idnits 2.17.1 draft-ietf-opsawg-capwap-alt-tunnel-11.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (December 18, 2017) is 2314 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Outdated reference: A later version (-13) exists of draft-ietf-intarea-tunnels-07 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Opsawg Working Group R. Zhang 3 Internet-Draft China Telecom 4 Intended status: Experimental R. Pazhyannur 5 Expires: June 21, 2018 S. Gundavelli 6 Cisco 7 Z. Cao 8 H. Deng 9 Z. Du 10 Huawei 11 December 18, 2017 13 Alternate Tunnel Encapsulation for Data Frames in CAPWAP 14 draft-ietf-opsawg-capwap-alt-tunnel-11 16 Abstract 18 Control and Provisioning of Wireless Access Points (CAPWAP) defines a 19 specification to encapsulate a station's data frames between the 20 Wireless Transmission Point (WTP) and Access Controller (AC). 21 Specifically, the station's IEEE 802.11 data frames can be either 22 locally bridged or tunneled to the AC. When tunneled, a CAPWAP data 23 channel is used for tunneling. In many deployments encapsulating 24 data frames to an entity other than the AC (for example to an Access 25 Router (AR)) is desirable. Furthermore, it may also be desirable to 26 use different tunnel encapsulation modes between the WTP and the 27 Access Router. This document defines extension to CAPWAP protocol 28 for supporting this capability and refers to it as alternate tunnel 29 encapsulation. The alternate tunnel encapsulation allows 1) the WTP 30 to tunnel non-management data frames to an endpoint different from 31 the AC and 2) the WTP to tunnel using one of many known encapsulation 32 types such as IP-IP, IP-GRE, CAPWAP. The WTP may advertise support 33 for alternate tunnel encapsulation during the discovery and join 34 process and AC may select one of the supported alternate tunnel 35 encapsulation types while configuring the WTP. 37 Status of This Memo 39 This Internet-Draft is submitted in full conformance with the 40 provisions of BCP 78 and BCP 79. 42 Internet-Drafts are working documents of the Internet Engineering 43 Task Force (IETF). Note that other groups may also distribute 44 working documents as Internet-Drafts. The list of current Internet- 45 Drafts is at https://datatracker.ietf.org/drafts/current/. 47 Internet-Drafts are draft documents valid for a maximum of six months 48 and may be updated, replaced, or obsoleted by other documents at any 49 time. It is inappropriate to use Internet-Drafts as reference 50 material or to cite them other than as "work in progress." 52 This Internet-Draft will expire on June 21, 2018. 54 Copyright Notice 56 Copyright (c) 2017 IETF Trust and the persons identified as the 57 document authors. All rights reserved. 59 This document is subject to BCP 78 and the IETF Trust's Legal 60 Provisions Relating to IETF Documents 61 (https://trustee.ietf.org/license-info) in effect on the date of 62 publication of this document. Please review these documents 63 carefully, as they describe your rights and restrictions with respect 64 to this document. Code Components extracted from this document must 65 include Simplified BSD License text as described in Section 4.e of 66 the Trust Legal Provisions and are provided without warranty as 67 described in the Simplified BSD License. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 72 1.1. Conventions used in this document . . . . . . . . . . . . 7 73 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7 74 1.3. History of the document . . . . . . . . . . . . . . . . . 8 75 2. Alternate Tunnel Encapsulation Overview . . . . . . . . . . . 8 76 3. CAPWAP Protocol Message Elements Extensions . . . . . . . . . 11 77 3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 11 78 3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 11 79 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 12 80 4. Alternate Tunnel Types . . . . . . . . . . . . . . . . . . . 13 81 4.1. CAPWAP based Alternate Tunnel . . . . . . . . . . . . . . 13 82 4.2. PMIPv6 based Alternate Tunnel . . . . . . . . . . . . . . 14 83 4.3. GRE based Alternate Tunnel . . . . . . . . . . . . . . . 15 84 5. Alternate Tunnel Information Elements . . . . . . . . . . . . 15 85 5.1. Access Router Information Elements . . . . . . . . . . . 15 86 5.1.1. AR IPv4 List Element . . . . . . . . . . . . . . . . 16 87 5.1.2. AR IPv6 List Element . . . . . . . . . . . . . . . . 16 88 5.2. Tunnel DTLS Policy Element . . . . . . . . . . . . . . . 17 89 5.3. IEEE 802.11 Tagging Mode Policy Element . . . . . . . . . 19 90 5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20 91 5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 22 92 5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 23 93 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 94 7. Security Considerations . . . . . . . . . . . . . . . . . . . 25 95 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25 96 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 97 9.1. Normative References . . . . . . . . . . . . . . . . . . 25 98 9.2. Informative References . . . . . . . . . . . . . . . . . 26 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 101 1. Introduction 103 Service Providers are deploying very large Wi-Fi deployments (ranging 104 from hundreds of thousands of Access Points, APs (referred to as WTPs 105 in CAPWAP terminology) to millions of APs. These networks are 106 designed to carry traffic generated from mobile users. The volume in 107 mobile user traffic is already very large and expected to continue 108 growing rapidly. As a result, operators are looking for scalable 109 solutions that can meet the increasing demand. The scalability 110 requirement can be met by splitting the control/management plane from 111 the data plane. This enables the data plane to scale independent of 112 the control/management plane. This specification provides a way to 113 enable such separation. 115 CAPWAP ([RFC5415], [RFC5416]) defines a tunnel mode that describes 116 how the WTP handles the data plane (user traffic). The following 117 types are defined: 119 o Local Bridging: All data frames are locally bridged. 120 o 802.3 Tunnel: All data frames are tunneled to the AC in 802.3 121 format. 122 o 802.11 Tunnel: All data frames are tunneled to the AC in 802.11 123 format. 