Non-routed ad-hoc networks, and in particular multi-homing to such things,
have been discussed on the list but I don't recall seeing a discussion
of how naming could work in such a case, hence this post.
[Note I say "non-routed" because there is the MANET type world where
there are routers that glue together multiple links and I don't
think they have this issue.]
For a single ad-hoc link I can see LLMNR work as a naming protocol
(and link-locals or any other IP address can be used - doesn't matter
since all IP addresses must either be local to the link or be unreachable).
Thus the user or devvice could pick a name (e.g. "laptop" or
"philips-coffee-maker") and check if any other node on the link is already
using that name (do an LLMNR lookup); if the name is already being used
pick another name ("eriks-laptop",
"philips-coffee-maker-serial-number-0345174").
Then LLMNR lookups would work just fine - users type "laptop" as the name;
all assuming there is no multi-homed nodes.
This seems like a useful and harmful application of IPv6 in the small.
But when multihoming enters, in particular there are nodes which have
multiple interfaces enabled at the same time, then things get more
difficult.
Imagine the multihomed node has two interfaces and there are multiple neighbors
on each of those interfaces. On interface A a node might pick the name
"laptop" and another node might pick the same name of interface B without
conflict; the lookup for duplications can't be forwarded since there is no
router between the two links. In this case, independently of what addressing
and scope-ids, a application looking up the name "laptop" will have a
non-unique name.
So either the LLMNR type lookup needs to be relayed by the multihomed node
(seems to have all the usual loop avoidance issues plus the inability
to treat the links as different from a security perspective; somebody on some
less trusted link can prevent me from using a name on my more trusted link),
or there has to be some infrastructure that can make sure that the names
become unique across the two links (e.g. by handing out different name suffixes
for the two links). Alternatively this could be made a routed ad-hoc network
using DNS for naming and avoid the issue.
My point is that even with applications and/or APIs that deal with scope ids,
there is a difficult naming issue when multihoming is applied to non-routed
ad-hoc networks.
This seems to be a more basic issue than whether or not link-local addresses
can be used by the applications in this case.
Erik
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