6man Working Group M. Boucadair Internet-Draft France Telecom Updates: 3306,3956,4291 (if approved) S. Venaas Intended status: Standards Track Cisco Expires: September 13, 2014 March 12, 2014 Updates to the IPv6 Multicast Addressing Architecture draft-ietf-6man-multicast-addr-arch-update-04 Abstract This document updates the IPv6 multicast addressing architecture by defining the 17-20 reserved bits as generic flag bits. The document provides also some clarifications related to the use of these flag bits. This document updates RFC 3956, RFC 3306 and RFC 4291. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 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 http://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 September 13, 2014. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. Boucadair & Venaas Expires September 13, 2014 [Page 1] Internet-Draft Multicast Flag bits March 2014 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Addressing Architecture Update . . . . . . . . . . . . . . . 2 3. Flag Bits: A Recommendation . . . . . . . . . . . . . . . . . 3 4. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. RFC 3306 . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. RFC 3956 . . . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 8. Normative References . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction This document updates the IPv6 multicast addressing architecture [RFC4291] by defining the 17-20 reserved bits as generic flag bits (Section 2). The document provides also some clarifications related to the use of these flag bits (Section 3). This document updates [RFC3956], [RFC3306], and [RFC4291]. These updates are logical consequences of the recommendation on the flag bits (Section 3). Textual representation of IPv6 addresses included in the RFC updates follows the recommendation in [RFC5952]. 2. Addressing Architecture Update Bits 17-20 of a multicast address are defined in [RFC3956] and [RFC3306] as reserved bits. This document defines these bits as generic flag bits so that they apply to any multicast address. Figure 1 and Figure 2 show the updated structure of the addressing architecture. The first diagram shows the update of the base IPv6 addressing architecture, and the second shows the update of so-called Embedded-RP. Boucadair & Venaas Expires September 13, 2014 [Page 2] Internet-Draft Multicast Flag bits March 2014 OLD: | 8 | 4 | 4 | 112 bits | +--------+----+----+----------------------------------------------+ |11111111|flgs|scop| group ID | +--------+----+----+----------------------------------------------+ NEW: | 8 | 4 | 4 | 4 | 108 bits | +--------+----+----+----------------------------------------------+ |11111111|ff1 |scop|ff2 | group ID | +--------+----+----+----+-----------------------------------------+ * ff1 refers to "flag field 1" * ff2 refers to "flag field 2" * flag bits denote both ff1 and ff2. Figure 1: Updated IPv6 Multicast Addressing Architecture OLD (RFC 3956): | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | +--------+----+----+----+----+--------+----------------+----------+ |11111111|flgs|scop|rsvd|RIID| plen | network prefix | group ID | +--------+----+----+----+----+--------+----------------+----------+ NEW: | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | +--------+----+----+----+----+--------+----------------+----------+ |11111111|ff1 |scop|ff2 |RIID| plen | network prefix | group ID | +--------+----+----+----+----+--------+----------------+----------+ Figure 2: Embedded-RP with Updated IPv6 Multicast Address Arch. Further specification documents may define a meaning for these flag bits. Defining the bits 17-20 as flags for all IPv6 multicast addresses allows addresses to be treated in a more uniform and generic way, and allows for these bits to be defined in the future for different purposes, irrespective of the specific type of multicast address. 3. Flag Bits: A Recommendation Some implementations and specification documents do not treat the flag bits as separate bits but tend to use their combined value as a 4-bit integer. This practice is a hurdle for assigning a meaning to the remaining flag bits. Below are listed some examples for illustration purposes: Boucadair & Venaas Expires September 13, 2014 [Page 3] Internet-Draft Multicast Flag bits March 2014 o the reading of [RFC3306] may lead to conclude that ff3x::/32 is the only allowed SSM IPv6 prefix block. o [RFC3956] states only ff70::/12 applies to Embedded-RP. Particularly, implementations should not treat the fff0::/12 range as Embedded-RP. To avoid such confusion and to unambiguously associate a meaning with the remaining flags, the following requirement is made Implementations MUST treat flag bits as separate bits. 4. RFC Updates 4.1. RFC 3306 This document changes Section 4 of [RFC3306] as follows: OLD: | 8 | 4 | 4 | 8 | 8 | 64 | 32 | +--------+----+----+--------+--------+----------------+----------+ |11111111|flgs|scop|reserved| plen | network prefix | group ID | +--------+----+----+--------+--------+----------------+----------+ +-+-+-+-+ flgs is a set of 4 flags: |0|0|P|T| +-+-+-+-+ o P = 0 indicates a multicast address that is not assigned based on the network prefix. This indicates a multicast address as defined in [ADDRARCH]. o P = 1 indicates a multicast address that is assigned based on the network prefix. o If P = 1, T MUST be set to 1, otherwise the setting of the T bit is defined in Section 2.7 of [ADDRARCH]. The reserved field MUST be zero. NEW: Boucadair & Venaas Expires September 13, 2014 [Page 4] Internet-Draft Multicast Flag bits March 2014 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | +--------+----+----+----+----+--------+----------------+----------+ |11111111|ff1 |scop|ff2 |rsvd| plen | network prefix | group ID | +--------+----+----+----+----+--------+----------------+----------+ +-+-+-+-+ ff1 (flag field 1) is a set of 4 flags: |X|Y|P|T| +-+-+-+-+ X and Y may each be set to 0 or 1. o P = 0 indicates a multicast address that is not assigned based on the network prefix. This indicates a multicast address