125 Figure 1 describes a system with Local Bridging. The AC is in a 126 centralized location. The data plane is locally bridged by the WTPs 127 leading to a system with centralized control plane with distributed 128 data plane. This system has two benefits: 1) reduces the scale 129 requirement on data traffic handling capability of the AC and 2) 130 leads to more efficient/optimal routing of data traffic while 131 maintaining centralized control/management. 133 Locally Bridged 134 +-----+ Data Frames +----------------+ 135 | WTP |===============| Access Router | 136 +-----+ +----------------+ 137 \\ 138 \\ CAPWAP Control Channel +----------+ 139 ++=========================| AC | 140 // CAPWAP Data Channel: | | 141 // IEEE 802.11 Mgmt traffic +----------+ 142 // 143 +-----+ +----------------+ 144 | WTP |============== | Access Router | 145 +-----+ +----------------+ 146 Locally Bridged 147 Data Frames 149 Figure 1: Centralized Control with Distributed Data 151 The AC handles control of WTPs. In addition, the AC also handles the 152 IEEE 802.11 management traffic to/from the stations. There is CAPWAP 153 Control and Data Channel between the WTP and the AC. Note that even 154 though there is no user traffic transported between the WTP and AC, 155 there is still a CAPWAP Data Channel. The CAPWAP Data Channel 156 carries the IEEE 802.11 management traffic (like IEEE 802.11 Action 157 Frames). 159 Figure 2 shows a system where the tunnel mode is configured to tunnel 160 data frames between the WTP and the AC either using 802.3 Tunnel or 161 802.11 Tunnel configurations. Operators deploy this configuration 162 when they need to tunnel the user traffic. The tunneling requirement 163 may be driven by the need to apply policy at the AC or a legal 164 requirement to support lawful intercept of user traffic. This 165 requirement could be met in the locally bridged system (Figure 1) if 166 the access router implemented the required policy. However, in many 167 deployments the operator managing the WTP is different than the 168 operator managing the Access Router. When the operators are 169 different, the policy has to be enforced in a tunnel termination 170 point in the WTP operator's network. 172 +-----+ 173 | WTP | 174 +-----+ 175 \\ 176 \\ CAPWAP Control Channel +----------+ 177 ++=========================| AC | 178 // CAPWAP Data Channel: | | 179 // IEEE 802.11 Mgmt traffic | | 180 // Data Frames +----------+ 181 // 182 +-----+ 183 | WTP | 184 +-----+ 186 Figure 2: Centralized Control and Centralized Data 188 The key difference with the locally bridged system is that the data 189 frames are tunneled to the AC instead of being locally bridged. 190 There are two shortcomings with the system in Figure 2. 1) They do 191 not allow the WTP to tunnel data frames to an endpoint different from 192 the AC and 2) They do not allow the WTP to tunnel data frames using 193 any encapsulation other than CAPWAP (as specified in Section 4.4.2 of 194 [RFC5415]). 196 Figure 3 shows a system where the WTP tunnels data frames to an 197 alternate entity different from the AC. The WTP also uses an 198 alternate tunnel encapsulation such as L2TP, L2TPv3, IP-in-IP, IP/ 199 GRE, etc. This enables 1) independent scaling of data plane and 2) 200 leveraging of commonly used tunnel encapsulations such as L2TP, GRE, 201 etc. 203 Alternate Tunnel to AR (L2TPv3, IP-IP, CAPWAP, etc.) 204 _________ 205 +-----+ ( ) +-----------------+ 206 | WTP |======+Internet +==============|Access Router(AR)| 207 +-----+ (_________) +-----------------+ 208 \\ ________ CAPWAP Control 209 \\ ( ) Channel +--------+ 210 ++=+Internet+========================| AC | 211 // (________)CAPWAP Data Channel: +--------+ 212 // IEEE 802.11 Mgmt traffic 213 // _________ 214 +-----+ ( ) +----------------+ 215 | WTP |====+Internet +================| Access Router | 216 +-----+ (_________) +----------------+ 217 Alternate Tunnel to AR (L2TPv3, IP-in-IP, CAPWAP, etc.) 219 Figure 3: Centralized Control with Alternate Tunnel for Data 221 The WTP may support widely used encapsulation types such as L2TP, 222 L2TPv3, IP-in-IP, IP/GRE, etc. The WTP advertises the different 223 alternate tunnel encapsulation types it can support. The AC 224 configures one of the advertised types. As shown in the figure there 225 is a CAPWAP control and data channel between the WTP and AC. The 226 CAPWAP data channel carries the stations' management traffic as in 227 the case of the locally bridged system. The main reason to maintain 228 a CAPWAP data channel is to maintain similarity with the locally 229 bridged system. The WTP maintains three tunnels: CAPWAP Control, 230 CAPWAP Data, and another alternate tunnel for the data frames. The 231 data frames are transported by an alternate tunnel between the WTP 232 and a tunnel termination point such as an Access Router. This 233 specification describes how the alternate tunnel can be established. 234 The specification defines message elements for the WTP to advertise 235 support for alternate tunnel encapsulation, for the AC to configure 236 alternate tunnel encapsulation, and for the WTP to report failure of 237 the alternate tunnel. 239 The alternate tunnel encapsulation also supports the third-party WLAN 240 service provider scenario (i.e. Virtual Network Operator, VNO). 241 Under this scenario, the WLAN provider owns the WTP and AC resources, 242 while the VNOs can rent the WTP resources from the WLAN provider for 243 network access. The AC belonging to the WLAN service provider 244 manages the WTPs in the centralized mode. 246 As shown in Figure 4, VNO 1&2 don't possess the network access 247 resources, however they provide services by acquiring resources from 248 the WLAN provider. Since a WTP is capable of supporting up to 16 249 Service Set Identifiers (SSIDs), the WLAN provider may provide 250 network access service for different providers with different SSIDs. 251 For example, SSID1 is advertised by the WTP for VNO1; while SSID2 is 252 advertised by the WTP for VNO2. Therefore the data traffic from the 253 user can be directly steered to the corresponding access router of 254 the VNO who owns that user. As shown in Figure 4, AC can notify 255 multiple AR addresses for load balancing or redundancy. 