[Babel-users] AHCP and IPv4 support

[Juliusz Chroboczek]

Mitar,

While it would certainly be possible to hack around the limitations of
IPv4 in order to make a v4-only version of AHCP, what is the
cost/benefit tradeoff?  Costs are high (a lot of difficult, non-portable
hacking), and the benefit is just supporting a number of
soon-to-be-obsolete systems.

> Why not use link-local addresses in IPv4?

Link-local IPv4 addresses are a temporary hack made in order to provide
Appletalk-like functionality to v4-only versions of Mac OS X.  They have
at least two very significant flaws:

  * as noted by Henning, they are not stable: since collisions are not
    that unlikely, a node may need to change its link-local address
    after an address collision.  This is unlike IPv6 link-local
    addresses, which are stable (both when chosen from the MAC address
    or drawn randomly).

  * More seriously, IPv4 link-local addresses are not properly scoped,
    which means that they don't work with multi-homed nodes.  I'm not
    interested in a castrated variant of AHCP that doesn't even work
    with multi-radio nodes.

                                        Juliusz