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Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) == Outdated reference: A later version (-13) exists of draft-ietf-intarea-tunnels-07 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--).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: March 9, 2018 S. Gundavelli 6 Cisco 7 Z. Cao 8 H. Deng 9 Z. Du 10 Huawei 11 September 5, 2017 13 Alternate Tunnel Encapsulation for Data Frames in CAPWAP 14 draft-ietf-opsawg-capwap-alt-tunnel-10 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 March 9, 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 . . . . . . . . . 18 90 5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20 91 5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 20 92 5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 21 93 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 94 7. Security Considerations . . . . . . . . . . . . . . . . . . . 23 95 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23 96 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 97 9.1. Normative References . . . . . . . . . . . . . . . . . . 23 98 9.2. Informative References . . . . . . . . . . . . . . . . . 24 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 101 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 system in Figure 2. 1) They do not 191 allow the WTP to tunnel data frames to an endpoint different from the 192 AC and 2) They do not allow the WTP to tunnel data frames using any 193 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 such as L2TP, L2TPv3, IP-in- 199 IP, IP/GRE, etc. This enables 1) independent scaling of data plane 200 and 2) leveraging of commonly used tunnel encapsulations such as 201 L2TP, GRE, 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-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 frame. 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, 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. AC can notify multiple AR addresses for 255 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 a historical reference for any future work as to 326 the operational and deployment requirements.. 328 2. Alternate Tunnel Encapsulation Overview 329 +-+-+-+-+-+-+ +-+-+-+-+-+-+ 330 | WTP | | AC | 331 +-+-+-+-+-+-+ +-+-+-+-+-+-+ 332 |Join Request[Supported Alternate Tunnel | 333 | Encapsulations ] | 334 |---------------------------------------->| 335 | | 336 |Join Response | 337 |<----------------------------------------| 338 | | 339 |IEEE 802.11 WLAN Config. 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 | | 353 |IEEE 802.11 WLAN Config. Response | 354 |---------------------------------------->| 355 | | 356 | | 357 +-+-+-+-+-+-+ | 358 | Tunnel | | 359 | Failure | | 360 +-+-+-+-+-+-+ | 361 |WTP Alternate Tunnel Failure Indication | 362 |(report failure (AR address(es))) | 363 |---------------------------------------->| 364 | | 365 +-+-+-+-+-+-+-+ | 366 | Tunnel | | 367 | Established | | 368 +-+-+-+-+-+-+-+ | 369 |WTP Alternate Tunnel Failure Indication | 370 |(report clearing failure) | 371 |---------------------------------------->| 372 | | 374 Figure 5: Setup of Alternate Tunnel 376 The above example describes how the alternate tunnel encapsulation 377 may be established. When the WTP joins the AC, it should indicate 378 its alternate tunnel encapsulation capability. The AC determines 379 whether an alternate tunnel configuration is required. If an 380 appropriate alternate tunnel type is selected, then the AC provides 381 the alternate tunnel encapsulation message element containing the 382 tunnel type and a tunnel-specific information element. The tunnel- 383 specific information element, for example, may contain information 384 like the IP address of the tunnel termination point. The WTP sets up 385 the alternate tunnel using the alternate tunnel encapsulation message 386 element. 388 Since AC can configure a WTP with more than one AR available for the 389 WTP to establish the data tunnel(s) for user traffic, it may be 390 useful for the WTP to communicate the selected AR. To enable this, 391 the IEEE 802.11 WLAN Configuration Response may contain the AR list 392 element containing the selected AR. 394 On detecting a tunnel failure, WTP SHALL forward data frames to the 395 AC and discard the frames. In addition, WTP may dissociate existing 396 clients and refuse association requests from new clients. Depending 397 on the implementation and deployment scenario, the AC may choose to 398 reconfigure the WLAN (on the WTP) to a local bridging mode or to 399 tunnel frames to the AC. When the WTP detects an alternate tunnel 400 failure, the WTP informs the AC using a message element, WTP 401 Alternate Tunnel Fail Indication (defined in this specification). It 402 MAY be carried in the CAPWAP Station Configuration Request message 403 which is defined in [RFC5415]. 