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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Basavaraj Patil 3 Internet-Draft Nokia 4 Intended status: Standards Track Frank Xia 5 Expires: July 16, 2007 Behcet Sarikaya 6 Huawei USA 7 JH. Choi 8 Samsung AIT 9 Syam Madanapalli 10 LogicaCMG 11 January 12, 2007 13 IPv6 Over the IP Specific part of the Packet Convergence sublayer in 14 802.16 Networks 15 draft-ietf-16ng-ipv6-over-ipv6cs-05 17 Status of this Memo 19 By submitting this Internet-Draft, each author represents that any 20 applicable patent or other IPR claims of which he or she is aware 21 have been or will be disclosed, and any of which he or she becomes 22 aware will be disclosed, in accordance with Section 6 of BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF), its areas, and its working groups. Note that 26 other groups may also distribute working documents as Internet- 27 Drafts. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 The list of current Internet-Drafts can be accessed at 35 http://www.ietf.org/ietf/1id-abstracts.txt. 37 The list of Internet-Draft Shadow Directories can be accessed at 38 http://www.ietf.org/shadow.html. 40 This Internet-Draft will expire on July 16, 2007. 42 Copyright Notice 44 Copyright (C) The IETF Trust (2007). 46 Abstract 48 IEEE Std 802.16 is an air interface specification. IEEE has 49 specified several service specific convergence sublayers (CS) for 50 802.16 which are used by upper layer protocols. The ATM CS and 51 Packet CS are the two main service specific convergence sublayers and 52 these are a part of the 802.16 MAC which the upper layers interface 53 to.The packet CS is used for transport for all packet-based protocols 54 such as Internet Protocol (IP), IEEE Std. 802.3 (Ethernet) and, IEEE 55 Std 802.1Q (VLAN). The IP specific part of the Packet CS enables 56 transport of IPv6 packets directly over the MAC. This document 57 specifies the addressing and operation of IPv6 over the IPv6 specific 58 part of the packet CS for hosts served by a network that utilizes the 59 IEEE Std 802.16 air interface. It recommends the assignment of a 60 unique prefix (or prefixes) to each host and allows the host to use 61 multiple identifiers within that prefix, including support for 62 randomly generated identifiers. 64 Table of Contents 66 1. Conventions used in this document . . . . . . . . . . . . . . 4 67 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 4. IEEE 802.16 convergence sublayer support for IPv6 . . . . . . 5 70 4.1. IPv6 encapsulation over the IP CS of the MAC . . . . . . . 7 71 5. Generic network architecture using the 802.16 air interface . 8 72 6. IPv6 link . . . . . . . . . . . . . . . . . . . . . . . . . . 9 73 6.1. IPv6 link in 802.16 . . . . . . . . . . . . . . . . . . . 9 74 6.2. IPv6 link establishment in 802.16 . . . . . . . . . . . . 10 75 6.3. Maximum transmission unit in 802.16 . . . . . . . . . . . 11 76 7. IPv6 prefix assignment . . . . . . . . . . . . . . . . . . . . 11 77 8. Router Discovery . . . . . . . . . . . . . . . . . . . . . . . 11 78 8.1. Router Solicitation . . . . . . . . . . . . . . . . . . . 11 79 8.2. Router Advertisement . . . . . . . . . . . . . . . . . . . 12 80 8.3. Router lifetime and periodic router advertisements . . . . 12 81 9. IPv6 addressing for hosts . . . . . . . . . . . . . . . . . . 12 82 9.1. Interface Identifier . . . . . . . . . . . . . . . . . . . 12 83 9.2. Duplicate address detection . . . . . . . . . . . . . . . 13 84 9.3. Stateless address autoconfiguration . . . . . . . . . . . 13 85 9.4. Stateful address autoconfiguration . . . . . . . . . . . . 13 86 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 87 11. Security Considerations . . . . . . . . . . . . . . . . . . . 13 88 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 89 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 90 13.1. Normative References . . . . . . . . . . . . . . . . . . . 14 91 13.2. Informative References . . . . . . . . . . . . . . . . . . 14 92 Appendix A. WiMAX network architecture and IPv6 support . . . . . 15 93 Appendix B. IPv6 link in WiMAX . . . . . . . . . . . . . . . . . 16 94 Appendix C. IPv6 link establishment in WiMAX . . . . . . . . . . 17 95 Appendix D. Maximum transmission unit in WiMAX . . . . . . . . . 17 96 Appendix E. Stateless address autoconfiguration . . . . . . . . . 18 97 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 98 Intellectual Property and Copyright Statements . . . . . . . . . . 