Nowadays ethernet uses csma/cd. But

  1. Have we ever used ethernet without csma/cd? What protocols used CSMA?
  2. What would be without a collision detection? They should somehow to know about transission problem. Any examples?
  3. How much speed gives to ethernet that improvement? Theoretically, lets imagine that ethernet uses CSMA without CD, how would be it?
  1. Switched full-duplex Ethernet is collision-free and doesn't require medium arbitration because it's point-to-point. CSMA/CA is used with Wi-Fi.

  2. You don't need collision detection when there can be no collisions - with a point-to-point connection or other ways of multiplexing a bus (e.g. time-division multiplex, tokens).

  3. With a collision-prone shared medium, there's no way for it to work reliably without collision detection unless you resort to requiring acknowledgements, thereby killing latency, wasting bandwidth and buffer resources.

CSMA/CD is (was) a trade-off between material cost, required logic and performance. When logic became cheaper Ethernet evolved away.

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