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Bob Metcalfe wins Turing Award

amturing.acm.org

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Re: Bob Metcalfe wins Turing Award

#121

Post by williamDafoe »

Sporktacular wrote: post #22

Ethernet was always inefficient, with a crazy amount of unused legacy space reserved in an unnecessarily large header. CSMA/CD for contention was one of the ugliest medium access solutions imaginable. The coax implementation needing termination plugs was also ugly. Its advantage was cost, having had no license fees, making it suited to consumer/commercial applications driving economies of scale. It's the VHS of datac…

You could not be more wrong! Efficiency and overhead are measured as a percent of frame size and 128-byte packets (X.25) or 48-byte frames (Atm) are abortions. 1500 bytes at the outset and the overhead is < 1% and < 0.2% with jumbograms (8kB). Every 802.11 standard is a superset of Ethernet and that makes DIX Ethernet the most scalable network protocol of all time!

Re: Bob Metcalfe wins Turing Award

#122

Post by williamDafoe »

agomez314 wrote: post #5

How is he only getting this award now?

ACM Turing award committee has its head up it's ass? Seriously 25% of winners have NO impact on the field ...

Metcalfe was controversial because Alohanet from university of Hawaii pioneered the idea and Metcalfe was seen as writing a nice proof in CACM of the 1/e capacity breakdown theorem and popularizing an already extant technology. He did not build it alone Chuck Thacker probably built most of it but didn't have a PhD! Oh the horror!

He should not have gotten it now - either give it sooner or not at all - and he should not be the only one getting it!

Re: Bob Metcalfe wins Turing Award

#123

Post by em-bee »

jacquesm wrote: post #37
asimpletune wrote: post #35

Earlier quoted context omitted.

Yeah, it’s a very cool trick that surprises a lot of people when they learn that only half the wires are used.

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

using a splitter is usually a temporary solution, and i am unlikely to be sharing a port with a PoE device. nor do i care about gigabit speed when the only reason to use a splitter is to make up for missing wifi.

Re: Bob Metcalfe wins Turing Award

#124

Post by jabl »

drewg123 wrote: post #66
jacquesm wrote: post #41

Earlier quoted context omitted.

I remember paying about $1000 per port for 100 megabit switches.

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.

Re: Bob Metcalfe wins Turing Award

#125

Post by jabl »

RF_Savage wrote: post #94
Sporktacular wrote: post #80

Earlier quoted context omitted.

The point was more about competing technical choices made by designers, rather than the choice of standards made by consumers. For example TDMA can be arguably more scalable, bandwidth and energy efficient than CSMA/CD and can give consistent PL, PD and PDV, so might have even allowed early business grade voice. Variable header sizes would have allowed efficient use over bandwidth constrained media like radio. But th…

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.

Re: Bob Metcalfe wins Turing Award

#126

Post by williamDafoe »

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 system design just about optimally - the most minimal MAC design of all time. EASY TO BUILD UPON AND ENHANCE.

Ethernet (CSMA/CD) is a protocol that copies human speech patterns. After someone stops speaking people hear the quiet (carrier sense multiple access / CSMA) and wait a very short and randomized amount of time and begin to speak. If two speakers collide they hear the collision and shut up (CD - collision detection). They both pick a randomized amount of time to pause before trying again. On the second third etc. collision people wait longer and longer before retrying.

The thing about original ethernet (1981) is that it wastes 2/3 of the channel because a highly loaded channel has too many collisions and too many back offs. But deployment and wiring were expensive so running a single wire throughout a building was the cheapest possible way to start (enhanced by thinwire Ethernet and twisted pair to have a less bulky cable a few years later). The frame design was PERFECT and within ~10 years people were using ethernet frames to build switched networks and today only radio networks are CSMA/CD = Ethernet.

Re: Bob Metcalfe wins Turing Award

#127

Post by chx »

magic_hamster wrote: post #69
passwordoops wrote: post #40

Earlier quoted context omitted.

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

It's worth mentioning Moore's Law, which was actually a short term prediction, arguably turned into a business goal. The "law" states that the number of transistors in integrated circuits (like CPUs) will be doubled every two years (or 18 months by some variations). It wasn't entirely made up, as it was mostly based on advances in manufacturing technology, but it was a prediction made in 1965 that was supposed to hol…

Moore's law is still going , or so I thought. It's Dennard scaling that stopped around 2006.

https://ourworldindata.org/grapher/transistors-per-microproc...

Re: Bob Metcalfe wins Turing Award

#128

Post by AlbertCory »

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.

ARCNet is mentioned heavily in The Big Bucks. I have to admit that I knew very little about it before doing research for the book.

Re: Bob Metcalfe wins Turing Award

#129

Post by xenadu02 »

zokier wrote: post #33
wistlo wrote: post #25

The archetypal "good enough" solution: Instead of preventing collisions, tolerating and managing them. I think of Ethernet often when assessing how close to perfection I need to get in my work.

It is also lesson of doing something now and rewriting it later. For example no modern ethernet network uses cd/csma anymore and it was pretty iconic part of original ethernet. Overall ethernet on physical layer has seen quite an evolution from coax and vampire taps, to twisted pair and hubs, to switched networks, and nowdays wireless, single-pair, optical, and virtual networks

Ethernet is also an example of a tech that has an easy scaling path: hubs with switched uplink ports made it really easy to divide collision domains. In the early days before everything was switched you could instantly reduce collision losses with a little bit of hardware in the server closet with no other changes to the network.

Re: Bob Metcalfe wins Turing Award

#130

Post by xenadu02 »

Sporktacular wrote: post #80
nine_k wrote: post #28

Earlier quoted context omitted.

What are some superior competing standards, and could they be implemented in a royalty-free way?

The point was more about competing technical choices made by designers, rather than the choice of standards made by consumers. For example TDMA can be arguably more scalable, bandwidth and energy efficient than CSMA/CD and can give consistent PL, PD and PDV, so might have even allowed early business grade voice. Variable header sizes would have allowed efficient use over bandwidth constrained media like radio. But th…

None of those things could be implemented in the 1970 or 1980s at reasonable cost so they're not actually solutions at all.

Hell even making Ethernet fully switched didn't really happen until the 1990s thanks to Moore's law making the ASICs cheap enough.

Without mass adoption there's no reason to invest. Look at Token Ring, Ethernet's only real competitor at scale: it quickly started to lag behind. Ethernet shipped 100Mbps several years before Token Ring. The 1Gbps Token Ring standard was never put to hardware.

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