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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) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Softwires D. Hankins 3 Internet-Draft Google 4 Intended status: Standards Track T. Mrugalski 5 Expires: June 2, 2011 Gdansk University of Technology 6 November 29, 2010 8 Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for Dual- 9 Stack Lite 10 draft-ietf-softwire-ds-lite-tunnel-option-06 12 Abstract 14 This document specifies a DHCPv6 option which is meant to be used by 15 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 June 2, 2011. 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 AFTR-Name DHCPv6 Option . . . . . . . . . . . . . . . . . . 3 55 4. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . . 5 56 5. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . . 5 57 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 58 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 59 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 60 9. Normative References . . . . . . . . . . . . . . . . . . . . . 6 61 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 63 1. Requirements Language 65 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 66 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 67 document are to be interpreted as described in RFC 2119 [RFC2119]. 69 2. Introduction 71 Dual-Stack Lite [I-D.softwire-ds-lite] is a solution to offer both 72 IPv4 and IPv6 connectivity to customers which are addressed only with 73 an IPv6 prefix (no IPv4 address is assigned to the attachment 74 device). One of its key components is an IPv4-over-IPv6 tunnel, 75 commonly referred to as a Softwire. A DS-Lite "Basic Bridging 76 BroadBand" (B4) device will not know if the network it is attached to 77 offers Dual-Stack Lite support, and if it did would not know the 78 remote end of the tunnel to establish a connection. 80 To inform the B4 of the Address Family Transition Router's (AFTR) 81 location, a DNS [RFC1035] hostname may be used. Once this 82 information is conveyed, the presence of the configuration indicating 83 the AFTR's location also informs a host to initiate Dual-Stack Lite 84 (DS-Lite) service and become a Softwire Initiator. 86 To provide the conveyance of the configuration information, a single 87 DHCPv6 [RFC3315] option is used, expressing the AFTR's Fully 88 Qualified Domain Name to the B4 element. 90 The details of how the B4 establishes an IPv4-in-IPv6 tunnel to the 91 AFTR are out of scope for this document. 93 3. The AFTR-Name DHCPv6 Option 95 The AFTR-Name option consists of option-code and option-len fields 96 (as all DHCPv6 options have), and a variable length tunnel-endpoint- 97 name field containing a fully qualified domain name that refers to 98 the AFTR which the client is asked to connect to. 100 The OPTION_AFTR_NAME option MAY appear in the root scope of a DHCPv6 101 packet. It MUST NOT appear inside any IA_NA, IA_TA, IA_PD, IAADDR, 102 or similar. Any OPTION_AFTR_NAME option received inside any other 103 option MUST be ignored. 105 The OPTION_AFTR_NAME option MUST NOT appear more than once in a 106 message. Clients that receive more than one OPTION_AFTR_NAME options 107 MUST discard all instances of that option, acting as if none were 108 sent. 110 The format of the AFTR-Name option is shown in the following figure: 112 0 1 2 3 113 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 1 114 +-------------------------------+-------------------------------+ 115 | OPTION_AFTR_NAME: (TBD) | option-len | 116 +-------------------------------+-------------------------------+ 117 | | 118 | tunnel-endpoint-name (FQDN) | 119 | | 120 +---------------------------------------------------------------+ 122 OPTION_AFTR_NAME: (TBD) 124 option-len: Length of the tunnel-endpoint-name field. 126 tunnel-endpoint-name: A fully qualified domain name identifying 127 the tunnel endpoint, located at the DS-Lite 128 AFTR. 130 Figure 1: AFTR-Name DHCPv6 Option Format 132 The tunnel-endpoint-name field is formatted as required in DHCPv6 133 [RFC3315] Section 8 ("Representation and Use of Domain Names"). 134 Briefly, the format described is using a single octet noting the 135 length of one DNS label (limited to at most 63 octets), followed by 136 the label contents. This repeats until all labels in the FQDN are 137 exhausted, including a terminating zero-length label. Any updates to 138 Section 8 of DHCPv6 [RFC3315] also apply to encoding of this field. 139 An example format for this option is shown in Figure 2, which conveys 140 the FQDN "aftr.example.com.". 