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Hinden 5 Intended status: Standards Track Check Point Software 6 Expires: October 23, 2017 April 21, 2017 8 Internet Protocol, Version 6 (IPv6) Specification 9 draft-ietf-6man-rfc2460bis-10 11 Abstract 13 This document specifies version 6 of the Internet Protocol (IPv6). 14 It obsoletes RFC2460 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on October 23, 2017. 33 Copyright Notice 35 Copyright (c) 2017 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 This document may contain material from IETF Documents or IETF 49 Contributions published or made publicly available before November 50 10, 2008. The person(s) controlling the copyright in some of this 51 material may not have granted the IETF Trust the right to allow 52 modifications of such material outside the IETF Standards Process. 53 Without obtaining an adequate license from the person(s) controlling 54 the copyright in such materials, this document may not be modified 55 outside the IETF Standards Process, and derivative works of it may 56 not be created outside the IETF Standards Process, except to format 57 it for publication as an RFC or to translate it into languages other 58 than English. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 3. IPv6 Header Format . . . . . . . . . . . . . . . . . . . . . 5 65 4. IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . 6 66 4.1. Extension Header Order . . . . . . . . . . . . . . . . . 8 67 4.2. Options . . . . . . . . . . . . . . . . . . . . . . . . . 9 68 4.3. Hop-by-Hop Options Header . . . . . . . . . . . . . . . . 12 69 4.4. Routing Header . . . . . . . . . . . . . . . . . . . . . 12 70 4.5. Fragment Header . . . . . . . . . . . . . . . . . . . . . 14 71 4.6. Destination Options Header . . . . . . . . . . . . . . . 20 72 4.7. No Next Header . . . . . . . . . . . . . . . . . . . . . 22 73 4.8. Defining New Extension Headers and Options . . . . . . . 22 74 5. Packet Size Issues . . . . . . . . . . . . . . . . . . . . . 23 75 6. Flow Labels . . . . . . . . . . . . . . . . . . . . . . . . . 24 76 7. Traffic Classes . . . . . . . . . . . . . . . . . . . . . . . 24 77 8. Upper-Layer Protocol Issues . . . . . . . . . . . . . . . . . 24 78 8.1. Upper-Layer Checksums . . . . . . . . . . . . . . . . . . 24 79 8.2. Maximum Packet Lifetime . . . . . . . . . . . . . . . . . 26 80 8.3. Maximum Upper-Layer Payload Size . . . . . . . . . . . . 26 81 8.4. Responding to Packets Carrying Routing Headers . . . . . 27 82 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 83 10. Security Considerations . . . . . . . . . . . . . . . . . . . 28 84 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30 85 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 86 12.1. Normative References . . . . . . . . . . . . . . . . . . 30 87 12.2. Informative References . . . . . . . . . . . . . . . . . 31 88 Appendix A. Formatting Guidelines for Options . . . . . . . . . 33 89 Appendix B. Changes Since RFC2460 . . . . . . . . . . . . . . . 36 90 B.1. Change History Since RFC2460 . . . . . . . . . . . . . . 39 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44 93 1. Introduction 95 IP version 6 (IPv6) is a new version of the Internet Protocol (IP), 96 designed as the successor to IP version 4 (IPv4) [RFC0791]. The 97 changes from IPv4 to IPv6 fall primarily into the following 98 categories: 100 o Expanded Addressing Capabilities 102 IPv6 increases the IP address size from 32 bits to 128 bits, to 103 support more levels of addressing hierarchy, a much greater 104 number of addressable nodes, and simpler auto-configuration of 105 addresses. The scalability of multicast routing is improved by 106 adding a "scope" field to multicast addresses. And a new type 107 of address called an "anycast address" is defined, used to send 108 a packet to any one of a group of nodes. 110 o Header Format Simplification 112 Some IPv4 header fields have been dropped or made optional, to 113 reduce the common-case processing cost of packet handling and 114 to limit the bandwidth cost of the IPv6 header. 116 o Improved Support for Extensions and Options 118 Changes in the way IP header options are encoded allows for 119 more efficient forwarding, less stringent limits on the length 120 of options, and greater flexibility for introducing new options 121 in the future. 123 o Flow Labeling Capability 125 A new capability is added to enable the labeling of sequences 126 of packets that the sender requests to be treated in the 127 network as a single flow. 129 o Authentication and Privacy Capabilities 131 Extensions to support authentication, data integrity, and 132 (optional) data confidentiality are specified for IPv6. 134 This document specifies the basic IPv6 header and the initially- 135 defined IPv6 extension headers and options. It also discusses packet 136 size issues, the semantics of flow labels and traffic classes, and 137 the effects of IPv6 on upper-layer protocols. The format and 138 semantics of IPv6 addresses are specified separately in [RFC4291]. 140 The IPv6 version of ICMP, which all IPv6 implementations are required 141 to include, is specified in [RFC4443] 143 The data transmission order for IPv6 is the same as for IPv4 as 144 defined in Appendix B of [RFC0791]. 146 Note: As this document obsoletes [RFC2460], any document referenced 147 in this document that includes pointers to RFC2460, should be 148 interpreted as referencing this document. 150 2. Terminology 152 node a device that implements IPv6. 154 router a node that forwards IPv6 packets not explicitly 155 addressed to itself. [See Note below]. 157 host any node that is not a router. [See Note below]. 159 upper layer a protocol layer immediately above IPv6. Examples are 160 transport protocols such as TCP and UDP, control 161 protocols such as ICMP, routing protocols such as OSPF, 162 and internet or lower-layer protocols being "tunneled" 163 over (i.e., encapsulated in) IPv6 such as IPX, 164 AppleTalk, or IPv6 itself. 166 link a communication facility or medium over which nodes can 167 communicate at the link layer, i.e., the layer 168 immediately below IPv6. Examples are Ethernets (simple 169 or bridged); PPP links; X.25, Frame Relay, or ATM 170 networks; and internet (or higher) layer "tunnels", such 171 as tunnels over IPv4 or IPv6 itself. 173 neighbors nodes attached to the same link. 175 interface a node's attachment to a link. 177 address an IPv6-layer identifier for an interface or a set of 178 interfaces. 180 packet an IPv6 header plus payload. 182 link MTU the maximum transmission unit, i.e., maximum packet size 183 in octets, that can be conveyed over a link. 185 path MTU the minimum link MTU of all the links in a path between 186 a source node and a destination node. 188 Note: it is possible for a device with multiple interfaces to be 189 configured to forward non-self-destined packets arriving from some 190 set (fewer than all) of its interfaces, and to discard non-self- 191 destined packets arriving from its other interfaces. Such a device 192 must obey the protocol requirements for routers when receiving 193 packets from, and interacting with neighbors over, the former 194 (forwarding) interfaces. It must obey the protocol requirements for 195 hosts when receiving packets from, and interacting with neighbors 196 over, the latter (non-forwarding) interfaces. 