Switches are the sophisticated computers that shunt streams of data from one track to another, like boxcars in a train yard. Millions of simultaneous streams of communications will flow on large networks, and no matter how many intermediate waypoints are required, all the different bits of information will have to be guided to their destinations, with an assurance they will arrive in the right places and on time. To grasp how big the task will be in the era of the information highway, imagine billions of boxcars that have to be routed along railroad tracks through vast systems of switches and arrive at their destinations on schedule. Because the cars are attached to one another, switchyards get clogged waiting for long, multicar trains to pass through. There would be fewer tie-ups if each boxcar could travel independently and find its own way through the switches, then reassemble as a train at the destination.
Information traversing the information highway will be broken up into tiny packets, and each packet will be routed independently through the network, the way individual automobiles navigate roads. When you order a movie, it will be broken into millions of tiny pieces, each one of which will find its way through the network to your television.
This routing of packets will be accomplished through the use of a communications protocol known as asynchronous transfer mode, or ATM (not to be confused with “automatic teller machine"). It will be one of the building blocks of the information highway. Phone companies around the world are already beginning to rely on ATM, because it takes great advantage of fiber’s amazing bandwidth. One strength of ATM is its ability to guarantee timely delivery of information. ATM breaks each digital stream into uniform packets, each of which contains 48 bytes of the information to be transported and 5 bytes of control information that allow the highway’s switches to route the packets very quickly to their destinations. At their destinations the packets are recombined into a stream.
ATM delivers streams of information at very high speeds—up to 155 million bits per second at first, later jumping to 622 million bits per second and eventually to 2 billion bits per second. This technology will make it possible to send video as easily as voice calls, and at very low cost. Just as advances in chip technology have driven down the cost of computing, ATM, because it will also be able to carry enormous numbers of old-fashioned voice calls, will drive down the cost of long-distance phone calls.
High-bandwidth cable connections will link most information appliances to the highway, but some devices will connect wirelessly. We already use a number of wireless communication devices—cellular telephones, pagers, and consumer-electronics remote controls. They send radio signals and allow us mobility, but the bandwidth is limited. The wireless networks of the future will be faster, but unless there is a major breakthrough, wired networks will have far greater bandwidth. Mobile devices will be able to send and receive messages, but it will be expensive and unusual to use them to receive an individual video stream.
The wireless networks that will allow us to communicate when we are mobile will grow out of today’s cellular-telephone systems and the new alternative wireless phone service, called PCS. When you are on the road and want information from your home or office computer, your portable information appliance will connect to the wireless part of the highway, a switch will connect that to the wired part, and then to the computer/server in your home or office and bring you the information you asked for.
There will also be local, less expensive kinds of wireless networks available inside businesses and most homes. These networks will allow you to connect to the highway or your own computer system without paying time charges so long as you are within a certain range. Local wireless networks will use technology different from the one used by the wide-area wireless networks. However, portable information devices will automatically select the least expensive network they are able to connect to, so the user won’t be aware of the technological differences. The indoor wireless networks will allow wallet PCs to be used in place of remote controls.
Wireless service poses obvious concerns about privacy and security, because radio signals can easily be intercepted. Even wired networks can be tapped. The highway software will have to encrypt transmission to avoid eavesdropping.
Governments have long understood the importance of keeping information private, for both economic and military reasons. The need to make personal, commercial, military, or diplomatic messages secure (or to break into them) has attracted powerful intellects through the generations. It is very satisfying to break an encoded message. Charles Babbage, who made dramatic advances in the art of code breaking in the mid-1800s, wrote: “Deciphering is, in my opinion, one of the most fascinating of arts, and I fear I have wasted upon it more time than it deserves.” I discovered its fascination as a kid when, like kids everywhere, a bunch of us played with simple ciphers. We would encode messages by substituting one letter of the alphabet for another. If a friend sent me a cipher that began “ULFW NZXX” it would be fairly easy to guess that this represented “DEAR BILL,” and that U stood for D, and L for E, and so forth. With those seven letters it wasn’t hard to unravel the rest of the cipher fairly quickly.
Past wars have been won or lost because the most powerful governments on earth didn’t have the cryptological power any interested junior high school student with a personal computer can harness today. Soon any child old enough to use a computer will be able to transmit encoded messages that no government on earth will find easy to decipher. This is one of the profound implications of the spread of fantastic computing power.
When you send a message across the information highway it will be “signed” by your computer or other information appliance with a digital signature that only you are capable of applying, and it will be encrypted so that only the intended recipient will be able to decipher it. You’ll send a message, which could be information of any kind, including voice, video, or digital money. The recipient will be able to be almost positive that the message is really from you, that it was sent at exactly the indicated time, that it has not been tampered with in the slightest, and that others cannot decipher it.
The mechanism that will make this possible is based on mathematical principles, including what are called “one-way functions” and “public-key encryption.” These are quite advanced concepts, so I’m only going to touch on them. Keep in mind that regardless of how complicated the system is technically, it will be extremely easy for you to use. You’ll just tell your information appliance what you want it to do and it will seem to happen effortlessly.
A one-way function is something that is much easier to do than undo. Breaking a pane of glass is a one-way function, but not one useful for encoding. The sort of one-way function required for cryptography is one that is easy to undo if you know an extra piece of information and very difficult to undo without that information. There are a number of such one-way functions in mathematics. One involves prime numbers. Kids learn about prime numbers in school. A prime number cannot be divided evenly by any number except 1 and itself. Among the first dozen numbers, the primes are 2, 3, 5, 7, and 11. The numbers 4, 6, 8, and 10 are not prime because 2 divides into each of them evenly. The number 9 is not prime because 3 divides into it evenly. There are an infinite number of prime numbers, and there is no known pattern to them except that they are prime. When you multiply two prime numbers together, you get a number that can be divided evenly only by those same two primes. For example, only 5 and 7 can be divided evenly into 35. Finding the primes is called “factoring” the number.