Category: Networking and Communications

Going Postal: A review

Semaphore tower showing all the flag positions
Image by Clker-Free-Vector-Images from Pixabay adapted by CS4FN

Any one claiming to be a hard-core Computer Scientist would be ashamed if they had to admit they hadn’t read Terry Pratchett. If you are and you haven’t, then ‘Going Postal’ is a good place to start.

‘Going Postal’, is a must for anyone interested in networks. Not because it has any bearing on reality. It doesn’t. It’s about Discworld, a flat world that is held up on the back of elephants, and where magic reigns. Technology is starting to get a foothold though. For example, cameras, computers and movies have all been invented…though they usually have an Elf inside. Take cameras: they work because the Elf has a paint box and an easel. Take too many sunsets and he’ll run out of pink! It is all incredibly silly…but it works and so does the technology.

Now telecommunications technology is gaining a foothold…Corrupt business is muscling in and the post office is struggling to survive. Who would want to send a letter when they can send a c-mail over the Clacks? The Clacks are a network of semaphore towers that allow messages to ‘travel at the speed of light’.

At each tower the operators

“pound keys, kick pedals and pull levers as fast as they can'”

to forward the message to the next tower in the network and so on to their destination. The clacks are so fashionable, people have even started carrying pocket semaphore flags everywhere they go, so they can send messages to people on the other side of the room.

“But can you write
S.W.A.L.K. on a clacks?
Can you seal it with
a loving kiss?
Can you cry tears
on to a clacks,
can you smell it,
can you enclose
a pressed flower?
A letter is more than
just a message.”

Moist von Lipwig, a brilliant con-artist who just did one con too many, is given the job of saving the Post-office…his choice was ‘Take the job or die’. Not, actually, such a good deal given the last few Postmasters all died on the job … in the space of a few weeks.

Will he save the post office, or is the march of technology unstoppable?…and just who are the ‘Smoking GNU’ that you hear whispers about on the Clacks?

Reading this book has got to be the most fun way imaginable of learning about telecom networks, not to mention entrepreneurship and the effect of computers on society. None of the actual technology is the same as in our world of course, but the principle is the same: transmission codes, data and control signals, simplex and duplex transmissions, image encoding, internet nodes, encryption, e-commerce, phreakers and more…they are all there, which just goes to show computer science is not just about our current computer technology. It all applies even when there is no silicon in sight.

Oh, and this is the 33rd Discworld novel, so if you do get hooked, don’t expect to get much more done for the next few weeks as you catch up.

Paul Curzon, Queen Mary University of London

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The first Internet concert

Severe Tire Damage
Severe Tire Damage. Image by Strubin, CC BY-SA 4.0 via Wikimedia Commons

Which band was the first to stream a concert live over the Internet? The Rolling Stones decided, in 1994, it should be them. After all, they were one of the greatest, most innovative rock bands of all time. A concert from their tour of that year, in Dallas, was therefore broadcast live. Mick Jagger addressed the world not just the 50,000 packed into the stadium welcoming the world with “I wanna say a special welcome to everyone that’s, climbed into the Internet tonight and, uh, has got into the MBone. And I hope it doesn’t all collapse.” Unknown to them, when planning this publicity coup, another band had got there first: a band of Computer Scientists from Xerox PARC, DEC and Apple, the research centres responsible for many innovations including many of the ideas around graphical user interfaces, networks and multimedia internet had played live on the Internet the year before!

The band which actually went down in history was called Severe Tire Damage. Its members were Russ Haines and Mark Manasse (from DEC), Steven Rubin (a Computer Aided design expert from Apple) and Mark Weiser (famous for the ideas behind calm computing, from Xerox PARC). They were playing a concert at Xerox PARC on  June 24, 1993. At the time researchers there were working on a system called MBone which provided a way to do multimedia over the Internet for the first time. Now we take that for granted (just about everyone with a computer or phone doing Zoom and Teams calls, for example) but then the Internet was only set up for exchanging text and images from one person to another. MBone, short for multicast backbone, allowed packets of data of any kind (so including video data) from one source to be sent to multiple Internet addresses rather than just to one address. Sites that joined the MBone could send and receive multimedia data, including video, live to all the others in one broadcast. This meant for the first time, video calls between multiple people over the Internet were possible. They needed to test the system, of course, so set up a camera in front of Severe Tire Damage and live-streamed their performance to other researchers on the nascent MBone round the world (research can be fun at the same time as being serious!). Possibly there was only a single Australian researcher watching at the time, but it is the principle that counts!

