Re: [Int-area] Revving draft-intarea-shared-addressing-issues

> -----Original Message-----
> From: Dave Thaler [mailto:dthaler@microsoft.com] 
> Sent: Monday, June 14, 2010 1:23 PM
> To: Dan Wing; 'Bernard Aboba'; ford@isoc.org
> Cc: int-area@ietf.org; brian.e.carpenter@gmail.com; 
> draft-ford-shared-addressing-issues@tools.ietf.org; lorenzo@google.com
> Subject: RE: [Int-area] Revving draft-intarea-shared-addressing-issues
> 
> > -----Original Message-----
> > From: Dan Wing [mailto:dwing@cisco.com]
> > Sent: Monday, June 14, 2010 1:16 PM
> > To: 'Bernard Aboba'; Dave Thaler; ford@isoc.org
> > Cc: int-area@ietf.org; brian.e.carpenter@gmail.com; 
> draft-ford-shared-
> > addressing-issues@tools.ietf.org; lorenzo@google.com
> > Subject: RE: [Int-area] Revving 
> draft-intarea-shared-addressing-issues
> > 
> > 
> > 
> > > -----Original Message-----
> > > From: Bernard Aboba [mailto:bernard_aboba@hotmail.com]
> > > Sent: Monday, June 14, 2010 1:05 PM
> > > To: dthaler@microsoft.com; dwing@cisco.com; ford@isoc.org
> > > Cc: int-area@ietf.org; brian.e.carpenter@gmail.com;
> > > draft-ford-shared-addressing-issues@tools.ietf.org; 
> lorenzo@google.com
> > > Subject: RE: [Int-area] Revving 
> draft-intarea-shared-addressing-issues
> > >
> > > The NAT box can use its public IPv4 address to enable 
> 6to4, thereby
> > > providing IPv6 support for hosts "behind" it.  Why would 
> this result
> > > in a disconnected IPv6 island?
> > 
> > Diagram of what I understand the problem to be with 6to4 
> behind another NAT:
> > 
> >   IPv6 host--+
> >               \
> >                +---[home NAT]----[Carrier's NAT]---[Internet]
> >               /      ^       ^                  ^
> >   IPv6 host--+       ^       ^                  ^
> >                      ^       ^             IP address sharing
> >                      ^       ^             with multiple
> >                      ^       ^             subscribers
> >                      ^       ^
> >                      ^     the in-home NAT's WAN address
> >                      ^     is not publicly routable
> >                      ^
> >                      ^
> >                this in-home
> >              NAT turns on 6to4
> 
> The in-home NAT cannot turn on 6to4, it's simply not possible.
> To turn on 6to4 per the RFC one has to have a globally unique
> IPv4 address, which it doesn't in the diagram above.

That works until the Carrier NAT provides a non-RFC1918 address
to the home NAT.  I don't believe anything requires the carrier's
NAT provide RFC1918 addresses.  draft-nishitani-cgn doesn't 
mention RFC1918.  Do we need such a requirement to avoid the
problem of 6to4 being enabled?

Things like draft-miles-behave-l2nat can give the NAT any
address it likes, including giving every NAT the same public,
non-RFC1918 IPv4 address:

   "... This
   technique can be leveraged post IPv4-exhaustion within the
   constraints of existing host and CPE implementations to assign the
   exact same public IPv4 address to every subscriber session and to
   then perform IPv4-to-IPv4 NAT on the subscriber traffic.  For
   example, multiple PPP subscribers could be assigned the exact same
   IPv4 address through IPCP and the L2-Aware NAT will translate all
   packets to an external/WAN public IPv4 address by including
   subscriber-identifier as an additional delimiter in the NAT mapping
   table."

-d

> -Dave
> 
> > 
> > -d
> > 
> > > > From: dthaler@microsoft.com
> > > > To: dwing@cisco.com; ford@isoc.org
> > > > Date: Mon, 14 Jun 2010 19:04:31 +0000
> > > > CC: int-area@ietf.org; brian.e.carpenter@gmail.com;
> > > draft-ford-shared-addressing-issues@tools.ietf.org; 
> lorenzo@google.com
> > > > Subject: Re: [Int-area] Revving
> > > draft-intarea-shared-addressing-issues
> > > >
> > > > > Some routers enable 6to4 [RFC3056] on their WAN link.
> > > 6to4 requires a
> > > > > publicly-routable IPv4 address. Enabling 6to4 behind a
> > > NAT causes a
> > > > > disconnected IPv6 island."
> > > >
> > > > The last sentence above is incorrect. The second sentence
> > > is correct.
> > > > So one cannot "enable" 6to4 behind a NAT since one has no
> > > > publically-routable IPv4 address. Hence one does not get an IPv6
> > > > island. One gets no IPv6 at all (from 6to4 anyway).
> > > >
> > > > -Dave
> > > >
> > > > _______________________________________________
> > > > Int-area mailing list
> > > > Int-area@ietf.org
> > > > https://www.ietf.org/mailman/listinfo/int-area
> > >
> > >
> > 
> 