[ipwave] link-local text (Re: [Int-dir] Intdir early review of draft-ietf-ipwave-ipv6-over-80211ocb-34)

[神明達哉 <[e-mail]>]

On Thu, Apr 11, 2019 at 6:59 AM Alexandre Petrescu <
[e-mail]> wrote:

>    The fe80::/10 word was removed.

So I've just checked draft-ietf-ipwave-ipv6-over-80211ocb-38.  It now
reads:

   A subnet is formed by the external 802.11-OCB interfaces of vehicles
   that are in close range (not by their in-vehicle interfaces).  This
   subnet MUST use at least the link-local prefix and the interfaces
   MUST be assigned IPv6 address(es) of type link-local.

Given that the use of non-0 values in the intermediate 54 bits of
link-local addresses is now out of scope of this specification, I
don't see the purpose of the second sentence.

"the interfaces MUST be assigned IPv6 address(es) of type link-local"
is redundant, since it's already a part of the very basic
specification of IPv6 addressing architecture (second paragraph of
RFC4291 Section 2.1).  According to a previous conversation, perhaps
it tries to re-emphasize the already-existing requirement?  In that
case, I think it better belongs to Section 4.3, since the requirement
of having a link-local address is not a requirement on a subnet, but
on an interface.  I'd suggest revising the first paragraph of Section
4.3 as follows:

   There are several types of IPv6 addresses [RFC4291], [RFC4193], that
   MAY be assigned to an 802.11-OCB interface.  Among these types of
   addresses, the interface MUST at least have one link-local IPv6
   unicast address as specified in [RFC4291].  Only those link-local
   addresses MAY be formed using an EUI-64 identifier, in particular
   during transition time.

And, beyond this obvious requirement, it's not clear to me what this
means: "This subnet MUST use at least the link-local prefix".  Perhaps
it also tries to say this must be a single-link subnet (so all nodes
in the subnet can communicate each either directly using their
link-local addresses)?  If so, it's better to say so explicitly, e.g:

   A subnet is formed by the external 802.11-OCB interfaces of vehicles
   that are in close range (not by their in-vehicle interfaces).  This
   MUST be a single-like subnet.  It means that all nodes in the
   subnet must be able to communicate directly using their link-local
   unicast addresses.

If there's no such special intention, I'd suggest just removing the
second sentence (with moving the requirement of having a LL address to
Section 4.3).

--
JINMEI, Tatuya