On hearing about the publicity around the Rolling Stones concert, and understanding the technology of course, they decided it was time for one more live internet gig to secure their place in history. Immediately, before the Rolling Stones started their gig, Severe Tire Damage broadcast their own live concert over the MBone to all those (including journalists) waiting for the main act to arrive online. In effect they had set themselves up as an Internet un-billed opening act for the Stones even though they were nowhere near Dallas. Of course that is partly the point, you no longer had to all be on one place to be part of the same concert. So, the Rolling Stones, sadly for them, weren’t even the first to play live over the Internet on that particular day, never mind ever!

– Paul Curzon, Queen Mary University of London

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Robert Weitbrecht and his telecommunication device for the deaf

Robert Weitbrecht was born deaf. He went on to become an award winning electronics scientist who invented the acoustic coupler (or modem) and a teletypewriter (or teleprinter) system allowing the deaf to communicate via a normal phone call.

A modem telephone: the telephone slots into a teletypewriter here with screen rather than printer.
A telephone modem: Image by Juan Russo from Pixabay

If you grew up in the UK in the 1970s with any interest in football, then you may think of teleprinters fondly. It was the way that you found out about the football results at the final whistle, watching for your team’s result on the final score TV programme. Reporters at football grounds across the country, typed in the results which then appeared to the nation one at a time as a teleprinter slowly typed results at the bottom of the screen. 

Teleprinters were a natural, if gradual, development from the telegraph and Morse code. Over time a different simpler binary based code was developed. Then by attaching a keyboard and creating a device to convert key presses into the binary code to be sent down the wire you code type messages instead of tap out a code. Anyone could now do it, so typists replaced Morse code specialists. The teleprinter was born. In parallel, of course, the telephone was invented allowing people to talk to each other by converting the sound of someone speaking into an electrical signal that was then converted back into sound at the other end. Then you didn’t even need to type, never mind tap, to communicate over long distances. Telephone lines took over. However, typed messages still had their uses as the football results example showed.

Another advantage of the teletypewriter/teleprinter approach over the phone, was that it could be used by deaf people. However, teleprinters originally worked over separate networks, as the phone network was built to take analogue voice data and the companies controlling them across the world generally didn’t allow others to mess with their hardware. You couldn’t replace the phone handsets with your own device that just created electrical pulses to send directly over the phone line. Phone lines were for talking over via one of their phone company’s handsets. However, phone lines were universal so if you were deaf you really needed to be able to communicate over the phone not use some special network that no one else had. But how could that work, at a time when you couldn’t replace the phone handset with a different device?

Robert Weitbrecht solved the problem after being prompted to do so by deaf orthodontist, James Marsters. He created an acoustic coupler – a device that converted between sound and electrical signals –  that could be used with a normal phone. It suppressed echoes, which improved the sound quality. Using old, discarded teletypewriters he created a usable system Slot the phone mouthpiece and ear piece into the device and the machine “talked” over the phone in an R2D2 like language of beeps to other machines like it. It turned the electrical signals from a teletypewriter into beeps that could be sent down a phone line via its mouthpiece. It also decoded beeps when received via the phone earpiece in the electrical form needed by the teleprinter. You typed at one end, and what you typed came out on the teleprinter at the other (and vice versa). Deaf and hard of hearing people could now communicate with each other over a normal phone line and normal phones! The idea of Telecommunications Device for the Deaf that worked with normal phones was born. However, they still were not strictly legal in the US so James Marsters and others lobbied Washington to allow such devices.

The idea (and legalisation) of acoustic couplers, however, then inspired others to develop similar modems for other purposes and in particular to allow computers to communicate via the telephone network using dial-up modems. You no longer needed special physical networks for computers to link to each other, they could just talk over the phone! Dial-up bulletin boards were an early application where you could dial up a computer and leave messages that others could dial up to read there via their computers…and from that idea ultimately emerged the idea of chat rooms, social networks and the myriad other ways we now do group communication by typing.

