Hello,
I understand the problems with 'redesigning' a core IPv6 protocol. However I'm curious about existing implementations that use full IPv6 ND, do you have details? I see the 6LoWPAN ND as a 'necessary evil', however I would love to be proven wrong! Regards, -Colin From: [email protected] [mailto:[email protected]] On Behalf Of Julien Abeille (jabeille) Sent: October 12, 2009 1:47 PM To: 6lowpan Subject: [6lowpan] Fundamental concerns about 6lowpan ND Dear WG, I have serious concerns about the 6lowpan ND draft and would like to have the WG opinion on this. I agree that a few issues arise in lowpan environments, which are mostly linked to the non transitivity of some link layers used in lowpans. However, my two major points of concern are: - RFC4861 and RFC4862, which are core to IPv6, are being very heavily redesigned. I believe that the proposal if it is done in 6lowpan MUST be designed as an optional extension to ND, not a redesign. The charter states that the draft should propose "optimizations" and "limited extensions" to ND. It is not the case at the moment. The proxy ND proposal, the mandatory addressing model proposed, also goes beyond the scope of the document as spelled out in the charter. - non transitivity is not a lowpan only issue, hence if adaptations to ND must be done, it should be in another WG, probably 6man If these two points are not respected, - it questions the applicability of IPv6 in smart object networks: the draft is redesigning roughly 80% of RFC4861 and RFC4862, which are core to IPv6 - existing IPv6 implementations will be strongly impacted, as a number of major components will have to become layer 2 dependant: -- address resolution will have to be disabled -- DAD will have to be modified -- NUD will have to be modified -- prefix discovery will have to be modified -- autoconf will have to be modified -- IPv6 addresses will not be configurable if their IID is not based on the MAC address -- ... all these changes are 6lowpan dependant, as they do not impact traditional links. This will raise important interoperability issues. - new layer 3 protocol designs will become layer 2 dependant. This is what is currently happenning in the ROLL WG by proposing to use a different message to transport routing information, depending on the medium. Moreover, a number of existing deployments show that the issues arised on lowpan networks as far as ND is concerned are not huge: the deployments work, and ND as it is has proven to be power consumption friendly. DAD is the most problematic procedure, that requires work, as two hop neighbors do not see NS sent for DAD (see at the bottom) In conclusion, I believe the advantages of rebuilding neighbor discovery for lowpans are by far inferior to those of keeping using the "same IP" on all medium. If some redesign has to be done, it MUST be done in a more general fashion, probably in 6man, and in a much lighter way. Best, Julien DAD issue description: node A and node C see node B, but not each other. nodes A and B boot, configure a link local address, perfom traditional DAD. It works. Node C boots with the same MAC address than A, configures the same IP address, sends a NS to perform traditional DAD. A does not see the NS hence C address configuration works. A and C have the same address. B will not differentiate A and
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