257 +----+ 258 | AC | 259 +--+-+ 260 CAPWAP-CTL | 261 +-----------------+ 262 | CAPWAP-DATA: IEEE 802.11 Mgmt traffic 263 | 264 WLAN Provider| VNO 1 265 +-----+ CAPWAP-DATA (SSID1) +---------------+ 266 SSID1 | WTP +--------------------------|Access Router 1| 267 SSID2 +--+-++ +---------------+ 268 | | 269 | | VNO 1 270 | | GRE-DATA (SSID1) +---------------+ 271 | +---------------------------|Access Router 2| 272 | +---------------+ 273 | 274 | VNO 2 275 | CAPWAP-DATA (SSID2) +---------------+ 276 +-----------------------------|Access Router 3| 277 +---------------+ 279 Figure 4: Third-party WLAN Service Provider 281 1.1. Conventions used in this document 283 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 284 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 285 document are to be interpreted as described in [RFC2119]. 287 1.2. Terminology 289 Station (STA): A device that contains an IEEE 802.11 conformant 290 medium access control (MAC) and physical layer (PHY) interface to the 291 wireless medium (WM). 293 Access Controller (AC): The network entity that provides WTP access 294 to the network infrastructure in the data plane, control plane, 295 management plane, or a combination therein. 297 Access Router (AR): A specialized router usually residing at the edge 298 or boundary of a network. This router ensures the connectivity of 299 its network with external networks, a wide area network or the 300 Internet. 302 Wireless Termination Point (WTP): The physical or network entity that 303 contains an RF antenna and wireless Physical Layer (PHY) to transmit 304 and receive station traffic for wireless access networks. 306 CAPWAP Control Channel: A bi-directional flow defined by the AC IP 307 Address, WTP IP Address, AC control port, WTP control port, and the 308 transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Control 309 packets are sent and received. 311 CAPWAP Data Channel: A bi-directional flow defined by the AC IP 312 Address, WTP IP Address, AC data port, WTP data port, and the 313 transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Data 314 packets are sent and received. In certain WTP modes, the CAPWAP Data 315 Channel only transports IEEE 802.11 management frames and not the 316 data plane (user traffic). 318 1.3. History of the document 320 This document was started to accommodate Service Provider's need of a 321 more flexible deployment mode with alternative tunnels [RFC7494]. 322 Experiments and tests have been done for this alt-tunnel network 323 infrastructure. However important, the deployment of relevant 324 technology is yet to complete. This experimental document is 325 intended to serve as an archival record for any future work as to the 326 operational and deployment requirements. 328 2. Alternate Tunnel Encapsulation Overview 329 +-+-+-+-+-+-+ +-+-+-+-+-+-+ 330 | WTP | | AC | 331 +-+-+-+-+-+-+ +-+-+-+-+-+-+ 332 |Join Request [ Supported Alternate | 333 | Tunnel Encapsulations ] | 334 |---------------------------------------->| 335 | | 336 |Join Response | 337 |<----------------------------------------| 338 | | 339 |IEEE 802.11 WLAN Configuration Request [ | 340 | IEEE 802.11 Add WLAN, | 341 | Alternate Tunnel Encapsulation ( | 342 | Tunnel Type, Tunnel Info Element) | 343 | ] | 344 |<----------------------------------------| 345 | | 346 | | 347 +-+-+-+-+-+-+ | 348 | Setup | | 349 | Alternate | | 350 | Tunnel | | 351 +-+-+-+-+-+-+ | 352 |IEEE 802.11 WLAN Configuration Response | 353 |[ Alternate Tunnel Encapsulation ( | 354 | Tunnel Type, Tunnel Info Element) ] | 355 |---------------------------------------->| 356 | | 357 | | 358 +-+-+-+-+-+-+ | 359 | Tunnel | | 360 | Failure | | 361 +-+-+-+-+-+-+ | 362 |WTP Alternate Tunnel Failure Indication | 363 |(report failure (AR address(es))) | 364 |---------------------------------------->| 365 | | 366 +-+-+-+-+-+-+-+ | 367 | Tunnel | | 368 | Established | | 369 +-+-+-+-+-+-+-+ | 370 |WTP Alternate Tunnel Failure Indication | 371 |(report clearing failure) | 372 |---------------------------------------->| 373 | | 375 Figure 5: Setup of Alternate Tunnel 377 The above example describes how the alternate tunnel encapsulation 378 may be established. When the WTP joins the AC, it should indicate 379 its alternate tunnel encapsulation capability. The AC determines 380 whether an alternate tunnel configuration is required. If an 381 appropriate alternate tunnel type is selected, then the AC provides 382 the alternate tunnel encapsulation message element containing the 383 tunnel type and a tunnel-specific information element. The tunnel- 384 specific information element, for example, may contain information 385 like the IP address of the tunnel termination point. The WTP sets up 386 the alternate tunnel using the alternate tunnel encapsulation message 387 element. 389 Since AC can configure a WTP with more than one AR available for the 390 WTP to establish the data tunnel(s) for user traffic, it may be 391 useful for the WTP to communicate the selected AR. To enable this, 392 the IEEE 802.11 WLAN Configuration Response may carry the alternate 393 tunnel encapsulation message element containing the AR list element 394 corresponding to the selected AR as shown in Figure 5. 396 On detecting a tunnel failure, WTP SHALL forward data frames to the 397 AC and discard the frames. In addition, WTP may dissociate existing 398 clients and refuse association requests from new clients. Depending 399 on the implementation and deployment scenario, the AC may choose to 400 reconfigure the WLAN (on the WTP) to a local bridging mode or to 401 tunnel frames to the AC. When the WTP detects an alternate tunnel 402 failure, the WTP informs the AC using a message element, WTP 403 Alternate Tunnel Fail Indication (defined in this specification). It 404 MAY be carried in the WTP Event Request message which is defined in 405 [RFC5415]. 407 The WTP also needs to notify the AC of which AR(s) are unavailable. 408 Particularly, in the VNO scenario, the AC of the WLAN service 409 provider needs to maintain the association of the AR addresses of the 410 VNOs and SSIDs, and provide this information to the WTP for the 411 purpose of load balancing or master-slave mode. 413 The message element has a status field that indicates whether the 414 message denotes reporting a failure or the clearing of the previously 415 reported failure. 