The first ever (long distance) phone call between two deaf people (Robert Weitbrecht and James Marsters) using a teletypewriter / teleprinter was:

“Are you printing now? Let’s quit for now and gloat over the success.”

Yes, let’s.

– Paul Curzon, Queen Mary University of London

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Adrian Stokes: Internet pioneer

An abstract schematic of the UK part of the ARPANET. RAL and others connect to UCL which connects to the US via Norway.
Image by Paul Curzon

We take the Internet for granted now, but it is not that long ago that it did not exist at all. Disabled from birth with spina bifida, Adrian Stokes, OBE was one of the people who helped build it: a celebrated “Internet pioneer”. He was, for example, responsible for setting up the first email service in the UK and so the first transatlantic email system, as well as providing the service linking other universities in the UK to the network making it work as a network of networks in different countries.

He worked on ARPANET, the precursor to the Internet. It was a research project funded by the US department of defence exploring the future of communication networks. Up to that point there were global networks but they were based on what is called circuit switching. Think of an old fashioned telephone exchange, Each person had a direct line – an electrical circuit – connecting them to the operator. When you talked to the operator and asked to talk to someone over the phone, the operator would plug a wire that connected your line to theirs, making a new direct circuit from you to them. When you talked, your voice was converted to an analogue signal (a changing electrical signal) which passed down that wire – along the circuit. Transatlantic telephone cables even allowed circuits, so phone calls, to be set up between countries. Early computers connected to each other, sending data over phone lines in this way by converting them into sounds.

ARPANET worked differently to a circuit-based system. It was a packet switched network. It worked by treating data sent over a network as binary, just as the computer itself does internally. This contrasted with the analogue system then used to send sound over early phones. Importantly, the binary data being sent was divided up into fixed size groups of bits called packets. Each packet was then sent separately over the network. In this system there is no fixed circuit from source to destination that the data travels down, just lots of different computers connected to each other, On receiving packets of data each computer or node of the network passes it on to another until eventually it arrives at the target computer. A key advantage to this is that each of those packets can go by a different route, travelling between different computers. They can even arrive out of order, The data no longer travels along a single circuit. The packets are put back together (in the right order) on reaching the destination, reconstructing the original so that the fact it was ever split up is invisible to the person receiving the data. Extra information is added to the packets beyond the actual data to make the system work: such as a destination address to indicate where it is going to and the number of the packet so the order can be reconstructed if they do arrive out of order. Managing the packets and their journey to the destination is done by software implementing a protocol (a set of communication rules agreed between the computers on the network, that allows them to interpret the streams of bits arriving from other computers).

So ARPANET consisted of a series of computers that acted as nodes of the network. Each had to be programmed with software to run the protocol, passing packets on in their journey to the destination and pulling the original data out and reconstructing it if that computer was their destination. UCL were working with the ARPANET team, exploring how to make it work across continents, so had to program one of their computers to make it an ARPANET node. Once done it could connect to the ARPANET via a satellite link in Norway.

At first, the ARPANET was set up as a way just to access data on other computers as though it was on your own local computer. However, other services could be provided on top of the basic protocols. It just amounts to writing code for your node’s computer to turn data into packets and interpret the data in packets arriving in the way needed for the new application. For example, a way to access files on other computers as though they were on yours were added. Much, much later of course code to allow communication through a web page service was written and the world wide web was born to sit on top of the Internet.

This was one of the jobs Adrian Stokes did. He wrote code for the UCL computers that could treat packets of data as email messages rather than just files. Users could write messages and send them to people on other computers on ARPANET without them needing to know where they actually were. It was the first UK email service.

Once UCL had a link to the ARPANET, they could also extend ARPANET. One of Adrian’s other jobs was in managing onward links around the UK, creating a UK ARPANET network. Researchers in other UK universities could set up their own computers as ARPANET nodes (write and run the software on their computer) and then connect their computers to the UCL one. Networks their computers were linked to could then also connect to the ARPANET. In doing so they created a UK ARPANET network but one that was also connected to the full ARPANET via the UCL computer. It meant, for example, that anyone on the ARPANET in the US could (with permission as UCL added password protection to their node – the first on the ARPANET!) access the powerful IBM System 360/195 computer at the Rutherford and Appleton Labs in Oxfordshire. ARPANET became a transatlantic network of connected networks. Any of those UK universities could also then connect to any computer anywhere on the ARPANET. Their packets just went to the UCL one and then to the US via the satellite link, before being forwarded onwards to other US computers. If these UK university computers had the programs for the file transfer or email services, for example, then they could seamlessly use them to access files anywhere else or send messages to anyone else connected to the ARPANET anywhere.

