Hi Richard, Thank you for your reply.
>These sections clearly indicate that addresses with the first 96 bits > all-zero have embedded IPv4 addresses. I don't think so. You have missed note below in Section 2.5.5.1. =================================================================== Note: The IPv4 address used in the "IPv4-Compatible IPv6 address" must be a globally-unique IPv4 unicast address. =================================================================== ::(Unspecified Address) and ::1(Loopback Address) are not globally-unique IPv4 unicast address. We should not use the 96-bit all-zeros prefix to identify embedded IPv4 addresses. We have to check last 32 bits of the address. Thus, we don't need any addition. It is not an error. >By the way, I want to thank you for authoring this RFC, since it solves > a major problem we have, which is searching for and matching IPv6 addresses > that are represented as text. Thank you for your feedback. I'm so glad to hear that. :-) Regards, Masanobu >RFC-4291 (IP Version 6 Addressing Architecture), which RFC-5952 references, >has a section 2.5.5 called "IPv6 Addresses with Embedded IPv4 Addresses". >Presumably, this is what RFC-5952 is referring to. Section 2.5.5 two >subsections. The first subsection 2.5.5.1 is called "IPv4-Compatible IPv6 >Address". Let me copy it here: > >2.5.5.1. IPv4-Compatible IPv6 Address > > The "IPv4-Compatible IPv6 address" was defined to assist in the IPv6 > transition. The format of the "IPv4-Compatible IPv6 address" is as > follows: > > | 80 bits | 16 | 32 bits | > +--------------------------------------+--------------------------+ > |0000..............................0000|0000| IPv4 address | > +--------------------------------------+----+---------------------+ > > Note: The IPv4 address used in the "IPv4-Compatible IPv6 address" > must be a globally-unique IPv4 unicast address. > > The "IPv4-Compatible IPv6 address" is now deprecated because the > current IPv6 transition mechanisms no longer use these addresses. > New or updated implementations are not required to support this > address type. > >In addition, in RFC-4291 has a section 2.2 called "Text Representation of >Addresses", which has the following paragraph regarding mixed IPv6 / IPv4 >addresses: > > 3. An alternative form that is sometimes more convenient when dealing > with a mixed environment of IPv4 and IPv6 nodes is > x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values of > the six high-order 16-bit pieces of the address, and the 'd's are > the decimal values of the four low-order 8-bit pieces of the > address (standard IPv4 representation). Examples: > > 0:0:0:0:0:0:13.1.68.3 > > 0:0:0:0:0:FFFF:129.144.52.38 > > or in compressed form: > > ::13.1.68.3 > > ::FFFF:129.144.52.38 > >These sections clearly indicate that addresses with the first 96 bits all-zero >have embedded IPv4 addresses. It does say that this prefix is deprecated, but >deprecated or not, RFC-4291 clearly defines 96 bits of zero to contain an >embedded IPv4 address, and then shows it in at least two examples. > >Thus my confusion from this paragraph in RFC-5952, section 5: > >5. Text Representation of Special Addresses > > Addresses such as IPv4-Mapped IPv6 addresses, ISATAP [RFC5214], and > IPv4-translatable addresses [ADDR-FORMAT] have IPv4 addresses > embedded in the low-order 32 bits of the address. These addresses > have a special representation that may mix hexadecimal and dot > decimal notations. The decimal notation may be used only for the > last 32 bits of the address. For these addresses, mixed notation is > RECOMMENDED if the following condition is met: the address can be > distinguished as having IPv4 addresses embedded in the lower 32 bits > solely from the address field through the use of a well-known prefix. > Such prefixes are defined in [RFC4291] and [RFC2765] at the time of > this writing. If it is known by some external method that a given > prefix is used to embed IPv4, it MAY be represented as mixed > notation. Tools that provide options to specify prefixes that are > (or are not) to be represented as mixed notation may be useful. > >specifically "solely... through the use of a well-known prefix" then citing >RFC-4291. > >RFC-4291 does define 96 bits of zero as a well-known IPv4 address prefix, as >I've pasted above. > >If it was your intention that readers of RFC-5952 IGNORE section 2.5.5.1 of >RFC-4291, then YOU MUST MAKE THAT CLEAR because NOTHING in RFC-5952 says to do >that. In fact, just the opposite is at least