> -----Original Message----- > From: Masataka Ohta [mailto:mo...@necom830.hpcl.titech.ac.jp] > Sent: Tuesday, June 19, 2012 6:10 AM > To: Templin, Fred L > Cc: Owen DeLong; nanog@nanog.org > Subject: Re: IPv6 day and tunnels > > Templin, Fred L wrote: > > >> Not necessarily, as IPv4 can take care of itself and IPv6 > >> is hopeless. > > > > IPv4 can take care of it how - with broken PMTUD or > > As you know, RFC1191 style PMTUD is broken both for IPv4 > and IPv6.
Unfortunately, there is evidence that this is the case. > > with broken fragmentation/reassembly? > > Fragmentation is fine, especially with RFC4821 style PMTUD, > even though RFC4821 tries to make people believe it is broken, > because accidental ID match is negligibly rare even with IPv4. The 16-bit IP ID, plus the 120sec MSL, limits the rate for fragmentable packets to 6.4Mbps for a 1500 MTU. Exceeding this rate leads to the possibility of fragment misassociations (RFC4963). This would not be a problem if there were some stronger integrity check than just the Internet checksum, but with the current system we don't have that. > > And, you won't > > get any argument from me that IPv6 has been stuck > > for years for good reasons - but MTU failures can > > soon be taken off the list. > > Now, it's time for you to return v6-ops to defend your > draft from Joe Touch. > > Note that there is no point for IPv6 forbid fragmentation > by intermediate routers. I wasn't there when the decision was made, but based on my findings I don't disagree. Fred fred.l.temp...@boeing.com > Masataka Ohta
