Cringely Wants To Save The Smart Network
from the good-luck-with-that-plan dept
Robert Cringely's latest column is all about trashing the telcos for actually recognizing the future and doing crazy things like building an all IP fiber network. His argument is that the circuit-switched networks are already built and paid for (which has been the argument the telcos have made all along) and there's simply no reason to throw that away. He brushes off the issue of competition (which is what's forcing the telcos to finally get moving), as if that's a minor issue to deal with. Instead, he comes up with a convoluted plan to give people all the bandwidth he thinks they need over a circuit-switched network, assuming that the biggest bandwidth issue anyone needs is the ability to see video over the network. Apparently, he doesn't think that applications are going to advance to the point where they need more bandwidth, which is incredibly short-sighted. There are, in fact, some make a very convincing case that even the RBOC's fiber plans will leave them far short of the amount of bandwidth they're going to need in the future. Obviously, if there are ways to make good use of the existing circuit-switched network, the RBOCs should go for it -- but to ignore where the world is heading is simply asking for disaster. It's like telling the horse and buggy makers that instead of figuring out how to make automobiles, they should keep their existing offering going, and work on ways to make horses run faster to better compete with cars. Sure, if they can pull it off, it may keep the old system relevant a little longer, but it's tough to do, and they'll still eventually be left in the dust.
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Cringely's column on circuit switching
Excerpt:
Anyway, the interesting part is Bob's argument that it should be possible to reduce the bandwidth needed for sending video by mimicking the protocol of the optic nerve, which according to Bob has a capacity of 100 Kbps. Now, I am no expert in optics or anatomy of the eye, but it occurs to me that one of the reasons the eye can do with relatively limited bandwidth is because so much filtering takes place before the picture gets transmitted. When I look at a movie, I don't take in the whole picture at once - I focus on some part of it, and am only dimly aware of the rest. I do this by positioning my eyes towards what I am looking at and then focusing it - in the process selecting just a few bits of all millions of "bits" the world insists on sending towards me in analog form. What I focus on comes through in glorious detail (at least when I have my glasses on) and the surrounding stuff is out of focus (and there are different physical sensors in the eye to handle this - two protocols, if you like).
Now, since no two people focus on the same part of the video picture through a movie, you either need to send the whole picture with the same quality, or you need to establish some form of two-way communication, so that only what the eye actually will look at will be transmitted towards it. So in other words, to send video down a 64Kbps connection, you need it to be two-way, with almost zero latency. Moreover, you would need one connection for each viewer.
The eye selects what to see, in communication with the brain. The world, which sends images to the eye, has unlimited bandwidth. I may be wrong, but in order to send video over 64K, as Bob proposes, it seems to me we need to extend the selection properties of the eye into the server rather than the send the whole image into each person's home - and communicating eye-tracking with focus information from each individual viewer back to be processed in time for the image to be selected and transmitted in optimized format seems to me to be a formidable challenge, circuit switching or not.
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Re: Cringely's column on circuit switching
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Re: Cringely's column on circuit switching
You cant just say "they're wrong" and then post fifty lines of text from the article without explaining it. You need to either come up with something a little more substantial or not post at all.
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the advantage of a circuit-switched network is its massive total bandwidth. ... all of those 64 kbps channels can operate at the same time.
This is not the case. The phone network is, and always has been, heavily over-subscribed in exactly the same way as IP networks are. In fact, AT&T literally wrote the book on determining just how much you can over-subscribe a given network. The central office does not have enough equipment to provide ISDN to every house it serves, nor even enough to provide a dial tone to every house at the same time. Moreover, the CO does not have enough bandwidth upstream to the network to carry all that traffic anyway.
The second fact which is pretty clearly false is:
The optic nerve is composed of approximately one million stringy cells called ganglia that fire in parallel over a distance of two to three centimeters with the actual visual signal travelling at about 4,400 feet-per-second. Taking into account recovery time between signals, the optic nerve has a total bandwidth of approximately 100 kbps.
Common sense dictates that this is false. If we assume that the first axiom (1 million nerves) and the last axiom (100kbps) are true, then we can easily compute that the bandwidth of the nerves must be about one bit every 10 seconds. But since nerves are analog and transmit a level, not just on/off, it takes even more bits, giving a refresh rate of once every 20, 40, 80 seconds or more depending on how many bits are represented.
I suppose it's possible that my optic nerves are only capable of responding once a minute or so, but it doesn't seem likely. Not in the least.
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