> -----Original Message----- > From: Rémi Després [mailto:despres.r...@laposte.net] > Sent: Monday, July 25, 2011 1:43 PM > To: Dan Wing > Cc: 'james woodyatt'; 'RJ Atkinson'; ipv6@ietf.org > Subject: Re: PMTUD and MTU < 1280 > > Dan, > > 1. > The point I wanted to check is just, slightly reformulated): > "May a simple IPv6 host have no support of packet-reassembly, and > simply accept packets up to 1280 octets."
The earlier part of this thread was talking about sending; you're now bringing up receiving. IMO, if the packet came from IPv4, and that IPv4 network had a small MTU (e.g., 576) causing fragmentation, then such an IPv6 receiver will be unable to receive the packet. > In my understanding, the answer should be yes. > - This doesn't depend on whether sources know or not whether their > destinations are IPv6 or IPv4 only. > - If the destination happens to be IPv6, current RFC's don't permit > intermediate nodes to refuse 1280 packets as being too big. > > 2. > How sources can be sure to have e2e transparency in IPv6 is a different > question, but IMHO an important one. > > For instance, if a destination address is obtained from the DNS in a > AAAA, with no A for the same URL and without any well-known prefix > indicating that there is an embedded-IPv4-address, I hope the source > can be guaranteed that e2e transparency won't be broken? I don't think so. DNS64 comes to mind. > I won't have time personally to contribute much on this, but the > subject would usefully be clarified, IMHO. The RFCs are pretty clear, IMO. Implementers don't want to read them all the way. -d > Regards, > RD > > > Le 25 juil. 2011 à 15:36, Dan Wing a écrit : > > >>>> > >>>> ... > >>> > >>> Its behavior violates the last paragraph of Section 5 of RFC2460. > >> > >> Violation _only in case_ of "an IPv6 packet that is sent to an IPv4 > >> destination". > > > > But how does one determine an IPv6 packet is, or isn't, going > > to an IPv4 destination? I don't think it's possible to determine > > if there is an IPv6/IPv4 translator on the path. > > > > -d > > > > > >> If the destination is IPv6, a PMTU below 1280 remains therefore a > >> network failure. > >> This authorizes a simple IPv6 host to refuse packets beyond 1280 > octets > >> and to have no support of packet-reassembly. > >> > >> Right? > >> > >> Regards, > >> RD > >> > >> > >> > >>> > >>> -d > >>> > >>>> > >>>> -- > >>>> james woodyatt <j...@apple.com> > >>>> member of technical staff, core os networking > >>>> > >>>> > >>>> > >>>> ------------------------------------------------------------------ > -- > >>>> IETF IPv6 working group mailing list > >>>> ipv6@ietf.org > >>>> Administrative Requests: > https://www.ietf.org/mailman/listinfo/ipv6 > >>>> ------------------------------------------------------------------ > -- > >>> > >>> ------------------------------------------------------------------- > - > >>> IETF IPv6 working group mailing list > >>> ipv6@ietf.org > >>> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > >>> ------------------------------------------------------------------- > - > > -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
