[6lo] Comment about "draft-thubert-6lo-rfc6775-update-reqs-06"

["Wang, Chonggang" <[e-mail]>]

Hi Pascal and All,

I reviewed draft-thubert-6lo-rfc6775-update-reqs-06 and had a few comments/questions below:


1.       In Section 3, the concept of a Multi-Link Subnet is presented. In it, it was mentioned that “The scope of the 6TiSCH Architecture is a Backbone Link that federates multiple LLNs (mesh) as a single IPv6 Multi-Link Subnet”.

a.       What is the significance of specifying “single” subnet?

b.      There could be multiple 6BBRs anchoring each LLN subnet. Would these subnets each have separate sub-prefixes within single IPv6 prefix similar to how IPv4 is deployed with a public address and subnets in the private address space? Granted in IPv6, the subnets do not need to be private.

c.       Further into section 3, there was a statement that an LLN can move freely within the multi-link subnet anchored by the same or different 6BBR while keeping its address. Is the assumption here that all the 6BBRs share the same prefix?

2.       The call flow in Figure 2 seems to apply to both registration and re-registration procedures – is this correct? If so, it seems during re-registration, the DAD should not need to be performed?

3.       Figure 2 shows the DAD going beyond the BBR, which based on Figure 1, implies that DAD is performed by the Gateway. Is this assumption correct?

4.       In Figure 2, is “Efficient ND” supposed to be compatible with traditional (6775) ND?

5.       In section 4.4, there is reference to a duty-cycled device needing the help of a 6LBR to perform registration to the 6BBR on its behalf. Does this statement imply that the device cannot stay awake long enough to receive the NA after sending an NS?

6.       Req5.4 specifies that a security mechanism lighter than SHA-1 should be preferred. Is it envisioned that LLN devices are constrained devices as specified by RFC 7228 (Class 0-2)?

7.       What is meant by Req6.1 in which a single 6LBR can register multiple thousands of devices? Any clarify the use case a little bit?

Thanks,
Chonggang