4 ms·
Just to add, ethernet uses csma/cd, WiFi uses csma/ca. Upgraded our DC switches to new ones around 2014 and needed to keep a few old ones because the new ones
by Hikikomori 10mo ago
Just to add, ethernet uses csma/cd, WiFi uses csma/ca.
Upgraded our DC switches to new ones around 2014 and needed to keep a few old ones because the new ones didn't support 10Mbit half duplex.
- anonymousiam 10mo agoThanks 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.
- reorder9695 10mo agoIs 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.
- anonymousiam 10mo agoBut CSMA/CD also has a backoff period.
- reorder9695 10mo agoCSMA/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.
- anonymousiam 10mo agoDepending 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. (My other post in this thread mentions it.) https://news.ycombinator.com/item?id=46360209#46361580 https://news.ycombinator.com/item?id=46360209#46361580
- mikestorrent 10mo agoWhat did you still need to connect with 10mbit half duplex in 2014? I had gigabit to the desktop for a relatively small company in 2007, by 2014 10mb was pretty dead unless you had something Really Interesting connected....
- consp 10mo agoThere is always some legacy device which does weird/old connections. I distinctly remember the debit card terminals in the late '00 required a 10mbit capable ethernet connection which allowed x25 to be transmitted over the network. It is not a stretch to add 5 to 10 more years to those kind of devices.
- mort96 10mo agoThere's plenty of use cases for small things which don't need any sorts of speeds, where you might as well have used a 115200 baud serial connection but ethernet is more useful. Designing electronics for 10Mbit/s is infinitely easier and cheaper than designing electronics for 100Mbit/s, so if you don't need 100Mbit/s, why would you spend the extra effort and expense?
- throw9023093209 10mo agoThere is also power consumption and reliability. I have part of my home network on 100Mbps. It eats about 60% less energy compared to Gb Ethernet. Less prone to interference from PoE.
- linohh 10mo agoTechnical debt goes hard, I had a discussion with a facilities guy why they never got around to ditch the last remnants of token ring in an office park. Fortunately in 2020 they had plenty of time to rip that stuff out without disturbing facility operation. Building automation, security and so on often lives way longer than you'd dare planning.
- BikiniPrince 10mo agoEveryone is forgetting the no delay is per application and not a system configuration. Yep, old things will still be old and that’s ok. That new fangled packet farter will need to set no delay which is a default in many scenarios. This article reminds us it is a thing and especially true for home grown applications.