Re: [6lowpan] Fundamental concerns about 6lowpan ND

["Mathilde Durvy (mdurvy)" <mdurvy at cisco.com>]

Hi Pascal, Brian,

A few comments below:

> ... RFC 2491 was written to capture those interfacing functions needed

> to allow NDP and such to operate correctly.

[Pascal] RFC 2491 expects a MARS based service to enable a multicast
emulation for ND and present a common face to ND.
So we do something similar with a registrar of sorts, but a lot simpler
and more economical as it is integrated in ND.

[Mathilde] This does not sound similar to me. In one case you emulate
multicast below ND; ND remains unchanged. In the other you redefine ND.


> Is it possible that standard IPv6 nodes could operate on a 
> 6lowpan network as well as a more traditional (e.g., ethernet) one? 

[Pascal] Another question is whether that is desirable. There are
assumptions behind classical NDP as described in RFC 4861. The farther
you go from those assumption, the least NDP as its stands applies, and
the more costly the adaptation layer becomes. Classical NDP being
optimized for potentially large transitive networks with a high degree
of trust and few specific destination. It is based on assumptions
like...

[Mathilde] What about a router with two interfaces, one Ethernet and one
802.15.4. With the current proposal this router will need two
implementation of ND, 4861 on the Ethernet interface and 6lowpan-ND on
the other. 
An important implication is that we need to modify the OS (where ND is
implemented) of exiting computers / routers / etc to allow them to use a
802.15.4 interface.

>> ...  Yet, IPv6 over 802.11 works relatively well.

[Pascal] Certainly not on flat 802.11 (aka adhoc mode)...

[Mathilde] So is there a strong push from 802.11 vendors to redefine ND?
I didn't hear anything on this list.

[Pascal] My conclusion:
Yes, we are definitely interested in bringing our NDP extension to a
larger audience because:
- a whole industry is waiting for us; that industry can hardly accept a
solution that would be constrained to a single type of interface

[Mathilde] If a 'larger audience' is needed, I definitely think that
this work should not be done in 6lowpan as it is clearly focusing on
802.15.4 and I'm not sure the whole industry is aware of the effort. 

Best,
Mathilde