can I ask mtu question

Sam Stickland sam_mailinglists at spacething.org
Tue Feb 3 06:04:22 CST 2009


Ricky Beam wrote:
> On Fri, 30 Jan 2009 17:00:00 -0500, Saku Ytti <saku+nanog at ytti.fi> wrote:
>> Which standard are you referring to? AFAIK, nothing above 1500 is
>> standardised
>
> None that have ever been accepted.  From a quick google for 
> manufacturer support, 9216 looks like the most popular number.  But, 
> as I said, it boils down to the largest frame *every* device on the 
> LAN will accept.  If there is a single device that only supports 
> "9000", then that's your limit.  And if there's a single non-JF device 
> in the LAN, it throws a wrench into the whole thing. (This appears to 
> be one of the sticking points as to why IEEE won't accept the addition 
> of JF to any specs.)
>
> --Ricky
>
> PS: The topic pops up again with super-jumbo frames in 10G networks.
>
For what it's worth, TCP will negiogate MSS and will work with 
mismatched MTU in a single LAN segment. Other protocols (e.g. UDP) will 
be borked though.

S




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