198 3. IPv6 Header Format 200 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 201 |Version| Traffic Class | Flow Label | 202 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 203 | Payload Length | Next Header | Hop Limit | 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 | | 206 + + 207 | | 208 + Source Address + 209 | | 210 + + 211 | | 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 | | 214 + + 215 | | 216 + Destination Address + 217 | | 218 + + 219 | | 220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 222 Version 4-bit Internet Protocol version number = 6. 224 Traffic Class 8-bit traffic class field. See section 7. 226 Flow Label 20-bit flow label. See section 6. 228 Payload Length 16-bit unsigned integer. Length of the IPv6 229 payload, i.e., the rest of the packet 230 following this IPv6 header, in octets. (Note 231 that any extension headers [section 4] present 232 are considered part of the payload, i.e., 233 included in the length count.) 235 Next Header 8-bit selector. Identifies the type of header 236 immediately following the IPv6 header. Uses 237 the same values as the IPv4 Protocol field 238 [IANA-PN]. 240 Hop Limit 8-bit unsigned integer. Decremented by 1 by 241 each node that forwards the packet. When 242 forwarding, the packet is discarded if Hop 243 Limit was zero when received or is decremented 244 to zero. A node that is the destination of a 245 packet should not discard a packet with hop 246 limit equal to zero, it should process the 247 packet normally. 249 Source Address 128-bit address of the originator of the 250 packet. See [RFC4291]. 252 Destination Address 128-bit address of the intended recipient of 253 the packet (possibly not the ultimate 254 recipient, if a Routing header is present). 255 See [RFC4291] and section 4.4. 257 4. IPv6 Extension Headers 259 In IPv6, optional internet-layer information is encoded in separate 260 headers that may be placed between the IPv6 header and the upper- 261 layer header in a packet. There is a small number of such extension 262 headers, each one identified by a distinct Next Header value. 264 Extension Headers are numbered from IANA IP Protocol Numbers 265 [IANA-PN], the same values used for IPv4 and IPv6. When processing a 266 sequence of Next Header values in a packet, the first one that is not 267 an Extension Header [IANA-EH] indicates that the next item in the 268 packet is the corresponding upper-layer header. A special "No Next 269 Header" value is used if there is no upper-layer header. 271 As illustrated in these examples, an IPv6 packet may carry zero, one, 272 or more extension headers, each identified by the Next Header field 273 of the preceding header: 275 +---------------+------------------------ 276 | IPv6 header | TCP header + data 277 | | 278 | Next Header = | 279 | TCP | 280 +---------------+------------------------ 282 +---------------+----------------+------------------------ 283 | IPv6 header | Routing header | TCP header + data 284 | | | 285 | Next Header = | Next Header = | 286 | Routing | TCP | 287 +---------------+----------------+------------------------ 289 +---------------+----------------+-----------------+----------------- 290 | IPv6 header | Routing header | Fragment header | fragment of TCP 291 | | | | header + data 292 | Next Header = | Next Header = | Next Header = | 293 | Routing | Fragment | TCP | 294 +---------------+----------------+-----------------+----------------- 296 With one exception, extension headers are not examined, processed, 297 inserted, or deleted by any node along a packet's delivery path, 298 until the packet reaches the node (or each of the set of nodes, in 299 the case of multicast) identified in the Destination Address field of 300 the IPv6 header. Note: If an intermediate forwarding node examines 301 an extension header for any reason, it must do so in accordance with 302 the provisions of [RFC7045]. At the Destination node, normal 303 demultiplexing on the Next Header field of the IPv6 header invokes 304 the module to process the first extension header, or the upper-layer 305 header if no extension header is present. The contents and semantics 306 of each extension header determine whether or not to proceed to the 307 next header. Therefore, extension headers must be processed strictly 308 in the order they appear in the packet; a receiver must not, for 309 example, scan through a packet looking for a particular kind of 310 extension header and process that header prior to processing all 311 preceding ones. 313 The exception referred to in the preceding paragraph is the Hop-by- 314 Hop Options header, which carries information that may be examined 315 and processed by every node along a packet's delivery path, including 316 the source and destination nodes. The Hop-by-Hop Options header, 317 when present, must immediately follow the IPv6 header. Its presence 318 is indicated by the value zero in the Next Header field of the IPv6 319 header. 321 NOTE: While [RFC2460] required that all nodes must examine and 322 process the Hop-by-Hop Options header, it is now expected that nodes 323 along a packet's delivery path only examine and process the Hop-by- 324 Hop Options header if explicitly configured to do so. 326 If, as a result of processing a header, the destination node is 327 required to proceed to the next header but the Next Header value in 328 the current header is unrecognized by the node, it should discard the 329 packet and send an ICMP Parameter Problem message to the source of 330 the packet, with an ICMP Code value of 1 ("unrecognized Next Header 331 type encountered") and the ICMP Pointer field containing the offset 332 of the unrecognized value within the original packet. The same 333 action should be taken if a node encounters a Next Header value of 334 zero in any header other than an IPv6 header. 336 Each extension header is an integer multiple of 8 octets long, in 337 order to retain 8-octet alignment for subsequent headers. Multi- 338 octet fields within each extension header are aligned on their 339 natural boundaries, i.e., fields of width n octets are placed at an 340 integer multiple of n octets from the start of the header, for n = 1, 341 2, 4, or 8. 343 A full implementation of IPv6 includes implementation of the 344 following extension headers: 346 Hop-by-Hop Options 347 Fragment 348 Destination Options 349 Routing 350 Authentication 351 Encapsulating Security Payload 353 The first four are specified in this document; the last two are 354 specified in [RFC4302] and [RFC4303], respectively. The current list 355 of IPv6 extension headers can be found at [IANA-EH]. 357 4.1. Extension Header Order 359 When more than one extension header is used in the same packet, it is 360 recommended that those headers appear in the following order: 362 IPv6 header 363 Hop-by-Hop Options header 364 Destination Options header (note 1) 365 Routing header 366 Fragment header 367 Authentication header (note 2) 368 Encapsulating Security Payload header (note 2) 369 Destination Options header (note 3) 370 upper-layer header 371 note 1: for options to be processed by the first destination that 372 appears in the IPv6 Destination Address field plus 373 subsequent destinations listed in the Routing header. 