Daily Archives: August 18, 2006

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…

So, where’s the evidence?

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Interesting piece by Craig Murray, the former British ambassador to Uzbekistan.

None of the alleged terrorists had made a bomb. None had bought a plane ticket. Many did not have passports. It could be pretty difficult to convince a jury that these individuals were about to go through with suicide bombings, whatever they bragged about on the net.

What is more, many of those arrested had been under surveillance for more than a year – like thousands of other British Muslims. And not just Muslims. Like me. Nothing from that surveillance had indicated the need for early arrests.

Then an interrogation in Pakistan revealed this amazing plot to blow up multiple planes. Of course, the interrogators of the Pakistani dictator have ways of making people sing like canaries. As I witnessed in Uzbekistan, you can get the most extraordinary information from people desperate to stop or avert torture. What you don’t get is the truth.

We also have the extraordinary question of Bush and Blair discussing arrests the weekend before they were made. Why? Both in domestic trouble, they longed for a chance to change the story. The intelligence from Pakistan, however dodgy, gave them a chance. Comparisons with 9/11 were all over front pages…

Txts R going thrU th ruf

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BBC NEWS | Technology | Texting levels reach record high
Mobile phone users in the UK sent a record 3.3 billion text messages in May, figures show.

The Big Brother TV show, the FA Cup and Champions League finals all helped boost numbers, according to the Mobile Data Association (MDA).

Person-to-person texts sent across all mobile phone networks averaged 106 million per day last month.

This figure was up 26% on May 2005 and beat the previous UK record of 3.2 billion texts sent in March.

That figure could rise higher this month due to a surge in World Cup-related messages.

An MDA spokeswoman said: “Texting has become second nature to UK mobile phone users, with many bank holiday arrangements being made via text.”

More than 120 million text messages were sent on FA Cup final day, rising to 124 million texts on Champions League final day.

A predicted 36.5 billion texts will be sent by UK mobile phone users this year – up from 32 billion in 2005, according to the MDA.

DVD sales slide as newspapers and magazines persist with giveaways

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From today’s Guardian…

Newspapers and magazines have given away as many free DVDs as have been sold in shops so far this year, according to researchers.More than 130m free DVDs, or an average of five per household, were handed out last year and 54m free DVDs have been given away in the first quarter of this year alone, data from Screen Digest shows.Analysts said the flood of free films boded ill for retailers such as HMV, which already faced tough competition from supermarkets and online stores. DVD sales have fallen as newspapers and magazines have given away films in an effort to increase circulation. The average household bought 11.4 DVDs last year, down from 12.5 in 2004…

Boeing Drops In-Flight Wi-Fi

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From PC World…

Boeing will phase out its Connexion by Boeing service, leaving what it once considered a promising market for in-flight Internet access.

Connexion offers broadband Internet access via Wi-Fi, using a satellite connection to the Internet, that costs about $10 to $30 per flight on commercial airlines. It also offers high-speed Internet access on executive jets and ships.

Connexion is offered on some commercial flights in Europe and Asia but was never adopted by a major U.S. carrier. First conceived in 2000, the service was approved by the Federal Aviation Administration in May 2002 as the nation’s airlines were reeling from a travel slump that followed the September 11, 2001, terrorist attacks.

Besides, it’s not that good when your laptop is in the hold!

The cluelessness of businessmen

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This obnoxious sign (photographed by Scott Beale, to whom many thanks) greeted visitors to LinuxWorld. The cretin responsible for it should be taken out and shot. It’s an example of what happens to a movement when idiots with MBAs get their hooks into it. Apart from anything else, Linux is the creation of people who did it for the love (or the sheer hell) of it. Since when did ‘professional’ become a term of approbation?

U2 can be a hypocrite

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If, like me, you are repelled by the spectacle of millionaire rock stars miming statemanship, then you will be cheered by John Harris’s acute piece in today’s Guardian…

In response to the fact that the Irish government has recently changed its notoriously cuddly fiscal regime, so that creative types can only earn a trifling £170,000 before paying tax, Bono and his friends have moved part of their empire to the Netherlands. This may seem like a rather cruel interpretation of the news, but I don’t think I can help it: though Bono is very keen on feeding, watering and healing the world, he and his group – collectively worth £460m, it says here – don’t seem to be too keen on paying for Irish schools and hospitals. That’s good, isn’t it?

Thanks to Pete for pointing it out.

The Constitution’s the boss

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From Good Morning Silicon Valley…

A federal judge in Detroit on Thursday struck down the National Security Agency’s warrantless domestic surveillance program, calling it unconstitutional and an illegal abuse of presidential power. In a 43-page opinion, Judge Anna Diggs Taylor made quick work of the Bush administration’s “it’s classified” defense, pointing out that the program is not beyond judicial scrutiny. “The Presidential Oath of Office is set forth in the Constitution and requires him to swear or affirm that he ‘will, to the best of my ability, preserve, protect and defend the Constitution of the United States,’ ” Taylor wrote. “The Government appears to argue here that, pursuant to the penumbra of Constitutional language in Article II, and particularly because the President is designated Commander in Chief of the Army and Navy, he has been granted the inherent power to violate not only the laws of the Congress but the First and Fourth Amendments of the Constitution, itself. We must first note that the Office of the Chief Executive has itself been created, with its powers, by the Constitution. There are no hereditary Kings in America and no powers not created by the Constitution. So all ‘inherent powers’ must derive from that Constitution.”

Yes, Ma’am. The Feds are appealing, of course. But an interesting question now looms, namely the legal liability of the phone and internet companies that have been doing the government’s dirty work for it if a higher court rules that it was illegal all along.