417 For the case where AC is unreachable but the tunnel end point is 418 still reachable, the WTP behavior is up to the implementation. For 419 example, the WTP could either choose to tear down the alternate 420 tunnel or let the existing user's traffic continue to be tunneled. 422 3. CAPWAP Protocol Message Elements Extensions 424 3.1. Supported Alternate Tunnel Encapsulations 426 This message element is sent by a WTP to communicate its capability 427 to support alternate tunnel encapsulations. The message element 428 contains the following fields: 430 0 1 2 3 431 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 1 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 | Tunnel-Type 1 | Tunnel-Type 2 | 434 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 435 | ... | Tunnel-Type N | 436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 438 Figure 6: Supported Alternate Tunnel Encapsulations 440 o Type: for Supported Alternate Tunnel Encapsulations 441 o Length: The length in bytes, two bytes for each Alternative tunnel 442 type that is included 443 o Tunnel-Type: This is identified by value defined in Section 3.2. 444 There may be one or more Tunnel-Types as shows in Figure 6. 446 3.2. Alternate Tunnel Encapsulations Type 448 This message element can be sent by the AC. This message element 449 allows the AC to select the alternate tunnel encapsulation. This 450 message element may be provided along with the IEEE 802.11 Add WLAN 451 message element. When the message element is present, the following 452 fields of the IEEE 802.11 Add WLAN element SHALL be set as follows: 453 MAC mode is set to 0 (Local MAC) and Tunnel Mode is set to 0 (Local 454 Bridging). Besides, the message element can also be sent by the WTP 455 to communicate the selected AR(s). 457 The message element contains the following fields: 459 0 1 2 3 460 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 1 461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 462 | Tunnel-Type | Info Element Length | 463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 464 | Info Element 465 +-+-+-+-+-+-+-+-+-+ 467 Figure 7: Alternate Tunnel Encapsulations Type 469 o Type: for Alternate Tunnel Encapsulation Type 470 o Length: > 4 471 o Tunnel-Type: The tunnel type is specified by a 2 byte value. This 472 specification defines the values from zero (0) to six (6) as given 473 below. The remaining values are reserved for future use. 475 * 0: CAPWAP. This refers to a CAPWAP data channel described in 476 [RFC5415] and [RFC5416]. 477 * 1: L2TP. This refers to tunnel encapsulation described in 478 [RFC2661]. 479 * 2: L2TPv3. This refers to tunnel encapsulation described in 480 [RFC3931]. 481 * 3: IP-in-IP. This refers to tunnel encapsulation described in 482 [RFC2003]. 483 * 4: PMIPv6-UDP. This refers to the UDP tunneling encapsulation 484 described in [RFC5844]. 485 * 5: GRE. This refers to GRE tunnel encapsulation as described 486 in [RFC2784]. 487 * 6: GTPv1-U. This refers to GTPv1 user plane mode as described 488 in [TS29281]. 489 o Info Element: This field contains tunnel specific configuration 490 parameters to enable the WTP to setup the alternate tunnel. This 491 specification provides details for this elements for CAPWAP, 492 PMIPv6, and GRE. This specification reserves the tunnel type 493 values for the key tunnel types and defines the most common 494 message elements. It is anticipated that message elements for the 495 other protocols (like L2TPv3, etc.) will be defined in other 496 specifications in the future. 498 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication 500 The WTP MAY include the Alternate Tunnel Failure Indication message 501 in a WTP Event Request message to inform the AC about the status of 502 the Alternate Tunnel. For the case where WTP establishes data 503 tunnels with multiple ARs (e.g., under VNO scenario), the WTP needs 504 to notify the AC of which AR(s) are unavailable. The message element 505 contains the following fields: 507 0 1 2 3 508 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 1 509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 510 | WLAN ID | Status | Reserved | 511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 512 . Access Router Information Element . 513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 Figure 8: IEEE 802.11 WTP Alternate Tunnel Failure Indication 517 o Type: for IEEE 802.11 WTP Alternate Tunnel Failure 518 Indication 519 o Length: > 4 520 o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value 521 MUST be between one (1) and 16. 522 o Status: An 8-bit boolean indicating whether the radio failure is 523 being reported or cleared. A value of zero is used to clear the 524 event, while a value of one is used to report the event. 525 o Reserved: MUST be set to a value of 0 and MUST be ignored by the 526 receiver. 527 o Access Router Information Element: IPv4 address or IPv6 address of 528 the Access Router that terminates the alternate tunnel. The 529 Access Router Information Elements allow the WTP to notify the AC 530 of which AR(s) are unavailable. 532 4. Alternate Tunnel Types 534 4.1. CAPWAP based Alternate Tunnel 536 If the CAPWAP encapsulation is selected by the AC and configured by 537 the AC to the WTP, the Info Element field defined in Section 3.2 538 SHOULD contain the following information: 540 o Access Router Information: IPv4 address or IPv6 address of the 541 Access Router for the alternate tunnel. 542 o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection 543 of data packets using DTLS. Use of data packet protection on a 544 WTP is not mandatory but determined by the associated AC policy 545 (This is consistent with the WTP behavior described in [RFC5415]). 546 o IEEE 802.11 Tagging Mode Policy: It is used to specify how the 547 CAPWAP data channel packet are to be tagged for QoS purposes (see 548 [RFC5416] for more details). 549 o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP 550 and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for 551 the CAPWAP data channels. When run over IPv6, the CAPWAP data 552 channel may use either UDP or UDP-lite. 554 The message element structure for CAPWAP encapsulation is shown in 555 Figure 9: 557 0 1 2 3 558 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 1 559 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 | Tunnel-Type=0 | Info Element Length | 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 . Access Router Information Element . 