20 100 1. Conventions used in this document 102 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 103 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT 104 RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as 105 described in BCP 14, RFC 2119 [RFC2119] and indicate requirement 106 levels for compliant implementations. 108 2. Introduction 110 IPv6 packets can be carried over the IEEE Std 802.16 specified air 111 interface via either: 113 1. the IP specific part of the Packet CS or, 114 2. the 802.3 specific part of the Packet CS or, 115 3. the 802.1Q specific part of the Packet CS. 117 The 802.16 [802.16] specification includes the Phy and MAC details. 118 The convergence sublayers are a part of the MAC. This document 119 specifies IPv6 from the perspective of the transmission of IPv6 over 120 the IP specific part of the packet convergence sublayer. The mobile 121 station/host is attached to an access router via a base station (BS). 122 The host and the BS are connected via the IEEE Std 802.16 air 123 interface at the link and physical layers. The IPv6 link from the MS 124 terminates at an access router which may be a part of the BS or an 125 entity beyond the BS. The base station is a layer 2 entity (from the 126 perspective of the IPv6 link between the MS and AR) and relays the 127 IPv6 packets between the AR and the host via a point-to-point 128 connection over the air interface. The WiMAX (Worldwide 129 Interoperability for Microwave Access) forum [WMF] has defined a 130 network architecture in which the air interface is based on the IEEE 131 802.16 standard. The addressing and operation of IPv6 described in 132 this document is applicable to the WiMAX network as well. The 133 various aspects of IPv6 over 802.16 as applicable to WiMAX are 134 captured in the appendix sections of this document. 136 3. Terminology 138 The terminology in this document is based on the definitions in 139 [PSDOC], in addition to the ones specified in this section. 141 Access Service Network (ASN) - The ASN is defined as a complete set 142 of network functions needed to provide radio access to a WiMAX 143 subscriber. The ASN is the access network to which the MS attaches. 144 The IPv6 access router is an entity within the ASN. The term ASN is 145 specific to the WiMAX network architecture. 147 4. IEEE 802.16 convergence sublayer support for IPv6 149 The IEEE 802.16 MAC specifies two main service specific convergence 150 sublayers: 152 1. ATM Convergence sublayer 153 2. Packet Convergence sublayer 155 The Packet CS is used for the transport of packet based protocols 156 which include: 158 1. IEEE Std 802.3(Ethernet) 159 2. IEEE Std 802.1Q(VLAN) 160 3. Internet Protocol (IPv4 and IPv6) 162 The service specific CS resides on top of the MAC Common Part 163 Sublayer (CPS). The service specific CS is responsible for: 165 o accepting packets (PDUs) from the upper layer, 166 o performing classification of the packet/PDU based on a set of 167 classifiers that are defined which are service specific, 168 o delivering the CS PDU to the appropriate service flow and 169 transport connection and, 170 o receiving PDUs from the peer entity. 172 Payload header suppression (PHS) is also a function of the CS but is 173 optional. 175 The figure below shows the concept of the service specific CS in 176 relation to the MAC: 178 -----------------------------\ 179 | ATM CS | Packet CS | \ 180 ----------------------------- \ 181 | MAC Common Part Sublayer | \ 182 | (Ranging, scheduling, etc)| 802.16 MAC 183 ----------------------------- / 184 | Security | / 185 |(Auth, encryption,key mgmt)| / 186 -----------------------------/ 187 | PHY | 188 ----------------------------- 190 Figure 1: The 802.16 MAC 192 Classifiers for each of the specific upper-layer protocols, i.e 193 Ethernet, VLAN and IP, are defined which enable the packets from the 194 upper layer to be processed by the appropriate service specific part 195 of the packet CS. IPv6 can be transported directly over the IP 196 specific part of the packet CS or over 802.3/Ethernet (which in turn 197 is handled by the Ethernet specific part of the packet CS) or over 198 802.1Q (which is handled by the 802.1Q specific part of the packet 199 CS). 201 The figure below shows the options for IPv6 transport over the packet 202 CS of 802.16: 204 ----------------- ----------------- 205 | IPv6 | | IPv6 | 206 ---------------- |---------------| |----------- | 207 | IPv6 | | Ethernet | | 802.1Q | 208 |--------------| |---------------| |----------- | 209 | IP Specific | | 802.3 specific| |802.1Q specific| 210 |part of Pkt CS| |part of Pkt CS | |part of Pkt CS | 211 |..............