6lo P. Thubert Internet-Draft Updates: 8928 (if approved) A. Rashid Intended status: Standards Track Politecnico di Bari Expires: 20 November 2025 19 May 2025 Fixing the C-Flag in EARO draft-ietf-6lo-updating-rfc-8928-04 Abstract This document updates RFC 8928, “Address-Protected Neighbor Discovery for Low-Power and Lossy Networks” (AP-ND), by updating the bit position for the C-flag in the Extended Address Registration Option (EARO) and registering it with IANA. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 20 November 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Thubert & Rashid Expires 20 November 2025 [Page 1] Internet-Draft RFC 8928-Fix May 2025 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2.2. References . . . . . . . . . . . . . . . . . . . . . . . 2 2.3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Updating RFC 8928 . . . . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5.1. Bit Position of the C-flag . . . . . . . . . . . . . . . 5 6. Normative References . . . . . . . . . . . . . . . . . . . . 5 7. Informative References . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction The Address-Protected Neighbor Discovery for Low-Power and Lossy Networks (AP-ND) [RFC8928] defined the C-flag in EARO. It is used to indicate that the Registration Ownership Verifier (ROVR) field contains a Crypto-ID and that the 6LoWPAN Node (6LN) may be challenged for ownership of the registered address. Initially [RFC8928] defined the C-flag in the EARO in bit position 3; later [RFC9685] defined the P-field in bits 2 and 3 of the EARO flags field with proper IANA registration, causing an overlap with Figure 1 of [RFC8928] which depicts the location of the C-flag. This specification updates [RFC8928] by repositioning the C-flag as bit 1 of the EARO flags field, thereby preventing conflicts. 2. Terminology 2.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2.2. References This document uses terms and concepts that are discussed in Neighbor Discovery (ND) for IPv6 [RFC4861], [RFC4862] and Subnet ND [RFC6775], [RFC8505] [RFC8928], [RFC8929] [RFC9685], and [I-D.ietf-6lo-prefix-registration]. Thubert & Rashid Expires 20 November 2025 [Page 2] Internet-Draft RFC 8928-Fix May 2025 2.3. Acronyms This document uses the following abbreviations: *6LN:* 6LoWPAN Node *EARO:* Extended Address Registration Option *ND:* Neighbor Discovery *RATInd:* Registered Address Type Indicator *ROVR:* Registration Ownership Verifier 3. Updating RFC 8928 [RFC8928] incorrectly refers to the Extended Address Registration Option (EARO) as the Enhanced Address Registration Option. This specification corrects this terminology throughout the document. In [RFC8928], the C-flag is specified in the EARO flags field at bit position 3 (as depicted in the Figure 1 of [RFC8928]); however, [RFC8928] fails to register its position with IANA. Later, [RFC9685] defined the P-field in bits 2 and 3 of the EARO flags field and obtained proper IANA registration, but this introduced an overlap with the representation in [RFC8928]. To resolve the conflict, this specification updates [RFC8928] by repositioning the C-flag to bit 1 of the EARO flags field, thereby avoiding the overlapping definitions. Figure 1 below replaces Figure 1 in [RFC8928] in the case of an EARO used in an NS message. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length |F|Prefix Length| Opaque | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |r|C| P | I |R|T| TID | Registration Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ... Registration Ownership Verifier (ROVR) ... | (64, 128, 192, or 256 bits) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Extended Address Registration Option (EARO) Format for use in NS messages Figure 2 below replaces Figure 1 in [RFC8928] in the case of an EARO used in an NA message. The difference between the two formats is in the usage of bits 16 to 23. Thubert & Rashid Expires 20 November 2025 [Page 3] Internet-Draft RFC 8928-Fix May 2025 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | r | Status | Opaque | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |r|C| P | I |R|T| TID | Registration Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ... Registration Ownership Verifier (ROVR) ... | (64, 128, 192, or 256 bits) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Extended Address Registration Option (EARO) Format for use in NA messages Option fields of interest for this specification: *Type:* 33 *Length:* Defined in [RFC8505]. *F:* Defined in [I-D.ietf-6lo-prefix-registration] *Prefix Length* Defined in [I-D.ietf-6lo-prefix-registration] *Status:* 6-bit unsigned integer. This field is used in NA(EARO) response messages only to indicate the status of a registration. This field is defined in [RFC8505] and resized by [RFC9010]. The values for the Status field are available in [IANA.ICMP.ARO.STAT]. This field MUST be set to 0 in NS(EARO) messages unless the registration is for a prefix, in which case the F-flag is set and the prefix length is provided. *Opaque:* Defined in [RFC8505] *r (reserved):* 1-bit reserved field in NS(EARO) and NA(EARO) as depicted in Figure 1 and Figure 2. 