Thanks for the clarification. They're so close to being the same thing that I always call it CSMA/CD. Avoiding a collision is far more preferable than just detecting one.
Yeah, many enterprise switches don't even support 100Base-T or 10Base-T anymore. I've had to daisy chain an old switch that supports 100Base-T onto a modern one a few times myself. If you drop 10/100 support, you can also drop HD (simplex) support. In my junk drawer, I still have a few old 10/100 hubs (not switches), which are by definition always HD.
Is avoiding a collision always preferable? CSMA/CA has significant overhead (backoff period) for every single frame sent, on a less congested line CSMA/CD has less overhead.
CSMA/CD only requires that you back off if there actually is a collision. CSMA/CA additionally requires that for every frame sent, after sensing the medium as clear, that you wait for a random amount of time before sending it to avoid collisions. If the medium is frequently clear, CA will still have the overhead of this initial wait where CD will not.
Depending upon how it's actually implemented, CSMA/CA may have the same (untended?) behavior of CSMA/CD in the sense that setting TCP_NODELAY will also set the backoff timer to zero. It would be interesting to test.
Yeah, many enterprise switches don't even support 100Base-T or 10Base-T anymore. I've had to daisy chain an old switch that supports 100Base-T onto a modern one a few times myself. If you drop 10/100 support, you can also drop HD (simplex) support. In my junk drawer, I still have a few old 10/100 hubs (not switches), which are by definition always HD.