RE: [DNA-BOF] DAD Optimization Problem Statement - Simple Solution -mDAD(minimized DAD)

[Soohong Daniel Park <soohong.park@samsung.com>]

Hi Greg.


> While the number of DAD transmissions defaults to 1,
> on a wireless link like you've described, we've
> seen packet loss rates of 1 in 100, which is certainly
> too high for reliable DAD, so we're looking at a system
> which  really needs more than one retransmission.
> (does this make it 100ms, 150ms?)

one retransmission is still short delay against 1000 ms.

> I think that one issue is that there is likely to be
> transient conditions leading to packet loss on the link.
> One reason why RetransTimer is so long is to avoid these
> on particular links.

I see. 

> Additionally, the time taken to wake up a wireless device
> in power-saving mode may be such that it cannot respond
> in 50ms.  In this case, if a node ever went into such a
> mode, it may never defend its address in time.

retransmission : 50 * 2 (about 100 ms)

> At the moment, the duration of the RetransTimer is
> settable by policy in Router Advertisement.
> Since the RA may not have been received before DAD
> on the link-local address is undertaken, this information
> may be unavailable.

Yes.

> I'm not sure whether we can just configure hosts to have
> a RetransTimer which they can use without referring to the
> RA on the link, which may have been set by the administrator.
> For example, the administrator may know of the presence of
> slow-responding nodes, or they may wish to rate-limit
> RS sends.

To be considered.

> Optimistic DAD doesn't modify these parameters, although it
> achieves an equivalent optimization without disrupting
> non-optimized devices.

Yes, for oDAD, there are some modifications.
I just want to discuss simple optimized DAD with few requirement.

Of course reasonable RetransTimer should be estimated from variuos
evaluation
Reducing RetransTimer is shoter than original DAD at lease, even if we
do retransmit
around two times ( 50 ms * 2 = 100).

Daniel