Re: RFC6085 update to rfc2464bis

[神明達哉 <[e-mail]>]

On Tue, Jan 10, 2017 at 9:26 AM <[e-mail]> wrote:

>>    An IPv6 multicast packet may also be mapped to a unicast Ethernet
>>    Link layer address as defined in Section 6.
>
> I think it's more helpful to refer to RFC6085 explicitly here.
> Otherwise the proposed text looks good to me.

On re-reading it more closely, I wonder whether "as defined in Section
6" may not be very appropriate.  RFC6085 intentionally left the
mapping open:

   [...]  The determination of the unicast Ethernet link-layer
   address and the construction of the outgoing IPv6 packet are out of
   scope for this document.

but I suspect it doesn't really intend to perform link-layer address
resolution using ND (which is in my understanding what "Section 6"
talks about) to determine the unicast Ethernet address.  In fact, the
address resolution itself uses a multicast IPv6 address, which is
derived from the target unicast IPv6 address.  So it would be a kind
of circular definition.

So it's probably even better to just refer to the RFC instead of
Section 6:

    An IPv6 multicast packet may also be mapped to a unicast Ethernet
    Link layer address as noted in [RFC6085].

And, for that matter, this text of Section 6 of rfc2464bis-01 now
looks a bit awkward to me:

   The procedure for mapping IPv6 unicast addresses into Ethernet link-
   layer addresses is described in [DISC].

On reading both Sections 6 and 7, this "the procedure for mapping"
could read some static mapping whereas it should actually refer to
dynamic link-layer address resolution.

I suggest revising the first paragraph from:

   The procedure for mapping IPv6 unicast addresses into Ethernet link-
   layer addresses is described in [DISC].  The Source/Target Link-layer
   Address option has the following form when the link layer is
   Ethernet.

to:

   When the link layer is Ethernet, the Ethernet address for an IPv6
   unicast address is resolved using the address resolution protocol
   as defined in [DISC].  The Source/Target Link-layer Address option
   used in that protocol has the following form.

--
JINMEI, Tatuya