Ask Slashdot: Past and Present Bandwidth Comparisions?

Jonathan Locke asks: "this "Ask Slashdot" question about comparative CPU power led me to wonder if there isn't some attempt somewhere to do the same thing for connectivity/communications. Obviously, we've come a long, long way since the days of semaphores, smoke signals and telegraphs. But how far have we come? What does the bandwidth curve look like? (I assume the Internet would represent a seriously non-linear change, but maybe not). What are the theoretical limits on communications (# of nodes and speed of access)? Does it even make sense to compare such qualitatively different technologies as semaphores and OC48 lines?" Good question! I figure average bandwidth curve over the last 10 years would be an interesting thing to see.

Comments

Probably not that much change since radio.

[kovacsp]

You have to admit, TV and Radio are high bandwidth communications. With the proliferation of TV channels and radio stations we even have more bandwidth. The real question is, who is listening. You can't really watch/listen to more than 1 station at a time, (and I'm sure most people don't browse with more than one browser either).

I think the only thing to change in the past few years is the way we communicate. Not the amount. I do agree that the amount of communication has risen over time (over thousands of years), but only because there are more people on the planet.

Truckload of Mag Tape (First!)

[gavinhall]

Posted by Lulu of the Lotus-Eaters:

Can it be... I am actually first post. (or maybe I just don't understand the new filtering)

Well, I may not have a *great* answer. But I was reminded of the old saying about the bandwidth of a truckload of magnetic tape. I.e. don't underestimate it.

I understand that X years ago, it really did turn out that this would be the fastest available way of transporting some large number of bytes from, say NY to LA. Tape has got bigger-capacity and more compact along the way, just like bandwidth has gotten faster. So do they balance, and does the comparison still hold?

Yours, Lulu...

Station Wagon of Mag Tape (First!)

[slk]

Let's figure the bandwidth of a station wagon of magnetic tape. We'll use DLT, since that's the current technology in tapes. To be specific, we will use a DLT-IV tape that holds 35GB uncompressed. We will assume no compression. According to Quantum's datasheet, a DLT-IV tape is 4.16 by 4.16 by 1 inch. A small to midsize station wagon gives you 4 feet by 4 feet by 3 feet. (i.e. Volvo 240 since I know the approximate measurements). This means that the said wagon can hold 11 by 11 by 36 tapes, for a total of 4356 tapes. This is only using the trunk, and ignoring the seats. This is also ignoring the possibility of packing a few extras on the side using the 'slack' space. These 4356 tapes hold a total of 152460 gigabytes. According to mapsonus.com, going from New York to Los Angeles by car takes 56 hours 34 minutes, which is 203640 seconds. This means that a small station wagon going from New York to Los Angeles, and with only the trunk filled with DLT, has a bandwidth of approximately 6 gigabits per second. Extrapolate this to an 18-wheeler and you can see that even the fastest fiber optic data lines have a long way to go to even come close to a truck of DLT.

Here's one bandwidth curve

[Mawbid]

This shows Iceland's connectivity since 1993. Note that this shows traffic in and out of the country, and not traffic within the country. I don't know if any conclusions can be drawn from this.

Hmm. I wonder if Iceland will be slashdotted :->
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How to measure bandwidth

[JanneM]

Interesting question. There is a real problem measuring bandwidth in preindustrial times. Let's say a cart fully loaded with codices; this would be the medieval analogue to the truckload of tapes. However, information was very rarely transported in this fashion, and never at the maximum speed. One example would be when Queen Kristina of Sweden abdicated and brought her library from Stockholm to Rome. She stopped at various places on the continent for over a year.

Probably a better measure would be a 'typical' message carried by a courier on horse and ship. Let's assume a typical royal decree to be 40 characters per line, 30 lines per page and 5 pages. This would give a message length of 6000 bytes. A messenger would rarely carry only one message, however - let's say our intrepid traveller carries an equivalent of forty decrees (he'd bring along letters, maybe a codex for a monastery and such as well). That gives a 'packet size' of around 250k.

