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Durand 5 Expires: March 2, 2012 Juniper Networks 6 August 30, 2011 8 RADIUS Extensions for Dual-Stack Lite 9 draft-ietf-softwire-dslite-radius-ext-06 11 Abstract 13 Dual-Stack Lite is a solution to offer both IPv4 and IPv6 14 connectivity to customers which are addressed only with an IPv6 15 prefix. Dual-Stack Lite requires to pre-configure the Dual-Stack 16 Lite Address Family Transition Router (AFTR) tunnel information on 17 the Basic Bridging BroadBand (B4) element. In many networks, the 18 customer profile information may be stored in Authentication 19 Authorization and Accounting (AAA) servers while client 20 configurations are mainly provided through Dynamic Host Configuration 21 Protocol (DHCP). This document specifies a new Remote Authentication 22 Dial In User Service (RADIUS) attribute to carry Dual-Stack Lite 23 Address Family Transition Router Tunnel name; the RADIUS attribute is 24 defined based on the equivalent DHCPv6 OPTION_AFTR_NAME option. This 25 RADIUS attribute is meant to be used between the RADIUS Server and 26 the Network Access Server (NAS), it is not intended to be used 27 directly between the Basic Bridging BroadBand element and the RADIUS 28 Server. 30 Status of this Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on March 2, 2012. 47 Copyright Notice 48 Copyright (c) 2011 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 This document may contain material from IETF Documents or IETF 62 Contributions published or made publicly available before November 63 10, 2008. The person(s) controlling the copyright in some of this 64 material may not have granted the IETF Trust the right to allow 65 modifications of such material outside the IETF Standards Process. 66 Without obtaining an adequate license from the person(s) controlling 67 the copyright in such materials, this document may not be modified 68 outside the IETF Standards Process, and derivative works of it may 69 not be created outside the IETF Standards Process, except to format 70 it for publication as an RFC or to translate it into languages other 71 than English. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 76 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 77 3. DS-Lite Configuration with RADIUS and DHCPv6 . . . . . . . . . 5 78 4. RADIUS Attribute . . . . . . . . . . . . . . . . . . . . . . . 8 79 4.1. DS-Lite-Tunnel-Name . . . . . . . . . . . . . . . . . . . 8 80 5. Table of attributes . . . . . . . . . . . . . . . . . . . . . 10 81 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 82 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 83 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 84 8.1. Normative References . . . . . . . . . . . . . . . . . . . 10 85 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 88 1. Introduction 90 Dual-Stack Lite [RFC6333] is a solution to offer both IPv4 and IPv6 91 connectivity to customers which are addressed only with an IPv6 92 prefix (no IPv4 address is assigned to the attachment device). One 93 of its key components is an IPv4-over-IPv6 tunnel, but a Dual-Stack- 94 Lite Basic Bridging BroadBand (B4) will not know if the network it is 95 attached to offers Dual-Stack Lite support, and if it did, would not 96 know the remote end of the tunnel to establish a connection. 98 To inform the Basic Bridging BroadBand (B4) of the Address Family 99 Transition Router's (AFTR) location, a Fully Qualified Domain Name 100 (FQDN) may be used. Once this information is conveyed, the presence 101 of the configuration indicating the AFTR's location also informs a 102 host to initiate Dual-Stack Lite (DS-Lite) service and become a 103 Softwire Initiator. 105 [RFC6334] specifies a DHCPv6 option which is meant to be used by a 106 Dual-Stack Lite client (Basic Bridging BroadBand element, B4) to 107 discover its Address Family Transition Router (AFTR) name. In order 108 to be able to populate such option the DHCPv6 Server must be pre- 109 provisioned with the Address Family Transition Router (AFTR) name. 111 In Broadband environments, customer profile may be managed by AAA 112 servers, together with user Authentication, Authorization, and 113 Accounting (AAA). Remote Authentication Dial In User Service 114 (RADIUS) protocol [RFC2865] is usually used by AAA Servers to 115 communicate with network elements. [I-D.ietf-radext-ipv6-access] 116 describes a typical broadband network scenario in which the Network 117 Access Server (NAS) acts as the access gateway for the users (hosts 118 or CPEs) and the NAS embeds a DHCPv6 Server function that allows it 119 to locally handle any DHCPv6 requests issued by the clients. 