What's the killer feature that differentiates Ethernet from other phy protocols?
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.
- (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!)
Around the same era, Myrinet switches with higher bandwidth (1.2Gb/s if I remember correctly) and higher density at a fraction of the port cost of slower ethernet switches. This was possible because the Myrinet switches were dumb.. The Myrinet network elected a "mapper" that distributed routes to all NICs. The NICs then pre-pended routing flits to the front of each packet. So to forward a packet to its destination, all a Myrinet switch had to do was strip off and then read the first flit, see that it said "exit this hop on port 7", and then forward it on to the next switch. Higher densities were achieved with multiple chips inside the cabinet.
In the mid 2000s we even built one of what was, at the time, one of the worlds largest ethernet switches using (newer, faster Myrinet) internally, and encapsulating the ethernet traffic inside Myrinet. That product died due to pressure from folks that were our partners, but felt threatened by our incredibly inexpensive high density switches.
https://www.networkworld.com/article/2323306/myricom-rolls-o...
EDIT: fixed routing flit description, added link to PR
Also Infiniband packets are power of two sized, making fast switching easier.
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.
We could do worse for a transformative technology ranking metric than "How overpriced was this when first released?" (significant look at Nvidia cards)
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.
Of course the jump from 10mb hub to 100mb switch was much larger than any of the later jumps, just because of the reduced noise.
Some of the captions are quite funny.
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.
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.