ARPANET ultimately turned into what we now call the Internet. No single person invented the Internet, it was a massive team effort with lots of people involved each responsible for getting some part of it to work. Those like Adrian who played a critical part in making it work, however, have been recognised as “Internet pioneers”: those who can justifiably claim they were part of the team that invented the Internet, and transformed all our lives as a result.

– Paul Curzon, Queen Mary University of London

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Why is your Internet so slow?

Red and white lights of cars on a a motorway at night
Image from Pixabay

The Internet is now so much a part of life that, unless you are over 50, it’s hard to remember what the world was like without it. Sometimes we enjoy really fast Internet access, and yet at other times it’s frustratingly slow! So the question is why, and what does this have to do with posting a letter, or cars on a motorway? And how did electronic engineers turn the problem into a business opportunity?.

The communication technology that powers the Internet is built of electronics. The building blocks are called routers, and these convert the light-streams of information that pass down the fibre-optic cables into streams of electrons, so that electronics can be used to switch and re-route the information inside the routers.

Enormously high capacities are achievable, which is necessary because the performance of your Internet connection is really important, especially if you enjoy online gaming or do a lot of video streaming. Anyone who plays online games would be familiar with the problem: opponents apparently popping out of nowhere, or stuttery character movement.

So the question is – why is communicating over a modern network like the Internet so prone to odd lapses of performance when traditional land-line telephone services were (and still are) so reliable? The answer is that traditional telephone networks send data as a constant stream of information, while over the Internet, data is transmitted as “packets”. Each packet is a large group of data bits stuck inside a sort of package, with a header attached giving the address of where the data is going. This is why it is like posting a letter: a packet is like a parcel of data sent via an electronic “postal service”.

But this still doesn’t really answer the question of why Internet performance can be so prone to slow down, sometimes seeming almost to stop completely. To see this we can use another analogy: the flow of packet data is also like the flow of cars on a motorway. When there is no congestion the cars flow freely and all reach their destination with little delay, so that good, consistent performance is enjoyed by the car’s users. But when there is overload and there are too many cars for the road’s capacity, then congestion results. Cars keep slowing down then speeding up, and journey times become horribly delayed and unpredictable. This is like having too many packets for the capacity in the network: congestion builds up, and bad delays – poor performance – are the result.

Typically, Internet performance is assessed using broadband speed tests, where lots of test data is sent out and received by the computer being tested and the average speed of sending data and of receiving it is measured. Unfortunately, speed tests don’t help anyone – not even an expert – understand what people will experience when using real applications like an online game.

Electronic engineering researchers at Queen Mary, University of London have been studying these congestion effects in networks for a long time, mainly by using probability theory, which was originally developed in attempts to analyse games of chance and gambling. In the past ten years, they have been evaluating the impact of congestion on actual applications (like web browsing, gaming and Skype) and expressing this in terms of real human experience (rather than speed, or other technical metrics). This research has been so successful that one of the Professors at Queen Mary, Jonathan Pitts, co-founded a spinout company called Actual Experience Ltd so the research could make a real difference to industry and so ultimately to everyday users.

For businesses that rely heavily on IT, the human experience of corporate applications directly affects how efficiently staff can work. In the consumer Internet, human experience directly affects brand perception and customer loyalty. Actual Experience’s technology enables companies to manage their networks and servers from the perspective of human experience – it helps them fix the problems that their staff and customers notice, and invest their limited resources to get the greatest economic benefit.

So Internet gaming, posting letters, probability theory and cars stuck on motorways are all connected. But to make the connection you first need to study electronic engineering.

– Paul Curzon, Queen Mary University of London.

This article was originally published on the CS4FN website. It was also published in our 2023 Advent Calendar.

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Claude Shannon: Inventing for the fun of it

Image by Paul Curzon

Claude Shannon, inventor of the rocket powered Frisbee, gasoline powered pogo stick, a calculator that worked using roman numerals, and discoverer of the fundamental equation of juggling! Oh yeah, and founder of the most important theory underpinning all digital communication: information theory.