563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 564 . Tunnel DTLS Policy Element . 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 . IEEE 802.11 Tagging Mode Policy Element . 567 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 568 . CAPWAP Transport Protocol Element . 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 571 Figure 9: Alternate Tunnel Encapsulation - CAPWAP 573 4.2. PMIPv6 based Alternate Tunnel 575 Proxy Mobile IPv6 (PMIPv6) (defined in [RFC5213]) based user plane 576 can also be used as alternate tunnel encapsulation between the WTP 577 and the AR. In this scenario, a WTP acts as the Mobile Access 578 Gateway (MAG) function that manages the mobility-related signaling 579 for a station that is attached to the WTP IEEE 802.11 radio access. 580 The Local Mobility Anchor (LMA) function is at the AR. If PMIPv6 UDP 581 encapsulation is selected by the AC and configured by the AC to a 582 WTP, the Info Element field defined in Section 3.2 SHOULD contain the 583 following information: 585 o Access Router (acting as LMA) Information: IPv4 or IPv6 address 586 for the alternate tunnel endpoint. 588 The message element structure for PMIPv6 encapsulation is shown in 589 Figure 10: 591 0 1 2 3 592 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 1 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Tunnel-Type=4 | Info Element Length | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 . Access Router Information Element . 597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 Figure 10: Alternate Tunnel Encapsulation - PMIPv6 601 4.3. GRE based Alternate Tunnel 603 Generic Routing Encapsulation (defined in [RFC2784]) mode based user 604 plane can also be used as alternate tunnel encapsulation between the 605 WTP and the AR. In this scenario, a WTP and the access router 606 represent the two end points of the GRE tunnel. If GRE encapsulation 607 is selected by the AC and configured by the AC to a WTP, the Info 608 Element field defined in Section 3.2 SHOULD contain the following 609 information: 611 o Access Router Information: IPv4 or IPv6 address for the alternate 612 tunnel endpoint. 613 o GRE Key Information: The Key field is intended to be used for 614 identifying an individual traffic flow within a tunnel [RFC2890]. 616 The message element structure for GRE encapsulation is shown in 617 Figure 11: 619 0 1 2 3 620 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 1 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 622 | Tunnel-Type=5 | Info Element Length | 623 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 624 . Access Router Information Element . 625 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 626 . GRE Key Element . 627 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 Figure 11: Alternate Tunnel Encapsulation - GRE 631 5. Alternate Tunnel Information Elements 633 This section defines the various elements described in Section 4.1, 634 Section 4.2, and Section 4.3. 636 These information elements can only be included in the Alternate 637 Tunnel Encapsulations Type message element, and the IEEE 802.11 WTP 638 Alternate Tunnel Failure Indication message element as their sub- 639 elements. 641 5.1. Access Router Information Elements 643 The Access Router Information Elements allow the AC to notify a WTP 644 of which AR(s) are available for establishing a data tunnel. The AR 645 information may be IPv4 address, or IPv6 address.This information 646 element SHOULD be contained whatever the tunnel type is. 648 If the Alternate Tunnel Encapsulations Type message element is sent 649 by the WTP to communicate the selected AR(s), this Access Router 650 Information Element SHOULD be contained. 652 The following are the Access Router Information Elements defined in 653 this specification. The AC can use one of them to notify the 654 destination information of the data tunnel to the WTP. The Elements 655 containing the AR IPv4 address MUST NOT be used if an IPv6 data 656 channel with IPv6 transport is used. 658 5.1.1. AR IPv4 List Element 660 This Element (see Figure 12) is used by the AC to configure a WTP 661 with the AR IPv4 address available for the WTP to establish the data 662 tunnel for user traffic. 664 0 1 2 3 665 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 1 666 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 667 | AR IPv4 Element Type | Length | 668 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 669 . AR IPv4 Address-1 . 670 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 671 . AR IPv4 Address-2 . 672 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 673 . AR IPv4 Address-N . 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 676 Figure 12: AR IPv4 List Element 678 Type: 0 680 Length: This refers to the total length in octets of the element 681 excluding the Type and Length fields. 683 AR IPv4 Address: The IPv4 address of the AR. At least one IPv4 684 address SHALL be present. Multiple addresses may be provided for 685 load balancing or redundancy. 687 5.1.2. AR IPv6 List Element 689 This Element (see Figure 13) is used by the AC to configure a WTP 690 with the AR IPv6 address available for the WTP to establish the data 691 tunnel for user traffic. 693 0 1 2 3 694 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 1 695 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 696 | AR IPv6 Element Type | Length | 697 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 698 . AR IPv6 Address-1 . 699 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 700 . AR IPv6 Address-2 . 701 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 702 . AR IPv6 Address-N . 703 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 Figure 13: AR IPv6 List Element 707 Type: 1 709 Length: This refers to the total length in octets of the element 710 excluding the Type and Length fields. 712 AR IPv6 Address: The IPv6 address of the AR. At least one IPv6 713 address SHALL be present. Multiple addresses may be provided for 714 load balancing or redundancy. 