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Krishnan 3 Internet-Draft Ericsson 4 Intended status: Standards Track November 6, 2007 5 Expires: May 9, 2008 7 Reserved IPv6 Interface Identifiers 8 draft-krishnan-ipv6-reserved-iids-02 10 Status of this Memo 12 By submitting this Internet-Draft, each author represents that any 13 applicable patent or other IPR claims of which he or she is aware 14 have been or will be disclosed, and any of which he or she becomes 15 aware will be disclosed, in accordance with Section 6 of BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on May 9, 2008. 35 Copyright Notice 37 Copyright (C) The IETF Trust (2007). 39 Abstract 41 Interface Identifiers in IPv6 unicast addresses are used to identify 42 interfaces on a link. They are required to be unique within a 43 subnet. Several RFCs have specified interface identifiers or 44 identifier ranges that have a special meaning attached to them. An 45 IPv6 node autoconfiguring an interface identifier in these ranges 46 will encounter unexpected consequences. Since there is no 47 centralized repository for such reserved identifiers, this document 48 aims to create one. 50 Table of Contents 52 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 53 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 54 3. Issues with reusing reserved Interface Identifiers . . . . . . 5 55 3.1. Possible solutions . . . . . . . . . . . . . . . . . . . . 5 56 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 57 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 58 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 59 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 60 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 61 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 62 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 63 Intellectual Property and Copyright Statements . . . . . . . . . . 11 65 1. Requirements notation 67 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 68 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 69 document are to be interpreted as described in [RFC2119]. 71 2. Introduction 73 An IPv6 unicast address is composed of two parts. A subnet prefix 74 and an interface identifier (IID) that identifies an unique interface 75 within the subnet prefix. The structure of an IPv6 unicast address 76 is depicted in the IPv6 Addressing Architecture [RFC4291] and is 77 replicated here for clarity. 79 | n bits | 128-n bits | 80 +------------------------------------------------+----------------+ 81 | subnet prefix | interface ID | 82 +------------------------------------------------+----------------+ 84 Figure 1: IPv6 Unicast Address Format 86 For all unicast addresses, except those that start with binary value 87 000, Interface identifiers are required to be 64 bits long (i.e. 88 n==64) . If the interface identifiers are generated from an unique 89 token like an ethernet MAC address, they need to set bit 6 of the 90 first octet to one. If they are not generated from an unique token 91 they need to set bit 6 to zero. Examples of mechanisms that generate 92 interface identifiers without an unique token include 93 Cryptographically Generated Addresses [RFC3972], Privacy Addresses 94 [PRIVACY], Hash Based Addresses [HBA] etc. Non-unique interface 95 identifiers can also be allocated using managed address assignment 96 mechanisms like DHCPv6 [RFC3315]. 98 3. Issues with reusing reserved Interface Identifiers 100 Let us assume a node comes up with an interface identifier that has 101 been reserved for use in some other capacity. e.g. An IPv6 node that 102 uses temporary IPv6 addresses [PRIVACY] comes up with an IID of fdff: 103 ffff:ffff:fffe . This node will receive requests from all nodes that 104 are requesting a service from a MobileIPv6 home agent. At best this 105 is an annoyance to the node that came up with this address. In the 106 worst case scenario another node on the link would be denied service 107 and may not look for other methods of acquiring a home agent. Thus, 108 such reserved interface identifiers MUST NOT be used for autonomous 109 auto-configuration or for managed address configuration. 111 3.1. Possible solutions 113 There are two possible ways to go about avoiding usage of these 114 reserved interface identifiers. One of them would be to add 115 normative reference to each specification that reserves an interface 116 identifier. The other one would be to create an IANA registry for 117 such interface identifiers. There are two disadvantages to the 118 normative reference approach. Firstly, this approach does not scale 119 well. This is because the number of such specifications can need to 120 be updated is large. Secondly, the maturity level of the document 121 reserving the IID might be lower than the one prohibited from using 122 it. This will cause a downward reference problem. Therefore the 123 better solution is to create an IANA registry for this purpose. e.g. 124 Reserving certain identifiers may be useful in certain protocols such 125 as PMIP in order to avoid duplicate address detection on point to 126 point links, but PMIP will be at a lower standardization level than 127 the address sutoconfiguration standards and hence not referable from 128 them. 130 4. IANA Considerations 132 This document requests the creation of an IANA registry for reserved 133 IPv6 Interface Identifiers. Initial values for the reserved IPv6 134 Interface Identifiers are given below. 