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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Dynamic Host Configuration (DHC) J. Korhonen, Ed. 3 Internet-Draft Nokia Siemens Networks 4 Updates: 3633 (if approved) T. Savolainen 5 Intended status: Standards Track Nokia 6 Expires: February 6, 2012 S. Krishnan 7 Ericsson 8 O. Troan 9 Cisco Systems, Inc 10 August 5, 2011 12 Prefix Exclude Option for DHCPv6-based Prefix Delegation 13 draft-ietf-dhc-pd-exclude-03.txt 15 Abstract 17 This specification defines an optional mechanism to allow exclusion 18 of one specific prefix from a delegated prefix set when using DHCPv6- 19 based prefix delegation. The new mechanism updates RFC 3633. 21 Status of this Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on February 6, 2012. 38 Copyright Notice 40 Copyright (c) 2011 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2. Requirements and Terminology . . . . . . . . . . . . . . . . . 3 57 3. Problem Background . . . . . . . . . . . . . . . . . . . . . . 3 58 4. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 4.1. Prefix Delegation with Excluded Prefixes . . . . . . . . . 4 60 4.2. Prefix Exclude Option . . . . . . . . . . . . . . . . . . . 4 61 5. Delegating Router Solicitation . . . . . . . . . . . . . . . . 6 62 5.1. Requesting Router . . . . . . . . . . . . . . . . . . . . . 6 63 5.2. Delegating Router . . . . . . . . . . . . . . . . . . . . . 7 64 6. Requesting Router Initiated Prefix Delegation . . . . . . . . . 7 65 6.1. Requesting Router . . . . . . . . . . . . . . . . . . . . . 7 66 6.2. Delegating Router . . . . . . . . . . . . . . . . . . . . . 8 67 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 68 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 69 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 70 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 71 10.1. Normative References . . . . . . . . . . . . . . . . . . . 9 72 10.2. Informative References . . . . . . . . . . . . . . . . . . 9 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 75 1. Introduction 77 This specification defines an optional mechanism and the related 78 DHCPv6 option to allow exclusion of one specific prefix from a 79 delegated prefix set when using DHCPv6-based prefix delegation. 81 The prefix exclusion mechanism is targeted to deployments where 82 DHCPv6-based prefix delegation is used but a single aggregatable 83 route/prefix has to represent one customer, instead of using one 84 prefix for the link between the delegating router and the requesting 85 router and another prefix for the customer network. The mechanism 86 defined in this specification allows a delegating router to use a 87 prefix out of the delegated prefix set on the link through which it 88 exchanges DHCPv6 messages with the requesting router. 90 2. Requirements and Terminology 92 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 93 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 94 document are to be interpreted as described in [RFC2119]. 96 3. Problem Background 98 DHCPv6 Prefix Delegation (DHCPv6-PD) [RFC3633] has an explicit 99 limitation described in Section 12.1 of [RFC3633] that a prefix 100 delegated to a requesting router cannot be used by the delegating 101 router. This restriction implies that the delegating router will 102 have two (non aggregatable) routes towards a customer, one for the 103 link between the requesting router and the delegating router, and one 104 for the customer site behind the requesting router. 106 There are architectures and link models, where a host (e.g. a mobile 107 router, also acting as a requesting router) always has a single (/64) 108 prefix configured on its uplink interface and the delegating router 109 is also requesting router's first hop router. Furthermore, it may be 110 required that the prefix configured on the uplink interface has to be 111 aggregatable with the delegated prefixes. This introduces a problem 112 in how to use DHCPv6-PD together with stateless [RFC4862] or stateful 113 [RFC3315] address autoconfiguration on a link, where the /64 114 advertised on the link is also part of the prefix delegated (e.g /56) 115 to the requesting router. 117 4. Solution 118 4.1. Prefix Delegation with Excluded Prefixes 120 This specification defines a new DHCPv6 option, OPTION_PD_EXCLUDE 121 (TBD1), that is used to exclude exactly one prefix from a delegated 122 prefix. The OPTION_PD_EXCLUDE is included in the OPTION_IAPREFIX 123 IAprefix-options field. There can be at most one OPTION_PD_EXCLUDE 124 option in one OPTION_IAPREFIX option. The OPTION_PD_EXCLUDE option 125 allows prefix delegation where a requesting router is delegated a 126 prefix (e.g. /56) and the delegating router uses one prefix (e.g. 127 /64) on the link through which it exchanges DHCPv6 messages with the 128 requesting router with a prefix out of the same delegated prefix set. 130 A requesting router includes an OPTION_ORO option with the 131 OPTION_PD_EXCLUDE option code in a Solicit, Request, Renew, Rebind or 132 Confirm message to inform the delegating router about the support for 133 the prefix delegation functionality defined in this specification. A 134 delegating router may include the OPTION_PD_EXCLUDE option code in an 135 OPTION_ORO option in a Reconfigure message for indicating that the 136 requesting router should request OPTION_PD_EXCLUDE from the 137 delegating router. 