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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Krishnan 3 Internet-Draft Ericsson 4 Intended status: Standards Track July 14, 2008 5 Expires: January 15, 2009 7 Reserved IPv6 Interface Identifiers 8 draft-ietf-6man-reserved-iids-01 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 January 15, 2009. 35 Abstract 37 Interface Identifiers in IPv6 unicast addresses are used to identify 38 interfaces on a link. They are required to be unique within a 39 subnet. Several RFCs have specified interface identifiers or 40 identifier ranges that have a special meaning attached to them. An 41 IPv6 node autoconfiguring an interface identifier in these ranges 42 will encounter unexpected consequences. Since there is no 43 centralized repository for such reserved identifiers, this document 44 aims to create one. 46 Table of Contents 48 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 49 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 50 3. Issues with reusing reserved Interface Identifiers . . . . . . 5 51 3.1. Possible solutions . . . . . . . . . . . . . . . . . . . . 5 52 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 53 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 54 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 55 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 56 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 57 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 58 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 59 Intellectual Property and Copyright Statements . . . . . . . . . . 11 61 1. Requirements notation 63 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 64 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 65 document are to be interpreted as described in [RFC2119]. 67 2. Introduction 69 An IPv6 unicast address is composed of two parts : A subnet prefix 70 and an interface identifier (IID) that identifies an unique interface 71 within the subnet prefix. The structure of an IPv6 unicast address 72 is depicted in the IPv6 Addressing Architecture [RFC4291] and is 73 replicated here for clarity. 75 | n bits | 128-n bits | 76 +------------------------------------------------+----------------+ 77 | subnet prefix | interface ID | 78 +------------------------------------------------+----------------+ 80 Figure 1: IPv6 Unicast Address Format 82 For all unicast addresses, except those that start with binary value 83 000, interface identifiers are required to be 64 bits long (i.e. 84 n==64) . If the interface identifiers are generated from an unique 85 token like an ethernet MAC address, they need to set bit 6 of the 86 first octet to one. If they are not generated from an unique token 87 they need to set bit 6 to zero. Examples of mechanisms that generate 88 interface identifiers without an unique token include 89 Cryptographically Generated Addresses [RFC3972], Privacy Addresses 90 [RFC4941], Hash Based Addresses [HBA] etc. Non-unique interface 91 identifiers can also be allocated using managed address assignment 92 mechanisms like DHCPv6 [RFC3315]. 94 3. Issues with reusing reserved Interface Identifiers 96 Let us assume a node comes up with an interface identifier that has 97 been reserved for use in some other capacity. e.g. An IPv6 node that 98 uses temporary IPv6 addresses [RFC4941] comes up with an IID of fdff: 99 ffff:ffff:fff . This node will receive requests from all nodes that 100 are requesting a service from a MobileIPv6 home agent since the above 101 mentioned interface identifier has been reserved in [RFC2526] to 102 serve as a MIPv6 home agents anycast address. At best this is an 103 annoyance to the node that came up with this address. In the worst 104 case scenario another node on the link would be denied service and 105 may not look for other methods of acquiring a home agent. Thus, such 106 reserved interface identifiers MUST NOT be used for autonomous auto- 107 configuration or for managed address configuration. 109 3.1. Possible solutions 111 There are two possible ways to go about avoiding usage of these 112 reserved interface identifiers. One of them would be to add 113 normative reference to each specification that reserves an interface 114 identifier. The other one would be to create an IANA registry for 115 such interface identifiers. There are two disadvantages to the 116 normative reference approach. Firstly, this approach does not scale 117 well. This is because the number of such specifications can need to 118 be updated is large. Secondly, the maturity level of the document 119 reserving the IID might be lower than the one prohibited from using 120 it. This will cause a downward reference problem. Therefore the 121 better solution is to create an IANA registry for this purpose. e.g. 122 Reserving certain identifiers may be useful in certain protocols such 123 as PMIP in order to avoid duplicate address detection on point to 124 point links, but PMIP will be at a lower standardization level than 125 the address sutoconfiguration standards and hence not referable from 126 them. 128 4. IANA Considerations 130 This document requests the creation of an IANA registry for reserved 131 IPv6 Interface Identifiers. Initial values for the reserved IPv6 132 Interface Identifiers are given below. 