121 Since the DS-Lite AFTR information can be stored in AAA servers and 122 the client configuration is mainly provided through Dynamic Host 123 Configuration Protocol (DHCP) running between the NAS and the 124 requesting clients, a new RADIUS attribute is needed to send AFTR 125 information from AAA server to the NAS. 127 This document aims at defining a new RADIUS attribute to be used for 128 carrying the DS-Lite Tunnel Name, based on the equivalent DHCPv6 129 option already specified in [RFC6334] 131 2. Terminology 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in [RFC2119]. 137 The terms DS-Lite Basic Bridging BroadBand element (B4) and the DS- 138 Lite Address Family Transition Router element (AFTR) are defined in 139 [RFC6333] 141 3. DS-Lite Configuration with RADIUS and DHCPv6 143 The Figure 1 illustrates how the RADIUS protocol and DHCPv6 work 144 together to accomplish DS-Lite configuration on the B4 element when a 145 PPP Session is used to provide connectivity to the user. 147 The Network Access Server (NAS) operates as a client of RADIUS and as 148 DHCP Server for DHC protocol. The NAS initially sends a RADIUS 149 Access Request message to the RADIUS server, requesting 150 authentication. Once the RADIUS server receives the request, it 151 validates the sending client and if the request is approved, the AAA 152 server replies with an Access Accept message including a list of 153 attribute-value pairs that describe the parameters to be used for 154 this session. This list MAY also contain the AFTR Tunnel Name. When 155 the NAS receives a DHCPv6 client request containing the DS-Lite 156 tunnel Option, the NAS SHALL use the name returned in the RADIUS DS- 157 Lite-Tunnel-Name attribute to populate the DHCPv6 OPTION_AFTR_NAME 158 option in the DHCPv6 reply message. 160 B4 NAS AAA 161 | | Server 162 | | | 163 |----PPP LCP Config Request------> | | 164 | | | 165 | |----Access-Request ---->| 166 | | | 167 | |<---- Access-Accept-----| 168 | | (DS-Lite-Tunnel-Name) | 169 |<-----PPP LCP Config ACK ------- | | 170 | | | 171 | | | 172 |------ PPP IPv6CP Config Req ---->| | 173 | | | 174 |<----- PPP IPv6CP Config ACK -----| | 175 | | | 176 |------- DHCPv6 Solicit -------->| | 177 | | | 178 |<-------DHCPv6 Advertisement -----| | 179 | (DHCPv6 OPTION_AFTR_NAME) | | 180 | | | 181 |------- DHCPv6 Request -------->| | 182 | | | 183 |<-------- DHCPv6 Reply ---------- | | 184 | (DHCPv6 OPTION_AFTR_NAME) | | 186 DHCPv6 RADIUS 188 Figure 1: RADIUS and DHCPv6 Message Flow for a PPP Session 190 The Figure 2 illustrates how the RADIUS protocol and DHCPv6 work 191 together to accomplish DS-Lite configuration on the B4 element when 192 an IP Session is used to provide connectivity to the user. 194 The only difference between this message flow and previous one is 195 that in this scenario the interaction between NAS and AAA/ RADIUS 196 Server is triggered by the DHCPv6 Solicit message received by the NAS 197 from the B4 acting as DHCPv6 client, while in case of a PPP Session 198 the trigger is the PPP LCP Config Request message received by the 199 NAS. 201 B4 NAS AAA 202 | | Server 203 |------ DHCPv6 Solicit ---------> | | 204 | | | 205 | |----Access-Request ---->| 206 | | | 207 | |<---Access-Accept-------| 208 | | (DS-Lite-Tunnel-Name) | 209 | | | 210 |<-------DHCPv6 Advertisement------| | 211 | (DHCPv6 OPTION_AFTR_NAME) | | 212 | | | 213 |------- DHCPv6 Request -------->| | 214 | | | 215 | | | 216 |<----- DHCPv6 Reply ------------- | | 217 | (DHCPv6 OPTION_AFTR_NAME) | | 219 DHCPv6 RADIUS 221 Figure 2: RADIUS and DHCPv6 Message Flow for an IP Session 223 In the scenario depicted in Figure 2 the Access-Request packet 224 contains a Service-Type attribute with the value Authorize Only (17), 225 thus according to [RFC5080] the Access-Request packet MUST contain a 226 State attribute. 