139 The delegating router includes the prefix in the OPTION_PD_EXCLUDE 140 option that is excluded from the delegated prefix set. The 141 requesting router MUST NOT assign the excluded prefix to any of its 142 downstream interfaces. 144 4.2. Prefix Exclude Option 146 0 1 2 3 147 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 1 148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 149 | OPTION_PD_EXCLUDE | option-len | 150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 151 | prefix-len | IPv6 subnet ID (1 to 16 octets) ~ 152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 Prefix Exclude Option 156 o option-code: OPTION_PD_EXCLUDE (TBD1). 158 o option-len: 1 + length of IPv6 subnet ID in octets. A valid 159 option-len is between 2 and 17. 161 o prefix-len: The length of the excluded prefix in bits. The 162 prefix-len MUST be between 'OPTION_IAPREFIX prefix-length'+1 and 163 128. 165 o IPv6 subnet ID: A variable length IPv6 subnet ID up to 128 bits. 167 The IPv6 subnet ID contains prefix-len minus 'OPTION_IAPREFIX prefix- 168 length' bits extracted from the excluded prefix starting from the bit 169 position 'OPTION_IAPREFIX prefix-length'. The extracted subnet ID 170 MUST be left shifted to start from a full octet boundary, i.e. left 171 shift of 'OPTION_IAPREFIX prefix-length' mod 8 bits. The subnet ID 172 MUST be zero padded to the next full octet boundary. 174 The encoding of the IPv6 subnet ID can be expressed in a C-like 175 pseudo code as shown below: 177 uint128_t p1; // the delegated IPv6 prefix 178 uint128_t p2; // the excluded IPv6 prefix 179 uint16_t a; // the OPTION_IAPREFIX prefix-length 180 uint8_t b; // the excluded IPv6 prefix length 181 uint8_t s; 183 // sanity checks 185 s = 128-a; // size of non-prefix bits 186 assert(b>a); // b must be at least a+1 187 assert(p1>>s == p2>>s); // p1 and p2 must share a common 188 // prefix of 'a' bits 190 // calculate the option content 192 uint16_t c = b-a-1; // the IPv6_subnet_ID_length-1 in bits 193 uint16_t d = (c/8)+1; // the IPv6_subnet_ID_length in octets 194 uint128_t p = p2< 0) { 206 *id++ = p>>120; 207 p <<= 8; 208 } 210 The OPTION_PD_EXCLUDE option MUST only be included in the 211 OPTION_IAPREFIX IAprefix-options [RFC3633] field. 213 Any prefix excluded from the delegated prefix MUST be contained in 214 OPTION_PD_EXCLUDE options within the corresponding OPTION_IAPREFIX. 216 The prefix included in the OPTION_PD_EXCLUDE option share the same 217 preferred-lifetime and valid-lifetime as the delegated prefix in the 218 encapsulating OPTION_IAPREFIX option. 220 The prefix in the OPTION_PD_EXCLUDE option MUST be part of the 221 delegated prefix in the OPTION_IAPREFIX. For example, the requesting 222 router has earlier been assigned a 2001:db8:dead:beef::/64 prefix by 223 the delegating router, and the delegated prefix in the 224 OPTION_IAPREFIX is 2001:db8:dead:bee0::/59. In this case, 2001:db8: 225 dead:beef::/64 is a valid prefix to be used in the OPTION_PD_EXCLUDE 226 option. The OPTION_PD_EXCLUDE option would be encoded as follows: 228 0 1 2 3 229 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 1 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 231 | OPTION_PD_EXCLUDE | 2 | 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 | 64 |0|1|1|1|1|0|0|0| 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 235 ^ ^ 236 | | 237 | +- 3 zero padded bits follow 238 | 239 +- using C syntax: 0xef << (59 % 8) 240 Note: 59 mod 8 = 3 242 5. Delegating Router Solicitation 244 The requesting router locates and selects a delegating router in the 245 same way as described in Section 11 [RFC3633]. This specification 246 only describes the additional steps required by the use of 247 OPTION_PD_EXCLUDE option. 249 5.1. Requesting Router 251 If the requesting router implements the solution described in 252 Section 4.1 then the requesting router SHOULD include the 253 OPTION_PD_EXCLUDE option code in the OPTION_ORO option in Solicit 254 messages. 256 Once receiving Advertise message, the requesting router MAY use the 257 prefix(es) received in OPTION_PD_EXCLUDE in addition to the 258 advertised prefixes to choose the delegating router. If Advertise 259 message did not include OPTION_PD_EXCLUDE option, then the requesting 260 router MUST fall back to normal [RFC3633] Section 11.1 behavior. 