Network Working Group R. Pashby Internet Draft Bowhead Support Document: draft-pashby-ipv6-mc-scoped-addr-00.txt July 2005 Expires: January 2006 Multicast Scoped Address Assignment Guidance draft-pashby-ipv6-mc-scoped-addr-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 2006. Abstract The purpose of this document is to define IPv6 Multicast Id ranges that will not allow overlap between dynamically assigned global scoped addresses and dynamically assigned non-global scoped addresses, specifically dynamically assigned link-local scoped addresses. [RFC3307] defines IPv6 Multicast Group ID ranges for the following Permanent Addresses, Permanent Identifiers and Dynamic Addresses. However, there are certain multicast addresses that need to be assigned for closed systems that should not collide with the Group IDs used within the Internet. This document further defines the Dynamic Addresses into two ranges Dynamically Assigned Global (DAG) addresses and Dynamically Assigned Non-Global (DANG) addresses. The DANG range is further broken down to Dynamically Assigned Link-Local (DALL) addresses and the rest reserved for future. Future uses might be for Site-Local Scoped and Organization Scoped ranges. The DALL range may be used to simplify the design of MLD Snooping layer 2 switches. [RFC3171] defines the Local Network Control Block address range for IPv4. A similar range should be defined to possibly simplify the design of MLD Snooping layer 2 switches. Table of Contents: 1. Introduction 2. Applicability 3. Multicast Group ID Assignment Guidelines 4. Modifications to RFC3307 5. Security Considerations 6. IANA Considerations 7. Acknowledgments 8. References 9. Author's Information 1. Introduction The purpose of this document is to define IPv6 Multicast Id ranges that will not allow overlap between dynamically assigned global scoped addresses and dynamically assigned non-global scoped addresses, specifically dynamically assigned link-local scoped addresses. [RFC3307] defines IPv6 Multicast Group ID ranges for the following Permanent Addresses, Permanent Identifiers and Dynamic Addresses. However, there are certain multicast addresses that need to be assigned for closed systems that should not collide with the Group IDs used within the Internet. This document further defines the Dynamic Addresses into two ranges Dynamically Assigned Global (DAG) addresses and Dynamically Assigned Non-Global (DANG) addresses. The DANG range is further broken down to Dynamically Assigned Link-Local (DALL) addresses and the rest reserved for future. Future uses might be for Site-Local Scoped and Organization Scoped ranges. The DALL range may be used to simplify the design of MLD Snooping layer 2 switches. It is understood that there is the Scope field in the IPv6 address, however the issue here is keeping unique ranges that are guaranteed not to overlap at the link-layer. Link-layer uniqueness is critical within organizations because most of the multicast will be controlled via layer 2 switches. Given the definitions in [RFC3307] the new ranges should be assigned from the currently defined Dynamically Assigned Addresses, since they are not Permanently Assigned Addresses (from the Internet perspective). - Dynamically Assigned Global (DAG) Addresses - Dynamically Assigned Non-Global (DANG) Addresses - Reserved Dynamically Assigned Non-Global Addresses - Dynamically Assigned Link-Local (DALL) Addresses The Solicited Node Multicast Addresses will fall into the last range. [RFC3171] also defines the Local Network Control Block (LNCB) address range for IPv4. A similar range should be defined to possibly simplify the design of MLD Snooping layer 2 switches, as defined by [mldsnoop]. This [mldsnoop] document also recommends that the DANG and LNCB addresses be forwarded to all layer 2 ports on a MLD snooping switch. 2. Applicability These guidelines are to be used in any environment in which IPv6 multicast addresses are delegated, assigned, or selected. They are critical to be used where overlap of multiple multicast flows can happen on layer 2 switches. 3. Multicast Group ID Assignment Guidelines 3.1 Permanent Assigned Addresses The range specified for Permanent Assigned Addresses is 0x00000001 û 0x3FFFFFFF. This is the same as defined in RFC3307. 3.1.1 Local Network Control Block The range specified for Local Network Control Block is 0x00000001 û 0x000000FF. There is a related document [snoop] that recommends that this range be sent to every interface on a layer 2 switches that supports MLD snooping [mldsnoop]. 3.2 Permanent Assigned IDs The range specified for Permanent Assigned Identifiers is 0x40000000 û 0x7FFFFFFF. This is the same as defined in RFC3307. 3.3 Dynamically Assigned Addresses This range was previously defined in RFC3307 but called Dynamic IPv6 Multicast Addresses. It is broken down into the following ranges. 3.3.1 Dynamically Assigned Global Scoped Addresses This range would be used for Scope field values 9 û E. The range specified for Dynamically Assigned Global Scoped Addresses 0x80000000 û 0xBFFFFFFF. This range was selected to provide the largest range of addresses for dynamic allocation. 3.3.2 Dynamically Assigned Non-Global Addresses This range would be used for Scope field values 1-8. The range specified for Dynamically Assigned Non-Global Scoped Addresses 0xC0000000 û 0xFFFFFFFF. 3.3.2.1 Reserved Dynamically Assigned Non-Global Addresses This range is reserved for future use. Possible future use would be for Site-Local Scoped and Organization Scoped addresses. The range is 0xC0000000 û 0xEFFFFFFF. 3.3.2.2 Dynamically Assigned Link-Local Addresses The range for Dynamically Assigned Link-Local Scoped Addresses is 0xF0000000 û 0xF0FFFFFF. This range was chosen so that it would include the Solicited Node Multicast Addresses 0xFF000000 û 0xFFFFFFFF. There is a related document [snoop] that recommends that this range be sent to every interface on a layer 2 switches that supports MLD snooping [mldsnoop]. 4. Modifications to RFC3307 4.1 Permanent IPv6 Multicast Addresses (section 4.1) Add the definitions of the LCNB ranges as defined above. 4.2 Dynamic IPv6 Multicast Addresses (section 4.3) Add the definitions of the DAG and DANG ranges as defined above. 4.3 Server Allocation (section 4.3.1) Change the range from 0x80000000 û 0xFFFFFFFF to 0x80000000 û 0xBFFFFFFF. 4.4 Host Allocation Section (section 4.3.2) Replace the last sentence with: This can be accomplished by setting the high-order two bits of the generated number to 10 (binary). 5. Security Considerations The allocation mechanisms described in this document do not alter the security properties of either the Any Source or Source Specific multicast service models of IPv4 and IPv6. The potential to allocate large blocks of addresses can lead to Denial-of-Service attacks. A more in-depth discussion of the security issues surrounding dynamic allocation of multicast addresses can be found in [RFC 2908]. 6. IANA Considerations This document defines the new LNCB range that IANA needs to assure that addresses assigned in this range are for Link-local Network Control. 7. Acknowledgments Brian Haberman, John Hopkins University Karen O'Donoghue, US Department of Navy 8. References [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast Addresses", RFC3307, August 2002 [RFC3171] Albanna, Z., Almeroth, K., Meyer, D., Schipper, M., "IANA Guidelines for IPv4 Multicast Address Assignments", RFC3171, August 2001 [mldsnoop] Pashby, R., "Simplifying IPv6 MLD Snooping Switches", draft-pashby-maga-simplify-mld-snooping-00, July 2005 9. Author's Information Ronald Pashby Bowhead Support Services Ronald.Pashby.ctr@navy.mil (540) 653-6070 Copyright (C) The Internet Society (2005) This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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