Claude Shannon is perhaps one of the most important engineers of the 20th century, but he did it for fun. Though his work changed the world, he was always playing with and designing things, simply because it amused him. Like his contemporary Richard Feynman, he did it for ‘the pleasure of finding things out.’

As a boy, Claude liked to build model planes and radio-controlled boats. He once built a telegraph system to a friend’s house half a mile away, though he got in trouble for using the barbed wires around a nearby pasture. He earned pocket money delivering telegrams and repairing radios.

He went to the University of Michigan, and then worked on his Masters at MIT. While there, he thought that the logic he learned in his maths classes could be applied to the electronic circuits he studied in engineering. This became his Masters thesis, published in 1938. It was described as ‘one of the most important Master’s theses ever written… helped to change digital circuit design from an art to a science.’

Claude Shannon is known for his serious research, but a lot of his work was whimsical. He invented a calculator called THROBAC (Thrifty Roman numerical BACkward looking computer), that performs all its operations in the Roman numeral system. His home was full of mechanical turtles that would wander around, turning at obstacles; a gasoline-powered pogostick and rocket-powered Frisbee; a machine that juggled three balls with two mechanical hands; a machine to solve the Rubik’s cube; and the ‘Ultimate Machine’, which was just a box that when turned on, would make an angry, annoyed sound, reach out a hand and turn itself off. As Claude once explained with a smile, ‘I’ve spent lots of time on totally useless things.’

A lot of the early psychology experiments used to involve getting a mouse to run through a maze to reach some food at the end. By performing these experiments over and over in different ways, they could figure out how a mouse learns. So Claude built a mouse-shaped robot called Theseus. Theseus could search a maze until he solved it, and then use this knowledge to find its way through the maze from any starting point.

Oh, and there’s one other paper of his that needs mentioning. No, not the one on the science of juggling, or even the one describing his ‘mind reading’ machine. In 1948 he published ‘A mathematical theory of communication.’ Quite simply, this changed the world, and changed how we think about information. It laid the groundwork for a lot of important theory used in developing modern cryptography, satellite navigation, mobile phone networks… and the internet.

– Paul Curzon, Queen Mary University of London.

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This article was first published on the original CS4FN website and there is a copy on page 19 of the 2nd issue of the EE4FN (Electronic Engineering For Fun) magazine, which you can download below – along with all of our back issues.

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This quantum message will self-destruct in 10 seconds…

by Paul Curzon, Queen Mary University of London

A fuse burning
Image by Rudy and Peter Skitterians from Pixabay edited by Paul Curzon

Mission Impossible always involved the team taking on apparently impossible missions, delivered by a message concluding with the famous line that “This message will self-destruct in 10 seconds”. It was always followed by the message physically destructing  in some dramatic way such as flames or smoke coming from the tape recorder. Now, it’s been shown that it is possible to actually do apparently impossible destruction of messages: to send holographic messages that the sender can just make disappear even after they have been sent. It relies on the apparently impossible, but real properties of quantum physics.

A hologram is a 3-dimensional image formed using laser light. It records light scattered from objects coming from lots of different directions. This differs from photography where the light recorded comes from one direction only. You can see examples on the back of bank cards (often a flying dove) where they are used as a hard-to-copy security device. 

Now researchers at the University of Exeter have shown it is possible to make quantum holograms that make use of quantum effects. They are made from entangled photons: pairs of light particles that have been linked together in a way that means that, after the entangling, what ever happens to one immediately affects the other too … however far apart they are. Entanglement is one of those weird properties of quantum physics, the physical properties of the very, very small. It means that subatomic particles, once entangled, can later instantly affect each other even when separated by large distances.

This effect has now been put to novel use by Jensen Li and team in their research at Exeter. They entangled streams of pairs of photons emitted from a crystal using lasers but then separated the pairs. One stream of photons from the pairs was used to create a holographic image on a special kind of material called a meta-material. Meta-materials are just materials engineered at very tiny scales so as to have properties not usually seen in nature. For example, they might be designed to carefully control light or radio waves by reflecting them very precisely in certain directions. One use of that might be so that the object bounces light round from behind it so appears invisible. Some butterfly wings and bird feathers (think peacocks and kingfishers) actually do a similar sort of thing with very precise microscopic scale surface structures that cause their startlingly bright, shimmering colours.

