Hi all, On 05.02.2013 16:51, Rémi Després wrote: > Several opinions against a 4rd-range reservation have also been > expressed, but they concern the purpose of 4rd, or its experimental > status, or personal feelings against one more specification. They are > not about technical compatibility with the IPv6 addressing > architecture. > > Keeping the 4rd answer separate from the general u/g bit discussion > will permit, I hope, to now finalize this answer asap.
My personal summary is as follows: - The u/g bits have no real meaning in an IID (though the original intention of mapping EUI-64/48 addresses as modified EUI-64 into the IID may have been to preserve their meaning), so using them as indicator for the presence of a particular "IID format" seems to be not a good idea (see Brian's draft as well as Randy's "magic bits are almost never worth the pain"). - I feel uncomfortable with reserving another range in the IID space for 4rd, since it is not clear what implementations should do with it - building exceptions into implementations (e.g., martian IIDs) is error prone and may cause conflicts with future IID uses, even if 4rd is experimental. So I'm also sharing Ole's concerns here: http://www.ietf.org/mail-archive/web/ipv6/current/msg16976.html - without knowing too many details of the 4rd solution I'd rather propose to use configured 4rd subnet-IDs as indicator that the IID has a special format: this would be IMHO far more reliable and consistent than relying on this "reserved IID range". Since 4rd will require configuration anyway, one can configure the right 4rd /64s. I'm aware of the counter arguments (j)(m) in http://www.ietf.org/mail-archive/web/ipv6/current/msg16949.html, i.e., "free choice of subnet prefixes at CE sites" and "IID assignments made before 4rd activation". But it is not clear to me how often this will be _actually_ the case in practice and whether it's worth to "sacrifice" IID space and IPv6 flexibility for keeping these requirements. IPv6 is flexible enough to automatically reassign subnet prefixes or IIDs, thus I'm still not buying the arguments yet... Regards, Roland -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