134 +-----------------------------------------+-------------------------+ 135 | Interface Identifier Range | Description | 136 +-----------------------------------------+-------------------------+ 137 | 0000:0000:0000:0000-0000:0000:0000:0000 | Subnet-Router Anycast | 138 | | [RFC4291] | 139 | | | 140 | fdff:ffff:ffff:ff80-fdff:ffff:ffff:fffd | Reserved Subnet Anycast | 141 | | [RFC2526] | 142 | | | 143 | fdff:ffff:ffff:fffe-fdff:ffff:ffff:fffe | MobileIPv6 Home Agents | 144 | | Anycast [RFC2526] | 145 | | | 146 | fdff:ffff:ffff:ffff-fdff:ffff:ffff:ffff | Reserved Subnet Anycast | 147 | | [RFC2526] | 148 +-----------------------------------------+-------------------------+ 150 Table 1: Current Assignments 152 It is possible that implementations might predate a specific 153 assignment from this registry and hence not be cognizant of the 154 reserved nature of the interface identifier. Hence. future 155 assignments from this registry are discouraged but in exceptional 156 circumstances are to be made through Standards Action [RFC5226]. 157 Assignments consist of a single interface identifier or a range of 158 interface identifiers. 160 NOTE: Please note that the address ::/128 (all zeros in the interface 161 identifier field) is used as an unspecified address and ::/0 (again 162 all zeros in the interface identifier field) is used as a default 163 route indicator as specified in [RFC5156]. These do not necessarily 164 conflict with the reserved interface identifiers defined here, since 165 the reserved identifiers defined in this document are used for 166 avoiding conflicts with stateless address autoconfiguration that uses 167 a 64 bit prefix length. 169 5. Acknowledgements 171 The author would like to thank Alain Durand, Alex Petrescu, Bernie 172 Volz, Bob Hinden, Christian Huitema, Fred Templin, Jordi Palet 173 Martinez, Pekka Savola, Remi Denis-Courmount, Tim Enos, Alex 174 Petrescu, Ed Jankiewicz and Brian Carpenter for reviewing this 175 document and suggesting changes. 177 6. Security Considerations 179 Information that creates or updates a registration needs to be 180 authenticated and authorized. By utilizing one of the reserved 181 interface identifiers an IPv6 node might receive requests that it is 182 not authorized to receive. 184 7. References 186 7.1. Normative References 188 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 189 Requirement Levels", BCP 14, RFC 2119, March 1997. 191 [RFC2526] Johnson, D. and S. Deering, "Reserved IPv6 Subnet Anycast 192 Addresses", RFC 2526, March 1999. 194 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 195 Architecture", RFC 4291, February 2006. 197 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 198 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 199 May 2008. 201 7.2. Informative References 203 [HBA] Bagnulo, M., "Hash Based Addresses (HBA)", 204 draft-ietf-shim6-hba-02 (work in progress), October 2006. 206 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 207 and M. Carney, "Dynamic Host Configuration Protocol for 208 IPv6 (DHCPv6)", RFC 3315, July 2003. 210 [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", 211 RFC 3972, March 2005. 213 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 214 Extensions for Stateless Address Autoconfiguration in 215 IPv6", RFC 4941, September 2007. 217 [RFC5156] Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156, 218 April 2008. 220 Author's Address 222 Suresh Krishnan 223 Ericsson 224 8400 Decarie Blvd. 225 Town of Mount Royal, QC 226 Canada 228 Phone: +1 514 345 7900 x42871 229 Email: suresh.krishnan@ericsson.com 231 Full Copyright Statement 233 Copyright (C) The IETF Trust (2008). 235 This document is subject to the rights, licenses and restrictions 236 contained in BCP 78, and except as set forth therein, the authors 237 retain all their rights. 239 This document and the information contained herein are provided on an 240 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 241 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 242 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 243 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 244 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 245 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 247 Intellectual Property 249 The IETF takes no position regarding the validity or scope of any 250 Intellectual Property Rights or other rights that might be claimed to 251 pertain to the implementation or use of the technology described in 252 this document or the extent to which any license under such rights 253 might or might not be available; nor does it represent that it has 254 made any independent effort to identify any such rights. 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