Exeter’s meta-material was flat but with a special surface designed to have tiny features that manipulate light in very precise ways that create a hologram based on the information encoded in the beam of laser light. In their first test that showed their quantum hologram system works, the hologram just showed the letters H,D,V, A. The light from this hologram continued on to a camera, so a picture of the hologram could be taken. So far so normal.

3D axes with different coloured clouds of particles on each with yellow in the centre
Image by Smiley _p0p from Pixabay

The cunning (and rather weird) thing though is due to what they did to the other stream of light. Each photon in this stream was entangled with a photon in the hologram light stream. Due to the quantum physics of entanglement, that meant that changes to these particles could affect those making the hologram. In particular, the Exeter team had this second stream pass through a polarising filter, essentially like the lens of polaroid sunglasses. Light vibrates in different directions. A sunglasses lens cuts out the light vibrating in a given direction. Now, the letter H in the message was created from light polarised horizontally unlike the other letters which were polarised vertically. This meant that when the second stream of light was passed through a polarising filter blocking out the horizontally polarised light, it also affected the photons entangled with the blocked photons. The other stream of light, that created the hologram, was affected even though it went nowhere near the polarising filter. The result was that the horizontally polarised H could be made to disappear from the message caught on camera. It really did self-destruct, just in a quantum way.

If scaled up such a system could be used to send messages that are still (instantly) controlled by the sender even after they have been sent, whether disappearing or being changed to say something else. The approach could also be incorporated into secure quantum computing communication systems, where the messages are also encrypted.

Fortunately, this blog is not a quantum blog, so will not self-destruct in 10 seconds … so please do share it with your friends!

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Scilly cable antics

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by Paul Curzon, Queen Mary University of London (from the archive)

Sunset over the Scilly Isles with a sailing boat in the foreground
Image by Mike Palmer from Pixabay

Undersea telecommunications cables let the world communicate and led to the world spanning Internet. It was all started by the Victorians. Continents were connected, but closer islands were too including the Scilly Isles.

Autumn 1869. There were great celebrations as the 31 mile long telecommunications cable was finally hauled up the shore and into the hut. The Scilly Isles now had a direct cable communication link to the mainland. But would it work? Several tests messages were sent and it was announced that all was fine. The journalists filed their story. The celebrations could begin.

Except it didn’t actually work! The cable wasn’t connected at all. The ship laying the cable had gone off course. Either that or someone’s maths had been shaky. The cable had actually run out 5 miles off the islands. Not wanting to spoil the party, the captain ordered the line to be cut. Then, unknown to the crowd watching, they just dragged the cut off end of the cable up the beach and pretended to do the tests. The Scilly Isles weren’t actually connected to Cornwall until the following year.

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Gutta-Percha: how a tree launched a global telecom revolution

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by Paul Curzon, Queen Mary University of London

(from the archive)

Rubber tree being tapped
Image  from Pixabay

Obscure plants and animals can turn out to be surprisingly useful. The current mass extinction of animal and plant species needs to be stopped for lots of reasons but an obvious one is that we risk losing forever materials that could transform our lives. Gutta-percha is a good example from the 19th century. It provided a new material with uses ranging from electronic engineering to bioengineering. It even transformed the game of golf. Perhaps its greatest claim to fame though is that it kick-started the worldwide telecoms boom of the 19th century that ultimately led to the creation of global networks including the Internet.

Gutta-percha trees are native to South East Asia and Australia. Their sap is similar to rubber. It’s actually a natural polymer: a kind of material made of gigantic molecules built up of smaller structures that are repeated over and over again. Plastics, amber, silk, rubber and wool are all made of polymers. Though very similar to it, unlike rubber, Gutta-percha is biologically inert – it doesn’t react with biological materials – and that was the key to its usefulness. It was discovered by Western explorers in the middle of the 17th century, though local Malay people already knew about it and used it.

