Point to Point Ethernet

William Herrin herrin-nanog at dirtside.com
Wed Jul 8 10:17:09 CDT 2009


On Wed, Jul 8, 2009 at 11:07 AM, <sthaug at nethelp.no> wrote:
>> My understanding is that 9000 is a standard for GigE and up but for
>> compatibility with earlier ethernets it's not the default.
>
> Your understanding is wrong. The only IEEE standard is 1500 bytes.

Steinar,

I 'spose I could have consulted wikipedia and gotten the answer:

"The IEEE 802 standards committee does not recognize jumbo frames, as
doing so would remove interoperability with other 802 protocols,
including 802.5 Token Ring and 802.11 Wireless LAN. The use of 9,000
bytes as preferred size for jumbo frames arose from discussions within
the Joint Engineering Team of Internet2 and the U.S. federal
government networks. Their recommendation has been adopted by all
other national research and education networks. In order to meet this
mandatory purchasing criterion, manufacturers have in turn adopted
9,000 bytes as the conventional jumbo frame size."

So 9000 for gige and up is a convention, not a standard. My bad.

Regards,
Bill Herrin






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