405 The WTP also needs to notify the AC of which AR(s) are unavailable. 406 Particularly, in the VNO scenario, the AC of the WLAN service 407 provider needs to maintain the association of the AR addresses of the 408 VNOs and SSIDs, and provide this information to the WTP for the 409 purpose of load balancing or master-slave mode. 411 The message element has a status field that indicates whether the 412 message denotes reporting a failure or the clearing of the previously 413 reported failure. 415 For the case where AC is unreachable but the tunnel end point is 416 still reachable, the WTP behavior is up to the implementation. For 417 example, the WTP could either choose to tear down the alternate 418 tunnel or let the existing user's traffic continue to be tunneled. 420 3. CAPWAP Protocol Message Elements Extensions 422 3.1. Supported Alternate Tunnel Encapsulations 424 This message element is sent by a WTP to communicate its capability 425 to support alternate tunnel encapsulations. The message element 426 contains the following fields: 428 0 1 2 3 429 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 1 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 431 | Tunnel-Type1 | Tunnel-Type [2...N] 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 Figure 6: Supported Alternate Tunnel Encapsulations 436 o Type: for Supported Alternate Tunnel Encapsulations 437 o Length: The length in bytes, two bytes for each Alternative tunnel 438 type that is included 439 o Tunnel-Type: This is identified by value defined in Section 3.2. 441 3.2. Alternate Tunnel Encapsulations Type 443 This message element is sent by the AC. This message element allows 444 the AC to select the alternate tunnel encapsulation. This message 445 element may be provided along with the IEEE 802.11 Add WLAN message 446 element. When the message element is present the following fields of 447 the IEEE 802.11 Add WLAN element SHALL be set as follows: MAC mode is 448 set to 0 (Local MAC) and Tunnel Mode is set to 0 (Local Bridging). 449 The message element contains the following fields: 451 0 1 2 3 452 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 1 453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 454 | Tunnel-Type | Info Element Length | 455 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 456 | Info Element 457 +-+-+-+-+-+-+-+-+-+ 459 Figure 7: Alternate Tunnel Encapsulations Type 461 o Type: for Alternate Tunnel Encapsulation Type 462 o Length: > 4 463 o Tunnel-Type: The tunnel type is specified by a 2 byte value. This 464 specification defines the values from zero (0) to six (6) as given 465 below. The remaining values are reserved for future use. 467 * 0: CAPWAP. This refers to a CAPWAP data channel described in 468 [RFC5415] and [RFC5416]. 469 * 1: L2TP. This refers to tunnel encapsulation described in 470 [RFC2661]. 471 * 2: L2TPv3. This refers to tunnel encapsulation described in 472 [RFC3931]. 473 * 3: IP-in-IP. This refers to tunnel encapsulation described in 474 [RFC2003]. 475 * 4: PMIPv6-UDP. This refers to the UDP tunneling encapsulation 476 described in [RFC5844]. 477 * 5: GRE. This refers to GRE tunnel encapsulation as described 478 in [RFC2784]. 479 * 6: GTPv1-U. This refers to GTPv1 user plane mode as described 480 in [TS29281]. 481 o Info Element: This field contains tunnel specific configuration 482 parameters to enable the WTP to setup the alternate tunnel. This 483 specification provides details for this elements for CAPWAP, 484 PMIPv6, and GRE. This specification reserves the tunnel type 485 values for the key tunnel types and defines the most common 486 message elements. It is anticipated that message elements for the 487 other protocols (like L2TPv3, etc.) will be defined in other 488 specifications in the future. 490 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication 492 The Alternate Tunnel Failure Indication message element is sent by 493 the WTP to inform the AC about the status of the Alternate Tunnel. 494 It MAY be included in the CAPWAP Station Configuration Request 495 message. For the case where WTP establishes data tunnels with 496 multiple ARs (e.g., under VNO scenario), the WTP needs to notify the 497 AC of which AR(s) are unavailable. The message element contains the 498 following fields: 500 0 1 2 3 501 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 1 502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 503 | WLAN ID | Status | Reserved | 504 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 . Access Router Information Element . 