Chomping wires

So how did it play a part in creating the first global telecom network? Back in the 19th century, the telegraph was revolutionising the way people communicated. It meant messages could be sent across the country in minutes. The trouble was when the messages got to the coast they ground to a halt. Messages could only travel across an ocean as fast as a boat could take them. They could whiz from one end of America to the other in minutes but would then take several weeks to make it to Europe. The solution was to lay down undersea telegraph cables. However, to carry electricity an undersea cable needs to be protected and no one had succeeded in doing that. Rubber had been tried as an insulating layer for the cables but marine animals and plants just attacked it, and once the cable was open to the sea it became useless for sending signals. Gutta-percha on the other hand is a great insulator too but it doesn’t degrade in sea-water.

As it was the only known material that worked, soon all marine cable used Gutta-percha and as a result the British businessmen who controlled its supply became very rich. Soon telegraph cables were being laid everywhere – the original global telecoms network. To start with the network carried telegraph signals then was upgraded to voice and now is based on fibre-optics – the backbone of the Internet.

Rotting teeth

Gutta-percha has also been used by dentists – just as marine animals don’t attack it, it doesn’t degrade inside the human body either. That together with it being easy to shape makes it perfect for dental work. For example, it is used in root canal operations. The pulp and other tissue deep inside a rotting tooth are removed by the dentist leaving an empty chamber. Gutta-percha turns out to be an ideal material to fill the space, though medical engineers and materials scientists are trying to develop synthetic materials like Gutta-percha, but that have even better properties for use in medicine and dentistry.

Dimpled balls

That just leaves golf! Early golf balls were filled with feathers. In 1848 Robert Adams Paterson came up with the idea of making them out of Gutta-percha since it was much easier to make than the laborious process of sewing balls of feathers. It was quickly realised, if by accident, that after they had been used a few times they would fly further. It turned out this was due to the dimples that were made in the balls each time they were hit. The dimples improved the aerodynamics of the ball. That’s why modern golf balls are intentionally covered in dimples.

So gutta-percha has revolutionised global communications, changed the game of golf and even helped people with rotting teeth. Not bad for a tree.

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This blog is funded through EPSRC grant EP/W033615/1.

Even the dolphins use pocket switched networks!

(from the archive)

Dolphin leaping in waves off Panama City
Image by Heather Williams from Pixabay

Email, texting, Instant Messaging, Instant response…one of the things about modern telecoms is that they fuel our desire to “talk” to people anytime, anywhere, instantly. The old kind of mail is dismissed as “snail mail”. A slow network is a frustrating network. So why would anyone be remotely interested in doing research into slow networks? Surprisingly, slow networks deserve study. Professor Jon Crowcroft of the University of Cambridge and his team were early researchers of this area, and this kind of network could be the network of the future. The idea is already being used by the dolphins (not so surprising I suppose given according to Douglas Adams’ “The HitchHiker’s Guide to the Galaxy” they are the second most intelligent species on Earth…after the mice).

From node to node

Traditional networks rely on having lots of fixed network “nodes” with lots of fast links between them. These network nodes are just the computers that pass on the messages from one to the other until the messages reach their destinations. If one computer in the network fails, it doesn’t matter too much because there are enough connections for the messages to be sent a different way.

There are some situations where it is impractical to set up a network like this though: in outer space for example. The distances are so far that messages will take a long time – even light can only go so fast! Places like the Arctic Circle are another problem: vast areas with few people. Similarly, it’s a problem under the sea. Signals don’t carry very well through water so messages, if they arrive at all, can be muddled. After major disasters like Hurricane Katrina or a Tsunami there are also likely to be problems.

It is because of situations like these that computer scientists started thinking about “DNTs”. The acronym can mean several similar things: Delay Tolerant Networks (like in space the network needs to cope with everything being slow), Disruption Tolerant Networks (like in the deep sea where the links may come and go) or Disaster tolerant networks (like a Tsunami where lots of the network goes down at once). To design networks that work well in these situations you need to think in a different way. When you also take into account that computers have gone mobile – they no longer just sit on desks but are in our pockets or handbags, this leads to the idea of a “ferrying network” or as Jon Crowcroft calls them: “Pocket Switched Network”. The idea is to use the moving pocket computers to make up a completely new kind of network, where some of the time messages move around because the computers carrying them are moving themselves, not because the message itself is moving. As they move around they pass near other computers and can exchange messages, carrying a message on for someone else until it is near another computer it can jump to.