375 note 2: additional recommendations regarding the relative order of 376 the Authentication and Encapsulating Security Payload 377 headers are given in [RFC4303]. 379 note 3: for options to be processed only by the final destination 380 of the packet. 382 Each extension header should occur at most once, except for the 383 Destination Options header which should occur at most twice (once 384 before a Routing header and once before the upper-layer header). 386 If the upper-layer header is another IPv6 header (in the case of IPv6 387 being tunneled over or encapsulated in IPv6), it may be followed by 388 its own extension headers, which are separately subject to the same 389 ordering recommendations. 391 If and when other extension headers are defined, their ordering 392 constraints relative to the above listed headers must be specified. 394 IPv6 nodes must accept and attempt to process extension headers in 395 any order and occurring any number of times in the same packet, 396 except for the Hop-by-Hop Options header which is restricted to 397 appear immediately after an IPv6 header only. Nonetheless, it is 398 strongly advised that sources of IPv6 packets adhere to the above 399 recommended order until and unless subsequent specifications revise 400 that recommendation. 402 4.2. Options 404 Two of the currently-defined extension headers defined in this 405 document -- the Hop-by-Hop Options header and the Destination Options 406 header -- carry a variable number of type-length-value (TLV) encoded 407 "options", of the following format: 409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - - 410 | Option Type | Opt Data Len | Option Data 411 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - - 413 Option Type 8-bit identifier of the type of option. 415 Opt Data Len 8-bit unsigned integer. Length of the Option 416 Data field of this option, in octets. 418 Option Data Variable-length field. Option-Type-specific 419 data. 421 The sequence of options within a header must be processed strictly in 422 the order they appear in the header; a receiver must not, for 423 example, scan through the header looking for a particular kind of 424 option and process that option prior to processing all preceding 425 ones. 427 The Option Type identifiers are internally encoded such that their 428 highest-order two bits specify the action that must be taken if the 429 processing IPv6 node does not recognize the Option Type: 431 00 - skip over this option and continue processing the header. 433 01 - discard the packet. 435 10 - discard the packet and, regardless of whether or not the 436 packet's Destination Address was a multicast address, send an 437 ICMP Parameter Problem, Code 2, message to the packet's 438 Source Address, pointing to the unrecognized Option Type. 440 11 - discard the packet and, only if the packet's Destination 441 Address was not a multicast address, send an ICMP Parameter 442 Problem, Code 2, message to the packet's Source Address, 443 pointing to the unrecognized Option Type. 445 The third-highest-order bit of the Option Type specifies whether or 446 not the Option Data of that option can change en-route to the 447 packet's final destination. When an Authentication header is present 448 in the packet, for any option whose data may change en-route, its 449 entire Option Data field must be treated as zero-valued octets when 450 computing or verifying the packet's authenticating value. 452 0 - Option Data does not change en-route 454 1 - Option Data may change en-route 456 The three high-order bits described above are to be treated as part 457 of the Option Type, not independent of the Option Type. That is, a 458 particular option is identified by a full 8-bit Option Type, not just 459 the low-order 5 bits of an Option Type. 461 The same Option Type numbering space is used for both the Hop-by-Hop 462 Options header and the Destination Options header. However, the 463 specification of a particular option may restrict its use to only one 464 of those two headers. 466 Individual options may have specific alignment requirements, to 467 ensure that multi-octet values within Option Data fields fall on 468 natural boundaries. The alignment requirement of an option is 469 specified using the notation xn+y, meaning the Option Type must 470 appear at an integer multiple of x octets from the start of the 471 header, plus y octets. For example: 473 2n means any 2-octet offset from the start of the header. 474 8n+2 means any 8-octet offset from the start of the header, plus 2 475 octets. 477 There are two padding options which are used when necessary to align 478 subsequent options and to pad out the containing header to a multiple 479 of 8 octets in length. These padding options must be recognized by 480 all IPv6 implementations: 482 Pad1 option (alignment requirement: none) 484 +-+-+-+-+-+-+-+-+ 485 | 0 | 486 +-+-+-+-+-+-+-+-+ 488 NOTE! the format of the Pad1 option is a special case -- it does 489 not have length and value fields. 491 The Pad1 option is used to insert one octet of padding into the 492 Options area of a header. If more than one octet of padding is 493 required, the PadN option, described next, should be used, rather 494 than multiple Pad1 options. 496 PadN option (alignment requirement: none) 498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - - 499 | 1 | Opt Data Len | Option Data 500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- - - - - - - - - 502 The PadN option is used to insert two or more octets of padding 503 into the Options area of a header. For N octets of padding, the 504 Opt Data Len field contains the value N-2, and the Option Data 505 consists of N-2 zero-valued octets. 507 Appendix A contains formatting guidelines for designing new options. 509 4.3. Hop-by-Hop Options Header 511 The Hop-by-Hop Options header is used to carry optional information 512 that may be examined and processed by every node along a packet's 513 delivery path. The Hop-by-Hop Options header is identified by a Next 514 Header value of 0 in the IPv6 header, and has the following format: 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 | Next Header | Hdr Ext Len | | 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 519 | | 520 . . 521 . Options . 522 . . 523 | | 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 526 Next Header 8-bit selector. Identifies the type of header 527 immediately following the Hop-by-Hop Options 528 header. Uses the same values as the IPv4 529 Protocol field [IANA-PN]. 531 Hdr Ext Len 8-bit unsigned integer. Length of the Hop-by- 532 Hop Options header in 8-octet units, not 533 including the first 8 octets. 535 Options Variable-length field, of length such that the 536 complete Hop-by-Hop Options header is an 537 integer multiple of 8 octets long. Contains 538 one or more TLV-encoded options, as described 539 in section 4.2. 541 The only hop-by-hop options defined in this document are the Pad1 and 542 PadN options specified in section 4.2. 