North American Network Operators Group

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Re: Thoughts on increasing MTUs on the internet

  • From: Douglas Otis
  • Date: Sat Apr 14 13:24:27 2007



On Apr 13, 2007, at 4:55 PM, Fred Baker wrote:

The biggest value in real practice is IMHO that the end systems deal with a lower interrupt rate when moving the same amount of data. That said, some who are asking about larger MTUs are asking for values so large that CRC schemes lose their value in error detection, and they find themselves looking at higher layer FEC technologies to make up for the issue. Given that there is an equipment cost related to larger MTUs, I believe that there is such a thing as an MTU that is impractical.

1500 byte MTUs in fact work. I'm all for 9K MTUs, and would recommend them. I don't see the point of 65K MTUs.

Keep in mind that a 9KB MTU still reduces the Ethernet CRC effectiveness by a fair amount. Adoption of CRC32c by SCTP and iSCSI has a larger Hamming distance restoring the detection rates for Jumbo packets.


-Doug