James Carlson wrote:
Alexandru Petrescu writes:
Finally, link-layer addresses have a tight relationship with
what goes in the last 64bits of an address. On ppp (and maybe
others?) links there's no link-layer address but there's means
to have something go into the last 64bits. So could we
consider that IID to be a link-layer address.
=> No we can't, the IID is in a completely different layer. The
fact that you can use an L2 address to generate the IID, does not
mean you can use the IID as an L2 address.
Ok, I tend to think the same, too. But ppp gives an Interface ID
and there's no other means in ppp to have an endpoint identifier.
So the easiest way for ND to run over ppp would be to build some
virtual link-layer headers with Interface IDs in it. All other ND
mechanisms (multicast, DAD, etc) would run unmodified.
I'm very much opposed to this idea. Those Interface IDs are not link
layer addresses. ND options including link layer addresses should
be added _only_ when link layer addresses exist on the underlying
media -- and they don't exist for point-to-point links.
I fear changing this behavior to include Interface IDs instead of
link layer addresses will confuse and break existing implementations.
Let's see... not that I've tried it.
If a ppp peer negotiates an Interface ID and puts it in the Neighbour
Cache attached to the ppp0 entry, won't break anything. When displaying
the NC the entry simply won't show up empty.
If same ppp peer declares that ppp0 interface nd-capable (instead of
currently declared nd-non-capable), and builds a virtual ll header
structure whose format is (src, dst on 64bits) and then declare some
other constants for special ll multicast addresses then that ppp peer
won't crash. The issue is what to declare on the other ppp peer.
By existing ND implementations I assume it's meant ND over an ll-full
(an interface with link-layer address). I think that as long as the
ND/ptp enhancements are applied only on ll-less interfaces that can
generate an IID then the other interfaces' implementations (eth, tun,
etc) won't be affected. No?
An "Interface ID" is exactly what ND needs on a ppp link.
Disagree. Why does it need _any_ link layer address? Why should it
care?
A main ND's goal is to resolve the IP address into a ll address, so if
there's no ll address then no need of ND exchanges (especially no need
of NS/NA). At which point it would be difficult to say that ND runs
over ll-less addresses ok. I think.
Alex
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