142 +------+------+------+------+------+------+------+------+------+ 143 | 0x04 | a | f | t | r | 0x07 | e | x | a | 144 +------+------+------+------+------+------+------+------+------+ 145 | m | p | l | e | 0x03 | c | o | m | 0x00 | 146 +------+------+------+------+------+------+------+------+------+ 148 Figure 2: Example tunnel-endpoint-name. 150 Note that in the specific case of the example tunnel-endpoint-name, 151 (Figure 2) the length of the tunnel-endpoint-name is 18 octets, and 152 so an option-len field value of 18 would be used. 154 The option is validated by confirming that the option-len is greater 155 than 3, that the option data can be contained by the option length 156 (that the option length does not run off the end of the packet), that 157 individual label lengths do not exceed the option length, and that 158 the tunnel-endpoint-name is of valid format as described in DHCPv6 159 Section 8 [RFC3315]; there are no compression tags, there is at least 160 one label of nonzero length. 162 4. DHCPv6 Server Behavior 164 A DHCPv6 server MUST NOT send more than one OPTION_AFTR_NAME option. 166 A DHCPv6 server MUST NOT send the OPTION_AFTR_NAME option as a 167 suboption in other options; it MUST appear only in the root scope of 168 any DHCPv6 messages made in response to clients (Reply, Advertise, et 169 al). 171 RFC 3315 Section 17.2.2 [RFC3315] describes how a DHCPv6 client and 172 server negotiate configuration values using the Option Request Option 173 (OPTION_ORO). As a convenience to the reader, we mention here that a 174 server will not reply with a value for the OPTION_AFTR_NAME if the 175 client has not explicitly enumerated it on its OPTION_ORO. 177 5. DHCPv6 Client Behavior 179 A client that supports the B4 functionality of DS-Lite (defined in 180 [I-D.softwire-ds-lite]) and conforms to this specification MUST 181 include OPTION_AFTR_NAME on its OPTION_ORO. 183 Because it requires DNS name to address resolution, a client MAY also 184 wish to include the OPTION_DNS_SERVERS option on its OPTION_ORO. 186 If the client receives the OPTION_AFTR_NAME option, it MUST verify 187 the option contents as described in Section 3. 189 If the client receives more than one OPTION_AFTR_NAME option, it MUST 190 discard all instances of that option. 192 The client performs standard DNS resolution using the provided FQDN 193 to resolve a AAAA record, as defined in [RFC3596] and STD 13 194 [RFC1034] [RFC1035]. 196 If any DNS response contains more than one IPv6 address, the client 197 picks only one IPv6 address and uses it as a remote tunnel endpoint. 198 The client MUST NOT establish more than one DS-Lite tunnel at the 199 same time. For a redundancy and high availability discussion, see 200 Section 7.2 "High availability" of [I-D.softwire-ds-lite]. 202 6. Security Considerations 204 This document does not present any new security issues, but as with 205 all DHCPv6-derived configuration state, it is completely possible 206 that the configuration is being delivered by a third party (Man In 207 The Middle). As such, there is no basis to trust that the access the 208 DS-Lite Softwire connection represents can be trusted, and it should 209 not therefore bypass any security mechanisms such as IP firewalls. 211 RFC 3315 [RFC3315] discusses DHCPv6-related security issues. 213 [I-D.softwire-ds-lite] discusses DS-Lite related security issues. 215 7. IANA Considerations 217 IANA is requested to allocate single DHCPv6 option code referencing 218 this document, delineating OPTION_AFTR_NAME. 220 8. Acknowledgements 222 Authors would like to thank Alain Durand, Rob Austein, Dave Thaler, 223 Paul Selkirk, Ralph Droms, Mohamed Boucadair and Maglione Roberta for 224 their valuable feedback and suggestions. 226 This work has been partially supported by the Polish Ministry of 227 Science and Higher Education under the European Regional Development 228 Fund, Grant No. POIG.01.01.02-00-045/09-00 (Future Internet 229 Engineering Project). 231 9. Normative References 233 [I-D.softwire-ds-lite] 234 Durand, A., Ed., "Dual-stack lite broadband deployments 235 post IPv4 exhaustion", draft-ietf-softwire-dual-stack-lite 236 (work in progress). 238 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 239 STD 13, RFC 1034, November 1987. 241 [RFC1035] Mockapetris, P., "Domain names - implementation and 242 specification", STD 13, RFC 1035, November 1987. 244 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 245 Requirement Levels", BCP 14, RFC 2119, March 1997. 247 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 248 and M. Carney, "Dynamic Host Configuration Protocol for 249 IPv6 (DHCPv6)", RFC 3315, July 2003. 251 [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, 252 "DNS Extensions to Support IP Version 6", RFC 3596, 253 October 2003. 255 Authors' Addresses 257 David W. Hankins 258 Google, Inc. 259 1600 Amphitheatre Parkway 260 Mountain View, CA 94043 261 USA 263 Email: dhankins@google.com 265 Tomasz Mrugalski 266 Gdansk University of Technology 267 Storczykowa 22B/12 268 Gdansk 80-177 269 Poland 271 Phone: +48 698 088 272 272 Email: tomasz.mrugalski@eti.pg.gda.pl