Dave Thaler and I are exchanging e-mail about this very topic. According to Dave, scope 3 was assigned for subnet-scoped multicast, to accommodate multi-link subnets. Then the IPng WG decided multi-link subnets is a bad idea and Dave wrote RFC 4903. One of the side-effects was to relabel scope 3 as 'reserved'.
Now, however, me have multi-link subnets in the 6lowpan/RPL architecture, picked up by ZigBee IP. Might be time to relabel scope 3 back to subnet-scope. - Ralph On Jun 27, 2012, at 2:47 PM 6/27/12, Kerry Lynn wrote: > On Wed, Jun 27, 2012 at 1:53 PM, Stig Venaas <s...@venaas.com> wrote: > On 6/27/2012 10:13 AM, Kerry Lynn wrote: > Greetings, > > RFC 3484 section 3.1 defines "subnet-local (0x03)" multicast scope, but > later RFC 4291 section 2.7 defines this multicast scope value as reserved. > Can I ask if the later interpretation is the correct one? > > I ask in the context of e.g. > http://tools.ietf.org/html/draft-lynn-homenet-site-mdns > where we need a scope greater than link-local in order to span a 6LoWPAN > subnet, but less than site-local in order to reserve the property "Each > interface > belongs to exactly one zone of each possible scope." for future site-local > protocols that might include the 6LoWPAN router port. > > Should I select admin-local scope, or is subnet-local scope available > for use? > > I've always been a bit curious why it got marked as reserved. It was > (unassigned) in RFC 2373, but reserved in RFC 3513. I don't remember > any discussion on this. > > It seems 4 admin-local would be appropriate then. Unless perhaps if 3 > is somehow reserved to allow for maybe future use like this... > > Perhaps it was originally discussed as an analog to IPv4 subnet broadcast, > but that usage was later thought unnecessary. Hopefully an IPv6 historian > will chime in... > > Thanks, -K- > > Stig > > > Thanks, -K- > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- > > > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- > > -------------------------------------------------------------------- > IETF IPv6 working group mailing list > ipv6@ietf.org > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 > -------------------------------------------------------------------- -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
