Re: [v6ops] new draft: draft-ietf-v6ops-6204bis

[Jeroen Massar <[e-mail]>]

On 2011-10-20 18:13 , james woodyatt wrote:
> On Oct 20, 2011, at 6:16 AM, Lorenzo Colitti wrote:
>>
>> Yes, if the upstream MTU is lower than the default LAN link MTU.
>> Otherwise you'll experience latency issues whenever you connect to a
>> new host on the Internet.
> 
> Because, as we all know, hosts on the LAN never ever communicate
> directly with one another at full media speeds using jumbo frames, as
> they all require every last one of their interactions to be mediated by
> the Cloud Buzzphrase Horsefeathers in the Sky™ or the terrorists win.

<sarcasme>
You mean iCloud? :)
</sarcasme>

I almost commented a similar thing about local MTU needing to be the
same, till I re-read it again and till I rephrased that sentence in my
head as:

"The MTU on the upstream might be different (be that lower or higher),
if you don't set it properly, then you might have extra latency because
of packets will get dropped when it is wrong and packets will disappear"

As such, according to that, the following setup, which is very common is
totally acceptable:

LAN (4000) -> upstream-link (1480) -> internet (1280) -> remote host (1500)

Which is of course very logical and why we have Path MTU discovery.

Maybe the better comment is to definitely not filter ICMP Packet Too
Bigs and friends unless really needed.

Greets,
 Jeroen