506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 508 Figure 8: IEEE 802.11 WTP Alternate Tunnel Failure Indication 510 o Type: for IEEE 802.11 WTP Alternate Tunnel Failure 511 Indication 512 o Length: > 4 513 o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value 514 MUST be between one (1) and 16. 516 o Status: An 8-bit boolean indicating whether the radio failure is 517 being reported or cleared. A value of zero is used to clear the 518 event, while a value of one is used to report the event. 519 o Reserved: MUST be set to a value of 0 and MUST be ignored by the 520 receiver. 521 o Access Router Information Element: IPv4 address or IPv6 address of 522 the Access Router that terminates the alternate tunnel. The 523 Access Router Information Elements allow the WTP to notify the AC 524 of which AR(s) are unavailable. 526 4. Alternate Tunnel Types 528 4.1. CAPWAP based Alternate Tunnel 530 If the CAPWAP encapsulation is selected by the AC and configured by 531 the AC to the WTP, the Info Element field defined in Section 3.2 532 SHOULD contain the following information: 534 o Access Router Information: IPv4 address or IPv6 address of the 535 Access Router for the alternate tunnel. 536 o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection 537 of data packets using DTLS. Use of data packet protection on a 538 WTP is not mandatory but determined by the associated AC policy 539 (This is consistent with the WTP behavior described in [RFC5415]). 540 o IEEE 802.11 Tagging Mode Policy: It is used to specify how the 541 CAPWAP data channel packet are to be tagged for QoS purposes (see 542 [RFC5416] for more details). 543 o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP 544 and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for 545 the CAPWAP data channels. When run over IPv6, the CAPWAP data 546 channel may use either UDP or UDP-lite. 548 The message element structure for CAPWAP encapsulation is shown in 549 Figure 9: 551 0 1 2 3 552 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 1 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | Tunnel-Type=0 | Info Element Length | 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 . Access Router Information Element . 557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 558 . Tunnel DTLS Policy Element . 559 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 560 . IEEE 802.11 Tagging Mode Policy Element . 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 . CAPWAP Transport Protocol Element . 563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 565 Figure 9: Alternate Tunnel Encapsulation - CAPWAP 567 4.2. PMIPv6 based Alternate Tunnel 569 Proxy Mobile IPv6 (PMIPv6) (defined in [RFC5213]) based user plane 570 can also be used as alternate tunnel encapsulation between the WTP 571 and the AR. In this scenario, a WTP acts as the Mobile Access 572 Gateway (MAG) function that manages the mobility-related signaling 573 for a station that is attached to the WTP IEEE 802.11 radio access. 574 The Local Mobility Anchor (LMA) function is at the AR. If PMIPv6 UDP 575 encapsulation is selected by the AC and configured by the AC to a 576 WTP, the Info Element field defined in Section 3.2 SHOULD contain the 577 following information: 579 o Access Router (acts as LMA) Information: IPv4 or IPv6 address for 580 the alternate tunnel endpoint. 582 The message element structure for PMIPv6 encapsulation is shown in 583 Figure 10: 585 0 1 2 3 586 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 1 587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 | Tunnel-Type=4 | Info Element Length | 589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 . Access Router (LMA) Information Element . 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 Figure 10: Alternate Tunnel Encapsulation - PMIPv6 595 4.3. GRE based Alternate Tunnel 597 Generic Routing Encapsulation (defined in [RFC2784]) mode based user 598 plane can also be used as alternate tunnel encapsulation between the 599 WTP and the AR. In this scenario, a WTP and the access routers 600 represent the two end points of the GRE tunnel. If GRE encapsulation 601 is selected by the AC and configured by the AC to a WTP, the Info 602 Element field defined in Section 3.2 SHOULD contain the following 603 information: 605 o Access Router Information: IPv4 or IPv6 address for the alternate 606 tunnel endpoint. 607 o GRE Key Information: The Key field is intended to be used for 608 identifying an individual traffic flow within a tunnel [RFC2890]. 