Die another Day? Or How Madonna crashed the Internet

A lone mike under bright stage lights

From the cs4fn archive …

When pop star Madonna took to the stage at Brixton Academy in 2001 for a rare appearance she made Internet history and caused more that a little Internet misery. Her concert performance was webcast; that is it was broadcast real time over the Internet. A record-breaking audience of 9 million tuned in, and that’s where the trouble started…

The Internet’s early career

The Internet started its career as a way of sending text messages between military bases. What was important was that the message got through, even if parts of the network were damaged say, during times of war. The vision was to build a communications system that could not fail; even if individual computers did, the Internet would never crash. The text messages were split up into tiny packets of information and each of these was sent with an address and their position in the message over the wire. Going via a series of computer links it reached its destination a bit like someone sending a car home bit by bit through the post and then rebuilding it. Because it’s split up the different bits can go by different routes.

Express yourself (but be polite please)

To send all these bits of information a set of protocols (ways of communicating between the computers making up the Internet) were devised. When passing on a packet of information the sending machine first asks the receiving machine if it is both there and ready. If it replies yes then the packet is sent. Then, being a polite protocol, the sender asks the receiver if the packets all arrived safely. This way, with the right address, the packets can find the best way to go from A to B. If on the way some of the links in the chain are damaged and don’t reply, the messages can be sent by a different route. Similarly if some of the packets gets lost in transit between links and need to be resent, or packets are delayed in being sent because they have to go by a round about route, the protocol can work round it. It’s just a matter of time before all the packets arrive at the final destination and can be put back in order. With text the time taken to get there doesn’t really matter that much.

The Internet gets into the groove

The problem with live pop videos, like a Madonna concert, is that it’s no use if the last part of the song arrives first, or you have to wait half an hour for the middle chorus to turn up, or the last word in a sentence vanishes. It needs to all arrive in real time. After all, that is how it’s being sung. So to make web casting work there needs to be something different, a new way of sending the packets. It needs to be fast and it needs to deal with lots more packets as video images carry a gigantic amount of data. The solution is to add something new to the Internet, called an overlay network. This sits on top of the normal wiring but behaves very differently.

The Internet turns rock and roll rebel

So the new real time transmission protocol gets a bit rock and roll, and stops being quite so polite. It takes the packets and throws them quickly onto the Internet. If the receiver catches them, fine. If it doesn’t, then so what? The sender is too busy to check like in the old days. It has to keep up with the music! If the packets are kept small, an odd one lost won’t be missed. This overlay network called the Mbone, lets people tune into the transmissions like a TV station. All these packages are being thrown around and if you want to you can join in and pick them up.

Crazy for you

Like dozens of cars

all racing to get through

a tunnel there were traffic jams.

It was Internet gridlock.

The Madonna webcast was one of the first real tests of this new type of approach. She had millions of eager fans, but it was early days for the technology. Most people watching had slow dial-up modems rather than broadband. Also the number of computers making up the links in the Internet were small and of limited power. As more and more people tuned in to watch, more and more packets needed to be sent and more and more of the links started to clog up. Like dozens of cars all racing to get through a tunnel there were traffic jams. Packets that couldn’t get through tried to find other routes to their destination … which also ended up blocked. If they did finally arrive they couldn’t get through onto the viewers PC as the connection was slow, and if they did, very many were too late to be of any use. It was Internet gridlock.

Who’s that girl?

Viewers suffered as the pictures and sound cut in and out. Pictures froze then jumped. Packets arrived well after their use by date, meaning earlier images had been shown missing bits and looking fuzzy. You couldn’t even recognise Madonna on stage. Some researchers found that packets had, for example, passed over seven different networks to reach a PC in a hotel just four miles away. The packets had taken the scenic route round the world, and arrived too late for the party. It wasn’t only the Madonna fans who suffered. The broadcast made use of the underlying wiring of the Internet and it had filled up with millions of frantic Madonna packets. Anyone else trying to use the Internet at the time discovered that it had virtually ground to a halt and was useless. Madonna’s fans had effectively crashed the Internet!

Webcasts in Vogue

Today’s webcasts have moved on tremendously using the lessons learned from the early days of the Madonna Internet crash. Today video is very much a part of the Internet’s day-to-day duties: the speed of the computer links of the Internet and their processing power has increased massively; more homes have broadband so the packets can get to your PC faster; satellite uplinks now allow the network to identify where the traffic jams are and route the data up and over them; extra links are put into the Internet to switch on at busy times; there are now techniques to unnoticeably compress videos down to small numbers of packets, and intelligent algorithms have been developed to reroute data effectively round blocks. We can also now combine the information flowing to the viewers with information coming back from them so allowing interactive webcasts. With the advent of digital television this service is now in our homes and not just on our PC’s.