2-bit reserved field (most significant bits of Status filed) in NA(EARO) as depicted in Figure 2. All reserved field MUST be set to zero by the sender and MUST be ignored by the receiver. *C:* 1-bit flag, moved from its position in Figure 1 of [RFC8928]. It is set to indicate that the ROVR field contains a Crypto-ID and that the 6LN MAY be challenged for ownership. *P:* 2-bit field for Registered Address Type Indicator (RATInd). Thubert & Rashid Expires 20 November 2025 [Page 4] Internet-Draft RFC 8928-Fix May 2025 Indicates whether the registered address is unicast, multicast, or anycast, or derived from the unicast prefix that is being registered. Used to transport the RATInd in different protocols. The values for the RATInd field are available in [IANA.ICMP.ARO.P-FIELD]. *I:* Defined in [RFC8505] *R:* Defined in [RFC8505] *T:* Defined in [RFC8505] *TID (Transaction ID):* Defined in [RFC8505] *Registration Lifetime:* Defined in [RFC8505] *Registration Ownership Verifier (ROVR):* Defined in [RFC8505]. Variable length field, used to verify who "owns" a registered IPv6 address. When the C-flag is set, this field contains a Crypto-ID [RFC8928]. 4. Security Considerations This specification does not introduce any new security considerations beyond those already discussed in [RFC8928] and [RFC8505]. 5. IANA Considerations 5.1. Bit Position of the C-flag This specification updates the location of the C-flag introduced in [RFC8928] to position it as bit 1 in the EARO flags field. IANA is requested to reference this RFC in addition to [RFC8928] when updating the "Address Registration Option Flags" [IANA.ICMP.ARO.FLG] registry under the heading "Internet Control Message Protocol version 6 (ICMPv6) Parameters" as specified in Table 1: +---------------+---------+-----------------------+ | EARO flag | Meaning | Reference | +---------------+---------+-----------------------+ | 1 (suggested) | C-Flag | RFC This and RFC 8928 | +---------------+---------+-----------------------+ Table 1: Bit Position of the C-flag 6. Normative References Thubert & Rashid Expires 20 November 2025 [Page 5] Internet-Draft RFC 8928-Fix May 2025 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 10.17487/RFC4861, September 2007, . [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, DOI 10.17487/RFC4862, September 2007, . [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. Bormann, "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)", RFC 6775, DOI 10.17487/RFC6775, November 2012, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. Perkins, "Registration Extensions for IPv6 over Low-Power Wireless Personal Area Network (6LoWPAN) Neighbor Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, . [RFC8928] Thubert, P., Ed., Sarikaya, B., Sethi, M., and R. Struik, "Address-Protected Neighbor Discovery for Low-Power and Lossy Networks", RFC 8928, DOI 10.17487/RFC8928, November 2020, . [RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL (Routing Protocol for Low-Power and Lossy Networks) Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021, . [RFC9685] Thubert, P., Ed., "Listener Subscription for IPv6 Neighbor Discovery Multicast and Anycast Addresses", RFC 9685, DOI 10.17487/RFC9685, November 2024, . Thubert & Rashid Expires 20 November 2025 [Page 6] Internet-Draft RFC 8928-Fix May 2025 [I-D.ietf-6lo-prefix-registration] Thubert, P., "IPv6 Neighbor Discovery Prefix Registration", Work in Progress, Internet-Draft, draft- ietf-6lo-prefix-registration-10, 17 April 2025, . [IANA.ICMP.ARO.FLG] IANA, "IANA Registry for the Address Registration Option Flags", IANA, https://www.iana.org/assignments/icmpv6- parameters/icmpv6-parameters.xhtml#icmpv6-adress- registration-option-flags. [IANA.ICMP.ARO.STAT] IANA, "IANA Registry for the Address Registration Option Status Value", IANA, https://www.iana.org/assignments/ icmpv6-parameters/icmpv6-parameters.xhtml#address- registration. [IANA.ICMP.ARO.P-FIELD] IANA, "IANA Registry for the Address Registration Option Status Value", IANA, https://www.iana.org/assignments/ icmpv6-parameters/icmpv6-parameters.xhtml#p-field-values. 7. Informative References [RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli, "IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929, November 2020, . Authors' Addresses Pascal Thubert 06330 Roquefort-les-Pins France Email: pascal.thubert@gmail.com Adnan Rashid Politecnico di Bari Via Edoardo Orabona 4 70126 Bari Italy Email: adnan.rashid@poliba.it Thubert & Rashid Expires 20 November 2025 [Page 7]