610 The message element structure for GRE encapsulation is shown in 611 Figure 11: 613 0 1 2 3 614 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 1 615 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 616 | Tunnel-Type=5 | Info Element Length | 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 . Access Router Information Element . 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 620 . GRE Key Element . 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 Figure 11: Alternate Tunnel Encapsulation - GRE 625 5. Alternate Tunnel Information Elements 627 This section defines the various elements described in Section 4.1, 628 Section 4.2, and Section 4.3. 630 These information elements can only be inluded in the Alternate 631 Tunnel Encapsulations Type message element, and the IEEE 802.11 WTP 632 Alternate Tunnel Failure Indication message element as their sub- 633 elements. 635 5.1. Access Router Information Elements 637 The Access Router Information Elements allow the AC to notify a WTP 638 of which AR(s) are available for establishing a data tunnel. The AR 639 information may be IPv4 address, or IPv6 address.This information 640 element SHOULD be contained whatever the tunnel type is. 642 The following are the Access Router Information Elements defined in 643 this specification. The AC can use one of them to notify the 644 destination information of the data tunnel to the WTP. The Elements 645 containing the AR IPv4 address MUST NOT be used if an IPv6 data 646 channel with IPv6 transport is used. 648 5.1.1. AR IPv4 List Element 650 This Element (see Figure 12) is used by the AC to configure a WTP 651 with the AR IPv4 address available for the WTP to establish the data 652 tunnel for user traffic. 654 0 1 2 3 655 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 1 656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 | AR IPv4 Element Type | Length | 658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 659 . AR IPv4 Address-1 . 660 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 661 . AR IPv4 Address-2 . 662 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 663 . AR IPv4 Address-N . 664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 Figure 12: AR IPv4 List Element 668 Type: 0 670 Length: This refers to the total length in octets of the element 671 excluding the Type and Length fields. 673 AR IPv4 Address: IPv4 address of the AR. At least one IPv4 address 674 SHALL be present. Multiple addresses may be provided for load 675 balancing or redundancy. 677 5.1.2. AR IPv6 List Element 679 This Element (see Figure 13) is used by the AC to configure a WTP 680 with the AR IPv6 address available for the WTP to establish the data 681 tunnel for user traffic. 683 0 1 2 3 684 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 1 685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 686 | AR IPv6 Element Type | Length | 687 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 688 . AR IPv6 Address-1 . 689 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 690 . AR IPv6 Address-2 . 691 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 692 . AR IPv6 Address-N . 693 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 695 Figure 13: AR IPv6 List Element 697 Type: 1 699 Length: This refers to the total length in octets of the element 700 excluding the Type and Length fields. 702 AR IPv6 Address: IPv6 address of the AR. At least one IPv6 address 703 SHALL be present. Multiple addresses may be provided for load 704 balancing or redundancy. 706 5.2. Tunnel DTLS Policy Element 708 The AC distributes its DTLS usage policy for the CAPWAP data tunnel 709 between a WTP and the AR. There are multiple supported options, 710 represented by the bit field below as defined in AC Descriptor 711 message elements. The WTP MUST abide by one of the options for 712 tunneling user traffic with AR. The Tunnel DTLS Policy Element obeys 713 the definition in [RFC5415]. If there are more than one ARs 714 information provided by the AC for reliability reasons, the same 715 Tunnel DTLS Policy (see Figure 14) is generally applied for all 716 tunnels associated with the ARs. Otherwise, Tunnel DTLS Policy MUST 717 be bonding together with each of the ARs, then WTP will enforce the 718 independent tunnel DTLS policy for each tunnel with a specific AR. 720 0 1 2 3 721 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 1 722 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 723 |Tunnel DTLS Policy Element Type| Length | 724 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 725 | Reserved |A|D|C|R| 726 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 727 . AR Information (optional) . 