How to report IPv6 bug to Microsoft - Vista and 7 won't "undeprecate" a prefix

[Mark Smith]

Hi Ole,

On 7/04/2011 5:29 PM, Ole Troan wrote:
> Mark,
>
>>>> A number of our customers are having trouble with IPv6 under Windows Vista and 7 on our IPv6 trial.
>>>>
>>>> Currently we are giving customers a static delegated prefix via DHCPv6-PD (a /60 currently). When they have an ADSL drop out, some IPv6 CPE is deprecating the assigned LAN interface global /64 prefix by sending an RA with a zero second preferred lifetime for the prefix. Windows Vista and 7 are quite correctly labelling the prefix as deprecated, as it still has a non-zero valid lifetime. Deprecating the prefix at this time makes sense as there is a possibility that the delegated prefix may not be re-assigned to the CPE after the ADSL link is restored, and may be re-assigned by the ISP to another customer. This is also the behavior specified in the recently published RFC6204, "Basic Requirements for IPv6 Customer Edge Routers".
>>>
>>> no, it isn't.
>>> this behaviour breaks local communication within the home.
>>>
>>
>> Hmm. Well that's the behavior this CPE seems to be exhibiting. I think I've been fooled a bit by misremembering this clause from the RFC -
>
> not one of ours? if so let me know.
>

No it isn't one of yours.

I've just had a closer look at what it is doing on it's LAN interface -

1. While the ADSL link is up, it advertises both it's global prefix and 
a "ULA" prefix in it's LAN interface RAs. The global prefix preferred 
lifetime is 3600, while the valid lifetime is 7200, regardless of what 
we are setting on the delegated prefix. The "ULA" prefix is announced 
with a 0 second preferred and valid lifetimes.

(I'm putting "ULA" in quotes because the random ID component is all 
zeros i.e. they've recreated the site-local problems in the ULA space.)

2. When the ADSL link fails, the prefix lifetime values are reversed - 
the global gets all zeros, while the "ULA"'s become 3600/7200.

3. When the ADSL link recovers, the prefix lifetime values are reversed 
again. This is where the Windows Vista and 7 bug bites when the same 
global prefix is re-announced with non-zero lifetimes.


>>
>>    L-13:  If the delegated prefix changes, i.e., the current prefix is
>>           replaced with a new prefix without any overlapping time
>>           period, then the IPv6 CE router MUST immediately advertise the
>>           old prefix with a Preferred Lifetime of zero and a Valid
>>           Lifetime of the lower of the current Valid Lifetime and 2
>>           hours (which must be decremented in real time) in a Router
>>           Advertisement message as described in Section 5.5.3, (e) of
>>           [RFC4862].
>>
>>
>> However, I don't think that means that Vista and Windows 7 doesn't have a bug though. Surely it is valid for a prefix to be "undeprecated"?
>
> absolutely. didn't mean to create any doubt that that is a bug.
>
> cheers,
> Ole
>

Regards,
Mark.