Re: ipv6 transit over tunneled connection

[Owen DeLong <owen () delong com>]

On May 14, 2010, at 11:57 AM, Christopher Morrow wrote:

> On Fri, May 14, 2010 at 2:29 PM, Franck Martin <franck () genius com> wrote:
> > I said somewhere in here... wierd quoting happened.
> > On Thu, May 13, 2010 at 6:18 PM, Michael Ulitskiy <mulitskiy () acedsl com>
> > wrote:
> > > Hello,
> > >
> > > We're in the early stage of planning ipv6 deployment -
> > > learning/labbing/experimenting/etc. We've got to the point when we're
> > > also planning to request initial ipv6 allocation from ARIN.
> > > So I wonder what ipv6 transit options I have if my upstreams do not
> > > support native ipv6 connectivity?
> > > I see Hurricane Electric tunnel broker BGP tunnel. Is there anything
> > > else? Either free or commercial?
> >
> > 1) see gblx/ntt/sprint/twt/vzb for transit-v6
> > 2) tunnel inside your domain (your control, your MTU issues, your
> > alternate pathing of tunnels vs pipe)
> > 3) don't tunnel beyond your borders, really just don't
> >
> > tunnels are bad, always.
> > -chris
> >
> > I see so many times, that tunnels are bad for IPv6, but this is the way IPv6 has been designed to work when you
> > cannot get direct IPv6. So I would not say tunnels are bad, but direct IPv6 is better (OECD document on IPv6
> > states the use of tunnels).
>
> Tunnels promote poor paths, they bring along LOTS of issues wrt PMTUD,
> asymmetry of paths, improper/inefficient paths (see example paths from
> several ripe preso's by jereon/others), longer latency. If the tunnel
> exits your border you can't control what happens and you can't affect
> that tunnels performance characteristics. it's 2010, get native v6.
I will point out that most of these issues apply to 6to4 and Teredo auto-
tunnels and not as much to GRE or 6in4 statically configured tunnels.

There is a juniper bug which makes PMTU-D a problem if your tunnel
is Juniper<->Juniper.

> > If the issue with tunnel is MTU, then a non-negligible part of IPv4 does not work well with MTU different of 1500.
> > With IPv6 we bring the concept of jumbo packets, with large MTU. If we cannot work with non standard MTUs in
> > IPv6 tunnels, how will we work with jumbo packets?
>
> a non-negligible part of the ipv6 internet doesn't work at all with
> > 1280 mtu... due to tunnels and some other hackery :( jumbo packets
> are a fiction, everyone should stop 10 years ago believing they will
> ever work end-to-end between random sites.
Jumbo packets do work end to end in some random cases and PMTU-D
works in most others. All of the tunnels I am using have at least a 1280 MTU,
so, I'm not sure why you would think a tunnel wouldn't support 1280.

Owen