Re: [DNA] Model: how to treat "link down" events

[JinHyeock Choi <jinchoe@gmail.com>]

Thomas

> Note: maybe ten years ago when we were doing the spec twisted
> pair ethernet was a lot less ubiquitous and the notion that one got
> 'link down' indications from the interface was a lot less
> common. Wireless was still a dream... :-)

Not anymore, I am happy to say. :-)

> > It might make sense. But I don't see how defining these things more
> > carefully, and making the above recommendations, would have any impact
> > on how we specify the behavior of the DNA.
>
> What I'm trying to get at is: what assumption can be made about the
> configuration information that is already associated with an interface
> (i.e., from 2461/2426) at the time a 'link up' event takes place?
>
> I guess the obvious model is that whatever IP configuraiton
> information  was associated with the interface before the link up
> (subject to any lifetime considerations) is assumed to still be
> associated with the interface.

Agree. However the host would better keep from using the information
(such as sending a packet with the existing IP address as a source
address) until DNA procedure determines that it really remains at the
same link.

> But think about this just from a 2461/2462 perspective (i.e., before
> we started thinking about DNA). What would happen in practice in a
> pre-DNA world?  Suppose an RA is received on an interface, but it
> indicates a new prefix that one has never heard of, and it doesn't
> include any prefixes currently associated with the
> interface. Shouldn't the old information be thrown away (since we
> might be at a new link).

This is the question we tried to answer with CPL.

When the host is sure that it knows all the prefixes on the link (i.e.
having the Complete Prefix List), it can throw away the old
information because a new prefix implies a new link. If it is not so
sure, it would better take some time before make a decision to throw
away.

Thanks for your kind consideration.

Best Regards

JinHyeock