Re: [6man] New Version Notification for draft-nordmark-6man-impatient-nud-00.txt

[Carsten Bormann <[e-mail]>]

On May 25, 2011, at 19:58, Ray Hunter wrote:

> I've just read the RFC covering the (very interesting) mesh under / route over mechanism used in 6LoWPAN http://tools.ietf.org/html/draft-ietf-6lowpan-nd-16 . Very cool stuff.

Thanks!

> Even there it was a requirement that all nodes taking part in the network behave the same way.
> > The applicability of this specification is limited to LoWPANs where all nodes on the subnet implement these optimizations in a homogeneous way.

The idea here is that this draft updates RFC 4944 (the IP-over-foo for IEEE 802.15.4, usually referred to as 6LoWPAN) so that *all* nodes on a 6LoWPAN MUST implement 6LoWPAN-ND as opposed to ND-classic.

> So if the point of this draft is really to limit multicast, then from an operational perspective don't you want ALL nodes on a link to avoid using multicast as much as possible?

Yes, that is one of the reasons why we didn't try to tackle the theoretical possibility of interoperation between nodes implementing 6LoWPAN-ND and other nodes implementing ND-classic on 6LoWPANs, because even listening for multicast is very expensive for some nodes there.

> So if the point of this draft is really to avoid operational problems with STP thrashing, then from an operational perspective don't you want ALL nodes on a link to avoid timing out too fast as much as possible?

There is no STP in 6LoWPAN, so that isn't a consideration for this draft.
Again, 6LoWPAN-ND is currently defined for non-Ethernet networks that are homogeneously 6LoWPAN-ND, i.e. 802.15.4 (and, most likely once their IP-over-foo documents stabilize, similar constrained networks such as BT-LE or DECT-ULE), 
However if people want to go ahead and do the work of adapting 6LoWPAN-ND (or some of its elements) to other networks,
e.g., Ethernet/WiFi, then one would have to open that can of worms.

Gruesse, Carsten