From Skidoo to you

A skiddo with driver standing next to it
Image by raul olave from Pixabay

How might such networks be useful in reality? Well one was set up for the reindeer farmers in the Arctic Circle. They roam vast icy wastelands on skidoos, following their reindeer. They are very isolated. There are no cell phone masts or internet nodes and for long periods they do not meet other people at all. The area is also too large to set up a traditional network cheaply. How could they communicate with others?

They set up a form of pocket switched network. Each carried a laptop on their skidoo. A series of computers were also set up sitting in tarns spread around the icy landscape. When the reindeer farmers using the network want a service, like delivering a message, the laptop stores the request until they pass within range of one of the other computers perhaps on someone else’s skidoo. The computer then automatically passes the message on. The new laptop takes the message with it and might later pass a tarn, where the message hops again then waits till someone else passes by heading in the right direction. Eventually it makes a hop to a computer that passes within range of a network point connected to the Internet. It may take a while but the mail eventually gets through – and much faster than waiting for the farmer to be back in net contact directly.

Chatting with Dolphins

Even the dolphins got in on the act. US scientists wanted to monitor coastal water quality. They hit on the idea of strapping sensors onto dolphins that measure the quality wherever they go. Only problem is dolphins spend a lot of time in deep ocean where the results can’t easily be sent back. The solution? Give them a normal (well dolphin adapted) cell phone. Their phone stores the results until it is in range of their service provider off the coast. By putting a receiver in the bays the dolphins return to most frequently, they can call home to pass on the data whenever there.

The researchers encountered an unexpected problem though. The dolphin’s memory cards kept inexplicably filling up. Eventually they realised this was because the dolphins kept taking trips across the Atlantic where they came in range of the European cell networks. The European telecom companies, being a friendly bunch, sent lots of text messages welcoming these newly appeared phones to their network. The memory cards were being clogged up with “Hellos”!

The Cambridge team investigated how similar networks might best be set up and used for people on the move, even in busy urban environments. To this end they designed a pocket switched network called Haggle. Using networks like Haggle, it is possible to have peer-to-peer style networks that side-step the commercial networks. If enough people join in then messages can just hop from phone to phone, using bluetooth links say, as they passed near each other. They might eventually get to the destination without using any long distance carriers at all.

The more the merrier

With a normal network, as more people join the network it clogs up as they all try to use the same links to send messages at the same time. Some fundamental theoretical results have shown that with a pocket switched network, the capacity of the network can actually go up as more people join – because of the way the movement of the people constantly make new links.

Pocket switched networks are a bit like gases – the nodes of the network are like gas molecules constantly moving around. A traditional network is like a solid – all the molecules, and so nodes, are stationary. As more people join a gaseous network it becomes more like a liquid, with nodes still moving but bumping into other nodes more often. The Cambridge team explored the benefits of networks that can automatically adapt in this way to fit the circumstances: making phase transitions just like water boiling or freezing.

One of the important things to understand to design such a network is how people pass others during a typical day. Are all people the same when it comes to how many people they meet in a day? Or are there some people that are much more valuable as carriers of messages. If so those are the people the messages need to get to to get to the destination the fastest!

To get some hard data Jon and his students handed out phones. In one study a student handed out adapted phones at random on a Hong Kong street, asking that they be returned a fixed time later. The phones recorded how often they “met” each other before being returned. In another similar experiment the phones were given out to a large number of Cambridge students to track their interactions. This and other research shows that to make a pocket switched network work well, there are some special people you need to get the messages to! Some people meet the same people over and over, and very few others. They are “cliquey” people. Other more “special” people regularly cross between cliques – the ideal people to take messages across groups. Social Anthropology results suggest there are also some unusual people who rather than just networking with a few people, have thousands of contacts. Again those people would become important message carriers.

So the dolphins may have been the “early adopters” of pocket switched networks but humans may follow. If we were to fully adopt them it could completely change the way the telecom industry works…and if we (or the dolphins) ever do decide to head en-mass for the far reaches of the solar system, pocket switched networks like Haggle will really come into their own.

– Paul Curzon, QMUL, based on a talk given by Jon Crowcroft at Queen Mary in Jan 2007.

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This blog is funded through EPSRC grant EP/W033615/1.