6 ms·

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

by hoseja 4y ago

roganp 4y ago
Packet collision detection vs. collision avoidance
deleted 4y ago
[deleted]
jacquesm 4y ago
The fact that it allowed for all kinds of topologies, and that it served as a bus (shared medium, hence the name 'Ether') rather than a point-to-point link is what I think made the biggest difference. Of course now that we all use switched links they are point-to-point again but an ethernet 'hub' gave you the same effect as a bus with all devices seeing all of the traffic. This made efficient broadcast protocols possible and also allowed for a historical - but interesting - trick: the screw-on taps that you could place on a single coaxial cable running down a department giving instant access without pulling another cable. Zero network configuration required, just get the tap in place and assign a new address. DHCP later took care of that need as well. This was fraught with problems, for instance a single transceiver going haywire could make a whole segment unusable and good luck finding the culprit. But compared to the competition it absolutely rocked.
- em-bee 4y ago
  for years i was carrying around an ethernet splitter that would allow me to connect two devices into one ethernet port. i last used it some 10 years ago in a place without wifi
  - asimpletune 4y ago
    Yeah, it’s a very cool trick that surprises a lot of people when they learn that only half the wires are used.
    - jacquesm 4y ago
      Not for gigabit ethernet and good luck picking up the pieces if you find yourself splitting a power-over-ethernet setup :)
      - bombcar 4y ago
        Reminds me of the "REAL" power over ethernet: http://www.fiftythree.org/etherkiller/ http://www.fiftythree.org/etherkiller/
        jacquesm 4y ago
        Hehe, I remember that page :) Thanks! Some of the captions are quite funny.
      - em-bee 4y ago
        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.
- ethbr0 4y ago
  To build on your comment, although it's been years since I studied Ethernet in depth... - (On the bus thread) Ethernet started from an assumption of bad behavior (out of spec cabling, misbehaving clients, etc.) and tighten requirements just enough to construct a useful network. Much better balance between de facto ruggedness vs performance than its peers. - From the beginning, Ethernet reasoned that it was cheaper to put logic in purpose-built networking hardware than endpoints (i.e. PC network adapters). This was a better scaling tradeoff. 1x $$$ network device + 100x $ client adapter vs 1x $$ networking device + 100x $$ client adapter. - Because of the above, you started to get really cost- and data-efficient networks when the cost of Ethernet switches plummeted. (Remember, in early Ethernet days, networks were hub/broadcast-only!)
  - jacquesm 4y ago
    I remember paying about $1000 per port for 100 megabit switches.
    - ethbr0 4y ago
      Ha! But they delivered that much value (or more), so the market supported the price until supply flooded. We could do worse for a transformative technology ranking metric than "How overpriced was this when first released?" (significant look at Nvidia cards)
      - jacquesm 4y ago
        I had a bunch of workloads that quite literally got cut down to about 15% or so of the original runtime (a cluster compressing a whole archive of CDs for a large broadcaster) so I happily paid up. But still... $1000 / port!! And here I have sitting next to me a 48 port gigabit switch that cost 15% of what that 100 megabit switch cost in 1996 or so. Iirc it was one of the first D-link products I bought, it definitely wasn't great (it ran pretty hot) but it worked quite well enough. Amazing progress.
        bombcar 4y ago
- gooroo 4y ago
  And it was sniffing heaven. Only paralleled by the brief period of nobody using any serious encryption on their wifi.
  - xbar 4y ago
    Where "brief" was about 10 years, which at the time was about 25% of all time that networks were common.
    - yuuho 4y ago
      At the time, maybe. Eventually it will be remembered as a short glitch in tech history.
- sriram_sun 4y ago
  Yup! A whole other real-time industrial protocol called EtherCAT has been built on top of the same hardware.
williamDafoe 4y ago
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.
- knuckleheadsmif 4y ago
  I was in Xerox SDD in the early 80’s I have lots of memories dealing with the large coax taps which we in the ceiling. I also remember setting up a Star demo at the NCC and someone forget coax cable terminators (or was short one terminator?) which was causing reflectance issues with the signal which was solved by cutting the cable to a precise length to get the demo working.
- irq-1 4y ago
  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.
  - williamDafoe 4y ago
e12e 4y ago
I recommend Bob's talk from 1978 posted by another commenter: https://www.youtube.com/watch?v=Fj7r3vYAjGY https://www.youtube.com/watch?v=Fj7r3vYAjGY