| |...............| |...............| 212 | MAC | | MAC | | MAC | 213 |--------------| |---------------| |---------------| 214 | PHY | | PHY | | PHY | 215 ---------------- ----------------- ----------------- 217 (1) IPv6 over (2) IPv6 over (3) IPv6 over 218 IP Specific part 802.3/Ethernet 802.1Q 219 of Packet CS 221 Figure 2: IPv6 over IP, 802.3 and 802.1Q specific parts of the Packet 222 CS 224 The scope of this document is limited to IPv6 operation over the IP 225 specific part of the Packet CS only. It should be noted that 226 immediately after ranging (802.16 air interface procedure), the MS 227 and BS exchange their capability negotiation via REG-REQ and REG-RSP. 228 These management frames negotiate parameters such as the Convergence 229 Sublayer support. By default, Packet, IPv4 and 802.3/Ethernet are 230 supported. IPv6 via the Packet CS is supported by the MS and the BS 231 only when the bit specifying such support is indicated in the 232 parameter "Classification/PHS options and SDU encapsulation support" 233 (Refer to [802.16]). Additionally during the establishment of the 234 transport connection for transporting IPv6 packets, the DSA-REQ and 235 DSA-RSP messages between the BS and MS indicate via the CS- 236 Specification TLV the CS that the connection being setup shall use. 237 When the IPv6 packet is encapsulated by the 802.16 six byte MAC 238 header there is no specific indication in the MAC header itself about 239 the payload type. The processing of the packet is based entirely on 240 the classifiers. 242 Transmission of IPv6 as explained above is possible via multiple 243 methods, i.e, via the IP specific part of the packet CS or via 244 Ethernet or 802.1Q interfaces. The choice of which method to use is 245 implementation specific. In order to ensure interoperability the BS 246 should at least support both the IP specific part of the packet CS 247 and the Ethernet specific part of the packet CS for IPv6 transport. 248 Hosts which may implement one or the other method for transmission 249 would be assured of the ability to establish a transport connection 250 that would enable the transport of IPv6 packets. Inability to 251 negotiate a common convergence sublayer for the transport connection 252 between the MS and BS will result in failure to setup the transport 253 connection and thereby render the host unable to send and receive 254 IPv6 packets. In the case of a host which implements more than one 255 method of transporting IPv6 packets, the choice of which method to 256 use (i.e IPv6 over the IP specific part of the packet CS or IPv6 over 257 802.3 or, IPv6 over 802.1Q) is implementation specific. 259 4.1. IPv6 encapsulation over the IP CS of the MAC 261 The IPv6 payload when carried over the IP specific part of the Packet 262 CS is encapsulated by the 6 byte 802.16 MAC header. Header 263 suppression can also be applied to the IP packet. The format of the 264 IPv6 packet with and without header suppression is shown in the 265 figure below: 267 ---------/ /----------- 268 | MAC SDU | 269 --------/ /------------ 270 || 271 || 272 \/ 273 --------------------------------------------------------- 274 | PHSI=0 | IPv6 Packet (including Header) | 275 --------------------------------------------------------- 276 (i) IPv6 packet without header suppression 278 --------------------------------------------------------- 279 | PHSI=1 | (Header suppressed IPv6 packet) | 280 --------------------------------------------------------- 281 (ii) IPv6 packet with header suppression 282 Figure 3: IPv6 encapsulation 284 For transmission of IPv6 packets via the IP specific part of the 285 Packet CS of 802.16, the IPv6 layer interfaces with the 802.16 MAC 286 directly. The IPv6 layer delivers the IPv6 packet to the Packet CS 287 of the 802.16. The packet CS defines a set of classifiers that are 288 used to determine how to handle the packet. The IP classifiers that 289 are used at the MAC operate on the fields of the IP header and the 290 transport protocol and these include the IP ToS/DSCP, IP Protocol 291 field, Masked IP source and destination addresses and, Protocol 292 source and destination port ranges. Using the classifiers, the MAC 293 maps an upper layer packet to a specific service flow and transport 294 connection to be used. The MAC encapsulates the IPv6 packet in the 6 295 byte MAC header and transmits it. 297 5. Generic network architecture using the 802.16 air interface 299 In a network that utilizes the 802.16 air interface the host/MS is 300 attached to an IPv6 access router (AR) in the network. The BS is a 301 layer 2 entity only. The AR can be an integral part of the BS or the 302 AR could be an entity beyond the BS within the access network. IPv6 303 packets between the MS and BS are carried over a point-to-point 304 transport connection which has a unique connection identifier (CID). 