728 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 730 Figure 14: Tunnel DTLS Policy Element 732 Type: 2 734 Length: This refers to the total length in octets of the element 735 excluding the Type and Length fields. 737 Reserved: A set of reserved bits for future use. All implementations 738 complying with this protocol MUST set to zero any bits that are 739 reserved in the version of the protocol supported by that 740 implementation. Receivers MUST ignore all bits not defined for the 741 version of the protocol they support. 743 A: If A bit is set, there is an AR information associated with the 744 DTLS policy. There may be an array of pairs binding DTLS policy 745 information and AR information contained in the Tunnel DTLS Policy 746 Element. Otherwise, the same Tunnel DTLS Policy (see Figure 14) is 747 generally applied for all tunnels associated with the ARs configured 748 by the AC. 750 D: DTLS-Enabled Data Channel Supported (see [RFC5415]). 752 C: Clear Text Data Channel Supported (see [RFC5415]). 754 R: A reserved bit for future use (see [RFC5415]). 756 5.3. IEEE 802.11 Tagging Mode Policy Element 758 In 802.11 networks, IEEE 802.11 Tagging Mode Policy Element is used 759 to specify how the WTP apply the QoS tagging policy when receiving 760 the packets from stations on a particular radio. When the WTP sends 761 out the packet to data channel to the AR(s), the packets have to be 762 tagged for QoS purposes (see [RFC5416]). 764 The IEEE 802.11 Tagging Mode Policy abides the IEEE 802.11 WTP 765 Quality of Service defined in Section 6.22 of [RFC5416]. 767 If there are more than one ARs information provided by the AC for 768 reliability reasons, the same IEEE 802.11 Tagging Mode Policy (see 769 Figure 15) is generally applied for all tunnels associated with the 770 ARs. Otherwise, IEEE 802.11 Tagging Mode Policy MUST be bonding 771 together with each of the ARs, then WTP will enforce the independent 772 tunnel IEEE 802.11 Tagging Mode Policy for each tunnel with a 773 specific AR. 775 0 1 2 3 776 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 1 777 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 778 | Tagging Mode Policy Ele. Type | Length | 779 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 780 | Reserved |A|P|Q|D|O|I| 781 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 782 . AR Information (optional) . 783 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 785 Figure 15: IEEE 802.11 Tagging Mode Policy Element 787 Type: 3 789 Length: This refers to the total length in octets of the element 790 excluding the Type and Length fields. 792 Reserved: A set of reserved bits for future use. 794 A: If A bit is set, there is an AR information associated with the 795 Tagging Mode policy. There may be an array of pairs binding Tagging 796 Mode policy information and AR information contained in the Tagging 797 Mode Policy Element. Otherwise, the same Tagging Mode Policy (see 798 Figure 15) is generally applied for all tunnels associated with the 799 ARs configured by the AC. 801 P: When set, the WTP is to employ the 802.1p QoS mechanism (see 802 [RFC5416]). 804 Q: When the 'P' bit is set, the 'Q' bit is used by the AC to 805 communicate to the WTP how 802.1p QoS is to be enforced. (see 806 [RFC5416]). 808 D: When set, the WTP is to employ the DSCP QoS mechanism (see 809 [RFC5416]). 811 O: When the 'D' bit is set, the 'O' bit is used by the AC to 812 communicate to the WTP how DSCP QoS is to be enforced on the outer 813 (tunneled) header (see [RFC5416]). 815 I: When the 'D' bit is set, the 'I' bit is used by the AC to 816 communicate to the WTP how DSCP QoS is to be enforced on the 817 station's packet (inner) header (see [RFC5416]). 819 5.4. CAPWAP Transport Protocol Element 821 The CAPWAP data tunnel supports both UDP and UDP-Lite (see 822 [RFC3828]). When run over IPv4, UDP is used for the CAPWAP data 823 channels. When run over IPv6, the CAPWAP data channel may use either 824 UDP or UDP-lite. The AC specifies and configure the WTP for which 825 transport protocol is to be used for the CAPWAP data tunnel. 827 The CAPWAP Transport Protocol Element abides the definition in 828 Section 4.6.14 of [RFC5415]. 