544 4.4. Routing Header 546 The Routing header is used by an IPv6 source to list one or more 547 intermediate nodes to be "visited" on the way to a packet's 548 destination. This function is very similar to IPv4's Loose Source 549 and Record Route option. The Routing header is identified by a Next 550 Header value of 43 in the immediately preceding header, and has the 551 following format: 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | Next Header | Hdr Ext Len | Routing Type | Segments Left | 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 | | 557 . . 558 . type-specific data . 559 . . 560 | | 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 563 Next Header 8-bit selector. Identifies the type of header 564 immediately following the Routing header. 565 Uses the same values as the IPv4 Protocol 566 field [IANA-PN]. 568 Hdr Ext Len 8-bit unsigned integer. Length of the Routing 569 header in 8-octet units, not including the 570 first 8 octets. 572 Routing Type 8-bit identifier of a particular Routing 573 header variant. 575 Segments Left 8-bit unsigned integer. Number of route 576 segments remaining, i.e., number of explicitly 577 listed intermediate nodes still to be visited 578 before reaching the final destination. 580 type-specific data Variable-length field, of format determined by 581 the Routing Type, and of length such that the 582 complete Routing header is an integer multiple 583 of 8 octets long. 585 If, while processing a received packet, a node encounters a Routing 586 header with an unrecognized Routing Type value, the required behavior 587 of the node depends on the value of the Segments Left field, as 588 follows: 590 If Segments Left is zero, the node must ignore the Routing header 591 and proceed to process the next header in the packet, whose type 592 is identified by the Next Header field in the Routing header. 594 If Segments Left is non-zero, the node must discard the packet and 595 send an ICMP Parameter Problem, Code 0, message to the packet's 596 Source Address, pointing to the unrecognized Routing Type. 598 If, after processing a Routing header of a received packet, an 599 intermediate node determines that the packet is to be forwarded onto 600 a link whose link MTU is less than the size of the packet, the node 601 must discard the packet and send an ICMP Packet Too Big message to 602 the packet's Source Address. 604 The currently defined IPv6 Routing Headers and their status can be 605 found at [IANA-RH]. Allocation guidelines for IPv6 Routing Headers 606 can be found in [RFC5871]. 608 4.5. Fragment Header 610 The Fragment header is used by an IPv6 source to send a packet larger 611 than would fit in the path MTU to its destination. (Note: unlike 612 IPv4, fragmentation in IPv6 is performed only by source nodes, not by 613 routers along a packet's delivery path -- see section 5.) The 614 Fragment header is identified by a Next Header value of 44 in the 615 immediately preceding header, and has the following format: 617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 618 | Next Header | Reserved | Fragment Offset |Res|M| 619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 620 | Identification | 621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 623 Next Header 8-bit selector. Identifies the initial header 624 type of the Fragmentable Part of the original 625 packet (defined below). Uses the same values 626 as the IPv4 Protocol field [IANA-PN]. 628 Reserved 8-bit reserved field. Initialized to zero for 629 transmission; ignored on reception. 631 Fragment Offset 13-bit unsigned integer. The offset, in 632 8-octet units, of the data following this 633 header, relative to the start of the 634 Fragmentable Part of the original packet. 636 Res 2-bit reserved field. Initialized to zero for 637 transmission; ignored on reception. 639 M flag 1 = more fragments; 0 = last fragment. 641 Identification 32 bits. See description below. 643 In order to send a packet that is too large to fit in the MTU of the 644 path to its destination, a source node may divide the packet into 645 fragments and send each fragment as a separate packet, to be 646 reassembled at the receiver. 648 For every packet that is to be fragmented, the source node generates 649 an Identification value. The Identification must be different than 650 that of any other fragmented packet sent recently* with the same 651 Source Address and Destination Address. If a Routing header is 652 present, the Destination Address of concern is that of the final 653 destination. 655 * "recently" means within the maximum likely lifetime of a 656 packet, including transit time from source to destination and 657 time spent awaiting reassembly with other fragments of the same 658 packet. However, it is not required that a source node knows 659 the maximum packet lifetime. Rather, it is assumed that the 660 requirement can be met by implementing an algorithm that 661 results in a low identification reuse frequency. Examples of 662 algorithms that can meet this requirement are described in 663 [RFC7739]. 665 The initial, large, unfragmented packet is referred to as the 666 "original packet", and it is considered to consist of three parts, as 667 illustrated: 669 original packet: 671 +------------------+-------------------------+---//----------------+ 672 | Per-Fragment | Extension & Upper-Layer | Fragmentable | 673 | Headers | Headers | Part | 674 +------------------+-------------------------+---//----------------+ 676 The Per-Fragment Headers must consist of the IPv6 header plus any 677 extension headers that must be processed by nodes en route to the 678 destination, that is, all headers up to and including the Routing 679 header if present, else the Hop-by-Hop Options header if present, 680 else no extension headers. 682 The Extension Headers are all other extension headers that are not 683 included in the Per-Fragment headers part of the packet. For this 684 purpose, the Encapsulating Security Payload (ESP) is not 685 considered an extension header. The Upper-Layer Header is the 686 first upper-layer header that is not an IPv6 extension header. 688 Examples of upper-layer headers include TCP, UDP, IPv4, IPv6, 689 ICMPv6, and as noted ESP. 691 The Fragmentable Part consists of the rest of the packet after the 692 upper-layer header or after any header (i.e., initial IPv6 header 693 or extension header) that contains a Next Header value of No Next 694 Header. 696 The Fragmentable Part of the original packet is divided into 697 fragments. The lengths of the fragments must be chosen such that the 698 resulting fragment packets fit within the MTU of the path to the 699 packets' destination(s). Each complete fragment, except possibly the 700 last ("rightmost") one, being an integer multiple of 8 octets long. 702 The fragments are transmitted in separate "fragment packets" as 703 illustrated: 705 original packet: 707 +-----------------+-----------------+--------+--------+-//-+--------+ 708 | Per-Fragment |Ext & Upper-Layer| first | second | | last | 709 | Headers | Headers |fragment|fragment|....