I've got an architectural issue with any protocol having specific
values in the RAO. In general, that's
a poor approach, as it will (in the long term) lead to multiple
protocols piggybacking on RAO. Why not simply allocate another
option on a per-protocol basis?
This also has the nice side effect that it ensures that things are
backward compatible.
Tony
On Oct 24, 2007, at 12:56 PM, Jukka MJ Manner wrote:
Hi Thomas, Bob,
Thanks for the discussion.
The specific application that needs (well, to be precise, would
greatly
benefit) RAO is NSIS. That is why NSIS ML is CC:d.
Moreover, the RSVP spec talks about multiple RAO values, but lets
it open
as to whether IPv4 should also have those, not just IPv6.
RFC2113 also says that "The semantics of other values in the Value
field
are for further study."
The point is, is it time to study those "other values" further? At
least
GIST and the whole NSIS framework would greatly benefit from more
values
than just "0" for IPv4, and these values should be the same for
IPv6 also,
for simplified implementations.
There is a lot of discussions about RAO in the GIST spec, e.g.,
Sections
4.3.1., 4.3.4., 5.3.2.1., 5.3.2.2., 6. IANA Considerations and
Appendix C:
http://tools.ietf.org/wg/nsis/draft-ietf-nsis-ntlp/
Regards,
Jukka
On Wed, 24 Oct 2007, Thomas Narten wrote:
Bob Hinden and I had some further offlist discussion about this.
My understanding is that the IPv4 RA option is very basic. It says
"look at this packet". The option itself doesn't contain any
additional information or "hint" as to what to look for or what the
packet contains.
The semantics of the IPv6 router alert option are different. The
value
itself is used to convey additional "hints" about processing.
My sense is that the semantics of the IPv4 and IPv6 Router Alert
option are sufficiently different that sharing the name space just
doesn't make any sense.
That is, the ID says:
This document proposes the creation of a new IANA registry for
managing IPv4 Router Alert Option Values. In conjunction with
this, it also proposes an update to the way in which IPv6 Router
Alert Option Values are assigned in the existing IANA registry.
But there are no defined IPv4 Router Alert Option values (other than
zero), and it would be inappropriate to change the semantics of any
existing usages (too late for that) and it would also be
inappropriate
to consider doing this in the absense of a specific new application
that would make use of a new value. This document does not propose
such a new usage.
Hence, at this point, I'm opposed to the actions called for in the
document.
Thomas
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