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Bob Metcalfe wins Turing Award

amturing.acm.org

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Re: Bob Metcalfe wins Turing Award

#191

Post by mixmastamyk »

lr4444lr wrote: post #56
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…

I respect Metcalfe a lot, but halfway through undergraduate discrete math it was pretty obvious to most people in the class even before seeing a formal proof that a fully connected graph has O(n^2) edges. I just figured that people wowed by "Metcalfe's Law" were business types who didn't any formal theory into computing.

I thought it was a "combinatorial explosion?"

https://en.wikipedia.org/wiki/Combinatorial_explosion#Commun...

Re: Bob Metcalfe wins Turing Award

#192

Post by fsckboy »

mixmastamyk wrote: post #191
lr4444lr wrote: post #56

Earlier quoted context omitted.

I respect Metcalfe a lot, but halfway through undergraduate discrete math it was pretty obvious to most people in the class even before seeing a formal proof that a fully connected graph has O(n^2) edges. I just figured that people wowed by "Metcalfe's Law" were business types who didn't any formal theory into computing.

I thought it was a "combinatorial explosion?" https://en.wikipedia.org/wiki/Combinatorial_explosion#Commun...

well, according to Alonzo Church, if this is x squared and that is x squared, then this is that.

Re: Bob Metcalfe wins Turing Award

#193

Post by riceart »

jacquesm wrote: post #49
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…

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.

Re: Bob Metcalfe wins Turing Award

#194

Post by NHQ »

btilly wrote: post #179
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…

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 precise machines, anything less than 99.999% is amateur, ergo the law obtains.

Re: Bob Metcalfe wins Turing Award

#195

Post by fsckboy »

ivalm wrote: post #164
oh_sigh wrote: post #102

Earlier quoted context omitted.

Metcalfe's law is about network impact or value, not about connections.

Yeah, but basically it’s a statement that value scales linearly with the number of pairwise connection.

but it's a loose approximation so it's not good to overanalyze it.

The number of pairwise connections grows as the number of pairwise connections, and connections ("how many people can you talk to") are valuable, so value grows. But individual connections to networks grow the pairwise connections by N, so that's even better.

broadcast (one to many connections, like giving a speech to a crowd) is an efficiency hack, which is good, and efficiency hacks grow as the number of connections grow, so that's good too...

... is more how I think about what Metcalfe was talking about. Which aspects are x, which are x squared, which are log x is interesting, but that's not all bound up in his simple statment, despite his "as the square" wording.

and Bob Metcalfe is personally a great guy in all the ways people are saying, but it's not soooo unique, that's the way a lot of tech types were as the mantle passed from the Greatest Generation to the Boomers (and what was that one in the middle, "lost" or "invisible" or something) I'm not suggesting we've lost that (we may have) just saying that's how it was, for instance as an undergrad you could walk into any professor's office and get serious attention.

Re: Bob Metcalfe wins Turing Award

#196

Post by ethbr0 »

jabl wrote: post #124
drewg123 wrote: post #66

Earlier quoted context omitted.

Ethernet switches are actually pretty complex things, when you think about it. They have to learn what MAC addresses are behind each port, and build a complex forwarding table and do table lookups in real time. The larger the switch, the more complex it is. Its hard to make it scale. Around the same era, Myrinet switches with higher bandwidth (1.2Gb/s if I remember correctly) and higher density at a fraction of the p…

Sounds similar to Infiniband where each subnet has a subnet manager which calculates routing tables for the entire subnet, and assigns 16-bit local identifiers (LID) so you stations don't need to use the full 16 byte GUID's. Also Infiniband packets are power of two sized, making fast switching easier.

Neat! (Re: you and parent)

At their core, most hardware evolutions seem like optimizing compute:memory:storage:functionality vs the (changing) current state of the art/economy.

When Ethernet was first released, compute was expensive. Made sense to centralize compute (in routers) and make everything else dumb-tolerant.

Now, compute is cheap and plentiful at network-calculating scales and throughout expectations are very high, so it makes sense to burn compute (including in clients) to simplify routing hardware.

Re: Bob Metcalfe wins Turing Award

#197

Post by nonrandomstring »

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.

Re: Bob Metcalfe wins Turing Award

#198

Post by ethbr0 »

mhandley wrote: post #79
ethbr0 wrote: post #30

Earlier quoted context omitted.

What would you have used (prior to affordable switches) instead of CSMA/CD?

There were a number of ring-based technologies such as Cambridge Ring that even predate Ethernet: https://en.wikipedia.org/wiki/Cambridge_Ring_(computer_netwo... The main reason Ethernet won, I think, is that it was really easy to deploy incrementally. It was much more plug-and-play than anything else at the time.

My memory is that every ring topology had pretty nasty failure characteristics around "a single misbehaving/failing client."

Which Ethernet has too, but can generally tolerate a much higher level of imperfect reality, while still providing degraded service.

Before you could get plentiful high-quality NICs and cabling, graceful degradation was a killer feature.

Re: Bob Metcalfe wins Turing Award

#199

Post by fsckboy »

passwordoops wrote: post #40
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…

HN comment of the year winner right here! Makes you wonder how many other laws are built on nothing. If there's one thing I leaned doing a Ph.D. is if you dig deep enough, you find many foundational laws of nature rely on some necessary assumption that, if proven incorrect, would topple the whole thing

> Makes you wonder how many other laws are built on nothing.

variance/standard deviation (also btw, a sum of squares concept)

it marks the inflection points on the gaussian curves, but so what, the 2nd derivative points to something significant about the integral? not really. But even if we accept that it does, what does two standard deviations mean? a linear double on the x coordinates says what about the a hairy population density function? nothing.

or similar to Metcalfe's Law, the very widely used Herfindahl Index (also squares!). It's a cross between a hash and a compression, it says something about the original numbers, but wildly different scenarios can collide.

Re: Bob Metcalfe wins Turing Award

#200

Post by irq-1 »

williamDafoe wrote: post #126
hoseja wrote: post #7

What's the killer feature that differentiates Ethernet from other phy protocols?

Original DIX Ethernet was standardized by my manager, David Redell of Xerox. It was the bare minimum to do the job, 6-byte station destination, 6-byte source address, 2-byte packet length, a 2-byte Ethertype field (the latter 2 were combined for networks with hardware framing), and 32-bit CRC. NO arc in the hardware. It leveraged the move to byte-based memories and small CPUs. It followed the end-to-end principle in…

Maybe you know, why isn't the CRC at the end? Then you could stream the packet instead of needing to construct it and then go back to the header to write the CRC.
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