Next, the travelling speed: If my memory serves, it would take three weeks between Copenhagen and Stockholm (a distance of 630km). This would give a bandwidth of 0.13 bytes/sec.

Of course, many manuscripts were illustrated, so in practice the bandwidth would be somewhat higher. Nevertheless, I would hate surfing the web in the fifteenth century :)

The Mathematical Theory of Communication

[craigly]

Check out "The Mathematical Theory of Communication" by Claude Shannon and Warren Weaver. It provides a formal model for talking about all of these different forms of communication.

current capacity...

[irish_spic]

accross the USA would be hard to measure, but the biggest single link accross el continente belongs to QWest communications. They just lit up an OC-192 network, i think at 4 lamdas, expandable to 32 using Nortel equipment; that is, 40Gb/s expandable to 320Gb/s.
They had some neat adds stating that it would take 17 or something seconds to tx the whole lib of congress, including pictures, accross the US; i should know the details better, i work in nortel; however...

by the way, some trivia: did you know that more than 75% of internet trafic is carried over nortel equipment?

hasta luego, compadre.

The other side: latency

[Bald Wookie]

Although bandwidth has increased steadily over the last hundred years, it has been the decrease in message latency that has really revolutionized communications. For George Washington to send a message to England, he could expect a transit time of about four months. In the days of the pony express, it took a bit over a week to send a message across the country. This slow speed at which messages were propagated had some pretty profound effects. Jamestown settlers couldnt send for more supplies in November and expect them for the winter. The king couldnt send timely orders to his governor, or keep abreast of current news. Moving up the timeline a bit we run into other considerations. What if the president had been shot? People in California couldn't know about it until at least a week later. Fundamental details such as who is in charge of the country are unknown to a substantial portion of the population for a long time. Everything on the other coast is old news, at least from our modern perspective.

When electronic communications became commonplace, these distances were greatly reduced. Messages get blasted across the country at around the speed of light. Newspapers could report current information. Important events of the day were on the evening news. Now our wars are fought halfway around the world on live TV. There is no more delay in getting a message across. Bandwidth will increase, allowing larger messages to get sent faster. Yet bandwidth only changes the content, and will not contribute in a measurable way to the revolution that has already taken place.

Bandwidth

[Webmonger]

Keep in mind, folks, that written messages are not the only information transferred. A painting, for example, is at least 300 dpi at 24-bit colour. At 8.5x11, that's 25 megabytes. Even books and scrolls had illustration, often with decorative initial letters that must have been several megabytes big.

And remember that the transportation of a human who bears information is equivalent to a videoconference with perfect audio and video fidelity.

Finally, if you just want to know about Internet bandwidth, Jakob Nielsen's got a nice chart.

Truckload of Mag Tape (First!)

[fred]

An interesting point, but its important to distinguish between bandwidth and latency. A truckload of tape would have monstrous bandwidth, but horrible latency.

Can you imagine playing Quake through a station wagon?

I am programmed to receive...

[DrBoom]

With apologies to the Eagles... if you don't get it, you didn't need to know anyway.

Well, it depends on what you mean -- data transmitted, or data received?

In the first case, a previous poster cited the old saw "Never underestimate the bandwidth of a station wagon full of tapes." The transmission rate of a Country Squire is stupendous, but how fast can it be received? Tape drives manage from under 500KB/sec on up...

Now consider the case of printed books. I'd hazard a guess that the average Tom Clancy potboiler contains something like a megabyte of information. Again, the transmission rate is very high (someone hands you the book), but the reception rate is very low (you have to read it) -- in my case, I manage about 350bits/second (550wpm, 5.5 letters/word, 7bit ASCII).

Now think about television. Uncompressed NTSC video has a transmission rate of around 25MB/sec. This works out to about 45GB for an episode of I Love Lucy, including commercials. Cynics will argue that the actual useful data rate is an inverse square of the amount watched.

I guess it all depends on what you're transmitting, and to what or whom. In most cases, I'd say that above a ceratin transmission rate it doesn't matter -- the process is cpu-bound anyway (whether by grey matter or otherwise)