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

[JinHyeock Choi <jinchoe@gmail.com>]

Dear Mohan

Thanks for your kind clarification which made me see the light. :-)

> When a host attaches to the new link, as per the solution
> document, the host sends a RS with TSLLAO option to determine
> whether it has changed links or not. The source address of the
> RS is a link-local address which was previously in preferred
> state but now in optimistic state. If it knows that it moved
> to a new link, it discards old information and starts
> configuring new addresses from the RA. In the above scenario,
> as the host has not seen the Link UP trigger yet, it does
> not send the RS, does not set the addresses to Optimistic
> and just sitting there thinking it is old link. If another
> node attached to the same link with the same link-local
> address, both the nodes will respond to the NS and override
> flag will not be cleared in both of the NAs.
> Eventually right things will happen, when the RS goes out,
> but in a small window, there can be this problem. This is
> not a opti-DAD problem, because you send NA with override
> flag cleared when you are in optimistic mode.
>
> It looked to me that if you go to optimistic on seeing
> Link Down (i understand that it is not reliable etc..), then
> this problem (assuming it is one) may not happen.

Now I understand, thanks. :-) I think that even after seeing Link Down
even, a host can maintain the current IP configuration information.
But the host would better keep from using it (it switches to a kind of
optimistic mode) until DNA procedure affirms that the host really is
attached to the same link.

Thanks for your kind consideration.

Best Regards

JinHyeock