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If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 14, 2008) is 5765 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 793 (Obsoleted by RFC 9293) ** Obsolete normative reference: RFC 4960 (Obsoleted by RFC 9260) Summary: 4 errors (**), 0 flaws (~~), 1 warning (==), 7 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Stewart 3 Internet-Draft The Resource Group 4 Intended status: Standards Track M. Tuexen 5 Expires: January 15, 2009 I. Ruengeler 6 Muenster Univ. of Applied Sciences 7 July 14, 2008 9 Stream Control Transmission Protocol (SCTP) Network Address Translation 10 draft-stewart-behave-sctpnat-04.txt 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This Internet-Draft will expire on January 15, 2009. 37 Abstract 39 Stream Control Transmission Protocol [RFC4960] provides a reliable 40 communications channel between two end-hosts in many ways similar to 41 TCP [RFC0793]. With the widespread deployment of Network Address 42 Translators (NAT), specialized code has been added to NAT for TCP 43 that allows multiple hosts to reside behind a NAT and yet use only a 44 single globally unique IPv4 address, even when two hosts (behind the 45 NAT) choose the same port numbers for their connection. This 46 additional code is sometimes classified as Network Address and Port 47 Translation or NAPT. To date, specialized code for SCTP has NOT yet 48 been added to most NAT's so that only pure NAT is available. The end 49 result of this is that only one SCTP capable host can be behind a 50 NAT. 52 This document describes an SCTP specific variant of NAT which 53 provides similar features of NAPT in the single point and multi-point 54 traversal scenario. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 4. SCTP NAT Traversal Scenarios . . . . . . . . . . . . . . . . . 4 62 4.1. Single Point Traversal . . . . . . . . . . . . . . . . . . 4 63 4.2. Multi Point Traversal . . . . . . . . . . . . . . . . . . 5 64 5. The SCTP specific variant of NAT . . . . . . . . . . . . . . . 6 65 6. Handling of local port number collisions . . . . . . . . . . . 8 66 7. Handling of local port number and verification tag 67 collisions . . . . . . . . . . . . . . . . . . . . . . . . . . 9 68 8. Handling of missing state . . . . . . . . . . . . . . . . . . 10 69 9. Multi Point Traversal considerations . . . . . . . . . . . . . 11 70 10. Handling of fragmented SCTP packets . . . . . . . . . . . . . 11 71 11. Simplification for small NATs . . . . . . . . . . . . . . . . 11 72 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 73 13. Security considerations . . . . . . . . . . . . . . . . . . . 12 74 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 75 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 76 15.1. Normative References . . . . . . . . . . . . . . . . . . . 12 77 15.2. Informative References . . . . . . . . . . . . . . . . . . 12 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 79 Intellectual Property and Copyright Statements . . . . . . . . . . 14 81 1. Introduction 83 Stream Control Transmission Protocol [RFC4960] provides a reliable 84 communications channel between two end-hosts in many ways similar to 85 TCP [RFC0793]. With the widespread deployment of Network Address 86 Translators (NAT), specialized code has been added to NAT for TCP 87 that allows multiple hosts to reside behind a NAT and yet use only a 88 single globally unique IPv4 address, even when both hosts (behind the 89 NAT) choose the same port numbers for their connection. This 90 additional code is sometimes classified as Network Address and Port 91 Translation or NAPT. To date, specialized code for SCTP has NOT yet 92 been added to most NAT's so that only true NAT is available. The end 93 result of this is that only one SCTP capable host can be behind a 94 NAT. 96 This document proposes an SCTP specific variant NAT that provides the 97 NAPT functionality without changing SCTP port numbers. The authors 98 feel it is possible and desirable to make these changes for a number 99 of reasons. 101 o It is desirable for SCTP end-hosts on multiple platforms to be 102 able to share a global IP address behind a NAT, much as TCP does 103 today. 105 o If a NAT does not need to change any data within an SCTP packet it 106 will reduce the processing burden of NAT'ing SCTP by NOT needing 107 to execute the CRC32c checksum required by SCTP. 109 o Not having to touch the IP payload makes the processing of ICMP 110 messages in NATs easier. 112 2. Conventions 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in [RFC2119]. 118 3. Terminology 120 For this discussion we will use several terms. For clarity we will 121 first define these terms. 123 o Global-Address - That address that a host behind a NAT is 124 attempting to contact. 126 o Global-Port - The port number of the peer process at the Global- 127 Address. 129 o Local-Address - The local address that is known to the host behind 130 the NAT, aka a private address [RFC1918]. 132 o Local-Port - The port number that is in use by the host holding 133 the Local-Address. Normally this is the port that will be 134 translated by the NAPT to a different port number. 136 o Nat-Global-Address - The global address assigned to the NAT box 137 which it uses as a source address when sending packets towards the 138 Global-Address. 