716 5.2. Tunnel DTLS Policy Element 718 The AC distributes its DTLS usage policy for the CAPWAP data tunnel 719 between a WTP and the AR. There are multiple supported options, 720 represented by the bit field below as defined in AC Descriptor 721 message elements. The WTP MUST abide by one of the options for 722 tunneling user traffic with AR. The Tunnel DTLS Policy Element obeys 723 the definition in [RFC5415]. If, for reliability reasons, the AC has 724 provided more than one AR address in the Access Router Information 725 Element, the same Tunnel DTLS Policy (the last one in Figure 14) is 726 generally applied for all tunnels associated with those ARs. 727 Otherwise, Tunnel DTLS Policy MUST be bonded together with each of 728 the Access Router Information Elements, and the WTP will enforce the 729 independent tunnel DTLS policy for each tunnel with a specific AR. 731 0 1 2 3 732 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 1 733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 734 |Tunnel DTLS Policy Element Type| Length | 735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 | Reserved |D|C|R| 737 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 738 . AR Information . 739 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 740 | Reserved |D|C|R| 741 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 742 . AR Information . 743 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 744 . ...... . 745 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 746 | Reserved |D|C|R| 747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 749 Figure 14: Tunnel DTLS Policy Element 751 Type: 2 753 Length: This refers to the total length in octets of the element 754 excluding the Type and Length fields. 756 Reserved: A set of reserved bits for future use. All implementations 757 complying with this protocol MUST set to zero any bits that are 758 reserved in the version of the protocol supported by that 759 implementation. Receivers MUST ignore all bits not defined for the 760 version of the protocol they support. 762 D: DTLS-Enabled Data Channel Supported (see [RFC5415]). 764 C: Clear Text Data Channel Supported (see [RFC5415]). 766 R: A reserved bit for future use (see [RFC5415]). 768 AR Information: This means Access Router Information Element. In 769 this context, each address in AR information MUST be one of 770 previously specified AR addresses. 772 The last element having no AR Information in Figure 14 is the default 773 tunnel DTLS policy, and provides options for any address not 774 previously mentioned. Therefore, the AR information field here is 775 optional. If all ARs share the same tunnel DTLS policy, in this 776 element, there will not be AR information field and its specific 777 tunnel DTLS policy. 779 5.3. IEEE 802.11 Tagging Mode Policy Element 781 In 802.11 networks, IEEE 802.11 Tagging Mode Policy Element is used 782 to specify how the WTP applies the QoS tagging policy when receiving 783 the packets from stations on a particular radio. When the WTP sends 784 out the packet to data channel to the AR(s), the packets have to be 785 tagged for QoS purposes (see [RFC5416]). 787 The IEEE 802.11 Tagging Mode Policy abides the IEEE 802.11 WTP 788 Quality of Service defined in Section 6.22 of [RFC5416]. 790 If, for reliability reasons, the AC has provided more than one AR 791 address in the Access Router Information Element, the same IEEE 792 802.11 Tagging Mode Policy (the last one in Figure 15) is generally 793 applied for all tunnels associated with those ARs. Otherwise, IEEE 794 802.11 Tagging Mode Policy MUST be bonded together with each of the 795 Access Router Information Elements, and the WTP will enforce the 796 independent IEEE 802.11 Tagging Mode Policy for each tunnel with a 797 specific AR. 799 0 1 2 3 800 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 1 801 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 802 | Tagging Mode Policy Ele. Type | Length | 803 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 804 | Reserved |P|Q|D|O|I| 805 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 806 . AR Information . 807 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 808 | Reserved |P|Q|D|O|I| 809 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 810 . AR Information . 811 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 812 . ...... . 813 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 814 | Reserved |P|Q|D|O|I| 815 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 817 Figure 15: IEEE 802.11 Tagging Mode Policy Element 819 Type: 3 821 Length: This refers to the total length in octets of the element 822 excluding the Type and Length fields. 824 Reserved: A set of reserved bits for future use. 826 P: When set, the WTP is to employ the 802.1p QoS mechanism (see 827 [RFC5416]). 829 Q: When the 'P' bit is set, the 'Q' bit is used by the AC to 830 communicate to the WTP how 802.1p QoS is to be enforced (see 831 [RFC5416]). 833 D: When set, the WTP is to employ the DSCP QoS mechanism (see 834 [RFC5416]). 836 O: When the 'D' bit is set, the 'O' bit is used by the AC to 837 communicate to the WTP how DSCP QoS is to be enforced on the outer 838 (tunneled) header (see [RFC5416]). 840 I: When the 'D' bit is set, the 'I' bit is used by the AC to 841 communicate to the WTP how DSCP QoS is to be enforced on the 842 station's packet (inner) header (see [RFC5416]). 844 AR Information: This means Access Router Information Element. In 845 this context, each address in AR information MUST be one of 846 previously specified AR addresses. 848 The last element having no AR Information in Figure 15 is the default 849 IEEE 802.11 Tagging Mode Policy, and provides options for any address 850 not previously mentioned. Therefore, the AR information field here 851 is optional. If all ARs share the same IEEE 802.11 Tagging Mode 852 Policy, in this element, there will not be AR information field and 853 its specific IEEE 802.11 Tagging Mode Policy. 855 5.4. CAPWAP Transport Protocol Element 857 The CAPWAP data tunnel supports both UDP and UDP-Lite (see 858 [RFC3828]). When run over IPv4, UDP is used for the CAPWAP data 859 channels. When run over IPv6, the CAPWAP data channel may use either 860 UDP or UDP-lite. The AC specifies and configures the WTP for which 861 transport protocol is to be used for the CAPWAP data tunnel. 863 The CAPWAP Transport Protocol Element abides the definition in 864 Section 4.6.14 of [RFC5415]. 