|fragment| 710 +-----------------+-----------------+--------+--------+-//-+--------+ 712 fragment packets: 714 +------------------+---------+-------------------+----------+ 715 | Per-Fragment |Fragment | Ext & Upper-Layer | first | 716 | Headers | Header | Headers | fragment | 717 +------------------+---------+-------------------+----------+ 719 +------------------+--------+-------------------------------+ 720 | Per-Fragment |Fragment| second | 721 | Headers | Header | fragment | 722 +------------------+--------+-------------------------------+ 723 o 724 o 725 o 726 +------------------+--------+----------+ 727 | Per-Fragment |Fragment| last | 728 | Headers | Header | fragment | 729 +------------------+--------+----------+ 731 The first fragment packet is composed of: 733 (1) The Per-Fragment Headers of the original packet, with the 734 Payload Length of the original IPv6 header changed to contain the 735 length of this fragment packet only (excluding the length of the 736 IPv6 header itself), and the Next Header field of the last header 737 of the Per-Fragment Headers changed to 44. 739 (2) A Fragment header containing: 741 The Next Header value that identifies the first header after 742 the Per-Fragment Headers of the original packet. 744 A Fragment Offset containing the offset of the fragment, in 745 8-octet units, relative to the start of the Fragmentable Part 746 of the original packet. The Fragment Offset of the first 747 ("leftmost") fragment is 0. 749 An M flag value of 1 as this is the first fragment. 751 The Identification value generated for the original packet. 753 (3) Extension Headers, if any, and the Upper-Layer header. These 754 headers must be in the first fragment. Note: This restricts the 755 size of the headers through the Upper-Layer header to the MTU of 756 the path to the packets' destinations(s). 758 (4) The first fragment. 760 The subsequent fragment packets are composed of: 762 (1) The Per-Fragment Headers of the original packet, with the 763 Payload Length of the original IPv6 header changed to contain the 764 length of this fragment packet only (excluding the length of the 765 IPv6 header itself), and the Next Header field of the last header 766 of the Per-Fragment Headers changed to 44. 768 (2) A Fragment header containing: 770 The Next Header value that identifies the first header after 771 the Per-Fragment Headers of the original packet. 773 A Fragment Offset containing the offset of the fragment, in 774 8-octet units, relative to the start of the Fragmentable part 775 of the original packet. 777 An M flag value of 0 if the fragment is the last ("rightmost") 778 one, else an M flag value of 1. 780 The Identification value generated for the original packet. 782 (3) The fragment itself. 784 Fragments must not be created that overlap with any other fragments 785 created from the original packet. 787 At the destination, fragment packets are reassembled into their 788 original, unfragmented form, as illustrated: 790 reassembled original packet: 792 +---------------+-----------------+---------+--------+-//--+--------+ 793 | Per-Fragment |Ext & Upper-Layer| first | second | | last | 794 | Headers | Headers |frag data|fragment|.....|fragment| 795 +---------------+-----------------+---------+--------+-//--+--------+ 797 The following rules govern reassembly: 799 An original packet is reassembled only from fragment packets that 800 have the same Source Address, Destination Address, and Fragment 801 Identification. 803 The Per-Fragment Headers of the reassembled packet consists of all 804 headers up to, but not including, the Fragment header of the first 805 fragment packet (that is, the packet whose Fragment Offset is 806 zero), with the following two changes: 808 The Next Header field of the last header of the Per-Fragment 809 Headers is obtained from the Next Header field of the first 810 fragment's Fragment header. 812 The Payload Length of the reassembled packet is computed from 813 the length of the Per-Fragment Headers and the length and 814 offset of the last fragment. For example, a formula for 815 computing the Payload Length of the reassembled original packet 816 is: 818 PL.orig = PL.first - FL.first - 8 + (8 * FO.last) + FL.last 820 where 821 PL.orig = Payload Length field of reassembled packet. 822 PL.first = Payload Length field of first fragment packet. 824 FL.first = length of fragment following Fragment header of 825 first fragment packet. 826 FO.last = Fragment Offset field of Fragment header of last 827 fragment packet. 828 FL.last = length of fragment following Fragment header of 829 last fragment packet. 831 The Fragmentable Part of the reassembled packet is constructed 832 from the fragments following the Fragment headers in each of 833 the fragment packets. The length of each fragment is computed 834 by subtracting from the packet's Payload Length the length of 835 the headers between the IPv6 header and fragment itself; its 836 relative position in Fragmentable Part is computed from its 837 Fragment Offset value. 839 The Fragment header is not present in the final, reassembled 840 packet. 842 If the fragment is a whole datagram (that is, both the Fragment 843 Offset field and the M flag are zero), then it does not need 844 any further reassembly and should be processed as a fully 845 reassembled packet (i.e., updating Next Header, adjust Payload 846 Length, removing the Fragmentation Header, etc.). Any other 847 fragments that match this packet (i.e., the same IPv6 Source 848 Address, IPv6 Destination Address, and Fragment Identification) 849 should be processed independently. 851 The following error conditions may arise when reassembling fragmented 852 packets: 854 o If insufficient fragments are received to complete reassembly 855 of a packet within 60 seconds of the reception of the first- 856 arriving fragment of that packet, reassembly of that packet 857 must be abandoned and all the fragments that have been received 858 for that packet must be discarded. If the first fragment 859 (i.e., the one with a Fragment Offset of zero) has been 860 received, an ICMP Time Exceeded -- Fragment Reassembly Time 861 Exceeded message should be sent to the source of that fragment. 863 o If the length of a fragment, as derived from the fragment 864 packet's Payload Length field, is not a multiple of 8 octets 865 and the M flag of that fragment is 1, then that fragment must 866 be discarded and an ICMP Parameter Problem, Code 0, message 867 should be sent to the source of the fragment, pointing to the 868 Payload Length field of the fragment packet. 870 o If the length and offset of a fragment are such that the 871 Payload Length of the packet reassembled from that fragment 872 would exceed 65,535 octets, then that fragment must be 873 discarded and an ICMP Parameter Problem, Code 0, message should 874 be sent to the source of the fragment, pointing to the Fragment 875 Offset field of the fragment packet. 