Re: Extending a /64 (ATN/IPS worked example)

[Michael Richardson <[e-mail]>]

Tony Whyman <[e-mail]> wrote:
    >>> Each aircraft operator could individually register (e.g.) a /32
    >>> with an RIR for their Home Network Prefix. However, there are more
    >>> than 5,000 airlines and if you want to have firewall rules that
    >>> refer to "all uplink packets", an un-coordinated registration of
    >>> Home Network Prefixes would lead to a big configuration maintenance
    >>> problem for every firewall in the ATN/IPS. The
    >>>
    >>> I believe that American Airlines currently has the largest fleet
    >>> with about 1,300 aircraft. You would need a minimum of 11 bits for
    >>> this fleet - rounded up to 12 for a nibble boundary.

    >> This a clear example of a bad addressing plan. If you have 5000 airlines and
    >> the biggest has 1300 aircraft then you don't give all tiny airlines the
    >> same amount of space you need for the biggest.

    > It's only a "bad addressing plan" if your sole success criteria is dense
    > allocation. IPv6 should have liberated us from such a narrow success
    > criteria. The success criteria that I am invoking include cost of
    > administration and legacy support.

You are both right.

Picking a median size and then allowing for multiple allocations to the
larger entities probably is a better plan.
Small airlines grow and bigger airlines fail, or merge, etc.

If tweaking the number of bits here could move us from 39 bits
(which I don't yet understand the math on), to say, 32 bits, then it might
work out better.

    > I also do not see the point in having a different (shorter) prefix length for
    > aircraft in smaller airlines compared with those in larger airlines.

    > If you are arguing for dense allocation as a general rule then this should
    > apply to the whole /64 prefix. I assume that you are demanding that ISPs
    > allocate a /64 to all their users unless they can make the case for multiple
    > subnets and, even then, are parsimonious in their attitude and push back hard
    > against any user that wants more than a /60, demanding proof that they have
    > more than 256 subnets.

This.

--
Michael Richardson <[e-mail]>   . o O ( IPv6 IøT consulting )
           Sandelman Software Works Inc, Ottawa and Worldwide