228 After receiving the DS-Lite-Tunnel-Name in the initial Access-Accept 229 the NAS MUST store the received AFTR Tunnel Name locally. When the 230 B4 sends a DHCPv6 Renew message to request an extension of the 231 lifetimes for the assigned address or prefix, the NAS does not have 232 to initiate a new Access-Request towards the AAA server to request 233 the AFTR tunnel name. The NAS retrieves the previously stored AFTR 234 tunnel name and uses it in its reply. 236 According to [RFC3315] if the DHCPv6 server to which the DHCPv6 Renew 237 message was sent at time T1 has not responded, the DHCPv6 client 238 initiates a Rebind/Reply message exchange with any available server. 239 In this scenario the NAS receiving the DHCPv6 rebind message MUST 240 initiate a new Access-Request towards the AAA server. The NAS MAY 241 include the DS-Lite-Tunnel-Name attribute in its Access-Request. 243 If the NAS does not receive the DS-Lite-Tunnel-Name attribute in the 244 Access-Accept it MAY fallback to a pre-configured default tunnel 245 name, if any. If the NAS does not have any pre-configured default 246 tunnel name or if the NAS receives an Access-Reject, the IPv4 over 247 IPv6 tunnel cannot be established, thus the B4 element has only IPv6 248 connectivity. 250 4. RADIUS Attribute 252 This section specifies the format of the new RADIUS attribute. 254 4.1. DS-Lite-Tunnel-Name 256 Description 258 The DS-Lite-Tunnel-Name RADIUS attribute contains a Fully Qualified 259 Domain Name that refers to the AFTR the client is requested to 260 establish a connection with. The NAS SHALL use the name returned in 261 the RADIUS DS-Lite-Tunnel-Name attribute to populate the DHCPv6 262 OPTION_AFTR_NAME option [RFC6334] 264 This attribute MAY be used in Access-Request packets as a hint to the 265 RADIUS server; for example if the NAS is pre-configured with a 266 default tunnel name, this name MAY be inserted in the attribute. The 267 RADIUS server MAY ignore the hint sent by the NAS and it MAY assign a 268 different AFTR tunnel name. 270 If the NAS includes the DS-Lite-Tunnel-Name attribute, but the AAA 271 server does not recognize it, this attribute MUST be ignored by the 272 AAA Server. 274 If the NAS does not receive DS-Lite-Tunnel-Name attribute in the 275 Access-Accept it MAY fallback to a pre-configured default tunnel 276 name, if any. If the NAS does not have any pre-configured default 277 tunnel name, the tunnel can not be established. 279 If the NAS is pre-provisioned with a default AFTR tunnel name and the 280 AFTR tunnel name received in Access-Accept is different from the 281 configured default, then the AFTR tunnel name received in the Access- 282 Accept message MUST be used for the session. 284 If the NAS cannot support the received AFTR tunnel name for any 285 reason, the tunnel SHOULD NOT be established. 287 When the Access-Request is triggered by a DHCPv6 Rebind message if 288 the AFTR tunnel name received in the Access-Accept is different from 289 the currently used one for that session, the NAS MUST force the B4 to 290 re-establish the tunnel using the new AFTR name received in the 291 Access-Accept message. 293 If an implementation includes the Change-of-Authorization (CoA) 294 messages [RFC5176], they could be used to modify the current 295 established DS-Lite tunnel. When the NAS receives a CoA Request 296 message containing the DS-Lite-Tunnel-Name attribute, the NAS MUST 297 send a Reconfigure message to a B4 to inform the B4 that the NAS has 298 new or updated configuration parameters and that the B4 is to 299 initiate a Renew/Reply or Information-request/Reply transaction with 300 the NAS in order to receive the updated information. 302 Upon receiving an AFTR tunnel name different from the currently used 303 one, the B4 MUST terminate the current DS-Lite tunnel and the B4 MUST 304 establish a new DS-LITE tunnel with the specified AFTR. 306 The DS-Lite-Tunnel-Name RADIUS attribute MAY be present in 307 Accounting-Request records where the Acct-Status-Type is set to 308 Start, Stop or Interim-Update. The DS-Lite-Tunnel-Name RADIUS 309 attribute MUST NOT appear more than once in a message. 