as defined in [RFC4291]. o P = 1 indicates a multicast address that is assigned based on the network prefix. o If P = 1, T MUST be set to 1, otherwise the setting of the T bit is defined in Section 2.7 of [RFC4291]. +-+-+-+-+ ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| +-+-+-+-+ where "rrrr" are for future assignment as additional flag bits. Flag bits denote both ff1 and ff2. This document changes Section 6 of [RFC3306] as follows: OLD: These settings create an SSM range of FF3x::/32 (where 'x' is any valid scope value). The source address field in the IPv6 header identifies the owner of the multicast address. NEW: If the flag bits in ff1 are set to 0011, these settings create an SSM range of ff3x::/32 (where 'x' is any valid scope value). The source address field in the IPv6 header identifies the owner of the multicast address. ff3x::/32 is not the only allowed SSM prefix range. For example if the most significant flag bit in ff1 is set, then we would get the SSM range ffbx::/32. Boucadair & Venaas Expires September 13, 2014 [Page 5] Internet-Draft Multicast Flag bits March 2014 4.2. RFC 3956 This document changes Section 2 of [RFC3956] as follows: OLD: As described in [RFC3306], the multicast address format is as follows: | 8 | 4 | 4 | 8 | 8 | 64 | 32 | +--------+----+----+--------+----+----------------+----------+ |11111111|flgs|scop|reserved|plen| network prefix | group ID | +--------+----+----+--------+----+----------------+----------+ Where flgs are "0011". (The first two bits are as yet undefined, sent as zero and ignored on receipt.) NEW: The multicast address format is as follows: | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | +--------+----+----+----+----+----+----------------+----------+ |11111111|ff1 |scop|ff2 |rsvd|plen| network prefix | group ID | +--------+----+----+----+----+----+----------------+----------+ +-+-+-+-+ ff1 (flag field 1) is a set of four flags: |X|R|P|T| +-+-+-+-+ X may be set to 0 or 1. +-+-+-+-+ ff2 (flag field 2) is a set of 4 flags: |r|r|r|r| +-+-+-+-+ where "rrrr" are for future assignment as additional flag bits. Flag bits denote both ff1 and ff2. This document changes Section 3 of [RFC3956] as follows: OLD: Boucadair & Venaas Expires September 13, 2014 [Page 6] Internet-Draft Multicast Flag bits March 2014 | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | +--------+----+----+----+----+----+----------------+----------+ |11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID | +--------+----+----+----+----+----+----------------+----------+ +-+-+-+-+ flgs is a set of four flags: |0|R|P|T| +-+-+-+-+ When the highest-order bit is 0, R = 1 indicates a multicast address that embeds the address on the RP. Then P MUST be set to 1, and consequently T MUST be set to 1, as specified in [RFC3306]. In effect, this implies the prefix FF70::/12. In this case, the last 4 bits of the previously reserved field are interpreted as embedding the RP interface ID, as specified in this memo. The behavior is unspecified if P or T is not set to 1, as then the prefix would not be FF70::/12. Likewise, the encoding and the protocol mode used when the two high-order bits in "flgs" are set to 11 ("FFF0::/12") is intentionally unspecified until such time that the highest-order bit is defined. Without further IETF specification, implementations SHOULD NOT treat the FFF0::/12 range as Embedded-RP. NEW: | 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 | +--------+----+----+----+----+----+----------------+----------+ |11111111|ff1 |scop|ff2 |RIID|plen| network prefix | group ID | +--------+----+----+----+----+----+----------------+----------+ +-+-+-+-+ ff1 is a set of four flags: |X|R|P|T| +-+-+-+-+ X may be set to 0 or 1. R = 1 indicates a multicast address that embeds the address of the RP. P MUST be set to 1, and consequently T MUST be set to 1, according to [RFC3306], as this is a special case of unicast-prefix based addresses. This implies that for instance prefixes ff70::/12 and fff0::/12 are embedded RP prefixes. The behavior is unspecified if P or T is not set to 1. When the R-bit is set, the last 4 bits of the field that were reserved in [RFC3306] are interpreted as embedding the RP interface ID, as specified in this memo. This document changes Section 4 of [RFC3956] as follows: OLD: Boucadair & Venaas Expires September 13, 2014 [Page 7] Internet-Draft Multicast Flag bits March 2014 It MUST be a multicast address with "flgs" set to 0111, that is, to be of the prefix FF70::/12, NEW: It MUST be a multicast address with R-bit set to 1. It MUST have P-bit and T-bit both set to 1 when using the embedding in this document as it is a prefix-based address. This document changes Section 7.1 of [RFC3956] as follows: OLD: To avoid loops and inconsistencies, for addresses in the range FF70::/12, the Embedded-RP mapping MUST be considered the longest possible match and higher priority than any other mechanism. NEW: To avoid loops and inconsistencies, for addresses with R-bit set to 1, the Embedded-RP mapping MUST be considered the longest possible match and higher priority than any other mechanism. 5. IANA Considerations This document does not require any action from IANA. 6. Security Considerations Security considerations discussed in [RFC3956], [RFC3306] and [RFC4291] MUST be taken into account. 7. Acknowledgements Special thanks to B. Haberman for the discussions prior to the publication of this document. Many thanks to J. Korhonen and T. Jinmei their comments. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 Multicast Addresses", RFC 3306, August 2002. Boucadair & Venaas Expires September 13, 2014 [Page 8] Internet-Draft Multicast Flag bits March 2014 [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address", RFC 3956, November 2004. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6 Address Text Representation", RFC 5952, August 2010. Authors' Addresses Mohamed Boucadair France Telecom Rennes 35000 France Email: mohamed.boucadair@orange.com Stig Venaas Cisco USA Email: stig@cisco.com Boucadair & Venaas Expires September 13, 2014 [Page 9]