262 5.2. Delegating Router 264 If the OPTION_ORO option in the Solicit message includes the 265 OPTION_PD_EXCLUDE option code, then the delegating router knows that 266 the requesting router supports the solution defined in this 267 specification. If the Solicit message also contains an IA_PD option, 268 the delegating router can delegate to the requesting router a prefix 269 which includes the prefix already assigned to the requesting router's 270 uplink interface. The delegating router includes the prefix 271 originally or to be assigned to the requesting router in the 272 OPTION_PD_EXCLUDE option within the OPTION_IAPREFIX IAprefix-option 273 in the Advertise message. 275 If the OPTION_ORO option in the Solicit message does not include the 276 OPTION_PD_EXCLUDE option code, then the delegating router MUST fall 277 back to normal [RFC3633] Section 11.2 behavior. 279 If the OPTION_ORO option in the Solicit message includes the 280 OPTION_PD_EXCLUDE option code but the delegating router does not 281 support the solution described in this specification, then the 282 delegating router acts as specified in [RFC3633]. The requesting 283 router MUST in this case also fall back to normal [RFC3633] behavior. 285 6. Requesting Router Initiated Prefix Delegation 287 The procedures described in the following sections are aligned with 288 Section 12 of [RFC3633]. In this specification we only describe the 289 additional steps required by the use of OPTION_PD_EXCLUDE option. 291 6.1. Requesting Router 293 The requesting router behavior regarding the use of the 294 OPTION_PD_EXCLUDE option is more or less identical to step described 295 in Section 5.1. The only difference really is different used DHCPv6 296 messages. The requesting router SHOULD include the OPTION_PD_EXCLUDE 297 option code in the OPTION_ORO option in DHCPv6 messages as described 298 in Section 22.7 of [RFC3315]. 300 The requesting router uses a Release message to return the delegated 301 prefix(es) to a delegating router. The prefix(es) to be released 302 MUST be included in the IA_PDs along with the excluded prefix 303 included in the OPTION_PD_EXCLUDE option. The requesting router MUST 304 NOT use the OPTION_PD_EXCLUDE option to introduce additional excluded 305 prefix in the Release message that it originally got a valid binding 306 for. 308 The requesting router must create sink routes for the delegated 309 prefixes minus the excluded prefixes. This may be done by creating 310 sink routes for delegated prefixes and more specific routes for the 311 excluded prefixes. 313 6.2. Delegating Router 315 The delegating router behavior regarding the use of the 316 OPTION_PD_EXCLUDE option is more or less identical to step described 317 in Section 5.2. The only difference really is DHCPv6 messages used 318 to carry the OPTION_PD_EXCLUDE option. 320 The delegating router may mark any prefix(es) in IA_PD Prefix options 321 in a Release message from a requesting router as 'available' 322 excluding the prefix included in the OPTION_PD_EXCLUDE options. If 323 the Release message contains 'new' excluded prefix in any 324 OPTION_PD_EXCLUDE option, the delegating router MUST send a Reply 325 message with Status Code set to NoBinding for that IA_PD option. 327 7. Security Considerations 329 Security considerations in DHCPv6 are described in Section 23 of 330 [RFC3315], and for DHCPv6 Prefix Delegation in Section 12 of 331 [RFC3633]. 333 8. IANA Considerations 335 A new DHCPv6 Option Code is reserved from DHCPv6 registry for DHCP 336 Option Codes. 338 OPTION_PD_EXCLUDE is set to TBD1 340 9. Acknowledgements 342 Authors would like to thank Ralph Droms, Frank Brockners, Ted Lemon, 343 Julien Laganier, Fredrik Garneij, Sri Gundavelli, Mikael Abrahamsson, 344 Behcet Sarikaya, Jyrki Soini, Deng Hui, Stephen Jacob and Tomasz 345 Mrugalski for their valuable comments and discussions. 347 10. References 348 10.1. Normative References 350 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 351 Requirement Levels", BCP 14, RFC 2119, March 1997. 353 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 354 and M. Carney, "Dynamic Host Configuration Protocol for 355 IPv6 (DHCPv6)", RFC 3315, July 2003. 357 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 358 Host Configuration Protocol (DHCP) version 6", RFC 3633, 359 December 2003. 361 10.2. Informative References 363 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 364 Address Autoconfiguration", RFC 4862, September 2007. 366 Authors' Addresses 368 Jouni Korhonen (editor) 369 Nokia Siemens Networks 370 Linnoitustie 6 371 FI-02600 Espoo 372 Finland 374 Email: jouni.nospam@gmail.com 376 Teemu Savolainen 377 Nokia 378 Hermiankatu 12 D 379 FI-33720 Tampere 380 Finland 382 Email: teemu.savolainen@nokia.com 384 Suresh Krishnan 385 Ericsson 386 8400 Decarie Blvd. 387 Town of Mount Royal, QC 388 Canada 390 Email: suresh.krishnan@ericsson.com 391 Ole Troan 392 Cisco Systems, Inc 393 Oslo 394 Norway 396 Email: ot@cisco.com