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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-11) exists of draft-ietf-softwire-dual-stack-lite-04 ** Obsolete normative reference: RFC 3315 (Obsoleted by RFC 8415) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Softwires D. Hankins 3 Internet-Draft ISC 4 Intended status: Standards Track T. Mrugalski 5 Expires: December 26, 2010 Gdansk University of Technology 6 June 24, 2010 8 Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Options for Dual- 9 Stack Lite 10 draft-ietf-softwire-ds-lite-tunnel-option-03 12 Abstract 14 This document specifies two DHCPv6 options which are meant to be used 15 by a Dual-Stack Lite client (Basic Bridging BroadBand element, B4) to 16 discover its Address Family Transition Router (AFTR) address. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on December 26, 2010. 35 Copyright Notice 37 Copyright (c) 2010 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 53 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 3. The Dual-Stack Lite Address DHCPv6 Option . . . . . . . . . . . 3 55 4. The Dual-Stack Lite Name DHCPv6 Option . . . . . . . . . . . . 4 56 5. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . . 6 57 6. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . . 7 58 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 59 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 60 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 61 10. Normative References . . . . . . . . . . . . . . . . . . . . . 8 62 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 64 1. Requirements Language 66 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 67 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 68 document are to be interpreted as described in RFC 2119 [RFC2119]. 70 2. Introduction 72 Dual-Stack Lite [I-D.softwire-ds-lite-04] is a solution to offer both 73 IPv4 and IPv6 connectivity to customers which are addressed only with 74 an IPv6 prefix (no IPv4 address is assigned to the attachment 75 device). One of its key components is an IPv4-over-IPv6 tunnel, 76 commonly referred to as a Softwire, but a DS-Lite Basic Bridging 77 BroadBand (B4) will not know if the network it is attached to offers 78 Dual-Stack Lite support, and if it did would not know the remote end 79 of the tunnel to establish a connection. 81 To inform the B4 of the AFTR's location, either an IPv6 address or 82 Fully Qualified Domain Name (FQDN) may be used. Once this 83 information is conveyed, the presence of the configuration indicating 84 the AFTR's location also informs a host to initiate Dual-Stack Lite 85 (DS-Lite) service and become a Softwire Initiator. 87 To provide the conveyance of the configuration information, two 88 DHCPv6 [RFC3315] options are used; one in the case where the host 89 receives an IPv6 address, and one in the case where the host receives 90 an FQDN in order to derive an IPv6 address. 92 The details of how the B4 establishes an IPv4-in-IPv6 tunnel to the 93 AFTR are out of scope for this document. 95 3. The Dual-Stack Lite Address DHCPv6 Option 97 The Dual-Stack Lite Address option consists of option-code and 98 option-len fields (common for all DHCPv6 options), and a 128 bit 99 tunnel-endpoint-addr field, containing one IPv6 address. The tunnel- 100 endpoint-addr specifies the location of the remote tunnel endpoint, 101 expected to be located at an AFTR. 103 The DS-Lite Address option MAY appear in the root scope of a DHCPv6 104 packet. It MUST NOT appear inside any IA_NA, IA_TA, IA_PD, IAADDR, 105 or similar. 107 The DS-Lite Address option MUST NOT appear more than once in a 108 message. 110 The format of the Dual-Stack Lite Address option is shown in the 111 following figure: 113 0 1 2 3 114 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 1 115 +-------------------------------+-------------------------------+ 116 | OPTION_DS_LITE_ADDR (TBD) | option-len: 16 | 117 +-------------------------------+-------------------------------+ 118 | | 119 | tunnel-endpoint-addr (IPv6 Address) | 120 | | 121 | | 122 +---------------------------------------------------------------+ 124 option-code: OPTION_DS_LITE_ADDR (TBD) 126 option-len: Length of the tunnel-endpoint-addr field, 127 which is precisely 16 octets. 