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Bob Metcalfe wins Turing Award

amturing.acm.org

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Re: Bob Metcalfe wins Turing Award

#201

Post by RF_Savage »

jabl wrote: post #125
RF_Savage wrote: post #94

Earlier quoted context omitted.

TDMA needs time synchronization and thus becomes more complex. Even in telecoms the packet switched connections are quickly replacing synchronous time division connections.

The recent-ish 10base-t1 uses something called PLCA instead of CSMA/CD which doesn't require time synchronization, and gives each node in a subnet a dedicated transmission slot.

10Base-T1L is point to point, 10Base-T1S is multidrop, but very limited in nodes and how long the branches/stubs can be.

We'll see how it actually performs in field. Microchip seems to be in the T1S boat and TI+AD in T1L.

Re: Bob Metcalfe wins Turing Award

#202

Post by cduzz »

This is like when I heard Roger Penrose won a Nobel Prize in 2020 and I thought for a second "wait is this his second? What? You mean he hadn't been awarded one until now? Who was in line ahead of him and for what?"

Re: Bob Metcalfe wins Turing Award

#203

Post by btilly »

NHQ wrote: post #194
btilly wrote: post #179

Earlier quoted context omitted.

Not only did he make it up, but it is false! Multiple lines of evidence point to a O(n log(n)) law instead. https://www-users.cse.umn.edu/~odlyzko/doc/metcalfe.pdf has the details.

From the paper: > In general, connections are not used with the same intensity... so assigning equal value to them is not justified. This is the basic objection to Metcalfe’s Law... In my architectonic opinion, the perfect network comprises all nodes operating equally. Ergo the ideal is indeed Metcalfe's law, but architecture and design can be costly, which is simple the inefficient use of resources. These being very…

We are talking about computer systems that connect a network of humans. Humans are notoriously imprecise and unreliable machines. Anything more than 0.00001% is therefore a miracle.

Re: Bob Metcalfe wins Turing Award

#204

Post by aidenn0 »

retrocryptid wrote: post #92
jacquesm wrote: post #4

Well deserved. I remember dealing with a whole raft of other networking technologies and Ethernet stood head-and-shoulders above anything else available at the time. One thing that is not well appreciated today is how power efficient Ethernet was, even on launch in the coax era. Other network technologies (Token Ring as embodied by IBMs network cards, for instance) consumed power like there was no tomorrow. Leading t…

I still have a soft spot in my heart for ARCNet. In the 80s it was cheaper than ethernet, but more reliable than token ring. And for the few places that prioritized determinism over throughput, it was indispensable. But ethernet kept improving speed and reliability while ARCnet retreated to shop-floor niche applications. Alas.

I get the impression that 10BASE-T killed ARCNet, and it was the "T" rather than the "10" that did so. Running cheap CAT-5 to a set of interconnected hubs was just so much easier and more reliable than t-connectors, terminators &c.

Re: Bob Metcalfe wins Turing Award

#206

Post by dwheeler »

caseysoftware wrote: post #24

Bob has been an active member of the Austin startup community for 10+ years and I've talked with him many times. As a EE, it was cool meeting him the first time and once I'd chatted with him a few times, I finally asked the question I'd been dying to ask: How'd you come up with "Metcalfe's Law"? Metcalfe's Law states the value of a network is proportional to the square of the number of devices of the system. When I f…

He may have "made it up" to improve sales, but from a certain viewpoint it's correct. If decide to measure the "value" of a network based on the number of node connections, then the number of connections for n nodes is n(n-1)/2 = 0.5n^2 - 0.5n which is O(n^2).

Of course, the value of something is hard to measure. Typically you measure value as "benefits - costs", and try to convert everything to a currency. E.g., see: https://www.investopedia.com/terms/c/cost-benefitanalysis.as... . But there are often many unknowns, as well as intangible benefits and costs. That make that process - which seems rigorous at first - a lot harder to do in reality.

So while he may have "made it up" on the spot, he had a deep understanding of networking, and I'm sure he knew that the number of connections is proportional to the square of the number of nodes. So I suspect his intuition grabbed a quick way to estimate value, using what he knew about connection growth. Sure, it's nowhere near as rigorous as "benefits - costs", but that is hard to really measure, and many decisions simply need adequate enough information to make a reasonable decision. In which case, he both "made it up" and made a claim that you can justify mathematically.

Re: Bob Metcalfe wins Turing Award

#207

Post by jacquesm »

riceart wrote: post #193
jacquesm wrote: post #49

Earlier quoted context omitted.

It is quite telling that when Bob Metcalfe 'makes stuff up' he still hits it out of the park.

A little confirmation bias on this one. In addition to the infamous internet will collapse prediction he was also pretty whole hog on the Segway scooter revolutionizing transit.

So let me enlighten you a bit: we did collapse the internet, and got a testy email from a bunch of backbone maintainers that they were going to block our live video streams (on port 2047) in four weeks time or so. Which resulted in us moving to the other side of the Atlantic to relieve the transatlantic cable. So even if it didn't make the news Metcalfe was 100% on the money on that particular prediction. The Segway never had a chance as far as I'm concerned but the other thing he got just so. But maybe he never knew (and I never knew about his bet).

Re: Bob Metcalfe wins Turing Award

#208

Post by cafeinux »

nonrandomstring wrote: post #197
caseysoftware wrote: post #24

Bob has been an active member of the Austin startup community for 10+ years and I've talked with him many times. As a EE, it was cool meeting him the first time and once I'd chatted with him a few times, I finally asked the question I'd been dying to ask: How'd you come up with "Metcalfe's Law"? Metcalfe's Law states the value of a network is proportional to the square of the number of devices of the system. When I f…

And yet it's trivially true. Value accrues with connectivity, which is number of the edges in a fully connected graph being n(n-1)/2, which as n grows larger approximates to n^2. I would be surprised he said he "made it up", other than as a joke about elementary computer science.

As n grows larger, the number of edges approximates n²/2. I may be pedantic but I feel that the difference between something and it's half is non-negligible.

Re: Bob Metcalfe wins Turing Award

#209

Post by jacquesm »

bombcar wrote: post #106
jacquesm wrote: post #37

Earlier quoted context omitted.

Not for gigabit ethernet and good luck picking up the pieces if you find yourself splitting a power-over-ethernet setup :)

Reminds me of the "REAL" power over ethernet: http://www.fiftythree.org/etherkiller/

Hehe, I remember that page :) Thanks!

Some of the captions are quite funny.

Re: Bob Metcalfe wins Turing Award

#210

Post by jandrese »

Dalewyn wrote: post #162
jandrese wrote: post #149

Earlier quoted context omitted.

The other issue is that unless your computer is acting as a router or a bridge, you need to do something with that 10GB data stream. SSDs have only recently gotten fast enough to just barely support reading or writing that fast. But even if you do find one that supports writes that fast a 10GbeE card could fill an expensive 4TB drive in less than an hour. Good luck decoding JPEGs and blitting them out to a web browse…

>10GB data stream. SSDs have only recently gotten fast enough to just barely support reading or writing that fast. 10gbps (gigabits per second) is not 10GB/s (gigabytes per second). Specifically, 10gbps is approximately 1.25GB/s or 1250MB/s.

Consumer SSDs used to max out at about 550MB/s, some still do. You need a larger and more modern drive to do 1.25GB/s sustained write. Even then buffering can get you.
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