305 The transport connection is a MAC layer link between the MS and the 306 BS. The figures below describe the possible network architectures 307 and are generic in nature. More esoteric architectures are possible 308 but not considered in the scope of this document. Option A: 310 +-----+ CID1 +--------------+ 311 | MS1 |------------/| BS/AR |-----[Internet] 312 +-----+ / +--------------+ 313 . /---/ 314 . CIDn 315 +-----+ / 316 | MSn |---/ 317 +-----+ 319 Figure 4: The IPv6 AR as an integral part of the BS 321 Option B: 323 +-----+ CID1 +-----+ +-----------+ 324 | MS1 |----------/| BS1 |----------| AR |-----[Internet] 325 +-----+ / +-----+ +-----------+ 326 . / ____________ 327 . CIDn / ()__________() 328 +-----+ / L2 Tunnel 329 | MSn |-----/ 330 +-----+ 332 Figure 5: The IPv6 AR is separate from the BS, which acts as a bridge 334 The above network models serve as examples and are shown to 335 illustrate the point to point link between the MS and the AR. 336 Appendix A shows a realization of the generic architecture by the 337 WiMAX forum. 339 6. IPv6 link 341 RFC 2461 defines link as a communication facility or medium over 342 which nodes can communicate at the link layer, i.e., the layer 343 immediately below IP [RFC2461]. A link is bounded by routers that 344 decrement the Hop limit field in the IPv6 header. When an MS moves 345 within a link, it can keep using its IP addresses. This is a layer 3 346 definition and note that the definition is not identical with the 347 definition of the term '(L2) link' in IEEE 802 standards. This 348 section presents a model for the last mile link, i.e. the link to 349 which MSs attach themselves. 351 6.1. IPv6 link in 802.16 353 In 802.16, the Transport Connection between an MS and a BS is used to 354 transport user data, i.e. IPv6 packets in this case. A Transport 355 Connection is represented by a CID (Connection Identifier) and 356 multiple Transport Connections can exist between an MS and BS. IEEE 357 802.16 also defines a secondary management connection that can be 358 used for host configuration. However support for secondary 359 management connections is not mandatory. A transport connection has 360 the advantage of it being used for host configuration as well as for 361 user data. 363 When an AR and a BS are collocated, the collection of Transport 364 Connections to an MS is defined as a single link. When an AR and a 365 BS are separated, it is recommended that a tunnel is established 366 between the AR and a BS whose granuality is no greater than 'per MS' 367 or 'per service flow' ( An MS can have multiple service flows which 368 are identified by a service flow ID). Then the tunnel(s) for an MS, 369 in combination with the MS's Transport connections, forms a single 370 point-to-point link. 372 The collection of service flows (tunnels) to an MS is defined as a 373 single link. Each link has only an MS and an AR. Each MS belongs to 374 a different link. No two MSs belong to the same link. A different 375 prefix should be assigned to each unique link. This link is fully 376 consistent with a standard IP link, without exception and conforms 377 with the definition of a point-to-point link in RFC2461 [RFC2461]. 378 Hence the point-to-point link model for IPv6 operation over the IP 379 specific part of the Packet CS in 802.16 is recommended. A unique 380 IPv6 prefix(es) per link (MS) is also recommended. 382 6.2. IPv6 link establishment in 802.16 384 In order to enable the sending and receiving of IPv6 packets between 385 the MS and the AR, the link between the MS and the AR via the BS 386 needs to be established. This section illustrates the link 387 establishment procedure. 389 The MS goes through the network entry procedure as specified by 390 802.16. A high level description of the network entry procedure is 391 as follows: 393 1. MS performs initial ranging with the BS. Ranging is a process by 394 which an MS becomes time aligned with the BS. The MS is 395 synchronized with the BS at the succesful completion of ranging 396 and is ready to setup a connection. 