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Re: WLAN (was Re: IPv6 Host Configuration of Recursive DNS Server)



Tailed down mailing lists to just IPv6 WG list..

On Tue, 8 Jun 2004, Masataka Ohta wrote:
> Mohacsi Janos wrote:
> ND is wrong, because it was designed to be applicable to all the
> link types.
> 
> ND deployed multicast only because some ATM guy said NBMA was
> capable of not broadcast but multicast, which is totaly denied
> by the current ND RFC stating that ND may not be applicable to
> NBMA.

I agree that using multicast for ND was probably not one of the wisest
choices in the long run, and we're suffering from it today (e.g., as
many WLAN APs working as bridges don't forward IPv6 neighbor discovery
frames because they are multicast).  There is only marginal value in
ND using multicast (compared to broadcast), as the typical number of
nodes per link is so low that broadcast storms are not a real problem.

However, that doesn't change your original argument about CSMA/CA,
because broadcast suffers from the same issues as well.

> The solution has been never bother to have standard way of
> address resolution.

I have to disagree here.  Just because broadcast/multicast (ND) isn't
optimized for WLAN (or CSMA/CA in general, I guess), that doesn't
nullify the usefulness of ND for all the other media for which this is
not a problem.

The right fix appears to be specifying an IPv6 over WLAN document (or 
the like) which specifies a possible way to optimize the situation for 
WLAN media.

But while IPv6 over WLAN may not be fully optimal, as it requires
link-layer acknowledgements of multicast packets, I think many already
deem it to work to a *sufficient* degree .. and I'm not sure whether
there would be consensus for specifying e.g. the changes you
suggested.  Data (simulations, measurements, etc.) about the
performance, latency, etc. increases might help.
 
-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings




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