Living in a material world

It’s because of thousands of scientists working on new and improved technology and software that we can now watch as the housemate’s antics stream live from the Big Brother house, vote from our armchair for our favourite talent show contestant or ‘press red’ and listen to the director’s commentary as we watch our favourite TV show. Like water and electricity the Internet is now an accepted part of our lives. However, as we come up with even more popular TV shows and concerts, strive to improve the quality of sound and pictures, more people upgrade to broadband and more and more video information floods the Internet … will the Internet Die another Day?

Peter W. McOwan and Paul Curzon, Queen Mary University of London, 2006

Read more about women in computing in the cs4fn special issue “The Woman are Here”.

Are you there yet?

Plenty of people love the Weasley family’s clock from the Harry Potter books and films. It shows where members of the family are at any given time. Instead of numbers giving the time, the clock face has locations where someone might be (home, school, shopping) and the many hands on the clock show the family members. The wizarding world uses magic to make their whereabouts clock work, but muggles (and squibs) can use mobile network data to build a simple version, and use Bayesian networks to improve it.

A cell phone tower looking up from inside to a blue sky

Your mobile phone is in contact with several cell towers in the mobile provider’s network. When you want to send a message, it goes first to the nearest cell tower before passing through the network, finally reaching your friend’s phone. As you move around, from home to school, for example, you will pass several towers. The closer you are to a tower the stronger the signal there, and the phone network uses this to estimate where you are, based on signal strength from several towers. This means that, as long as your phone is with you, it can act as a sensor for your location and track you, just like the Weasley’s whereabouts clock.

You could also have a similar system at home that monitors your location, so that it switches on the lights and heating as you get closer to home to welcome you back. On a typical day you might head home somewhere between 3 and 6pm (depending on after-school events) and as you leave school the connection to your phone from the tower nearest the school will weaken, but connections will strengthen with the other cell towers on your route home. But what if you appear to be heading home at 11 in the morning? Perhaps you are, or maybe actually the signal has just dropped from the tower nearest to the school so a tower nearer your home is now getting the strongest signal!

A system using Bayesian logic to determine ‘near home’ or ‘not near home’ can be trained to put things into context. Unless you are ill, it’s unlikely that you’d be heading home before the afternoon so you can use these predicted timings to give a likelihood score of an event (such as you heading home). A Bayesian network takes a piece of information (‘person might be nearby’) and considers this in the context of previous knowledge (‘and that’s expected at this time of day so probably true’ or ‘but is unlikely to be nearby now so more information is needed’). Unlike machine learning which just looks for any patterns in data, in a Bayesian networks approach the way one thing being considered does or does not cause other things is built in from the outset. Here it builds in the different possible causes of the signal dropping at a cell tower.

You could also set up a similar system in a home using wifi points to predict where you are and so what you are doing. Information like that could then feed data into a personalised artificial intelligence looking after you. Not all magic has to be run by magic!

-Jo Brodie, Queen Mary University of London, Spring 2021

Download Issue 27 of the cs4fn magazine on Smart Health here.

This post and issue 27 of the cs4fn magazine have been funded by EPSRC as part of the PAMBAYESIAN project. This article was inspired by

Inspired by the blog on Presence Detection Part 1: Home Assistant & Bayesian Probability and a previous cs4fn article on making a Whereabouts Clock.

In a New York nanosecond

New technology can have unforeseen effects. The Law in particular can sometimes struggle to keep up, but for the IT savvy lawyer that can mean opportunity. For example, one bunch of lawyers realised that the way money moves round the world electronically could give their clients the edge. Nanoseconds are all it takes. As a result, a bunch of New York nanoseconds gave Judges in the Southern district court of the city a real headache.

Image by Gerd Altmann from Pixabay 

Different countries have different laws. That means lawyers will go out of their way to apply the law for their clients in the right country. It can make all the difference. Unlike some other countries US maritime law allows a person to freeze a person’s assets, even before a decision has been reached, when there is a maritime claim against them. For example, if a merchant hasn’t been paid for a shipload of cargo, or if a shipyard hasn’t been paid for ship repairs, then they can use this rule to freeze the defaulter’s money. Otherwise a win, when it comes, could be rather hollow, with the money long placed out of reach. The only trouble for the lawyers is that the money has to be in the US for the US law to apply.

