happened than dear old Gutenberg could…

To get a handle on the scale of what has happened, think back to what the world was like 15 years ago. Amazon was a large river in South America. Ryanair was an Irish airline that flew to places nobody had ever heard of. eBay was a typo. Yahoo was a term from Gulliver’s Travels. A googol was a very large number (one followed by a hundred zeroes). Classified ads were densely printed matter in newspapers. ‘Encyclopedia’ was a synonym for Encyclopedia Britannica. And if you wanted to read what your MP had said in the Commons yesterday you had to queue at the Stationery Office in London to buy Hansard. Oh, and there were quaint little shops in high streets called ‘travel agents’…

Posted in Web

Phishing is so yesterday

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A new use for VoIP. From Internet News…

Just as Internet surfers have gotten wise to the fine art of phishing, along comes a new scam utilizing a new technology.

Creative thieves are now switching their efforts to “vishing,” which uses Voice over Internet Protocol (VoIP) phones instead of a misdirected Web link to steal user information.

Phishing (define) is the sneaky art of sending an e-mail to people pretending to be from a bank or major online merchant, such as Amazon (Quote, Chart)or EBay (Quote, Chart), asking them to click on a link and verify their account information.

The user is then directed to a fake site that collects the login and password information.

Repeated efforts on the part of security firms have educated users to be cautious about clicking on links from unknown senders.

But now, the criminal element has shifted from asking people to click on links to placing a phone call instead. Only the number isn’t to a bank or credit card, it’s to a VoIP phone that can recognize telephone keystrokes.

The thieves don’t even use an e-mail blast, they use a war dial over a VoIP system to blanket an area. A recorded message tells the person receiving the call that their credit card has been breached and to “call the following (regional) phone number immediately.”

When the user calls the number, another message is played stating “this is account verification please enter your 16 digit account number.” The rest is academic.

Secure Computing, which specializes in secure connections over networks, sent up the red flag over this new method. Secure Computing engineers have been tracking news group sites and open disclosure discussion groups discussing vishing.

“This is just a natural evolution of phishing itself,” said Paul Henry, vice president of strategic accounts for Secure Computing….

Thanks to Kevin Cryer for the link.

Microsoft to unveil $100 laptop killer?

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Hot on the heels of the news that the Indian government has rejected the ‘One Laptop per Child’ idea comes an Engadget story that Microsoft, stung by the OLPC team’s decision to adopt Linux rather than Windows CE, is going to release a ‘foneplus’ — i.e. a mobile phone with port for connecting a TV screen and a keyboard. No pics, and maybe it’s just a rumour, but…

The Scaredy Cat Encyclopedia

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From David Weinberger’s journal…

The Encyclopedia Britannica has refused my request to interview an editor for 15 minutes about the process by which it chooses authors. I explained that this is for a book. But, the head of the Britannica’s communications group decided – based on what? – that they don’t want to support people who are “cheerleading for the downfall of businesses that they deem to be part of an old regime.”

All systems go (on my Mac)

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This morning’s Observer column — about virtualisation…

At this point, dear reader, I know what you’re thinking. However fascinating this ‘virtual machine’ nonsense may be to geeks, it’s of no interest to normal human beings. You may feel as Mrs Dave Barry did when her husband, the Miami Herald humorist, took her for a spin in a Humvee and proudly explained that the vehicle could inflate and deflate its tyres while in motion. Why, she asked, would anyone want to do that?

So what’s the point of virtualisation? Simply that it provides a vivid illustration of the most disruptive attribute of digital technology – its capability to break the link between an application and a physical platform. Once upon a time, if you bought a PC it ran Windows, and if you bought a Mac it ran Apple’s operating system. But now Macs run Windows, and IBM ThinkPads – which have the same processor – can run OS X (though of course Apple is doing its best to head off that possibility). And Linux runs on everything.

This disconnection of application/ service from hardware is happening all over the place…

Back to the future

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I know it’s not a very exciting photograph, (Quentin has a much better one on his Blog) but it’s significant in its way. It shows Ubuntu Linux running faultlessly alongside Mac OS X on my Dual Core Mac, courtesy of Parallels Workstation. If I had more RAM (and a Windows licence) I could also run Windows XP (as Quentin does). Virtualisation is an old idea, but it’s really coming of age now. And what it means is that the one-to-one bonding between the platform and the application is being eroded. So not only is the network becoming the computer, but the computer is becoming any operating system you like. Quentin thinks that virtualisation — or virtualization, as Google likes it — is going to be a very hot topic from now on, and I think he’s right. Just look at this experiment he set up at Ndiyo.

Desert Island Discs

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Image (c) bp plc

While driving yesterday I was listening to John ‘Lord’ Browne, CEO of BP, being interviewed on Radio 4’s Desert Island Discs programme and was struck by one of his choices — a song by Diana Krall. But of course I was unable to make a note of it at the time. It turns out that the BBC maintains a useful web page detailing the choices of current and past guests on the programme. Later, I bought the track — ‘Narrow Daylight’, written by Diana Krall and Elvis Costello — from iTunes, and very nice it is too.

I met Browne at a college dinner a few months back and discovered that we have two interests in common — photography and cigars. We use similar cameras, but he has much better smokes. Which is not entirely surprising: after all, he’s the one with money to burn.