[dnsext] draft-andrews-dnsext-ipv6-fragmentation

["Stephan Lagerholm" <[e-mail]>]

Hi Mark,

You can get blocked ICMP 'packet too big' even if you have the MTU set
to 1280. 

RFC 2460:
In response to an IPv6 packet that is sent to an IPv4 destination (i.e.,
a packet that undergoes translation from IPv6 
to IPv4), the originating IPv6 node may receive an ICMP Packet Too Big
message reporting a Next-Hop MTU less than 1280. 
In that case, the IPv6 node is not required to reduce the size of
subsequent packets to less than 1280, but must include 
a Fragment header in those packets so that the IPv6-to-IPv4 translating
router can obtain a suitable Identification 
value to use in resulting IPv4 fragments. Note that this means the
payload may have to be reduced to 1232 octets (1280 
minus 40 for the IPv6 header and 8 for the Fragment header), and smaller
still if additional extension headers are used.

/Stephan

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On
> Behalf Of Mark Andrews
> Sent: Sunday, December 04, 2011 6:02 PM
> To: Paul Hoffman
> Cc: [e-mail]; Olafur Gudmundsson
> Subject: Re: [dnsext] draft-levine-dnsextlang-02
> 
> On a similar matter I was in the process of submitting the following.
> I just needed to address internal comments.  I also think my EDNS
> expire option still needs to be addressed though I suspect I'll do
that
> as a individual submission.
> 
> Mark
> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: [phone]                 INTERNET: [e-mail]