877 o If the first fragment does not include all headers through an 878 Upper-Layer header, then that fragment should be discarded and 879 an ICMP Parameter Problem, Code 3, message should be sent to 880 the source of the fragment, with the Pointer field set to zero. 882 o If any of the fragments being reassembled overlaps with any 883 other fragments being reassembled for the same packet, 884 reassembly of that packet must be abandoned and all the 885 fragments that have been received for that packet must be 886 discarded and no ICMP error messages should be sent. 888 It should be noted that fragments may be duplicated in the 889 network. Instead of treating these exact duplicate fragments 890 as overlapping fragments, an implementation may choose to 891 detect this case and drop exact duplicate fragments while 892 keeping the other fragments belonging to the same packet. 894 The following conditions are not expected to occur frequently, but 895 are not considered errors if they do: 897 The number and content of the headers preceding the Fragment 898 header of different fragments of the same original packet may 899 differ. Whatever headers are present, preceding the Fragment 900 header in each fragment packet, are processed when the packets 901 arrive, prior to queueing the fragments for reassembly. Only 902 those headers in the Offset zero fragment packet are retained in 903 the reassembled packet. 905 The Next Header values in the Fragment headers of different 906 fragments of the same original packet may differ. Only the value 907 from the Offset zero fragment packet is used for reassembly. 909 4.6. Destination Options Header 911 The Destination Options header is used to carry optional information 912 that need be examined only by a packet's destination node(s). The 913 Destination Options header is identified by a Next Header value of 60 914 in the immediately preceding header, and has the following format: 916 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 917 | Next Header | Hdr Ext Len | | 918 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 919 | | 920 . . 921 . Options . 922 . . 923 | | 924 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 926 Next Header 8-bit selector. Identifies the type of header 927 immediately following the Destination Options 928 header. Uses the same values as the IPv4 929 Protocol field [IANA-PN]. 931 Hdr Ext Len 8-bit unsigned integer. Length of the 932 Destination Options header in 8-octet units, 933 not including the first 8 octets. 935 Options Variable-length field, of length such that the 936 complete Destination Options header is an 937 integer multiple of 8 octets long. Contains 938 one or more TLV-encoded options, as described 939 in section 4.2. 941 The only destination options defined in this document are the Pad1 942 and PadN options specified in section 4.2. 944 Note that there are two possible ways to encode optional destination 945 information in an IPv6 packet: either as an option in the Destination 946 Options header, or as a separate extension header. The Fragment 947 header and the Authentication header are examples of the latter 948 approach. Which approach can be used depends on what action is 949 desired of a destination node that does not understand the optional 950 information: 952 o If the desired action is for the destination node to discard 953 the packet and, only if the packet's Destination Address is not 954 a multicast address, send an ICMP Unrecognized Type message to 955 the packet's Source Address, then the information may be 956 encoded either as a separate header or as an option in the 957 Destination Options header whose Option Type has the value 11 958 in its highest-order two bits. The choice may depend on such 959 factors as which takes fewer octets, or which yields better 960 alignment or more efficient parsing. 962 o If any other action is desired, the information must be encoded 963 as an option in the Destination Options header whose Option 964 Type has the value 00, 01, or 10 in its highest-order two bits, 965 specifying the desired action (see section 4.2). 967 4.7. No Next Header 969 The value 59 in the Next Header field of an IPv6 header or any 970 extension header indicates that there is nothing following that 971 header. If the Payload Length field of the IPv6 header indicates the 972 presence of octets past the end of a header whose Next Header field 973 contains 59, those octets must be ignored, and passed on unchanged if 974 the packet is forwarded. 976 4.8. Defining New Extension Headers and Options 978 New extension headers that require hop-by-hop behavior must not be 979 defined because, as specified in Section 4 of this document, the only 980 Extension Header that has hop-by-hop behavior is the Hop-by-Hop 981 Options header. 983 New hop-by-hop options are not recommended because nodes may be 984 configured to ignore the Hop-by-Hop Option header, drop packets 985 containing a hop-by-hop header, or assign packets containing a hop- 986 by-hop header to a slow processing path. Designers considering 987 defining new hop-by-hop options need to be aware of this likely 988 behaviour. There has to be a very clear justification why any new 989 hop-by-hop option is needed before it is standardized. 991 Defining new IPv6 extension headers is not recommended. There has to 992 be a very clear justification why any new extension header is needed 993 before it is standardized. Instead of defining new Extension 994 Headers, it is recommended that the Destination Options header is 995 used to carry optional information that must be examined only by a 996 packet's destination node(s), because they provide better handling 997 and backward compatibility. 999 If new Extension Headers are defined, they need to use the following 1000 format: 1002 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1003 | Next Header | Hdr Ext Len | | 1004 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 1005 | | 1006 . . 1007 . Header Specific Data . 1008 . . 1009 | | 1010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1012 Next Header 8-bit selector. Identifies the type of 1013 header immediately following the extension 1014 header. Uses the same values as the IPv4 1015 Protocol field [IANA-PN]. 1017 Hdr Ext Len 8-bit unsigned integer. Length of the 1018 Destination Options header in 8-octet units, 1019 not including the first 8 octets. 1021 Header Specific Data Variable-length field. Fields specific to 1022 the extension header. 1024 5. Packet Size Issues 1026 IPv6 requires that every link in the internet have an MTU of 1280 1027 octets or greater. On any link that cannot convey a 1280-octet 1028 packet in one piece, link-specific fragmentation and reassembly must 1029 be provided at a layer below IPv6. 1031 Links that have a configurable MTU (for example, PPP links [RFC1661]) 1032 must be configured to have an MTU of at least 1280 octets; it is 1033 recommended that they be configured with an MTU of 1500 octets or 1034 greater, to accommodate possible encapsulations (i.e., tunneling) 1035 without incurring IPv6-layer fragmentation. 1037 From each link to which a node is directly attached, the node must be 1038 able to accept packets as large as that link's MTU. 1040 It is strongly recommended that IPv6 nodes implement Path MTU 1041 Discovery [RFC1981], in order to discover and take advantage of path 1042 MTUs greater than 1280 octets. However, a minimal IPv6 1043 implementation (e.g., in a boot ROM) may simply restrict itself to 1044 sending packets no larger than 1280 octets, and omit implementation 1045 of Path MTU Discovery. 