Re: ULA scope [draft-ietf-6man-rfc3484-revise-05.txt]

[Mark Andrews <[e-mail]>]

In message <[e-mail]>, Brian E Carpenter writes:
> On 2012-03-16 23:30, Arifumi Matsumoto wrote:
> ...
> > Rather, my question was about the design choice.
> > 
> > Regarding the design of ULA and how to use the ULA, can we agree that 
> > ULA-to-ULA communication within the same /48 prefix is not always preferred
> > over other communications using IPv4 or IPv6 global addresses ?
> 
> I would expect it to be preferred as a result of longest match; I would
> not expect it to be a special case in the default policy for global
> scope addresses, if that is the question.
> 
> >>> Second,
> >>> when a user configures his policy table, the configured table is overwrit
> ten by
> >>> this implementation dependent policy injection behavior ?
> >>> Can the user suppress this behavior of policy injection ?
> >>> This issue should arise also when a policy distributing mechanism is read
> y.
> >> Good questions.  Do you have suggested answers to those questions?
> >> I might throw out a strawman of:
> >>
> >> Any automatic rows added by the implementation as a result of address
> >> acquisition MUST NOT override a row for the same prefix configured
> >> via other means.   That is, rows can be added but never updated
> >> automatically.   An implementation SHOULD provide a means for
> >> an administrator to disable automatic row additions.
> > 
> > 
> > My suggested answer for this was to use macros, which can be
> > added/deleted by a user, and interpreted as the actual prefix
> > attached to the hosts.
> 
> That's an implementation method. I think Dave's proposed rule is
> correct.
> 
>     Brian

What I see missing is a way for a node to know what the site boundaries
are with respect to address selection.   Adding a site prefix length
to RA Prefix Information would provide a 99.99% solution to this.  If
the Site Prefix field is non-zero it is valid.

e.g.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |    Length     | Prefix Length |L|A| Reserved1 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Valid Lifetime                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Preferred Lifetime                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Site Prefix  |           Reserved2                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                            Prefix                             +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: [phone]                 INTERNET: [e-mail]