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High-Tech Times Article 021

Comparing Data-Transfer Speeds

Do you have a need for speed? With a Pentium III-550 sitting here connected to a cable-modem, it’s hard to imagine that I’d ever need anything faster. But history has proven that to be a mistake. No matter how fast our current system is, a year or two from now, you’ll wonder how you ever managed with such “slow” systems. Let’s take a look at the evolution and future of data communications.

It wasn’t that many years ago when I was ecstatic as I was able to replace my ancient 300-baud acoustic modem with a super-fast 1200-baud modem! This was back when owning your own telephone equipment was a no-no with the phone company, and they encouraged those weird-looking couplers because they could be easily removed. This speed demon was followed by 2400-, 4800-, and 9600-baud modems, all of which used the same technology.

The 14,400- and 28,800-baud modems used advanced modulation, but today’s 56 kilobit/second (Kb/s) modems needed some help from the phone company. When telcos around the U.S. decided that digital was the wave of the future for voice communications, they needed to choose a data rate, and rather arbitrarily selected 56 Kb/s. I say arbitrary because the phone systems in this country all work on 64 Kb/s, also known as “DS0" (that’s a zero at the end). But, hey, who’s counting a few lost bits per second....

Anyway, stacking two 64 Kb/s DSO’s gives you 128 Kb/s, another standard data speed. And stacking 24 of them gives you what’s called a “T-1" line, at 1.544 megabits/second (Mb/s); if you’re a real stickler for terminology, this is also called DS1. [Please, no calls that T-1 actually offers only 23 DS0's, with the extra one for control.] T-1 lines are the most common links by Internet Service Providers to the Internet. And Universal Serial Bus (USB) currently tops out at 1.5 Mb/s, which is still 10 times faster than your standard serial (RS-232C) port, and can link up to 127 devices.

The next major jump from there is to Ethernet at 10 Mb/s, which is found on many Local Area Networks (LANs), and has served a generation of network users quite well. The Oceanic Cable RoadRunner cable modem on my desktop pumps data to my computer at up to 26.97 Mb/s, depending how many simultaneous users are on my node. Fast Ethernet at 100 Mb/s is becoming the current standard for LANs, allowing multimedia-based transmissions across a network.

The phone company likes to stack digital data streams for transmission, and stacking 32 DS1's gives a DS3 data-line at 44.736 Mb/s, also known as T-3, which is the pipeline between the Maui High Performance Computing Center and Oahu. For about $100,000 a month, you can move massive amounts of data from coast to coast.  As we continue to stack, we reach the “Optical Character,” or OC-series of data pipes. These range from OC-1 (44.736 Mb/s) through OC-384 (20 Gb/s). These are lines that are leased from major telecommunications providers, and are usually used by supercomputers.  Oh, and, yes, they are full-duple (bi-directional), so you really have up to twice as much data being pumped through these massive pipes.

Somewhere between 133 Mb/s and 1.3 gigabits/second (Gb/s), we reach the maximum data-transfer rate of FireWire, also known as IEEE-1394. We’re seeing FireWire becoming more common on new Windows 98 computers and the newest Macintoshes, and I expect it to become a high-speed standard that will replace slower serial and parallel interfaces in the near future. Watch for a lot more FireWire when Microsoft gets Windows 2000 up, running, and debugged.

We’re starting to reach rarefied atmosphere now. At 1 Gb/s, Gigabit Ethernet is making a run for standardization, and we’ll see more of it as fiber optics becomes more prevalent, both within the office and as the backbone for cable and utility companies. Most of the Next-Generation Internet (NGI) backbone will be running over a Synchronous Optical Network (SONET) link at around 2.4 Gb/s. Several of these SONET testbeds are currently being operated by the National Science Foundation (NSF) and the Advanced Research Projects Agency (ARPA). ARPA was the creator of the Internet back in the late 1960s (then called ARPANET).

So where do we go from here? First, have a look at the data chart to have a more graphical look at what we’ve been discussing. Then take a look back just a few years: remember when an international phone call could wreak havoc on your budget? Now it costs about a dollar. From this, we can easily say that the cost of bandwidth always approaches zero. The more bandwidth that becomes available, the cheaper it gets, the faster the demand increases, and then someone makes even more bandwidth. Every time you think you’re winning the rat-race, they come up with faster rats! And I know of no one who is ever satisfied with the speed of their computer system...are you?

Don’t forget to e-mail me at with your questions, complaints, and comments. See you next month.