140 o Natted-Port - The port number that the NAT is using to represent 141 the Local-Port when send data packets toward the Global-Address 142 and Global-Port. 144 o Local-Vtag - The Verification Tag that the host inside the natted 145 address space has chosen for its communication. The V-Tag is a 146 unique 32 bit tag that must accompany any incoming SCTP packet for 147 this association to the Local-Address. 149 o Remote-Vtag - The Verification Tag that the host holding the 150 Global-Address has chosen for its communication. The V-Tag is a 151 unique 32 bit tag that must accompany any incoming SCTP packet for 152 this association to the Global-Address. 154 4. SCTP NAT Traversal Scenarios 156 4.1. Single Point Traversal 158 In this case, all packets in the SCTP association go through a single 159 NAT, as shown below: 161 +---------+ +---------+ 162 | SCTP | +-----+ | SCTP | 163 |end point|==========| NAT |==========|end point| 164 | A | +-----+ | B | 165 +---------+ +---------+ 167 A variation of this case is shown below, i.e., multiple NATs in a 168 single path: 170 +---------+ +---------+ 171 | SCTP | +-----+ +-----+ | SCTP | 172 |end point|====| NAT |=::==| NAT |====|end point| 173 | A | +-----+ +-----+ | B | 174 +---------+ +---------+ 176 The two SCTP endpoints in this case can be either single-homed or 177 multi-homed. However, the important thing is that the NAT (or NATs) 178 in this case sees ALL the packets of the SCTP association. 180 In this single traverse point scenario, we must acknowledge that 181 while one of the main benefits of SCTP multi-homing is redundant 182 paths, the NAT function represents a single point of failure in the 183 path of the SCTP multi-home association. However, the rest of the 184 path may still benefit from path diversity provided by SCTP multi- 185 homing. 187 4.2. Multi Point Traversal 189 This case involves multiple NATs and each NAT only sees some of the 190 packets in the SCTP association. An example is shown below: 192 +------+ 193 +---------+ /====|NAT A |====\ +---------+ 194 | SCTP | / +------+ \ | SCTP | 195 |end point|/ ... \|end point| 196 | A |\ /| B | 197 +---------+ \ +------+ / +---------+ 198 \====|NAT B |====/ 199 +------+ 201 This case does NOT apply to a singly-homed SCTP association (i.e., 202 BOTH endpoints in the association use only one IP address). The 203 advantage here is that the existence of multiple NAT traverse points 204 can preserve the path diversity of a multi-homed association for the 205 entire path. This in turn can improve the robustness of the 206 communication. 208 To make this work, however, all the NATs involved must recognize the 209 packets they see as belonging to the same SCTP association and 210 perform address translation in a consistent way. It may be required 211 that a pre-defined table of ports and addresses would be shared 212 between the NAT's. Other external management schemes that help 213 multiple NAT's coordinate a multi-homed SCTP association could be 214 investigated. 216 5. The SCTP specific variant of NAT 218 In this section we assume that we have multiple SCTP capable hosts 219 behind a NAT which has one Nat-Global address. Furthermore we are 220 focusing in this section on the single point traversal scenario. 222 The modification of SCTP packets sent to the public Internet is easy. 223 The source address of the packet has to be replaced with the Nat- 224 Global-Address. It may also be necessary to establish some state in 225 the NAT box to handle incoming packets, which is discussed later. 227 For SCTP packets coming from the public Internet the destination 228 address of the packets has to be replaced with the Local-Address of 229 the host the packet has to be delivered to. The lookup of the Local- 230 Address is based on the Global-VTag, Global-Port, Global-Address, 231 Local-Vtag and the Local-Port. 233 For the SCTP NAT processing the NAT box has to maintain a table of 234 Global-VTag, Global-Port, Global-Address, Local-VTag, Local-Port and 235 Local-Address. An entry in that table is called a NAT state control 236 block. 238 The processing of outgoing SCTP packets containing an INIT-chunk is 239 described in the following figure. 241 Local-Network Global-Internet 243 [From(Local-Address,Local-Port), 244 To(Global-Address:Global-Port) 245 INIT(Initiate-Tag)]-------> 247 Create(Global-Port,Global-Address,Initiate-Tag, 248 Local-Port,Local-Address) 249 Returns(NAT-State control block) 251 Translate To: 253 [From(Nat-Global-Address:Local-Port), 254 To(Global-Address:Global-Port) 255 INIT(Initiate-Tag)]-------> 257 It should be noted that normally no NAT control block will be 258 created. However it is possible that that there is already a NAT 259 control block with the same Global-Port, Global-Address, Initiate- 260 Tag, Local-VTag but different Local-Address. In this case the INIT 261 SHOULD be dropped and an ABORT MAY be sent back. 263 The processing of outgoing SCTP packets containing no INIT-chunk is 264 described in the following figure. 266 Local-Network Global-Internet 268 [From(Local-Address,Local-Port), 269 To(Global-Address:Global-Port)]-------> 271 Translate To: 273 [From(Nat-Global-Address:Local-Port), 274 To(Global-Address:Global-Port)]-------> 276 The processing of incoming SCTP packets containing INIT-ACK chunks is 277 described in the following figure. 