129 tunnel-endpoint-addr: A single IPv6 address in binary 130 representation of the remote tunnel 131 endpoint, located at the DS-Lite AFTR. 133 Figure 1: DS-Lite IPv6 Address DHCPv6 Option Format 135 The client validates the DS-Lite Address option by confirming the 136 option is of 16 octets in length or greater. The client MUST ignore 137 any tunnel-endpoint-addr shorter than 16 octets. In the event the 138 option is greater than 16 octets in length, only the first 16 octets 139 are interpreted. 141 Because this option conveys the tunnel-endpoint-addr value, no 142 further processing is required of the client. 144 This option conveys a single IPv6 address, as the Dual-Stack Lite 145 specification [I-D.softwire-ds-lite-04] defines only one Softwire 146 connection between a B4 and any AFTR. Multiple connections or 147 endpoints are undefined. For more information, see Section 7.2 "High 148 Availability" of [I-D.softwire-ds-lite-04]. 150 4. The Dual-Stack Lite Name DHCPv6 Option 152 The Dual-Stack Lite Name option consists of option-code and option- 153 len fields (common for all DHCPv6 options), and a variable length 154 tunnel-endpoint-name field, containing a Fully Qualified Domain Name 155 that refers to the AFTR the client is requested to establish a 156 connection with. 158 The DS-Lite Name option MAY appear in the root scope of a DHCPv6 159 packet. It MUST NOT appear inside any IA_NA, IA_TA, IA_PD, IAADDR, 160 or similar. 162 The DS-Lite Name option MUST NOT appear more than once in a message. 164 The format of the Dual-Stack Lite Name option is shown in the 165 following figure: 167 0 1 2 3 168 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 1 169 +-------------------------------+-------------------------------+ 170 | OPTION_DS_LITE_NAME (TBD) | option-len | 171 +-------------------------------+-------------------------------+ 172 | tunnel-endpoint-name (FQDN) | 173 +---------------------------------------------------------------+ 175 option-code: OPTION_DS_LITE_NAME (TBD) 177 option-len: Length in octets of the tunnel-endpoint- 178 name field. 180 tunnel-endpoint-name: A single Fully Qualified Domain Name of the 181 remote tunnel endpoint, located at the 182 DS-Lite AFTR. 184 Figure 2: DS-Lite Name DHCPv6 Option Format 186 The tunnel-endpoint-name field is formatted as required in DHCPv6 187 [RFC3315] Section 8 ("Representation and Use of Domain Names"). 188 Briefly, the format described is using a single octet noting the 189 length of one DNS label (limited to at most 64 octets), followed by 190 the label. This repeats until all labels in the FQDN are exhausted. 191 The root label (or the end of the FQDN) is denoted as a zero length 192 label. An example FQDN format for this option is shown in Figure 3. 194 +------+------+------+------+------+------+------+------+------+ 195 | 0x07 | e | x | a | m | p | l | e | 0x03 | 196 +------+------+------+------+------+------+------+------+------+ 197 | i | s | c | 0x03 | o | r | g | 0x00 | 198 +------+------+------+------+------+------+------+------+ 200 Figure 3: Example tunnel-endpoint-name. 202 Note that in the specific case of the example tunnel-endpoint-name, 203 (Figure 3) the length of the option is 17 octets, and so an option- 204 len field value of 17 would be used. 206 The client (B4) validates the option in this format by first 207 confirming that the option length is greater than 3, that the option 208 data can be contained by the option length (that the option length 209 does not run off the end of the packet), and that the tunnel- 210 endpoint-name is of valid format as described in DHCPv6 Section 8 211 [RFC3315]; there are no compression tags, there is at least one label 212 of nonzero length. 214 The client (B4) determines a value for the tunnel-endpoint-addr from 215 the tunnel-endpoint-name using standard DNS resolution, as defined in 216 [RFC3596]. If the DNS response contains more than one IPv6 address, 217 the client picks only one IPv6 address and uses it as a remote tunnel 218 endpoint. The client MUST NOT establish more than one DS-Lite tunnel 219 at the same time. For a redundancy and high availability discussion, 220 see Section 7.2 "High availability" of [I-D.softwire-ds-lite-04]. 222 5. DHCPv6 Server Behavior 224 DHCP servers must translate user input from their own specific and 225 unique operator's interfaces into configuration state for the client. 