866 If, for reliability reasons, the AC has provided more than one AR 867 address in the Access Router Information Element, the same CAPWAP 868 Transport Protocol (the last one in Figure 16) is generally applied 869 for all tunnels associated with those ARs. Otherwise, CAPWAP 870 Transport Protocol MUST be bonded together with each of the Access 871 Router Information Elements, and the WTP will enforce the independent 872 CAPWAP Transport Protocol for each tunnel with a specific AR. 874 0 1 2 3 875 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 1 876 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 877 | Type=4 | Length | 878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 879 | Transport | Reserved | 880 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 881 . AR Information . 882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 883 | Transport | Reserved | 884 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 885 . AR Information . 886 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 887 . ...... . 888 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 889 | Transport | Reserved | 890 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 892 Figure 16: CAPWAP Transport Protocol Element 894 Type: 4 896 Length: 1 898 Transport: The transport to use for the CAPWAP Data channel. The 899 following enumerated values are supported: 901 1 - UDP-Lite: The UDP-Lite transport protocol is to be used for the 902 CAPWAP Data channel. Note that this option MUST NOT be used if the 903 CAPWAP Control channel is being used over IPv4 and AR address is IPv4 904 contained in the AR Information Element. 906 2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data 907 channel. 909 AR Information: This means Access Router Information Element. In 910 this context, each address in AR information MUST be one of 911 previously specified AR addresses. 913 The last element having no AR Information in Figure 16 is the default 914 CAPWAP Transport Protocol, and provides options for any address not 915 previously mentioned. Therefore, the AR information field here is 916 optional. If all ARs share the same CAPWAP Transport Protocol, in 917 this element, there will not be AR information field and its specific 918 CAPWAP Transport Protocol. 920 5.5. GRE Key Element 922 If a WTP receives the GRE Key Element in the Alternate Tunnel 923 Encapsulation message element for GRE selection, the WTP MUST insert 924 the GRE Key to the encapsulation packet (see [RFC2890]). An AR 925 acting as decapsulating tunnel endpoint identifies packets belonging 926 to a traffic flow based on the Key value. 928 The GRE Key Element field contains a four octet number defined in 929 [RFC2890]. 931 If, for reliability reasons, the AC has provided more than one AR 932 address in the Access Router Information Element, a GRE Key Element 933 MAY be bonded together with each of the Access Router Information 934 Elements, and the WTP will enforce the independent GRE Key for each 935 tunnel with a specific AR. 937 0 1 2 3 938 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 1 939 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 940 | GRE Key Element Type | Length | 941 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 942 | GRE Key | 943 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 944 . AR Information . 945 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 946 | GRE Key | 947 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 948 . AR Information . 949 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 950 . ...... . 951 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 953 Figure 17: GRE Key Element 955 Type: 5 957 Length: This refers to the total length in octets of the element 958 excluding the Type and Length fields. 960 GRE Key: The Key field contains a four octet number which is inserted 961 by the WTP according to [RFC2890]. 963 AR Information: This means Access Router Information Element. In 964 this context, it SHOULD be restricted to a single address, and MUST 965 be the address of one of previously specified AR addresses. 967 Any address not explicitly mentioned here does not have a GRE key. 969 5.6. IPv6 MTU Element 971 If AC has chosen a tunneling mechanism based on IPv6, it SHOULD 972 support the minimum IPv6 MTU requirements [RFC8200]. This issue is 973 described in [I-D.ietf-intarea-tunnels]. AC SHOULD inform the WTP 974 about the IPv6 MTU information in the "Tunnel Info Element" field. 976 If, for reliability reasons, the AC has provided more than one AR 977 address in the Access Router Information Element, an IPv6 MTU Element 978 MAY be bonded together with each of the Access Router Information 979 Elements, and the WTP will enforce the independent IPv6 MTU for each 980 tunnel with a specific AR. 982 0 1 2 3 983 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 1 984 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 985 | IPv6 MTU Element Type | Length | 986 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 987 | Minimum IPv6 MTU | Reserved | 988 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 989 . AR Information . 990 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 991 | Minimum IPv6 MTU | Reserved | 992 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 993 . AR Information . 994 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 995 | ...... | 996 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 998 Figure 18: IPv6 MTU Element 1000 Type: 6 1002 Length: This refers to the total length in octets of the element 1003 excluding the Type and Length fields. 1005 Minimum IPv6 MTU: The field contains a two octet number indicate the 1006 minimum IPv6 MTU in the tunnel. 1008 AR Information: This means Access Router Information Element. In 1009 this context, each address in AR information MUST be one of 1010 previously specified AR addresses. 1012 6. IANA Considerations 1014 This document requires the following IANA considerations. 1016 o . This specification defines the Supported Alternate 1017 Tunnel Encapsulations Type message element in Section 3.1. This 1018 elements needs to be registered in the existing CAPWAP Message 1019 Element Type registry, defined in [RFC5415]. The Type value for 1020 this element needs to be between 1 and 1023 (see Section 15.7 in 1021 [RFC5415]). 1022 o . This specification defines the Alternate Tunnel 1023 Encapsulations Type message element in Section 3.2. This element 1024 needs to be registered in the existing CAPWAP Message Element Type 1025 registry, defined in [RFC5415]. The Type value for this element 1026 needs to be between 1 and 1023. 