397 2. MS and BS perform capability exchange as per 802.16 procedures. 398 The CS capability parameter indicates which classification/PHS 399 options and SDU encapsulation the MS supports. By default, 400 Packet, IPv4 and 802.3/Ethernet shall be supported, thus absence 401 of this parameter in REG-REQ (802.16 message) means that named 402 options are supported by the MS/SS. Support for IPv6 over the IP 403 specific part of the packet CS is indicated by Bit#2 of the CS 404 capability parameter (Refer to [802.16]). 405 3. The MS progresses to an authentication phase. Authentication is 406 based on PKMv2 as defined in the IEEE Std 802.16 specification. 407 4. On succesful completion of authentication, the MS performs 802.16 408 registration with the network. 409 5. The MS can request the establishment of a service flow for IPv6 410 packets over the IP specific part of the Packet CS. The service 411 flow can also be triggered by the network as a result of pre- 412 provisioning. The service flow establishes a link between the MS 413 and the AR over which IPv6 packets can be sent and received. 414 6. The AR sends a router advertisement to the MS. Alternatively or 415 in addition, the MS can also send a router solicitation. 417 The above flow does not show the actual 802.16 messages that are used 418 for ranging, capability exchange or service flow establishment. 419 Details of these are in [802.16]. 421 6.3. Maximum transmission unit in 802.16 423 The 802.16 MAC PDU (Protocol Data Unit) is composed by a 6 byte 424 header followed by an optional payload and an optional CRC covering 425 the header and the payload. The length of the PDU is indicated by 426 the Len parameter in the Generic MAC HDR. The Len parameter has a 427 size of 11 bits. Hence the total PDU size is 2048 bytes. The IPv6 428 payload can be a max value of 2038 bytes ( Total PDU size minus (MAC 429 Header + CRC)). The Max value of the IPv6 MTU for 802.16 is 2038 430 bytes and the minimum value of 1280 bytes. The default MTU for IPv6 431 over 802.16 SHOULD be the same as specified in RFC2460 which is 1500 432 octets. RFC2461 defines an MTU option that an AR can advertise to an 433 MN. If an AR advertises an MTU via the RA MTU option, the MN should 434 use the MTU from the RA. 436 7. IPv6 prefix assignment 438 The MS and the AR are connected via a point-to-point connection at 439 the IPv6 layer. Hence each MS can be considered to be on a separate 440 subnet. A CPE (Customer Premise Equipment) type of device which 441 serves multiple IPv6 hosts, may be the end point of the connection. 442 Hence one or more /64 prefixes should be assigned to a link. The 443 prefixes are advertised with the on-link (L-bit) flag set as 444 specified in RFC2461 [RFC2461]. The size and number of the prefixes 445 is a configuration issue. Also, prefix delegation may be used to 446 provide additional prefixes for a router connected over 802.16. The 447 other properties of the prefixes are also dealt via configuration. 449 8. Router Discovery 451 8.1. Router Solicitation 453 On completion of the establishment of the IPv6 link, the MS may send 454 a router solicitation message to solicit a Router Advertisement 455 message from the AR to acquire necessary information as per RFC2461. 456 An MS that is network attached may also send router solicitations at 457 any time as per RFC2461. Movement detection at the IP layer of an MS 458 in many cases is based on receiving periodic router advertisements. 459 An MS may also detect changes in its attachment via link triggers or 460 other means. The MS can act on such triggers by sending router 461 solicitations. The router solicitation is sent over the IPv6 link 462 that has been previously established. The MS sends router 463 solicitations to the all-routers multicast address. It is carried 464 over the point-to-point link to the AR via the BS. The MS does not 465 need to be aware of the link-local address of the AR in order to send 466 a router solicitation at any time. 468 8.2. Router Advertisement 470 The AR should send a number (configurable value) of router 471 advertisements as soon as the IPv6 link is established, to the MS. 472 The AR sends unsolicited router advertisements periodically as per 473 RFC2461. The interval between periodic router advertisements is 474 however greater than the specification in RFC2461 and is discussed in 475 the following section. 