Re: [DNA-BOF] Attachment Detection charter text for discussion

[Jari Arkko <jari.arkko@kolumbus.fi>]

Brett Pentland wrote:

>> What does "active" mean?  When the interface senses carrier? Or when all
>> tasks necessary to make the interface ready for L3 connectivity are
>> completed (e.g. L2 authentication & association, etc.
> 
> 
> Yeah, good point.  I meant the latter but that was not obvious.  I think 
> that at that instant "network attachment" has occurred (others may have 
> their own ideas), but I think that the job of detecting network 
> attachment may go beyond that instant.  Even a "perfect" link-up trigger 
> that doesn't provide any extra information just tells you that you've 
> attached to something, but not what that network is.  I think that part 
> of the job in detecting network attachment is finding out which network 
> you have attached to and whether that means that further action is 
> required (like configuring a new address).

Most of the time, there appears to be a specific instant in time where
IP connectivity becomes enabled. This is the hint that should be given
to the stack. There may be some earlier hints as well for different types
of events. For instance, when your driver decides to switch to a new
link, you'll probably receive a link down from the previous one, and
maybe some "802.1X in progress" events. But from the point of view
of DNA, its the "link is ready for IP" that is significant. We "just"
need to ensure that 1X or whatever weird stuff that is going on at
the lower layer will be taken in account in the hint given to the
stack.

However, note that there are situations where "link is ready for
IP" is not the same as "you have IP connectivity beyond the link".
For instance, the webpage grabbing login screens or PANA.

--Jari