I've found one more thing that may need a discussion on the
relationship between rfc2462bis and stateful address autoconfiguration
(DHCPv6).
RFC2462 currently says in Section 5.5.3 that
e) If the advertised prefix matches the prefix of an autoconfigured
address (i.e., one obtained via stateless or stateful address
^^^^^^^^^^^^^^^^^^^
autoconfiguration) in the list of addresses associated with the
interface, the specific action to perform depends on the Valid
Lifetime in the received advertisement and the Lifetime
associated with the previously autoconfigured address (which we
call StoredLifetime in the discussion that follows):
1) If the received Lifetime is greater than 2 hours or greater
than StoredLifetime, update the stored Lifetime of the
corresponding address.
[...snipped]
That is, the valid and preferred lifetimes of an address configured by
DHCPv6 (the "stateful" protocol) can be updated by succeeding RAs.
Does this really make sense? For example, consider the following
scenario:
- a host configures an IPv6 address by DHCPv6. The preferred and
valid lifetimes of the address and the T1/T2 parameters for renewal
are reasonably large (e.g., order of weeks).
- the host then receives an RA that contains a prefix information
option matching the configured address with very small lifetimes (at
least smaller than the T1 value).
- if the host does not see further RAs, the address will soon expire,
since the host will not try to renew the address before the address
expires.
Does RFC2462 really intend to allow this kind of scenario? I don't
think so; this should usually be an undesirable scenario by accident.
On the other hand, if the site administrator wants sudden expiration
of the address, they can use the DHCPv6 reconfigure mechanism, at
least in theory.
Besides, this part of the specification seems a bit too specific about
stateful autoconfiguration, considering we are now going to separate
particular behavior on the stateful configuration part from
rfc2462bis.
So, I personally would like to propose removing "stateful" from the
above part, that is, revise the original text to:
e) If the advertised prefix matches the prefix of an address
configured by stateless autoconfiguration in the list of
addresses associated with the interface, the specific action to
perform depends on the Valid Lifetime in the received
advertisement [...]
Note that this does not necessarily break existing implementations
that implement this part for statefully configured addresses; we could
mention this particular case in a separate document specific to the
use of stateful address autoconfiguration.
Does this proposal make sense to others?
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
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