477 8.3. Router lifetime and periodic router advertisements 479 The router lifetime should be set to a large value, preferably in 480 hours. This document over-rides the specification for the value of 481 the router lifetime in RFC2461 [RFC2461]. The AdvDefaultLifetime in 482 the router advertisement MUST be either zero or between 483 MaxRtrAdvInterval and 43200 seconds. The default value is 2 * 484 MaxRtrAdvInterval. 486 802.16 hosts have the capability to transition to an idle mode in 487 which case the radio link between the BS and MS is torn down. Paging 488 is required in case the network needs to deliver packets to the MS. 489 In order to avoid waking a mobile which is in idle mode and consuming 490 resources on the air interface, the interval between periodic router 491 advertisements should be set quite high. The MaxRtrAdvInterval value 492 specified in this document over-rides the recommendation in RFC2461 493 [RFC2461]. The MaxRtrAdvInterval MUST be no less than 4 seconds and 494 no greater than 21600 seconds. The default value for 495 MaxRtrAdvInterval is 10800 seconds. 497 9. IPv6 addressing for hosts 499 The addressing scheme for IPv6 hosts in 802.16 network follows the 500 IETFs recommendation for hosts specified in RFC 4294. The IPv6 node 501 requirements RFC RFC4294 [RFC4294] specifies a set of RFCs that are 502 applicable for addressing and the same is applicable for hosts that 503 use 802.16 as the link layer for transporting IPv6 packets. 505 9.1. Interface Identifier 507 The MS has a 48-bit MAC address as specified in 802.16 [802.16]. 508 This MAC address can be used if EUI-64 based interface identifier is 509 needed for autoconfiguration RFC4291 [RFC4291]. As in other links 510 that support IPv6, EUI-64 based interface identifiers are not 511 mandatory and other mechanisms, such as random interface identifiers 512 RFC3041 [RFC3041] may also be used. 514 9.2. Duplicate address detection 516 DAD is performed as per RFC2461 [RFC2461] and, RFC2462 [RFC2462]. 518 9.3. Stateless address autoconfiguration 520 If the A-bit in the prefix information option (PIO) is set, the MS 521 performs stateless address autoconfiguration as per RFC 2461, 2462. 522 The AR is the default router that advertises a unique prefix (or 523 prefixes) that is used by the MS to configure an address. 525 9.4. Stateful address autoconfiguration 527 The Stateful Address Autoconfiguration is invoked if the M-flag is 528 set in the Router Advertisement. Obtaining the IPv6 address through 529 stateful address autoconfiguration method is specified in RFC3315 530 [RFC3315]. 532 10. IANA Considerations 534 This draft does not require any actions from IANA. 536 11. Security Considerations 538 This document does not introduce any new vulnerabilities to IPv6 539 specifications or operation. The security of the 802.16 air 540 interface is the subject of [802.16]. In addition, the security 541 issues of the network architecture spanning beyond the 802.16 base 542 stations is the subject of the documents defining such architectures, 543 such as WiMAX Network Architecture [WiMAXArch]. 545 12. Acknowledgments 547 The authors would like to acknowledge the contributions of the 16NG 548 working group chairs Soohong Daniel Park and Gabriel Montenegro as 549 well as Jari Arkko, Jonne Soininen, Max Riegel, Prakash Iyer, DJ 550 Johnston, Dave Thaler, Bruno Sousa and Alexandru Petrescu for their 551 review and comments. 553 13. References 554 13.1. Normative References 556 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 557 Requirement Levels", RFC 2119, March 1997, 558 . 560 [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor 561 Discovery for IP Version 6 (IPv6)", RFC 2461, 562 December 1998, . 564 [RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address 565 Autoconfiguration", RFC 2462, December 1998, 566 . 568 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 569 Architecture", RFC 4291, February 2006, 570 . 572 13.2. Informative References 574 [802.16] "IEEE Std 802.16e: IEEE Standard for Local and 575 metropolitan area networks, Amendment for Physical and 576 Medium Access Control Layers for Combined Fixed and Mobile 577 Operation in Licensed Bands", October 2005. 579 [PSDOC] Jee, J., Madanapalli, S., Montenegro, G., Riegel, M., 580 Mandin, J., and S. Park, "IP over 802.16 Problem Statement 581 and Goals", October 2006, . 584 [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet 585 Networks", RFC 2464, December 1998, 586 . 