136 +-----------------------------------------+-------------------------+ 137 | Interface Identifier Range | Description | 138 +-----------------------------------------+-------------------------+ 139 | 0000:0000:0000:0000-0000:0000:0000:0000 | Subnet Router Anycast | 140 | | [RFC4291] | 141 | | | 142 | fdff:ffff:ffff:ff80-fdff:ffff:ffff:fffd | Reserved Subnet Anycast | 143 | | [RFC2526] | 144 | | | 145 | fdff:ffff:ffff:fffe-fdff:ffff:ffff:fffe | MobileIPv6 Home Agents | 146 | | Anycast [RFC2526] | 147 | | | 148 | fdff:ffff:ffff:ffff-fdff:ffff:ffff:ffff | Reserved Subnet Anycast | 149 | | [RFC2526] | 150 +-----------------------------------------+-------------------------+ 152 Table 1: Current Assignments 154 It is possible that implementations might predate a specific 155 assignment from this registry and hence not be cognizant of the 156 reserved nature of the interface identifier. Hence. future 157 assignments from this registry are discouraged but in exceptional 158 circumstances are to be made through Standards Action [IANABIS]. 159 Assignments consist of a single interface identifier or a range of 160 interface identifiers. 162 5. Acknowledgements 164 The author would like to thank Alain Durand, Alex Petrescu, Bernie 165 Volz, Bob Hinden, Christian Huitema, Fred Templin, Jordi Palet 166 Martinez, Pekka Savola, Remi Denis-Courmount and Tim Enos for 167 reviewing this document and suggesting changes. 169 6. Security Considerations 171 Information that creates or updates a registration needs to be 172 authenticated and authorized. By utilizing one of the reserved 173 interface identifiers an IPv6 node might receive requests that it is 174 not authorized to receive. 176 7. References 178 7.1. Normative References 180 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 181 Requirement Levels", BCP 14, RFC 2119, March 1997. 183 [RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast 184 Addresses", RFC 2526, March 1999. 186 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 187 Architecture", RFC 4291, February 2006. 189 7.2. Informative References 191 [HBA] Bagnulo, M., "Hash Based Addresses (HBA)", 192 draft-ietf-shim6-hba-02 (work in progress), October 2006. 194 [IANABIS] Narten, T. and H. Alvestrand, "Guidelines for Writing an 195 IANA Considerations Section in RFCs", 196 draft-narten-iana-considerations-rfc2434bis-05 (work in 197 progress), September 2006. 199 [PRIVACY] Narten, T., Draves, R., and S. Krishnan, "Privacy 200 Extensions for Stateless Address Autoconfiguration in 201 IPv6", draft-ietf-ipv6-privacy-addrs-v2-05 (work in 202 progress), October 2006. 204 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 205 and M. Carney, "Dynamic Host Configuration Protocol for 206 IPv6 (DHCPv6)", RFC 3315, July 2003. 208 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 209 RFC 3972, March 2005. 211 Author's Address 213 Suresh Krishnan 214 Ericsson 215 8400 Decarie Blvd. 216 Town of Mount Royal, QC 217 Canada 219 Phone: +1 514 345 7900 x42871 220 Email: suresh.krishnan@ericsson.com 222 Full Copyright Statement 224 Copyright (C) The IETF Trust (2007). 226 This document is subject to the rights, licenses and restrictions 227 contained in BCP 78, and except as set forth therein, the authors 228 retain all their rights. 230 This document and the information contained herein are provided on an 231 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 232 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 233 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 234 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 235 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 236 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 238 Intellectual Property 240 The IETF takes no position regarding the validity or scope of any 241 Intellectual Property Rights or other rights that might be claimed to 242 pertain to the implementation or use of the technology described in 243 this document or the extent to which any license under such rights 244 might or might not be available; nor does it represent that it has 245 made any independent effort to identify any such rights. 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