Iljitsch Van beijnum
Forum Replies Created
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Probably not. The way TSO works in network interface cards is that the software hands over a big packet and then the NIC slices it into MTU-sized chunks. In that case, lowering the MTU makes no difference at all to the sending TCP stack, which is in charge of setting the transmit rate.
But I suspect what’s happening with Thunderbolt networking is that the segmentation step is simply skipped. In that case the MTU value is completely meaningless.
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Right. I just wanted to see if it made a difference just in case there was some bug in that code or some kind of unexpected interaction that is triggered by the very large segments, because those don’t happen in “normal” networks.
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Thanks for the invite!
It’s very disappointing that this issue persists with the latest and greatest hardware. I was hoping it was caused by an immature Thunderbolt implementation in my 2011 MacBook Air, but apparently not.
One thing I wanted to try was disable TCP segmentation offloading (TSO) to see if that would help but unfortunately the ifconfig en2 -mediaopt tso command doesn’t work.
I don’t think CPU usage is an issue here, as even between my sub-3 GHz laptops with only dual core CPUs the speeds can be good, they’re just not consistent.
It’s too bad that this doesn’t work as it should, as other ways to do > 1 Gbps networking on the Mac Pro are cumbersome and expensive, as I wrote in a blog post the other day:
https://www.muada.com/2014/01-03-the-mac-pro-needs-10-gigabit-ethernet.html