IPv6 network policies

[Mark Smith]

On Sat, 10 Apr 2010 16:47:16 +0200
Ole Troan <otroan at employees.org> wrote:

> > So it seems to me that the IPv6 protocol is being blamed for a problem
> > that has been created by not implementing ND completely on P2P to
> > links. If there is no text in RFCs allowing ND NS/NAs to be avoided on
> > P2P links, then I wonder what impact that has on claims of IPv6
> > compliance that these implementations might be making.
> 
> ND has many functions. one of them is address resolution. that's not done on a link without L2 addresses.

IPv6 PPP does negotiate 64 bit IIDs, so in effect I think it's going
close to creating L2 addresses on P2P links. I think that as those IIDs
are not a single bit in size (i.e. "are you going to be 0, because then
I'll be 1"), that also supports the idea that P2P links aren't meant
to be treated specially by IPv6. 

> NUD could be done, but on most router to router links it is
> unnecessary and not used.
> 

I suppose this comes down to if you don't agree with (or maybe just
don't fully understand) the way something works in an RFC, does that
mean it's ok for you not to implement it the way the RFC says?

For a long time, IPv6 has been designed on the assumption of a
single 64 bit IIDs and therefore subnets that have very large amounts
of address space. Running ND NS/NA on all link types, as the ND RFCs
say should be done, protects against the ping pong problem.

It seems to me that in this case people have used existing IPv4
(P2P) methods to guide their IPv6 implementation too much, rather than
putting more weight on the IPv6 RFCs.

> is it a requirement to verify reachability before communicating with any node on an IPv6 link? no, and I can find little support for that position in any IPv6 RFC.
> 

> note, that the ping pong problem isn't an IPv6 problem as such, the same problem exists with IPv4.
> 

True. However, although IPv4 PPP doesn't protect against it, IPv4 PPP
did a lot more neighbor discovery functions i.e. IPCP address
negotation. As a lot of that functionality has been generalised to to
over the top of ICMPv6, i.e. a significant design change over IPv4, as
I said above, IPv4 is probably not a strong model of how IPv6 over P2P
links was expected to operate.

Regards,
Mark.