Android (lack of) support for DHCPv6

Wed Jun 10 03:01:52 UTC 2015

On Wed, Jun 10, 2015 at 3:20 AM, Ray Soucy <rps at maine.edu> wrote:

> Clients should support a verity of methods and let network operators choose
> the solution that fits the environment.  The whole premise for not
> supporting DHCPv6 seems to be that mobile networks don't need it, but that
> totally ignores 802.11 which is equally important.
>

No, the premise is that from a user's point of view, DHCPv6-only networks
cause regressions in functionality compared to IPv4-only or dual-stack
networks. For example: IPv4 apps cannot be supported at all due because
464xlat cannot be made to work, and functions such as tethering cannot be
implemented because there are no IP addresses to assign to downstream
devices.

Implementing IPv6 NAT can resolve some but not all of these regressions
(for example, IPv4 apps still cannot be supported). Thus, attempting to
operate on DHCPv6-only networks a) will create pressure to implement IPv6
NAT, which causes lots of issues like application complexity, battery life
issues due to keepalives, etc. b) impose user-visible regressions even if
we do implement IPv6 NAT.

>From a user's point of view, that's just a bad deal, especially since
IPv4-only networks, dual-stack networks, and IPv6-only networks using SLAAC
do not have any of those issues. Stateless DHCP and stateful DHCPv6 PD have
none of those issues, either. If we really need stateful addressing, then
we should statefully assign prefixes, not single addresses.

I understand that "stateful-one-address-per-device-DHCPv6-only" is easier
for network operators, but SLAAC really isn't that much harder, and in the
long run, we'll get more robust apps, better battery life, more innovation,
and happier users.