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

by hoseja 4y ago

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

roganp 4y ago

Packet collision detection vs. collision avoidance

deleted 4y ago

[deleted]

jacquesm 4y ago

The fact that it allowed for all kinds of topologies, and that it served as a bus (shared medium, hence the name 'Ether') rather than a point-to-point link is what I think made the biggest difference. Of course now that we all use switched links they are point-to-point again but an ethernet 'hub' gave you the same effect as a bus with all devices seeing all of the traffic. This made efficient broadcast protocols possible and also allowed for a historical - but interesting - trick: the screw-on taps that you could place on a single coaxial cable running down a department giving instant access without pulling another cable. Zero network configuration required, just get the tap in place and assign a new address. DHCP later took care of that need as well. This was fraught with problems, for instance a single transceiver going haywire could make a whole segment unusable and good luck finding the culprit. But compared to the competition it absolutely rocked.

em-bee 4y ago
for years i was carrying around an ethernet splitter that would allow me to connect two devices into one ethernet port. i last used it some 10 years ago in a place without wifi
- asimpletune 4y ago
  Yeah, it’s a very cool trick that surprises a lot of people when they learn that only half the wires are used.
  - jacquesm 4y ago
    Not for gigabit ethernet and good luck picking up the pieces if you find yourself splitting a power-over-ethernet setup :)
    - bombcar 4y ago
      Reminds me of the "REAL" power over ethernet: http://www.fiftythree.org/etherkiller/ http://www.fiftythree.org/etherkiller/
      - jacquesm 4y ago
        Hehe, I remember that page :) Thanks! Some of the captions are quite funny.
    - em-bee 4y ago
      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.
ethbr0 4y ago
To build on your comment, although it's been years since I studied Ethernet in depth... - (On the bus thread) Ethernet started from an assumption of bad behavior (out of spec cabling, misbehaving clients, etc.) and tighten requirements just enough to construct a useful network. Much better balance between de facto ruggedness vs performance than its peers. - From the beginning, Ethernet reasoned that it was cheaper to put logic in purpose-built networking hardware than endpoints (i.e. PC network adapters). This was a better scaling tradeoff. 1x $$$ network device + 100x $ client adapter vs 1x $$ networking device + 100x $$ client adapter. - Because of the above, you started to get really cost- and data-efficient networks when the cost of Ethernet switches plummeted. (Remember, in early Ethernet days, networks were hub/broadcast-only!)
- jacquesm 4y ago
  I remember paying about $1000 per port for 100 megabit switches.
  - ethbr0 4y ago
    Ha! But they delivered that much value (or more), so the market supported the price until supply flooded. We could do worse for a transformative technology ranking metric than "How overpriced was this when first released?" (significant look at Nvidia cards)
    - jacquesm 4y ago
      I had a bunch of workloads that quite literally got cut down to about 15% or so of the original runtime (a cluster compressing a whole archive of CDs for a large broadcaster) so I happily paid up. But still... $1000 / port!! And here I have sitting next to me a 48 port gigabit switch that cost 15% of what that 100 megabit switch cost in 1996 or so. Iirc it was one of the first D-link products I bought, it definitely wasn't great (it ran pretty hot) but it worked quite well enough. Amazing progress.
      - bombcar 4y ago
gooroo 4y ago
And it was sniffing heaven. Only paralleled by the brief period of nobody using any serious encryption on their wifi.
- xbar 4y ago
  Where "brief" was about 10 years, which at the time was about 25% of all time that networks were common.
  - yuuho 4y ago
    At the time, maybe. Eventually it will be remembered as a short glitch in tech history.
sriram_sun 4y ago
Yup! A whole other real-time industrial protocol called EtherCAT has been built on top of the same hardware.

williamDafoe 4y ago

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.

knuckleheadsmif 4y ago
I was in Xerox SDD in the early 80’s I have lots of memories dealing with the large coax taps which we in the ceiling. I also remember setting up a Star demo at the NCC and someone forget coax cable terminators (or was short one terminator?) which was causing reflectance issues with the signal which was solved by cutting the cable to a precise length to get the demo working.
irq-1 4y ago
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.
- williamDafoe 4y ago

e12e 4y ago

I recommend Bob's talk from 1978 posted by another commenter: https://www.youtube.com/watch?v=Fj7r3vYAjGY https://www.youtube.com/watch?v=Fj7r3vYAjGY