830 0 1 2 3 831 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 1 832 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 833 | Type=4 | Length | 834 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 835 | Transport | 836 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 838 Figure 16: CAPWAP Transport Protocol Element 840 Type: 4 842 Length: 1 844 Transport: The transport to use for the CAPWAP Data channel. The 845 following enumerated values are supported: 847 1 - UDP-Lite: The UDP-Lite transport protocol is to be used for the 848 CAPWAP Data channel. Note that this option MUST NOT be used if the 849 CAPWAP Control channel is being used over IPv4 and AR address is IPv4 850 contained in the AR Information Element. 852 2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data 853 channel. 855 5.5. GRE Key Element 857 If a WTP receives the GRE Key Element in the Alternate Tunnel 858 Encapsulation message element for GRE selection, the WTP MUST insert 859 the GRE Key to the encapsulation packet (see [RFC2890]). An AR 860 acting as decapsulating tunnel endpoint identifies packets belonging 861 to a traffic flow based on the Key value. 863 The GRE Key Element field contains a four octet number defined in 864 [RFC2890]. 866 0 1 2 3 867 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 1 868 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 869 | GRE Key Element Type | Length | 870 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 871 | GRE Key | 872 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 874 Figure 17: GRE Key Element 876 Type: 5 878 Length: This refers to the total length in octets of the element 879 excluding the Type and Length fields. 881 GRE Key: The Key field contains a four octet number which is inserted 882 by the WTP according to [RFC2890]. 884 5.6. IPv6 MTU Element 886 If AC has chosen a tunneling mechanism based on IPv6, it SHOULD 887 support the minimum IPv6 MTU requirements [RFC2460]. This issue is 888 described in [I-D.ietf-intarea-tunnels]. AC SHOULD inform the WTP 889 about the IPv6 MTU information in the "Tunnel Info Element" field. 891 0 1 2 3 892 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 1 893 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 894 | IPv6 MTU Element Type | Length | 895 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 896 | Minimum IPv6 MTU | Reserved | 897 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 899 Figure 18: IPv6 MTU Element 901 Type: 6 903 Length: This refers to the total length in octets of the element 904 excluding the Type and Length fields. 906 Minimum IPv6 MTU: The field contains a two octet number indicate the 907 minimum IPv6 MTU in the tunnel. 909 6. IANA Considerations 911 This document requires the following IANA considerations. 913 o . This specification defines the Supported Alternate 914 Tunnel Encapsulations Type message element in Section 3.1. This 915 elements needs to be registered in the existing CAPWAP Message 916 Element Type registry, defined in [RFC5415]. The Type value for 917 this element needs to be between 1 and 1023 (see Section 15.7 in 918 [RFC5415]). 919 o . This specification defines the Alternate Tunnel 920 Encapsulations Type message element in Section 3.2. This element 921 needs to be registered in the existing CAPWAP Message Element Type 922 registry, defined in [RFC5415]. The Type value for this element 923 needs to be between 1 and 1023. 924 o . This specification defines the IEEE 802.11 WTP 925 Alternate Tunnel Failure Indication message element in 926 Section 3.3. This element needs to be registered in the existing 927 CAPWAP Message Element Type registry, defined in [RFC5415]. The 928 Type value for this element needs to be between 1024 and 2047. 929 o Alternate Tunnel-Types Registry: This specification defines the 930 Alternate Tunnel Encapsulations Type message element. This 931 element contains a field Tunnel-Type. The namespace for the field 932 is 16 bits (0-65535). This specification defines values, zero (0) 933 through six (6) and can be found in Section 3.2. Future 934 allocations of values in this name space are to be assigned by 935 IANA using the "Specification Required" policy. IANA needs to 936 create a registry called CAPWAP Alternate Tunnel-Types. The 937 registry format is given below. 939 Tunnel-Type Type Value Reference 940 CAPWAP 0 [RFC5415],[RFC5416] 941 L2TP 1 [RFC2661] 942 L2TPv3 2 [RFC3931] 943 IP-IP 3 [RFC2003] 944 PMIPv6-UDP 4 [RFC5844] 945 GRE 5 [RFC2784] 946 GTPv1-U 6 [3GPP TS 29.281] 948 o Alternate Tunnel Sub-elements Registry: This specification defines 949 the Alternate Tunnel Sub-elements. Currently, these information 950 elements can only be inluded in the Alternate Tunnel 951 Encapsulations Type message element, and the IEEE 802.11 WTP 952 Alternate Tunnel Failure Indication message element as their sub- 953 elements. These information elements contains a Type field. The 954 namespace for the field is 16 bits (0-65535). This specification 955 defines values, zero (0) through six (6) in Section 5. This 956 namespace is managed by IANA and assignments require an Expert 957 Review. 