Bandwidth - will there be enough?

PDM editor Neil McNaughton wonders what will limit the growth of Internet traffic. He concludes that as long as the world has an appetite for voice telephony and commodity traffic like MP3, the future for data intensive usage is good.

This month’s editorial starts with a confession. I am a BBC radio addict. I even listen in bed, in the wee hours with an earphone plugged in. I sometimes wake up in the morning with the thing twisted round my neck. I can admit to this pathetic vice because I met someone recently who does the same thing. Only he uses an infra red headset linked to his satellite box. His wife sometimes wakes up, to find an alien-like beast with red lights flashing on its headset, snoring away beside her.

Terabits per second

This silliness does expose one to some fascinating facts. One night, I heard an Indian telecoms engineer describe a new cable link from India to the far east, and was amazed to hear that its bandwidth will be a staggering 9 terabits per second. That works out at very nearly 100 peta bytes per day! In other words, the stuff pumping in and out of this one undersea cable could fill up the largest tape robotics installation in a few hours. As a friend remarked, how on earth do you manage the stuff coming out of the cable?

No ‘management’

Much reflection later I realized that such traffic was only possible exactly because it isn’t ‘managed’ at all. To understand this you need to know something of the subtle differences between telephony and data and just what is involved in their ‘convergence.’ Today, both telecoms and data are as near as damn it all digital. OK you may be unlucky and have some non digital technology such as a modem on your local loop, but as soon as your telephone gets to a local exchange, your voice is digitized, and can and will be commingled with data and other voices traveling down wider and wider pipes (such as the one of my ‘dreams’) before being separated out again and served up to your listener.


Modern transport technologies such as ATM allow this mixing of digitized voice and data. Multiplexed phone calls share the same infrastructure as Internet and other data traffic. But while the Internet traffic goes out onto disks chez your ISP, the telephony world is different on two counts. First telephone traffic is switched, not managed - it is the ultimate in ‘hot’ data (see Van Kuijk on page 7) - You talk, and someone listens, nothing is stored anywhere.


Second, telephony has a real-time component that is absent from most data traffic. There is a need for constant end-to-end bandwidth. Otherwise, you’ll talk, and someone will fall asleep waiting to hear you. Data on the other hand is mostly not real time. Email for instance, can tolerate relatively long delays in transmission. Each category of data transmission, or interaction will require a certain amount of bandwidth to operate without unduly frustrating the user.


Infrastructure providers - like the people laying the Indian fiber link - neither know nor care what traffic goes down the tube. Others, telcos, ISPs and governments fight over that. Bandwidth has become a commodity. You can pay a lot - for guaranteed quality of service suitable for a dedicated link, in fact you pay quite a lot for a telephone conversation. Or you can pay a vanishingly small amount for non urgent bandwidth such as email. The huge price differentials are due to the way the bandwidth is carved up. Figuratively, the cable operator will sell as much as he can to the high added value telcos etc. But any gaps in transmission, the drop off in traffic when America goes to bed, to the single pause for breath in a phone call will be plugged with lower cost data traffic.

Here at The Data Room we have just been equipped with ADSL and a router, and immediately became involved in higher bandwidth activities such as online radio (I said I was an addict!) and downloading MP3 files. The question many are asking is - will the Internet hold up to such increasingly intensive use? The answer depends on what your expectations are. At any point in time, the very top end of quality-of-service assured bandwidth will cost. But in general it is the demand for commodity applications - from voice though MP3 to video - that ensures that your basic IP traffic is getting a faster and faster cheap ride by piggy-backing the bandwidth bulimics.


Claude Shannon

One can hardly talk about communications without recording the death this month of the Mr. Bandwidth himself, Claude Shannon, formerly of Bell Labs and MIT. Shannon was one of the first workers in the telecoms industry to realize that all ‘signals’ - a single voice channel, multiplexed voice or color television can be represented and analyzed as the passage of ones and zeros - ‘bits’ - along the wire. Shannon realized the overlap between telecoms and computing very early on. In fact his expectations of the future impact of technology were boundless.


Alan Turing, on a fishing trip to Bell Labs in 1943, from his base in Bletchley Park, found a kindred spirit. “Shannon wants to feed not just data to a Brain [a computer] but cultural things! He wants to play music to it!” Subsequent IT developments must have seemed rather lackluster to such a visionary. But that didn’t stop him enjoying life after early retirement in 1972. Apart from the occasional lecture and scientific paper, the great man enjoyed himself, inventing motorized pogo-sticks. He also developed a theory of juggling. More from

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