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Jumbo frames notes
Apr 26, 2017
Sep 16, 2017
Thanks! I think you summed this up quite nicely. It certainly aligns with my personal experiences.
Jul 31, 2017
Some of the listed limitations do not apply with current O/S's. Example: MTU of different sizes will cause failures. I use different size jumbo frames all the time (4K, 7K, 9K, etc.) without a problem...
If you attempt to send a 9K jumbo frame to a host whose hardware cannot receive larger than 4K, you're going to have problems. I've debugged too many issues with jumbo frames on networks over the years, and lots of them come down to people thinking what you've just said, but the reality being somewhat different. The damnable thing about it is that problems only show up when a sufficiently large jumbo packet is sent, or sometimes even large numbers of jumbo packets. This results in curious things such as "we just added wifi and it doesn't work" or "the printer randomly doesn't work."
Most of the truly important reasons that jumbo is significant have to do with interrupt load, and most of the current hardware and drivers have various mitigation strategies such as interrupt coalescing and packet processing offload features. Today's modern systems aren't taxed by it in the same way that an old 2005-era PCI based system was. As a result, there's much less value to dealing with all the annoyance of jumbo.