Where's Our Terabit Ethernet?

carusoj writes "Five years ago, we were talking about using Terabit Ethernet in 2008. Those plans have been pushed back a bit, but Ethernet inventor Bob Metcalfe this week is starting to throw around a new date for Terabit Ethernet: 2015. He's also suggesting that this be done in a non-standard way, at least at first, saying it's an opportunity to "break loose from the stranglehold of standards and move into some fun new technologies.""

Comments

Wait... you believe Metcalfe WHY?

[1336]

As in the Robert Metcalfe whose Wikipedia article has an "Incorrect predictions" section listing where he wrongly thought that "the internet would suffer a catastrophic collapse" in 1996 and this gem:

Metcalfe is also known for his harsh criticism of open source software, and Linux in particular, predicting that the latter would be obliterated after Microsoft released Windows 2000:

The Open Source Movement's ideology is utopian balderdash [... that] reminds me of communism. [...] Linux [is like] organic software grown in utopia by spiritualists [...] When they bring organic fruit to market, you pay extra for small apples with open sores - the Open Sores Movement. When [Windows 2000] gets here, goodbye Linux.

Just because he did something really cool 35 years ago doesn't make him an expert on related matters now.

It's about Shannon's law too.

[Z00L00K]

For everyone that has been working with communication since the early datacom ages Shannon's law has been important. It's still important, and it means that you can't just push everything through, you have to consider the media used.

In a way it can be tweaked a bit, and that has caused a confusion among those that aren't well into the technological difference between Baud (modulation changes per second) and BPS (bits per second).

Anyway - The classical phone modems can have a speed up to 56kbps, but effectively they stay at 28 to 33kbps. And that on a line that actually only provides 3kHz bandwidth. The trick is that in the 3KHz bandwidth you can have a carrier with less than 3000 modulation changes per second, often 2400. In each modulation change you not only have one bit transferred, but multiple bits. This is achieved by having a variation in both phase and amplitude of the signal.

So to utilize the cabling at the extreme speeds that a terabit Ethernet is you may have to resort to the same technique.

There have also been other techniques in use like using multiple carrier frequencies, like what the Telebit Trailblazer modems did. That technology was very resilient to interference compared to the CCITT standards, but it had other disadvantages instead.

Re:Stranglehold?

[KublaiKhan]

Not entirely.

There are still a few token rings and other such mesozoic cruft wandering around in the wild out there, but they still work--because some clever folks invented a way to get from one kind of network to another.

Keep in mind, also, that it's really only the early adopters--those who are willing to buy 1st-generation equipment--who would get 'screwed over', and they have, by definition (as the first generation of a given kind of thing is always several times more expensive than the 'production' generations), the money to waste on this sort of thing.