588 [RFC3041] Narten, T., Draves, R., and S. Krishnan, "Privacy 589 Extensions for Stateless Address Autoconfiguration in 590 IPv6", August 2006, . 593 [RFC3315] Droms, Ed., R., Bound, J., Volz, B., Lemon, T., Perkins, 594 C., and M. Carney, "Dynamic Host Configuration Protocol 595 for IPv6 (DHCPv6)", RFC 3315, July 2003, 596 . 598 [RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor 599 Discovery (ND) Trust Models and Threats", RFC 3756, 600 May 2004, . 602 [RFC4294] Loughney, Ed., J., "IPv6 Node requirements", RFC 4294, 603 April 2006, . 605 [WMF] "http://www.wimaxforum.org". 607 [WiMAXArch] 608 "WiMAX End-to-End Network Systems Architecture 609 http://www.wimaxforum.org/technology/documents", 610 August 2006. 612 Appendix A. WiMAX network architecture and IPv6 support 614 The WiMAX network architecture consists of the Access Service Network 615 (ASN) and the Connectivity Service Network (CSN). The ASN is the 616 access network which includes the BS and the AR in addition to other 617 functions such as AAA, Mobile IP Foreign agent, Paging controller, 618 Location Register etc. The CSN is the entity that provides 619 connectivity to the Internet and includes functions such as Mobile IP 620 Home agent and AAA. The figure below shows the WiMAX reference 621 model: 623 ------------------- 624 | ---- ASN | |----| 625 ---- | |BS|\ R6 -------| |---------| | CSN| 626 |MS|-----R1----| ---- \---|ASN-GW| R3 | CSN | R5 | | 627 ---- | |R8 /--|------|----| |-----|Home| 628 | ---- / | | visited| | NSP| 629 | |BS|/ | | NSP | | | 630 | ---- | |---------| | | 631 | NAP | \ |----| 632 ------------------- \---| / 633 | | / 634 | (--|------/----) 635 |R4 ( ) 636 | ( ASP network ) 637 --------- ( or Internet ) 638 | ASN | ( ) 639 --------- (----------) 641 Figure 6: WiMAX Network reference model 643 Three different types of ASN realizations called profiles are defined 644 by the architecture. ASNs of profile types A and C include BS' and 645 ASN-gateway(s) (ASN-GW) which are connected to each other via an R6 646 interface. An ASN of profile type B is one in which the 647 functionality of the BS and other ASN functions are merged together. 648 No ASN-GW is specifically defined in a profile B ASN. The absence of 649 the R6 interface is also a profile B specific characteristic. The MS 650 at the IPv6 layer is associated with the AR in the ASN. The AR may 651 be a function of the ASN-GW in the case of profiles A and C and is a 652 function in the ASN in the case of profile B. When the BS and the AR 653 are separate entities and linked via the R6 interface, IPv6 packets 654 between the BS and the AR are carried over a GRE tunnel. The 655 granularity of the GRE tunnel should be on a per MS basis or on a per 656 service flow basis (an MS can have multiple service flows, each of 657 which are identified uniquely by a service flow ID). The protocol 658 stack in WiMAX for IPv6 is shown below: 660 |-------| 661 | App |- - - - - - - - - - - - - - - - - - - - - - - -(to app peer) 662 | | 663 |-------| /------ ------- 664 | | / IPv6 | | | 665 | IPv6 |- - - - - - - - - - - - - - - - / | | |--> 666 | | --------------- -------/ | | IPv6| 667 |-------| | \Relay/ | | | |- - - | | 668 | | | \ / | | GRE | | | | 669 | | | \ /GRE | - | | | | | 670 | |- - - | |-----| |------| | | | 671 | IPv6CS| |IPv6CS | IP | - | IP | | | | 672 | ..... | |...... |-----| |------|--------| |-----| 673 | MAC | | MAC | L2 | - | L2 | L2 |- - - | L2 | 674 |-------| |------ |-----| |----- |--------| |-----| 675 | PHY |- - - | PHY | L1 | - | L1 | L1 |- - - | L1 | 676 -------- --------------- ----------------- ------- 678 MS BS AR/ASN-GW CSN Rtr 680 Figure 7: WiMAX protocol stack 682 As can be seen from the protocol stack description, the IPv6 end- 683 points are constituted in the MS and the AR. The BS provides lower 684 layer connectivity for the IPv6 link. 686 Appendix B. IPv6 link in WiMAX 688 WiMAX is an example of a network based on the IEEE Std 802.16 air 689 interface. This section describes the IPv6 link in the context of a 690 WiMAX network. The MS and the AR are connected via a combination of 691 : 693 1. The transport connection which is identified by a Connection 694 Identifier (CID) over the air interface, i.e the MS and BS and, 695 2. A GRE tunnel between the BS and AR which transports the IPv6 696 packets 698 From an IPv6 perspective the MS and the AR are connected by a point- 699 to-point link. The combination of transport connection over the air 700 interface and the GRE tunnel between the BS and AR creates a (point- 701 to-point) tunnel at the layer below IPv6. 