1027 o . This specification defines the IEEE 802.11 WTP 1028 Alternate Tunnel Failure Indication message element in 1029 Section 3.3. This element needs to be registered in the existing 1030 CAPWAP Message Element Type registry, defined in [RFC5415]. The 1031 Type value for this element needs to be between 1024 and 2047. 1032 o Alternate Tunnel-Types Registry: This specification defines the 1033 Alternate Tunnel Encapsulations Type message element. This 1034 element contains a field Tunnel-Type. The namespace for the field 1035 is 16 bits (0-65535). This specification defines values, zero (0) 1036 through six (6) and can be found in Section 3.2. Future 1037 allocations of values in this name space are to be assigned by 1038 IANA using the "Specification Required" policy. IANA needs to 1039 create a registry called CAPWAP Alternate Tunnel-Types. The 1040 registry format is given below. 1042 Tunnel-Type Type Value Reference 1043 CAPWAP 0 [RFC5415],[RFC5416] 1044 L2TP 1 [RFC2661] 1045 L2TPv3 2 [RFC3931] 1046 IP-IP 3 [RFC2003] 1047 PMIPv6-UDP 4 [RFC5844] 1048 GRE 5 [RFC2784] 1049 GTPv1-U 6 [3GPP TS 29.281] 1051 o Alternate Tunnel Sub-elements Registry: This specification defines 1052 the Alternate Tunnel Sub-elements. Currently, these information 1053 elements can only be included in the Alternate Tunnel 1054 Encapsulations Type message element, and the IEEE 802.11 WTP 1055 Alternate Tunnel Failure Indication message element as their sub- 1056 elements. These information elements contains a Type field. The 1057 namespace for the field is 16 bits (0-65535). This specification 1058 defines values, zero (0) through six (6) in Section 5. This 1059 namespace is managed by IANA and assignments require an Expert 1060 Review. 1062 Type Type Value 1063 AR IPv4 List 0 1064 AR IPv6 List 1 1065 Tunnel DTLS Policy 2 1066 IEEE 802.11 Tagging Mode Policy 3 1067 CAPWAP Transport Protocol 4 1068 GRE Key 5 1069 IPv6 MTU 6 1071 7. Security Considerations 1073 This document introduces three new CAPWAP WTP message elements. 1074 These elements are transported within CAPWAP Control messages as the 1075 existing message elements. Therefore, this document does not 1076 introduce any new security risks to the control plane compared to 1077 [RFC5415] and [RFC5416]. In the data plane, if the encapsulation 1078 type selected itself is not secured, it is suggested to protect the 1079 tunnel by using known secure methods, such as IPSec. 1081 8. Contributors 1083 The authors would like to thank Andreas Schultz, Hong Liu, Yifan 1084 Chen, Chunju Shao, Li Xue, Jianjie You, Jin Li, Joe Touch, Alexey 1085 Melnikov, Kathleen Moriarty, Mirja Kuehlewind, Catherine Meadows, and 1086 Paul Kyzivat for their valuable comments. 1088 9. References 1090 9.1. Normative References 1092 [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, 1093 DOI 10.17487/RFC2003, October 1996, 1094 . 1096 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1097 Requirement Levels", BCP 14, RFC 2119, 1098 DOI 10.17487/RFC2119, March 1997, 1099 . 1101 [RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, 1102 G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"", 1103 RFC 2661, DOI 10.17487/RFC2661, August 1999, 1104 . 1106 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1107 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1108 DOI 10.17487/RFC2784, March 2000, 1109 . 1111 [RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE", 1112 RFC 2890, DOI 10.17487/RFC2890, September 2000, 1113 . 1115 [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed., 1116 and G. Fairhurst, Ed., "The Lightweight User Datagram 1117 Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July 1118 2004, . 1120 [RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed., 1121 "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", 1122 RFC 3931, DOI 10.17487/RFC3931, March 2005, 1123 . 1125 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1126 Ed., "Control And Provisioning of Wireless Access Points 1127 (CAPWAP) Protocol Specification", RFC 5415, 1128 DOI 10.17487/RFC5415, March 2009, 1129 . 1131 [RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1132 Ed., "Control and Provisioning of Wireless Access Points 1133 (CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416, 1134 DOI 10.17487/RFC5416, March 2009, 1135 . 1137 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1138 (IPv6) Specification", STD 86, RFC 8200, 1139 DOI 10.17487/RFC8200, July 2017, 1140 . 1142 9.2. Informative References 1144 [I-D.ietf-intarea-tunnels] 1145 Touch, J. and M. Townsley, "IP Tunnels in the Internet 1146 Architecture", draft-ietf-intarea-tunnels-07 (work in 1147 progress), June 2017. 1149 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1150 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1151 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1152 . 1154 [RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy 1155 Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010, 1156 . 1158 [RFC7494] Shao, C., Deng, H., Pazhyannur, R., Bari, F., Zhang, R., 1159 and S. Matsushima, "IEEE 802.11 Medium Access Control 1160 (MAC) Profile for Control and Provisioning of Wireless 1161 Access Points (CAPWAP)", RFC 7494, DOI 10.17487/RFC7494, 1162 April 2015, . 1164 [TS29281] "3rd Generation Partnership Project; Technical 1165 Specification Group Core Network and Terminals; General 1166 Packet Radio System (GPRS) Tunnelling Protocol User Plane 1167 (GTPv1-U)", 2016. 1169 Authors' Addresses 1171 Rong Zhang 1172 China Telecom 1173 No.109 Zhongshandadao avenue 1174 Guangzhou 510630 1175 China 1177 Email: zhangr@gsta.com 1179 Rajesh S. Pazhyannur 1180 Cisco 1181 170 West Tasman Drive 1182 San Jose, CA 95134 1183 USA 1185 Email: rpazhyan@cisco.com 1187 Sri Gundavelli 1188 Cisco 1189 170 West Tasman Drive 1190 San Jose, CA 95134 1191 USA 1193 Email: sgundave@cisco.com 1195 Zhen Cao 1196 Huawei 1197 Xinxi Rd. 3 1198 Beijing 100085 1199 China 1201 Email: zhencao.ietf@gmail.com 1202 Hui Deng 1203 Huawei 1204 Xinxi Rd. 3 1205 Beijing 100085 1206 China 1208 Email: denghui02@gmail.com 1210 Zongpeng Du 1211 Huawei 1212 No.156 Beiqing Rd. Z-park, HaiDian District 1213 Beijing 100095 1214 China 1216 Email: duzongpeng@huawei.com