226 The server MUST provide a way to configure the OPTION_DS_LITE_ADDR, 227 and SHOULD allow the operator to enter a Fully Qualified Domain Name, 228 upon which the server performs DNS Resolution to assemble its 229 OPTION_DS_LITE_ADDR contents. The server MAY either provide the same 230 Fully Qualified Domain Name as OPTION_DS_LITE_NAME contents, or 231 simply provide a distinct method of configuring it. 233 If configured with values, DHCPv6 servers will include the DS-Lite 234 Address and/or Name options if either or both appear on the client's 235 Option Request Option (OPTION_ORO). RFC 3315 Section 17.2.2 236 [RFC3315] describes how a DHCPv6 client and server negotiate 237 configuration values using the ORO. 239 A DHCPv6 server MUST NOT send either option if it has not been 240 explicitly requested by the client. 242 If the server is configured with an FQDN as the tunnel endpoint 243 locator, the configured FQDN value MUST contain a resolvable Fully 244 Qualified Domain Name, having appropriate delegations from the root, 245 and having a AAAA record locating the Softwire Concentrator. 247 If OPTION_DS_LITE_NAME is being configured, the server MUST be 248 configured to provide OPTION_DNS_SERVERS defined in [RFC3646] 249 together with the DS-Lite Name option, so that clients will be able 250 to ask for DNS servers locations to resolve the domain name provided 251 in the DS-Lite Name option. 253 6. DHCPv6 Client Behavior 255 A client that supports B4 functionality of DS-Lite (defined in 256 [I-D.softwire-ds-lite-04]) MUST include OPTION_DS_LITE_ADDR on its 257 OPTION_ORO, and MAY include OPTION_DS_LITE_NAME at its option and 258 ability. 260 If requesting the OPTION_DS_LITE_NAME option, the client also SHOULD 261 request OPTION_DNS_SERVERS defined in [RFC3646] to be able to resolve 262 any received domain name. 264 If the client receives either DS-Lite option, it MUST verify the 265 option contents as described in Section 3 and Section 4. The client 266 (B4) SHOULD establish a softwire tunnel to the tunnel-endpoint-addr 267 IPv6 address it determines from either of these options. 269 If the client requests and receives both the OPTION_DS_LITE_ADDR and 270 the OPTION_DS_LITE_NAME options, it MUST proceed with resolving the 271 OPTION_DS_LITE_NAME. 273 7. Security Considerations 275 This document does not present any new security issues, but as with 276 all DHCPv6-derived configuration state, it is completely possible 277 that the configuration is being delivered by a third party (Man In 278 The Middle). As such, there is no basis to trust that the access the 279 DS-Lite Softwire connection represents can be trusted, and it should 280 not therefore bypass any security mechanisms such as IP firewalls. 282 RFC 3315 [RFC3315] discusses DHCPv6-related security issues. 284 [I-D.softwire-ds-lite-04] discusses DS-Lite related security issues. 286 8. IANA Considerations 288 IANA is requested to allocate two DHCPv6 option codes referencing 289 this document. One delineating OPTION_DS_LITE_ADDR, and one 290 delineating OPTION_DS_LITE_NAME. 292 9. Acknowledgements 294 Authors would like to thank Alain Durand, Rob Austein, Dave Thaler 295 and Paul Selkirk for their valuable feedback and suggestions. 297 10. Normative References 299 [I-D.softwire-ds-lite-04] 300 Durand, A., Ed., "Dual-stack lite broadband deployments 301 post IPv4 exhaustion", 302 draft-ietf-softwire-dual-stack-lite-04 (work in progress), 303 March 2010. 305 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 306 Requirement Levels", BCP 14, RFC 2119, March 1997. 308 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 309 and M. Carney, "Dynamic Host Configuration Protocol for 310 IPv6 (DHCPv6)", RFC 3315, July 2003. 312 [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, 313 "DNS Extensions to Support IP Version 6", RFC 3596, 314 October 2003. 316 [RFC3646] Droms, R., "DNS Configuration options for Dynamic Host 317 Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, 318 December 2003. 320 Authors' Addresses 322 David W. Hankins 323 Internet Systems Consortium, Inc. 324 950 Charter Street 325 Redwood City, CA 94063 326 US 328 Phone: +1 650 423 1307 329 Email: David_Hankins@isc.org 331 Tomasz Mrugalski 332 Gdansk University of Technology 333 Storczykowa 22B/12 334 Gdansk 80-177 335 Poland 337 Phone: +48 698 088 272 338 Email: tomasz.mrugalski@eti.pg.gda.pl