279 Local-Network Global-Internet 281 <-----[From(Global-Address,Global-Port), 282 To(Nat-Global-Address,Local-Port), 283 SCTP(Local-VTag), 284 INIT-ACK(Initiate-Tag)] 286 Lookup(0,Global-Port,Global-Address,Local-VTag,Local-Port) 287 Update(Initiate-Tag,Global-Port,Global-Address, 288 Local-VTag,Local-Port) 289 Returns(NAT-State control block containing Local-Address) 291 <-----[From(Global-Address:Global-Port), 292 To(Local-Address,Local-Port) 293 SCTP(Local-VTag)] 295 In the case Lookup fails, the SCTP packet is dropped. The Update 296 routine inserts the Global-VTag in the NAT state control block. 298 The processing of incoming SCTP packets containing and ABORT or 299 SHUTDOWN-COMLETE chunk with the T-Bit set is described in the 300 following figure. 302 Local-Network Global-Internet 304 <-----[From(Global-Address,Global-Port), 305 To(Nat-Global-Address,Local-Port), 306 SCTP(Global-VTag)] 308 Lookup(Global-VTag,Global-Port,Global-Address,0,Local-Port) 309 Returns(NAT-State control block containing Local-Address) 311 <-----[From(Global-Address:Global-Port), 312 To(Local-Address,Local-Port) 313 SCTP(Global-VTag)] 315 The processing of other incoming SCTP packets is described in the 316 following figure. 318 Local-Network Global-Internet 320 <-----[From(Global-Address,Global-Port), 321 To(Nat-Global-Address,Local-Port), 322 SCTP(Local-VTag)] 324 Lookup(0,Global-Port,Global-Address,Local-VTag,Local-Port) 325 Returns(NAT-State control block containing Local-Address) 327 <-----[From(Global-Address:Global-Port), 328 To(Local-Address,Local-Port) 329 SCTP(Local-VTag)] 331 For an incoming packet containing an INIT-chunk a table lookup is 332 made only based on the addresses and port numbers. If an entry with 333 a local vtag of zero is found, it is considered a match and the local 334 v-tag is updated. 336 This allows the handling of INIT-collision through NAT. 338 6. Handling of local port number collisions 340 There is one drawback of the SCTP specific variant of NAT compared to 341 a NAPT solution like the ones available for TCP. Consider the case 342 where two hosts in the Local-Address space want to setup an SCTP 343 association with the same server running on the same host in the 344 Internet. This means that the Global-Port and the Global-Address are 345 the same. If they both chose the same Local-Port the server can not 346 distinguish both associations based on the address and port numbers. 347 For the server it looks like the association is being restarted. To 348 overcome this limitation the client sends a NAT_SUPPORTED parameter 349 in the INIT-chunk which is defined as follows: 351 0 1 2 3 352 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 1 353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 354 | Type = 0xC007 | Length=4 | 355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 357 When the server receives this parameter it will also use the 358 verification tag to look up the association. However, this will make 359 it impossible to restart such associations. 361 7. Handling of local port number and verification tag collisions 363 Consider the case where two hosts in the Local-Address space want to 364 setup an SCTP association with the same server running on the same 365 host in the Internet. This means that the Global-Port and the 366 Global-Address are the same. If they both chose the same Local-Port 367 and Local-VTag, the NAT box can not distinguish incoming packets 368 anymore. But this is very unlikely. The Local-Vtags are chosen by 369 random and if the Local-Ports are also chosen ephemeral an random 370 this gives a 46 bit random number which has to match. In the TCP 371 like NAPT case the NAT box can control the 16 bit Natted Port. 373 However, if this unlikely happens the NAT box MUST respond to the 374 INIT chunk by sending an ABORT chunk with the M-bit set. The source 375 address of the packet containing the ABORT chunk MUST be the 376 destination address of the SCTP packet containing the INIT chunk. 377 The sender of the packet containing the INIT chunk MAY start the 378 association setup procedure after choosing a new initiate tag. 380 The ABORT chunk defined in [RFC4960] is therefore extended by using 381 the following format: 383 0 1 2 3 384 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 1 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 | Type = 6 | Reserved |M|T| Length | 387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 388 \ \ 389 / zero or more Error Causes / 390 \ \ 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 The following error cause with cause code 0x00b0 (Colliding NAT table 393 entry) SHOULD be included in the ABORT chunk: 395 0 1 2 3 396 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 1 397 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 398 | Cause Code=0x00b0 | Cause Length=Variable | 399 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 400 \ INIT chunk / 401 / \ 402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 404 8. Handling of missing state 406 If the NAT box receives a packet for which the lookup procedure does 407 not find an entry in the NAT table, a packet containing an ERROR 408 packet is sent back with the M-bit set. The source address of the 409 packet containing the ERROR chunk MUST be the destination address of 410 the incoming SCTP packet. The verification tag is reflected. 