[manet] Re: BABEL question

On Fri, Jul 25, 2025 at 12:22 AM Templin (US), Fred L
<[email protected]> wrote:
> Here I have to respectfully disagree - RFC9374 is an example of the type of
> IPv6 prefix I am postulating. Bits 28-63 of the prefix Identify administrative
> authorities responsible for keeping track of /128 addresses assigned from
> their portion of the prefix. The parent prefix 2001:30::/28 would make
> a good MLA candidate.
>
> > (Henning is right, by the way, a /64 is good enough.  If I recall my
> > undergrad combinatorics correctly, a /64 gives a vanishingly small
> > probability of collision when the total number of nodes is less than
> > 4.2 billion.  For a /48, the value is roughly 10¹².)

Thats the whole reason why IPv6 got host-parts that big... to be able
to randomly choose an address and not worry about a collision.

> Here again, the service I am suggesting is one where a registration authority
> keeps track of the /128 addresses provisioned from an IPv6 ::/N prefix for
> N <= 64. It is like a DHCPv6 service for host routes. Whether the host generates
> Its own /128 and then registers it with the registration authority, or whether
> the registration authority generates a /128 and provides it to the host is a
> small detail - they key thing is that there is a registration authority that
> vouches for the uniqueness of the address and the host's authorization
> to use it.

I have no clue why you want to use a registration for a MANET... if
you fear to generate a collision (e.g. because your node lacks a good
source of randomness), just use a local unique ID (e.g. mac address,
wifi calibration data, ect) as input for a hash function to generate
an unique IP.

I would also suggest not abusing parts of an IP address for
"administrative purpose", e.g. selecting the registration authority
you talked about. Its a common pitfall suggested over and over and it
not getting any better.

Henning Rogge

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