311 A summary of the DS-Lite-Tunnel-Name RADIUS attribute format is shown 312 below. The fields are transmitted from left to right. 314 0 1 2 3 315 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 1 316 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 317 | Type | Length | DS-Lite-Tunnel-Name(FQDN)... 318 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 Type: 322 TBA1 for DS-Lite-Tunnel-Name. 323 Length: 324 This field indicates the total length in octets of this 325 attribute including the Type, the Length fields and the length 326 in octets of the DS-Lite-Tunnel-Name field 328 DS-Lite-Tunnel-Name: 329 A single Fully Qualified Domain Name of the remote tunnel 330 endpoint, located at the DS-Lite AFTR. 332 As the DS-Lite-Tunnel-Name attribute is used to populate the DHCPv6 333 OPTION_AFTR_NAME option, the DS-Lite-Tunnel-Name field is formatted 334 as required in DHCPv6 (Section 8 of [RFC3315] "Representation and Use 335 of Domain Names"). Briefly, the format described is using a single 336 octet noting the length of one DNS label (limited to at most 63 337 octets), followed by the label contents. This repeats until all 338 labels in the FQDN are exhausted, including a terminating zero-length 339 label. Any updates to Section 8 of [RFC3315] also apply to encoding 340 of this field. 342 The data type of DS-Lite-Tunnel-Name RADIUS attribute is a string 343 with opaque encapsulation, according to section 5 of [RFC2865] 345 5. Table of attributes 347 The following tables provide a guide to which attributes may be found 348 in which kinds of packets, and in what quantity. 350 Access- Access- Access- Challenge Accounting # Attribute 351 Request Accept Reject Request 352 0-1 0-1 0 0 0-1 TBA1 DS-Lite-Tunnel-Name 354 CoA-Request CoA-ACK CoA-NACK # Attribute 355 0-1 0 0 TBA1 DS-Lite-Tunnel-Name 357 The following table defines the meaning of the above table entries. 359 0 This attribute MUST NOT be present in packet. 360 0+ Zero or more instances of this attribute MAY be present in 361 packet. 362 0-1 Zero or one instance of this attribute MAY be present in packet. 364 6. Security Considerations 366 This document has no additional security considerations beyond those 367 already identified in [RFC2865] 369 [RFC6333] discusses Dual-Stack Lite related security issues. 371 7. IANA Considerations 373 This document requests the allocation of a new Radius attribute types 374 from the IANA registry "Radius Attribute Types" located at 375 http://www.iana.org/assignments/radius-types 377 DS-Lite-Tunnel-Name - TBA1 379 8. References 381 8.1. Normative References 383 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 384 Requirement Levels", BCP 14, RFC 2119, March 1997. 386 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 387 "Remote Authentication Dial In User Service (RADIUS)", 388 RFC 2865, June 2000. 390 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., 391 and M. Carney, "Dynamic Host Configuration Protocol for 392 IPv6 (DHCPv6)", RFC 3315, July 2003. 394 [RFC5080] Nelson, D. and A. DeKok, "Common Remote Authentication 395 Dial In User Service (RADIUS) Implementation Issues and 396 Suggested Fixes", RFC 5080, December 2007. 398 [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- 399 Stack Lite Broadband Deployments Following IPv4 400 Exhaustion", RFC 6333, August 2011. 402 [RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration 403 Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite", 404 RFC 6334, August 2011. 406 8.2. Informative References 408 [I-D.ietf-radext-ipv6-access] 409 Lourdelet, B., Dec, W., Sarikaya, B., Zorn, G., and D. 410 Miles, "RADIUS attributes for IPv6 Access Networks", 411 draft-ietf-radext-ipv6-access-05 (work in progress), 412 July 2011. 414 [RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. 415 Aboba, "Dynamic Authorization Extensions to Remote 416 Authentication Dial In User Service (RADIUS)", RFC 5176, 417 January 2008. 419 Authors' Addresses 421 Roberta Maglione 422 Telecom Italia 423 Via Reiss Romoli 274 424 Torino 10148 425 Italy 427 Phone: 428 Email: roberta.maglione@telecomitalia.it 429 Alain Durand 430 Juniper Networks 431 1194 North Mathilda Avenue 432 Sunnyvale, CA 94089-1206 433 USA 435 Phone: 436 Fax: 437 Email: adurand@juniper.net 438 URI: