Re: [DNA-BOF] Detecting Network Attachment BoF description (rev 2)

[Brett Pentland <brett.pentland@monash.edu>]

Hi Alper,

Alper Yegin wrote:

<snip>

>>>I also think that talking about re-visiting same links/subnets is about some
>>>(risky/not_so_trivial) optimizations.
>>>
>>>    This information may be used to distinguish between
>>>    events where configuration must be initiated, or a
>>>    host already has valid configuration.
>>>
>>>Nothing guarantees the validity of the previous configs once the host moves
>>>off-link. There still needs to be some protocol exchange between the host
>>>and the network elements to ensure validity of the parameters.
>>
>>I guess you are right for the general case, although
>>the concept is not that "we're safe" no signalling,
>>but the distinction between already configured (maybe
>>needs update later) and needs update now.
>>The critical path is important in this.
>>
>>In these cases, we certainly don't want to initiate
>>MIPv6 binding signalling when the node detaches from an
>>AP, and then reattaches immediately afterward, for example.
> 
> 
> It depends on how quickly this happens, right? As the disconnection duration
> increases, the chances that the CoA is allocated to some other node
> increases. Hence the safest would be to re-do DAD.

Yes.  Or possibly Optimistic DAD.
> 
> If we are talking about short disconnections from the same link, the
> question is, how often does this happen, and is this worth optimizing.
>
If short disconnections are really rare, then perhaps not.  However I 
think there may be some value to be had.  If we can determine rapidly 
that the link we have attached to is the one that we just left, then 
after performing Optimistic DAD there is no need to perform any further 
configuration and it may be reasonable to start using our old AR 
immediately, rather than confirming that it is reachable first.

> Also, if all we are dealing is detecting new network attachment, and
> figuring out if the config parameters might have to change, then
> optimizing the new configuration process is not really in scope. Or, maybe
> it is. It really depends on how we set the scope of this WG.
> 
> 
>>Similarly, it may be worthwhile to initiate Optimistic
>>DAD rather than full DAD, if a node re-attaches to the
>>same link (regardless of how the IID was chosen) if the
>>detachment was under RetransTimer (since no-one can claim
>>the address in this time).  This would allow reception of
>>packets while maintaining some of the safety.
>>
>>Of course these are just illustrative ideas.
>>
>>I still think that the statement is useful, though.
> 
> 
> Alper
> 
> 
> 
>>Greg
>>
>>
Brett