959 Type Type Value 960 AR IPv4 List 0 961 AR IPv6 List 1 962 Tunnel DTLS Policy 2 963 IEEE 802.11 Tagging Mode Policy 3 964 CAPWAP Transport Protocol 4 965 GRE Key 5 966 IPv6 MTU 6 968 7. Security Considerations 970 This document introduces three new CAPWAP WTP message elements. 971 These elements are transported within CAPWAP Control messages as the 972 existing message elements. Therefore, this document does not 973 introduce any new security risks to the control plane compared to 974 [RFC5415] and [RFC5416]. In the data plane, if the encapsulation 975 type selected itself is not secured, it is suggested to protect the 976 tunnel by using known secure methods, such as IPSec. 978 8. Contributors 980 The authors would like to thank Andreas Schultz, Hong Liu, Yifan 981 Chen, Chunju Shao, Li Xue, Jianjie You, Jin Li, Joe Touch, Alexey 982 Melnikov, Kathleen Moriarty, Mirja Kuehlewind, Catherine Meadows, and 983 Paul Kyzivat for their valuable comments. 985 9. References 987 9.1. Normative References 989 [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, 990 DOI 10.17487/RFC2003, October 1996, 991 . 993 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 994 Requirement Levels", BCP 14, RFC 2119, 995 DOI 10.17487/RFC2119, March 1997, 996 . 998 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 999 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 1000 December 1998, . 1002 [RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, 1003 G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"", 1004 RFC 2661, DOI 10.17487/RFC2661, August 1999, 1005 . 1007 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1008 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1009 DOI 10.17487/RFC2784, March 2000, 1010 . 1012 [RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE", 1013 RFC 2890, DOI 10.17487/RFC2890, September 2000, 1014 . 1016 [RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed., 1017 and G. Fairhurst, Ed., "The Lightweight User Datagram 1018 Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July 1019 2004, . 1021 [RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed., 1022 "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", 1023 RFC 3931, DOI 10.17487/RFC3931, March 2005, 1024 . 1026 [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1027 Ed., "Control And Provisioning of Wireless Access Points 1028 (CAPWAP) Protocol Specification", RFC 5415, 1029 DOI 10.17487/RFC5415, March 2009, 1030 . 1032 [RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, 1033 Ed., "Control and Provisioning of Wireless Access Points 1034 (CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416, 1035 DOI 10.17487/RFC5416, March 2009, 1036 . 1038 9.2. Informative References 1040 [I-D.ietf-intarea-tunnels] 1041 Touch, J. and M. Townsley, "IP Tunnels in the Internet 1042 Architecture", draft-ietf-intarea-tunnels-07 (work in 1043 progress), June 2017. 1045 [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., 1046 Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", 1047 RFC 5213, DOI 10.17487/RFC5213, August 2008, 1048 . 1050 [RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy 1051 Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010, 1052 . 1054 [RFC7494] Shao, C., Deng, H., Pazhyannur, R., Bari, F., Zhang, R., 1055 and S. Matsushima, "IEEE 802.11 Medium Access Control 1056 (MAC) Profile for Control and Provisioning of Wireless 1057 Access Points (CAPWAP)", RFC 7494, DOI 10.17487/RFC7494, 1058 April 2015, . 1060 [TS29281] "3rd Generation Partnership Project; Technical 1061 Specification Group Core Network and Terminals; General 1062 Packet Radio System (GPRS) Tunnelling Protocol User Plane 1063 (GTPv1-U)", 2016. 1065 Authors' Addresses 1067 Rong Zhang 1068 China Telecom 1069 No.109 Zhongshandadao avenue 1070 Guangzhou 510630 1071 China 1073 Email: zhangr@gsta.com 1075 Rajesh S. Pazhyannur 1076 Cisco 1077 170 West Tasman Drive 1078 San Jose, CA 95134 1079 USA 1081 Email: rpazhyan@cisco.com 1083 Sri Gundavelli 1084 Cisco 1085 170 West Tasman Drive 1086 San Jose, CA 95134 1087 USA 1089 Email: sgundave@cisco.com 1091 Zhen Cao 1092 Huawei 1093 Xinxi Rd. 3 1094 Beijing 100085 1095 China 1097 Email: zhencao.ietf@gmail.com 1098 Hui Deng 1099 Huawei 1100 Xinxi Rd. 3 1101 Beijing 100085 1102 China 1104 Email: denghui02@gmail.com 1106 Zongpeng Du 1107 Huawei 1108 No.156 Beiqing Rd. Z-park, HaiDian District 1109 Beijing 100095 1110 China 1112 Email: duzongpeng@huawei.com