-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Thanks for the comments. This also should go to the 6man list.
Regards, Seiichi - -------- Original Message -------- Subject: Re: Further Comment to RFC 5952 Date: Thu, 14 Oct 2010 17:02:10 +0200 From: Test <[email protected]> To: [email protected], [email protected] References: <[email protected]> Typos corrected. Sorry. Test wrote: > Sirs, > > Excuse me for bombarding you with questions and comments, but I think > that if I have questions there must be many other programmers out > there who are making dangerous assumptions and not asking you. > > I have come across another ambiguity whilst testing my library that is > not clarified by reading the RFC 5952. > > It regards the handling of prefixes in mixed representation of > addresses handled under section 5, such as IPv4-Mapped IPv6 addresses. > > The question is how to handle the mask length of prefixes in such cases. > > Is it correct to write an IPv4 mapped IPv6 address prefix > corresponding to the old Class A network 10.0.0.0 = IPv4 CIDR > 10.0.0.0/8 as IPv4 mapped IPv6 with the notation > > ::FFFF:10.0.0.0/8 [prefix relative to 32 bits of IPv4 because the > mechanism clearly maps IPv4 into IPv6 notation] > > or should this be > > ::FFFF:10.0.0.0/104 [prefix relative to 128 bits of IPv6] > > This is of course has potentially an equivalent problem in pure IPv6 > format with two options. > > ::ffff:0a00:0000/8 > or > ::ffff:0a00:0000/104 > > My gut feeling says less programmes will break with > ::ffff:10.0.0.0/104, but it is potentially more confusing to humans to > say the least. > > The hex representation of this IPv6 address ::ffff:0a00:0000/104 would > be handled correctly by all IPv6 programmes even if they do not > recognise all of the special embedded IPv4 mechanisms mentioned in > RFC4291. > > Whereas ::ffff:0a00:0000/8 would almost certainly break the programme > if it did not understand the specifics of IPv4 mapped IPv6 addresses, > as it would be interpreted as far too big a range. > > On the other hand, humans might get confused when they read > ::FFFF:10.0.0.0/104, and prefer ::FFFF:10.0.0.0/8 although potentially > less so than I would imagine. > > Tough call. > > I think some clarification text in Section 7 would be useful. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) iEYEARECAAYFAky3mIsACgkQcrhTYfxyMkKH5QCfW+Liv4t3TFIcrqvviwBJqGYB iVAAn11swbhUVLmI3F0fockmWGdkp23o =Q8xF -----END PGP SIGNATURE----- -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