412 The ERROR chunk defined in [RFC4960] is therefore extended by using 413 the following format: 415 0 1 2 3 416 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 1 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 | Type = 9 | Reserved |M|T| Length | 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 \ \ 421 / zero or more Error Causes / 422 \ \ 423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 425 The following error cause with cause code 0x00b1 (Missing NAT table 426 entry) SHOULD be included in the ERROR chunk: 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 | Cause Code=0x00b0 | Cause Length=Variable | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 \ Incoming Packet / 434 / \ 435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 437 If an end-point receives a packet with this ERROR chunk it MAY send 438 an SCTP packet with a ASCONF chunk containing an Add IP Address 439 parameter followed by a vtag parameter: 441 0 1 2 3 442 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 1 443 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 444 | Parameter Type = 0xC007 | Parameter Length = 12 | 445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 | Local Verification Tag | 447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 448 | Remote Verification Tag | 449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 451 If the NAT box receives a packet for which it has no NAT table entry 452 and the packet contains an ASCONF chunk with a vtag parameter, the 453 NAT box MUST update its NAT table according to the verification tags 454 in the vtag parameter. 456 9. Multi Point Traversal considerations 458 If a multi-homed SCTP end-point behind a NAT connects to a peer, it 459 first sets up the association single-homed. Then it adds each IP 460 address using ASCONF chunks. The address to add is the wildcard 461 address and the lookup address also. The ASCONF chunks SHOULD also 462 contain a vtag parameter. 464 10. Handling of fragmented SCTP packets 466 A NAT box MUST support IP reassembly of received fragmented SCTP 467 packets. The fragments may arrive in any order. 469 When an SCTP packet has to be fragmented by the NAT box and the IP 470 header forbids fragmentation a correspond ICMP packet SHOULD be sent. 472 11. Simplification for small NATs 474 Small NAT boxes, i.e. NAT boxes which only have to support a small 475 number of concurrent SCTP associations, MAY not take the global 476 address into account when processing packets. Therefore the global- 477 address could also be removed from the NAT table. 479 This simplification may make implementing a NAT box easier, however, 480 the collision probability is higher than using a mapping which takes 481 the global address into account. 483 12. IANA Considerations 485 TBD 487 13. Security considerations 489 State maintenance within a NAT is always a subject of possible Denial 490 Of Service attack. This document recommends that at a minimum a NAT 491 run a timer on any SCTP state so that old association state can be 492 cleaned up. 494 14. Acknowledgments 496 The authors wish to thank Qiaobing Xie, Henning Peters, Bryan Ford, 497 David Hayes, and Jason But for their invaluable comments. 499 15. References 501 15.1. Normative References 503 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 504 RFC 793, September 1981. 506 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 507 Requirement Levels", BCP 14, RFC 2119, March 1997. 509 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", 510 RFC 4960, September 2007. 512 15.2. Informative References 514 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 515 E. Lear, "Address Allocation for Private Internets", 516 BCP 5, RFC 1918, February 1996. 518 Authors' Addresses 520 Randall R. Stewart 521 The Resource Group 522 1700 Pennsylvania Ave NW 523 Suite 56 524 Washington, DC 20006 525 USA 527 Phone: 528 Email: randall.stewart@trgworld.com 530 Michael Tuexen 531 Muenster Univ. of Applied Sciences 532 Stegerwaldstr. 39 533 48565 Steinfurt 534 Germany 536 Email: tuexen@fh-muenster.de 538 Irene Ruengeler 539 Muenster Univ. of Applied Sciences 540 Stegerwaldstr. 39 541 48565 Steinfurt 542 Germany 544 Email: i.ruengeler@fh-muenster.de 546 Full Copyright Statement 548 Copyright (C) The IETF Trust (2008). 550 This document is subject to the rights, licenses and restrictions 551 contained in BCP 78, and except as set forth therein, the authors 552 retain all their rights. 554 This document and the information contained herein are provided on an 555 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 556 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 557 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 558 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 559 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 560 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 562 Intellectual Property 564 The IETF takes no position regarding the validity or scope of any 565 Intellectual Property Rights or other rights that might be claimed to 566 pertain to the implementation or use of the technology described in 567 this document or the extent to which any license under such rights 568 might or might not be available; nor does it represent that it has 569 made any independent effort to identify any such rights. 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