Re: Minimum IPv6 MTU

Jeroen Massar <jeroen@unfix.org> Thu, 10 July 2008 21:34 UTC

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Date: Thu, 10 Jul 2008 23:34:44 +0200
From: Jeroen Massar <jeroen@unfix.org>
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To: Fernando Gont <fernando@gont.com.ar>
Subject: Re: Minimum IPv6 MTU
References: <200807102034.m6AKYGnc004166@venus.xmundo.net>
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Fernando Gont wrote:
> Folks,
> 
> RFC 2460 states that every link in an internet have an MTU of 1280 
> octets or greater, and that any link that cannot convey a 1280-octet 
> packet in one piece must provide fragmentation and reassembly at a layer 
> bellow IPv6.
> 
> However, while talking about the specs with a few folks (who preferred 
> to remain anonymous), it was mentioned to me that in a number of 
> scenarios (not necessarily those that involve tunnels), some links have 
> an MTU smaller than 1280, and they do not perform the "fragmentation and 
> reassembly function at a layer bellow IP" that RFC 2460 requires.

Then those links have to be fixed. Simple, nothing to it ;)

This is why there are a couple of RFC's that explicitly detail how these 
links are used to transmit/use IPv6. Some for instance don't support 
multicast which thus breaks the whole concept of Neighbor Discovery etc.

Thus if you know any linktype which is not able yet to properly do IPv6, 
document them as a draft and submit it.

Greets,
  Jeroen

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