RE: IPv6 day and tunnels

["Templin, Fred L" <Fred.L.Templin () boeing com>]

> -----Original Message-----
> From: Masataka Ohta [mailto:mohta () 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.templin () boeing com
 
>                                               Masataka Ohta