On 3-aug-2005, at 10:59, Syam Madanapalli wrote:
I think a case can be made for the notion that most routers and most
networks don't implement the bits today, so seeing MO==00 doesn't
really authoratively say there is no DHCP service, but just that the
routers operate in a default configuration.
Does this mean that the current implementations always do the DHCPv6
irrespective of the bits?
I only know a limited number of DHCPv6 implementations (KAME, Cisco)
but those don't consider the bits. Apparently, they assume the daemon
is only run when the bits are set in some way, and/or when the daemon
is run, DHCPv6 should be done period.
So it would be useful to redefine MO==00 to mean "no opinion" and
come up with a new value that indicates authoritative information
that DHCPv6 is unavailable and/or shouldn't be used.
If we define the 00=No Opinion, then we may need to use 11 to convey
unavailability of DHCPv6, may not be good symantics.
I agree that it's contrary to the existing definition of the bits,
and it no longer allows considering either bit individually.
Actually on rereading RFC 2462:
In addition, when the value of the
ManagedFlag is
TRUE, the value of OtherConfigFlag is
implicitely
TRUE as well. It is not a valid configuration
for
a host to use stateful address autoconfiguration
to request addresses only, without also
accepting
other configuration
information.
it seems that the "unused" bit combination would be MO==10.
If we agree that we need to convey 'availability', 'unavailability'
and
'no opinion; then how about the following combination
M O
0 0 - DHCPv6 Not avaialble
0 1 - Only DHCP6v lite
1 0 - Full DHCPv6
1 1 - No opinion (router does not know if the DHCPv6
avaialble or not)
This requires that routers are explicitly configured to allow DHCPv6.
Personally, that doesn't bother me, but this goes against requirement
3 on Jinmei's now infamous list of three requirements.
It's probably better to have a value that authoratively indicates
that DHCPv6 MUST NOT be used rather than use the current 00 value
that is present on all routers out of the box, so 00 can easily be
interpreted as laziness rather than the desire to not run DHCPv6.
Answering points brought up by others in other messages: requiring
hosts to know which interfaces they should and shouldn't run DHCPv6
on by default seems very unattractive to me, to say the least. This
doesn't allow for bridges between different network types and it also
doesn't address the desire to avoid running DHCP for various reasons
other than resource conservation.
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