In message <[email protected]>, "Ste phan Lagerholm" writes: > Hi Mark, > > You can get blocked ICMP 'packet too big' even if you have the MTU set > to 1280.=20 > > RFC 2460: > In response to an IPv6 packet that is sent to an IPv4 destination (i.e., > a packet that undergoes translation from IPv6=20 > to IPv4), the originating IPv6 node may receive an ICMP Packet Too Big > message reporting a Next-Hop MTU less than 1280.=20 > In that case, the IPv6 node is not required to reduce the size of > subsequent packets to less than 1280, but must include=20 > a Fragment header in those packets so that the IPv6-to-IPv4 translating > router can obtain a suitable Identification=20 > value to use in resulting IPv4 fragments. Note that this means the > payload may have to be reduced to 1232 octets (1280=20 > minus 40 for the IPv6 header and 8 for the Fragment header), and smaller > still if additional extension headers are used.
Which just mean that 6man needs to extend the IPv6 socket API so that the insertion of a fragment header can be signaled. Or IPV6_USE_MIN_MTU=1 needs to imply that a fragment header needs to be added to packets that are not fragmented. Currently IPV6_USE_MIN_MTU doesn't quite fully disable PMTUD. RFC 3542 allows you to turn off adding the adding of Fragment headr by there is no mechanism to force the adding of a Fragment header. > /Stephan > > > -----Original Message----- > > From: [email protected] [mailto:[email protected]] On > > Behalf Of Mark Andrews > > Sent: Sunday, December 04, 2011 6:02 PM > > To: Paul Hoffman > > Cc: [email protected]; Olafur Gudmundsson > > Subject: Re: [dnsext] draft-levine-dnsextlang-02 > >=20 > > 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. > >=20 > > Mark > > -- > > Mark Andrews, ISC > > 1 Seymour St., Dundas Valley, NSW 2117, Australia > > PHONE: +61 2 9871 4742 INTERNET: [email protected] -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: [email protected] -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