703 The collection of service flows (tunnels) to an MS is defined as a 704 single link. Each link has only an MS and an AR. Each MS belongs to 705 a different link. No two MSs belong to the same link. A different 706 prefix should be assigned to each unique link. This link is fully 707 consistent with a standard IP link, without exception and conforms 708 with the definition of a point-to-point link in RFC2461 [RFC2461]. 710 Appendix C. IPv6 link establishment in WiMAX 712 The mobile station performs initial network entry as specified in 713 802.16. On succesful completion of the network entry procedure the 714 ASN gateway/AR triggers the establishment of the initial service flow 715 (ISF) for IPv6 towards the MS. The ISF is a GRE tunnel between the 716 ASN-GW/AR and the BS. The BS in turn requests the MS to establish a 717 transport connection over the air interface. The end result is a 718 transport connection over the air interface for carrying IPv6 packets 719 and a GRE tunnel between the BS and AR for relaying the IPv6 packets. 720 On succesful completion of the establishment of the ISF, IPv6 packets 721 can be sent and received between the MS and AR. The ISF enables the 722 MS to communicate with the AR for host configuration procedures. 723 After the establishment of the ISF, the AR can send a router 724 advertisement to the MS. An MS can establish multiple service flows 725 with different QoS characteristics. The ISF can be considered as the 726 primary service flow. The ASN-GW/ AR treats each ISF, along with the 727 other service flows to the same MS, as a unique link which is managed 728 as a (virtual) interface. 730 Appendix D. Maximum transmission unit in WiMAX 732 The WiMAX forum [WMF] has specified the Max SDU size as 1522 octets. 733 Hence the IPv6 path MTU can be 1500 octets. However because of the 734 overhead of the GRE tunnel used to transport IPv6 packets between the 735 BS and AR and the 6 byte MAC header over the air interface, using a 736 value of 1500 would result in fragmentation of packets. It is 737 recommended that the default MTU for IPv6 be set to 1400 octets for 738 the MS in WiMAX networks. Note that the 1522 octet specification is 739 a WiMAX forum specification and not the size of the SDU that can be 740 transmitted over 802.16, which has a higher limit. 742 Appendix E. Stateless address autoconfiguration 744 The MS can perform stateless address autoconfiguration as per 745 RFC2461, 2462 if the A-bit in the prefix information option (PIO) is 746 set. The AR is the default router that advertises a unique /64 747 prefix (or prefixes) that is used by the MS to configure an address. 749 Authors' Addresses 751 Basavaraj Patil 752 Nokia 753 6000 Connection Drive 754 Irving, TX 75039 755 USA 757 Email: basavaraj.patil@nokia.com 759 Frank Xia 760 Huawei USA 761 1700 Alma Dr. Suite 100 762 Plano, TX 75075 764 Email: xiayangsong@huawei.com 766 Behcet Sarikaya 767 Huawei USA 768 1700 Alma Dr. Suite 100 769 Plano, TX 75075 771 Email: sarikaya@ieee.org 772 JinHyeock Choi 773 Samsung AIT 774 Networking Technology Lab 775 P.O.Box 111 776 Suwon, Korea 440-600 778 Email: jinchoe@samsung.com 780 Syam Madanapalli 781 LogicaCMG 782 125 Yemlur P.O. 783 Off Airport Road 784 Bangalore, India 560037 786 Email: smadanapalli@gmail.com 788 Full Copyright Statement 790 Copyright (C) The IETF Trust (2007). 792 This document is subject to the rights, licenses and restrictions 793 contained in BCP 78, and except as set forth therein, the authors 794 retain all their rights. 796 This document and the information contained herein are provided on an 797 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 798 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 799 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 800 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 801 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 802 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 804 Intellectual Property 806 The IETF takes no position regarding the validity or scope of any 807 Intellectual Property Rights or other rights that might be claimed to 808 pertain to the implementation or use of the technology described in 809 this document or the extent to which any license under such rights 810 might or might not be available; nor does it represent that it has 811 made any independent effort to identify any such rights. 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