1047 In order to send a packet larger than a path's MTU, a node may use 1048 the IPv6 Fragment header to fragment the packet at the source and 1049 have it reassembled at the destination(s). However, the use of such 1050 fragmentation is discouraged in any application that is able to 1051 adjust its packets to fit the measured path MTU (i.e., down to 1280 1052 octets). 1054 A node must be able to accept a fragmented packet that, after 1055 reassembly, is as large as 1500 octets. A node is permitted to 1056 accept fragmented packets that reassemble to more than 1500 octets. 1057 An upper-layer protocol or application that depends on IPv6 1058 fragmentation to send packets larger than the MTU of a path should 1059 not send packets larger than 1500 octets unless it has assurance that 1060 the destination is capable of reassembling packets of that larger 1061 size. 1063 6. Flow Labels 1065 The 20-bit Flow Label field in the IPv6 header is used by a source to 1066 label sequences of packets to be treated in the network as a single 1067 flow. 1069 The current definition of the IPv6 Flow Label can be found in 1070 [RFC6437]. 1072 7. Traffic Classes 1074 The 8-bit Traffic Class field in the IPv6 header is used by the 1075 network for traffic management. The value of the Traffic Class bits 1076 in a received packet or fragment might be different from the value 1077 sent by the packet's source. 1079 The current use of the Traffic Class field for Differentiated 1080 Services and Explicit Congestion Notification is specified in 1081 [RFC2474] and [RFC3168]. 1083 8. Upper-Layer Protocol Issues 1085 8.1. Upper-Layer Checksums 1087 Any transport or other upper-layer protocol that includes the 1088 addresses from the IP header in its checksum computation must be 1089 modified for use over IPv6, to include the 128-bit IPv6 addresses 1090 instead of 32-bit IPv4 addresses. In particular, the following 1091 illustration shows the TCP and UDP "pseudo-header" for IPv6: 1093 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1094 | | 1095 + + 1096 | | 1097 + Source Address + 1098 | | 1099 + + 1100 | | 1101 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1102 | | 1103 + + 1104 | | 1105 + Destination Address + 1106 | | 1107 + + 1108 | | 1109 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1110 | Upper-Layer Packet Length | 1111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1112 | zero | Next Header | 1113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1115 o If the IPv6 packet contains a Routing header, the Destination 1116 Address used in the pseudo-header is that of the final 1117 destination. At the originating node, that address will be in 1118 the last element of the Routing header; at the recipient(s), 1119 that address will be in the Destination Address field of the 1120 IPv6 header. 1122 o The Next Header value in the pseudo-header identifies the 1123 upper-layer protocol (e.g., 6 for TCP, or 17 for UDP). It will 1124 differ from the Next Header value in the IPv6 header if there 1125 are extension headers between the IPv6 header and the upper- 1126 layer header. 1128 o The Upper-Layer Packet Length in the pseudo-header is the 1129 length of the upper-layer header and data (e.g., TCP header 1130 plus TCP data). Some upper-layer protocols carry their own 1131 length information (e.g., the Length field in the UDP header); 1132 for such protocols, that is the length used in the pseudo- 1133 header. Other protocols (such as TCP) do not carry their own 1134 length information, in which case the length used in the 1135 pseudo-header is the Payload Length from the IPv6 header, minus 1136 the length of any extension headers present between the IPv6 1137 header and the upper-layer header. 1139 o Unlike IPv4, the default behavior when UDP packets are 1140 originated by an IPv6 node is that the UDP checksum is not 1141 optional. That is, whenever originating a UDP packet, an IPv6 1142 node must compute a UDP checksum over the packet and the 1143 pseudo-header, and, if that computation yields a result of 1144 zero, it must be changed to hex FFFF for placement in the UDP 1145 header. IPv6 receivers must discard UDP packets containing a 1146 zero checksum, and should log the error. 1148 o As an exception to the default behaviour, protocols that use 1149 UDP as a tunnel encapsulation may enable zero-checksum mode for 1150 a specific port (or set of ports) for sending and/or receiving. 1151 Any node implementing zero-checksum mode must follow the 1152 requirements specified in "Applicability Statement for the Use 1153 of IPv6 UDP Datagrams with Zero Checksums" [RFC6936]. 1155 The IPv6 version of ICMP [RFC4443] includes the above pseudo-header 1156 in its checksum computation; this is a change from the IPv4 version 1157 of ICMP, which does not include a pseudo-header in its checksum. The 1158 reason for the change is to protect ICMP from misdelivery or 1159 corruption of those fields of the IPv6 header on which it depends, 1160 which, unlike IPv4, are not covered by an internet-layer checksum. 1161 The Next Header field in the pseudo-header for ICMP contains the 1162 value 58, which identifies the IPv6 version of ICMP. 1164 8.2. Maximum Packet Lifetime 1166 Unlike IPv4, IPv6 nodes are not required to enforce maximum packet 1167 lifetime. That is the reason the IPv4 "Time to Live" field was 1168 renamed "Hop Limit" in IPv6. In practice, very few, if any, IPv4 1169 implementations conform to the requirement that they limit packet 1170 lifetime, so this is not a change in practice. Any upper-layer 1171 protocol that relies on the internet layer (whether IPv4 or IPv6) to 1172 limit packet lifetime ought to be upgraded to provide its own 1173 mechanisms for detecting and discarding obsolete packets. 1175 8.3. Maximum Upper-Layer Payload Size 1177 When computing the maximum payload size available for upper-layer 1178 data, an upper-layer protocol must take into account the larger size 1179 of the IPv6 header relative to the IPv4 header. For example, in 1180 IPv4, TCP's MSS option is computed as the maximum packet size (a 1181 default value or a value learned through Path MTU Discovery) minus 40 1182 octets (20 octets for the minimum-length IPv4 header and 20 octets 1183 for the minimum-length TCP header). When using TCP over IPv6, the 1184 MSS must be computed as the maximum packet size minus 60 octets, 1185 because the minimum-length IPv6 header (i.e., an IPv6 header with no 1186 extension headers) is 20 octets longer than a minimum-length IPv4 1187 header. 1189 8.4. Responding to Packets Carrying Routing Headers 1191 When an upper-layer protocol sends one or more packets in response to 1192 a received packet that included a Routing header, the response 1193 packet(s) must not include a Routing header that was automatically 1194 derived by "reversing" the received Routing header UNLESS the 1195 integrity and authenticity of the received Source Address and Routing 1196 header have been verified (e.g., via the use of an Authentication 1197 header in the received packet). In other words, only the following 1198 kinds of packets are permitted in response to a received packet 1199 bearing a Routing header: 1201 o Response packets that do not carry Routing headers. 