implied, and implied because >sections 2.2 and 2.5.5.1 clearly show 96-bit all-zeros prefix indicate an >embedded IPv4 address, and RFC-5952 references this standard with no >additional clarification other than to go solely by the address prefix. > >So, I want it made clear EITHER: a) Ignore section 2.5.5.1 of RFC-4291, which >is to say that the 96-bit all-zero prefix is NOT intended to indicate an >embedded IPv4 address, or b) make it clear that at least :: and ::1 are not to >be treated as embedded IPv4 addresses because they are, in fact, well-known >IPv6 addresses. The latter was my suggestion from the original errata. > >If you require further clarification, then let me know. I don't know if I can >make it any clearer. I've pasted the relevant sections of RFC-5952 and >RFC-4291. But, if this is not enough, then I can try to provide more >information if you need it. > >By the way, I want to thank you for authoring this RFC, since it solves a >major problem we have, which is searching for and matching IPv6 addresses that >are represented as text. > >Thanks. > > --Rich > > >-----Original Message----- >From: Masanobu Kawashima [mailto:kawashi...@vx.jp.nec.com] >Sent: Thursday, July 28, 2011 5:04 PM >To: Rich Smith (rjsmith2); ipv6@ietf.org >Subject: Re: [Technical Errata Reported] RFC5952 (2872) > > >Hi Richard, > >Thank you for your report. >I think this is better discussed in 6man. > >But I think it is not an error. >Section 5 describes "Embedded IPv4 Addresses" for mixed notation. >IPv6 unspecified address and IPv6 loopback address are out of scope. > >Moreover, the 80-bit all-zeros prefix is not "IPv4-compatible IPv6 address". >We should not use the 80-bit all-zeros prefix to identify embedded IPv4 >addresses. > >I didn't understand what you mean. >Please describe more detail. > >Regards, >Masanobu > > >> >>The following errata report has been submitted for RFC5952, >>"A Recommendation for IPv6 Address Text Representation". >> >>-------------------------------------- >>You may review the report below and at: >>http://www.rfc-editor.org/errata_search.php?rfc=5952&eid=2872 >> >>-------------------------------------- >>Type: Technical >>Reported by: Richard J. Smith <rjsmi...@cisco.com> >> >>Section: 5 >> >>Original Text >>------------- >>For these addresses, mixed notation is RECOMMENDED if the following condition >>is met: the address can be distinguished as having IPv4 addresses embedded in >>the lower 32 bits solely from the address field through the use of a >>well-known prefix. >> >> >>Corrected Text >>-------------- >>For these addresses, mixed notation is RECOMMENDED if the following >>conditions are met: the address can be distinguished as having IPv4 addresses >>embedded in the lower 32 bits solely from the address field through the use >>of a well-known prefix, and the entire address is not either the unspecified >>IPv6 address "::" or the loopback IPv6 address "::1". >> >> >>Notes >>----- >>RFC-4291 defines the 80-bit all-zeros prefix as indicating an >>"IPv4-compatible IPv6 address". Without further clarification in section 5 of >>RFC-5952, the recommended formatting of the IPv6 unspecified address would be >>"::0.0.0.0", and the recommended formatting of the IPv6 loopback address >>would be "::0.0.0.1". Neither of these recommended representations is >>desirable. >> >>Instructions: >>------------- >>This errata is currently posted as "Reported". If necessary, please >>use "Reply All" to discuss whether it should be verified or >>rejected. When a decision is reached, the verifying party (IESG) >>can log in to change the status and edit the report, if necessary. >> >>-------------------------------------- >>RFC5952 (draft-ietf-6man-text-addr-representation-07) >>-------------------------------------- >>Title : A Recommendation for IPv6 Address Text Representation >>Publication Date : August 2010 >>Author(s) : S. Kawamura, M. Kawashima >>Category : PROPOSED STANDARD >>Source : IPv6 Maintenance >>Area : Internet >>Stream : IETF >>Verifying Party : IESG > >¢(._.) >======================================== > NEC AccessTechnica, Ltd. > Product Development Department > Masanobu Kawashima > kawashi...@vx.jp.nec.com > http://www.necat.co.jp/ >======================================== > ¢(._.) ======================================== NEC AccessTechnica, Ltd. Product Development Department Masanobu Kawashima kawashi...@vx.jp.nec.com http://www.necat.co.jp/ ======================================== -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
