Thanks for the response, and sorry for my delayed reaction.
>>>>> On Fri, 03 Jan 2003 12:54:19 -0500,
>>>>> Thomas Narten <[EMAIL PROTECTED]> said:
>> However, there seems to be no description about the case in RFC 2461.
>> This is perhaps intentional, because the preferred lifetime does not
>> affect on-link prefix configuration. So my question is:
>> - is RFC 2461 intentionally silent about the case of preferred
>> lifetime > valid lifetime?
>> - if so, what should a host do when, for example, it receives a prefix
>> with the L bit being set, the A bit being set, and preferred LT >
>> valid LT? Should it just regard the prefix as on-link and not
>> configure a corresponding address?
>> - or, do I miss something in RFC 2461?
> I don't know that it really matters that much whether one ignores the
> on-link determiniation or not in this case. Neither seems particularly
> catastrophic.
> Note the follow words in 2461:
> Stateless address autoconfiguration [ADDRCONF] may in some
> circumstances increase the Valid Lifetime of a prefix or ignore it
> completely in order to prevent a particular denial of service attack.
> However, since the effect of the same denial of service targeted at
> the on-link prefix list is not catastrophic (hosts would send packets
> to a default router and receive a redirect rather than sending
> packets directly to a neighbor) the Neighbor Discovery protocol does
> not impose such a check on the prefix lifetime values.
> I think similar logic applies to the case you describe.
Hmm, so your point is that even if the receiving host ignores the
prefix, it can still send a packet (whose destination address is
covered by the prefix) to the router, which will then forward the
packet back to the link.
There's still an interoperability issue if a non forwarding node sends
router advertisements with:
+ the router lifetime being 0
+ a prefix where valid lifetime < preferred lifetime.
though such a case may be too pathological to be covered in the spec.
As a result, I tend to agree that it doesn't matter whether the
receiving host ignores the prefix or not. However, it would be good
for routers to have an additional clarification like
for each advertised prefix, a router SHOULD ensure that the valid
lifetime is not smaller than the valid lifetime.
to reduce the possibility of interoperability issue when the spec is
ever revised.
Thanks,
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
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