Re: [DNA-BOF] Do we need a separate DAD Problem Statement? (was Re:About Charter, DAD, and SEND)

[Greg Daley <greg.daley@eng.monash.edu.au>]

Hi Youn-Hee,

Youn-Hee Han wrote:
> Hi Greg,
> 
> Greg wrote:
> 
>>>>I agree that it is important to be able to do DAD (optimized)
>>>>before DNA has occurred. Maybe we need to say:
>>>>
>>>>"3.N+1  Simultaneous operation with DNA
>>>>
>>>> It SHOULD be possible to use DAD optimization procedures
>>>> to ensure availability of link-local addresses before DNA
>>>> has been completed.  This would allow DNA procedures to
>>>> be undertaken without needing to wait for [RFC-2462] style
>>>> DAD completion."
>>>>
>>>>I think this separates the optimism (which may provide a solution)
>>>
>>>>from the goal.
>>>
>>>
>>>Does "DAD optimization" include the validity check of previous 
>>>IP address on a new link? IMO, we had better confine "DAD 
>>>optimization" only to the matter reducing the delay time.
>>>
>>>We should not be confused between "the validity check of
>>>previous IP address on new link" and "the reduction of 
>>>delay incurred by duplicate address detection", although the
>>>two schemes help send and receive packets immediately after
>>>network attachment.
>>
>>I think that if we're checking the validity of a _global_ address
>>which has been previously used on another link (through DNA),
>>then that shouldn't interfere with DAD optimization.
> 
> 
> I completely agree.
> 
> 
>>It may be valuable to check previous link-local address or get a new 
>>valid link-local address with an Optimized DAD scheme.  I don't
>>mind which.
>>
>>We are talking about the validation occurring on the new link,
>>performed by the host (or by the host's signalling request sent on
>>the new link), though, aren't we?
> 
> 
> What I am concerned about is that the word "optimization" includes
> the validity check of previous IP address on new link.
> IMO, the validity check should not be in scope of "optimization" 
> works. It is just one of the matters of network attachment. 
> Do you agree? If you do not agree, we may update the meaning
> of "DAD optimization" in our charter.
> 
> To check IP layer connection (network attachment), a node 
> should check wheter
> 1) it has reachable default router.
> 2) it has valid IP address.
> 
> I agree that the check of 2) and the (optimistic) use of 
> previous IP address can be done before DNA has 
> been completed.
> But, I am not sure that DAD optimization (new IP address
> configuration while reducing the delay) can be done before
> DNA has been completed. Do you think it can?

I'm not sure if we can use the global addres optimistically
or not (I haven't finished thinking about it).

I'm pretty sure that we shouldn't do DAD for a global
address unless the link had changed (and the global address
wasn't valid). This implies DNA completion (although
configuring a new address may be applicable as soon as a new
prefix is received).

For the link-local address, I think we can say that we don't
need to wait to hear what DNA says, since I may want to use an
Optimized DAD procedure so I have a link-local address for use
in DNA (for neighbour discovery for example).

Do you agree with the distinction?