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  • Jumbo frames conundrum

    Here is a riddle I'm hoping anyone tech-savvy might be able to help with:

    Mac Pro 8-core running Cubase 6 64-bit

    5 external PCs running VE Pro servers

    All static IPs on a closed, dedicated gigabit switch.

    Each PC is set to Jumbo frames (9K MTU)

    When the Mac is set to 9K Jumbo frames, I get stuttering and big audio-over-LAN issues.

    When the Mac is set to normal 1500 MTU, audio-over-LAN streaming is almost flawless.


  • Jumbo frames should really only be used for bulk data transfer setups. They will give worse performance in a low-latency application.

  • Wow, OK-- I have been using jumbo frames since I started using VEP. Should Mac OSX users be using full duplex, or full duplex with flow control? I don't believe the VEP manual ever really addresses the specific optimal settings for system preferences.

  • It's only interesting because I've had 9K frames on all of my equipment for quite a while and it actually improved VE Pro performance. I only found out by accident that recently, my Mac's MTU mysteriously reset itself to the default 1500 - perhaps after a system software update or something. I put it back to 9K and then all the problems started with audio streaming. It's a mystery at this moment. But it's working fine at 1500, so I'm not complaining.

  • I don't have the link in front of me -- but I remember reading that Apple has been playing whack-a-mole with the ethernet NIC for years -- some machines have 9k support, some don't. The most recent macpros support 9k, but there were some that didn't. Same for i7 iMacs... some support it, some don't.

    It's not an OS thing. It's the NIC controller -- and there was no rhyme or reason to it. Simply, some models support 9k MTU, some don't. And it is (has been) a moving target.

    Just thought this was worth tossing into the discussion.


  • jeremyroberts - I had not heard of that, that sounds pretty dodgy. But I'm pretty certain this machine has the capability. I've done extensive ping tests with packet sizes to confirm.