IPv6 MTUs smaller than 1280 bytes?
Brian E Carpenter
brian.e.carpenter at gmail.com
Sun Sep 12 22:40:12 CEST 2010
On 2010-09-12 23:56, Gert Doering wrote:
> On Sun, Sep 12, 2010 at 05:51:22AM +0000, bmanning at vacation.karoshi.com wrote:
>> On Sat, Sep 11, 2010 at 09:09:52PM +0200, Gert Doering wrote:
>>> On Sat, Sep 11, 2010 at 12:49:19AM +0000, bmanning at vacation.karoshi.com wrote:
>>>> i will admit to truting what my tools tell me, and
>>>> they report an MTU of 1220. It appears to be from a
>>>> single vendors kit.
>>> Is that due to a broken implementation, or due to actual link-layer
>>> technology that cannot handle more than 1220?
>> are these two different?
> Yes. Broken implementations can be fixed or replaced by a different
> vendor's working implementation.
> Technology that cannot do larger MTUs because of the way the technology
> is specified (imagine ATM without SAR at the VC endpoints) cannot be
> fixed without changing standards, upgrading lots of different vendor
> implementations, etc.
What's supposed to happen then is that the logical link layer handles
fragmentation as a link layer (or maybe layer 2.5) function, so that
the IPv6 layer still sees at least 1280.
> Just to spell out why I think there is a difference :-) - in the specific
> moment in time "I want to transfer a packet now and it does not go through",
> there is no effective difference, of course.
> Gert Doering
> -- NetMaster
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