Frozen money

That is where the technology comes in. Bankers don’t ship physical money from country to country, it’s all done electronically now… A consequence of the way the banking system was set up is that dollar transactions had to pass through the US banking centre in Manhattan as the money has to move from place to place. That’s an easy thing to require data to do in the age of the Internet. It only spends a fraction of a second in New York before it jumps on somewhere else. The law, of course, makes no distinction over shrinking timescales in which computers make things happen. A prepared lawyer can have the money frozen in that instant as just at that moment it is in the US.

That was great for people wanting to hold up money. It was a nightmare for the New York judges, though. Once the lawyers caught on about those nanoseconds the work started stacking up for the judges. All those fractions of a second added up to hours of the Judges’ time granting permission for the money to be seized. Every day the poor New York judges had to process hundreds and hundreds of requests, just in case some disputed money happened to pass through that day. To seize the money, it wasn’t enough just to put in a request and wait, ready to pounce when the money lands in Manhattan. Instead, just like a Spider re-spinning its web every morning, the trap had to be renewed daily. To do that the lawyers had to serve the bank daily with notice that if any money passed through that day it had to be stopped in its high speed tracks.

New technology constantly brings up new problems like this, when old laws or procedures are found to be wanting when technology changes the way things are done: changes things far beyond the imagination of those who drafted the laws. Just as technology never stands still, neither does the law…or the IT savvy lawyer.

Paul Curzon, Queen Mary University of London, Summer 2017, updated Spring 2021

Who invented Morse code?

by Paul Curzon, Queen Mary University of London

Morse code tapper: www.istock.com 877875

Who invented Morse code? Silly question, surely! Samuel Morse, of course. He is one of the most celebrated inventors on the planet as a result. Morse code helped revolutionise global communications. It was part of the reason the telegraph made fast, world-wide communication a practical reality. Morse did invent a code to use for the telegraph, but not Morse code. His code was, by comparison, a poor, inflexible solution. He was a great businessman, focussed on making his dream a reality, but perhaps not so good at computational thinking! The code that bears his name was largely invented by his partner Alfred Vail.

Samuel Morse was originally a painter. However, his life changed when his wife died suddenly. He was away doing a portrait commission at the time. On hearing of his wife’s illness he rushed home, but the message, delivered by a horse rider had taken too long to reach him and she died and was buried before he got there. He dedicated his life to giving the world a better way of communicating as a result. Several different people were working on the idea of a way to send messages by electricity over wires, but no one had really come up with a usable, practical system. The physics had largely been sorted, but the engineering was still lacking.

Morse came up with a basic version of an electrical telegraph system and he demonstrated it. Alfred Vail saw the demonstration and persuaded Morse to take him on as a partner. His father built a famous ironworks, and so he had worked as a machinist. He improved Morse’s system enormously including making the tapping machine used to send messages.

He wasn’t just good at engineering though. He was good at computational thinking, so he also worked on the code used for sending messages. Having a machine that can send taps down a wire is no use unless you can also invent a simple, easy to use algorithm that turns words into those taps, and back again once it arrives. Morse came up with a code based on words not letters. It was a variation of the system already used by semaphore operators. It involved a code book: essentially a list of words. Each word in the book was given a number. A second code turned numbers in to taps – in to dots and dashes. The trouble with this system is it is not very general. If the word you want to send isn’t in the code book you are stuffed! To cover every possibility it has to be the size of a dictionary, with every word numbered. But that would make it very slow to use. Vail came up with a version where the dots and dashes represented letters instead of numbers, allowing any message to be sent letter by letter.

He also realised that some letters are more common than others. He therefore included the results of what we now call “frequency analysis” to make the system faster, working out the order of letters based on how common they are. He found a simple way to do it. He went to his local newspaper offices! To print a page of text, printing presses used metal letters called movable type. Each page was built up out of the individual metal letters slotted in to place. Vail realised that the more common a letter was, the more often it appeared on any page, and the more metal versions the newspaper office would therefore need if they wasn’t to keep running out of the right letters before the page was done. He therefore counted how many of each “movable type” letter the newspaper printers had in their trays. He gave the letters that were most common the shortest codes. So E, for example, is just a single dot as it is the most common letter in American English. T, which is also common, is a single dash. It is this kind of attention to detail that made Morse code so successful. Vail was really good at computational thinking!

Morse and Vail worked really well as a team, though Morse then took all the credit because the original idea to solve the problem had been his, and their agreement meant the main rights were with Morse. They almost certainly worked together to some extent on everything to do with the telegraph. It is the small details that meant their version of the telegraph was the one that took over the world though and that was largely down to Vail. Morse maybe the famous one but the invention of the telegraph needed them both working together.

More on …