1203 o Response packets that carry Routing headers that were NOT 1204 derived by reversing the Routing header of the received packet 1205 (for example, a Routing header supplied by local 1206 configuration). 1208 o Response packets that carry Routing headers that were derived 1209 by reversing the Routing header of the received packet IF AND 1210 ONLY IF the integrity and authenticity of the Source Address 1211 and Routing header from the received packet have been verified 1212 by the responder. 1214 9. IANA Considerations 1216 RFC2460 is referenced in a number of IANA registries. These include: 1218 o Internet Protocol Version 6 (IPv6) Parameters [IANA-6P] 1220 o Assigned Internet Protocol Numbers [IANA-PN] 1222 o ONC RPC Network Identifiers (netids) [IANA-NI] 1224 o Technical requirements for authoritative name servers [IANA-NS] 1226 o Network Layer Protocol Identifiers (NLPIDs) of Interest 1227 [IANA-NL] 1229 o Protocol Registries [IANA-PR] 1230 o Structure of Management Information (SMI) Numbers (MIB Module 1231 Registrations) [IANA-MI] 1233 The IANA should update these references to point to this document. 1235 10. Security Considerations 1237 IPv6, from the viewpoint of the basic format and transmission of 1238 packets, has security properties that are similar to IPv4. These 1239 security issues include: 1241 o Eavesdropping, On-path elements can observe the whole packet 1242 (including both contents and metadata) of each IPv6 datagram. 1243 o Replay, where attacker records a sequence of packets off of the 1244 wire and plays them back to the party which originally received 1245 them. 1246 o Packet insertion, where the attacker forges a packet with some 1247 chosen set of properties and injects it into the network. 1248 o Packet deletion, where the attacker remove a packet from the 1249 wire. 1250 o Packet modification, where the attacker removes a packet from 1251 the wire, modifies it, and re-injects it into the network. 1252 o Man in the Middle attacks, where the attacker subverts the 1253 communication stream in order to pose as the sender to receiver 1254 and the receiver to the sender. 1255 o Denial of Service Attacks, where the attacker sends large 1256 amounts of legitimate traffic to a destination to overwhelm it. 1258 IPv6 packets can be protected from eavesdropping, replay, packet 1259 insertion, packet modification, and man in the middle attacks by use 1260 of the "Security Architecture for the Internet Protocol" [RFC4301]. 1261 In addition, upper-layer protocols such as TLS or SSH can be used to 1262 protect the application layer traffic running on top of IPv6. 1264 There is not any mechanism to protect against "denial of service 1265 attacks". Defending against these type of attacks is outside the 1266 scope of this specification. 1268 IPv6 addresses are significantly larger than IPv4 address making it 1269 much harder to scan the address space across the Internet and even on 1270 a single network link (e.g., Local Area Network). See [RFC7707] for 1271 more information. 1273 IPv6 addresses of nodes are expected to be more visible on the 1274 Internet as compared with IPv4 since the use of address translation 1275 technology is reduced. This creates some additional privacy issues 1276 such as making it easier to distinguish endpoints. See [RFC7721] for 1277 more information. 1279 The design of IPv6 extension headers architecture, while adding a lot 1280 of flexibility, also creates new security challenges. As noted 1281 below, issues relating the fragment extension header have been 1282 resolved, but it's clear that for any new extension header designed 1283 in the future, the security implications need to be examined 1284 throughly, and this needs to include how the new extension header 1285 works with existing extension headers. See [RFC7045] for more 1286 information. 1288 This version of the IPv6 specification resolves a number of security 1289 issues that were found with the previous version [RFC2460] of the 1290 IPv6 specification. These include: 1292 o Revised the text to handle the case of fragments that are whole 1293 datagrams (i.e., both the Fragment Offset field and the M flag 1294 are zero). If received they should be processed as a 1295 reassembled packet. Any other fragments that match should be 1296 processed independently. The Fragment creation process was 1297 modified to not create whole datagram fragments (Fragment 1298 Offset field and the M flag are zero). See [RFC6946] for more 1299 information. 1301 o Changed the text to require that IPv6 nodes must not create 1302 overlapping fragments. Also, when reassembling an IPv6 1303 datagram, if one or more its constituent fragments is 1304 determined to be an overlapping fragment, the entire datagram 1305 (and any constituent fragments) must be silently discarded. 1306 Includes clarification that no ICMP error message should be 1307 sent if overlapping fragments are received. See [RFC5722] for 1308 more information. 1310 0 Revised the text to require that all headers through the first 1311 Upper-Layer Header are in the first fragment. See [RFC6946] 1312 for more information. 1314 o Removed the paragraph in Section 5 that required including a 1315 fragment header to outgoing packets if a ICMP Packet Too Big 1316 message reporting a Next-Hop MTU less than 1280. See [RFC7112] 1317 for more information. 1319 o Incorporated the updates from [RFC5095] and [RFC5871] to remove 1320 the description of the RH0 Routing Header, that the allocations 1321 guidelines for routing headers are specified in RFC5871, and 1322 removed RH0 Routing Header from the list of required extension 1323 headers. 1325 Security issues relating to other parts of IPv6 including addressing, 1326 ICMPv6, Path MTU Discovery, etc., are discussed in the appropriate 1327 specifications. 1329 11. Acknowledgments 1331 The authors gratefully acknowledge the many helpful suggestions of 1332 the members of the IPng working group, the End-to-End Protocols 1333 research group, and the Internet Community At Large. 1335 The authors would also like to acknowledge the authors of the 1336 updating RFCs that were incorporated in this version of the document 1337 to move the IPv6 specification to Internet Standard. They are Joe 1338 Abley, Shane Amante, Jari Arkko, Manav Bhatia, Ronald P. Bonica, 1339 Scott Bradner, Brian Carpenter, P.F. Chimento, Marshall Eubanks, 1340 Fernando Gont, James Hoagland, Sheng Jiang, Erik Kline, Suresh 1341 Krishnan, Vishwas Manral, George Neville-Neil, Jarno Rajahalme, Pekka 1342 Savola, Magnus Westerlund, and James Woodyatt. 1344 12. References 1346 12.1. Normative References 1348 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, DOI 1349 10.17487/RFC0791, September 1981, 1350 . 1352 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1353 "Definition of the Differentiated Services Field (DS 1354 Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 1355 10.17487/RFC2474, December 1998, 1356 . 1358 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1359 of Explicit Congestion Notification (ECN) to IP", RFC 1360 3168, DOI 10.17487/RFC3168, September 2001, 1361 . 1363 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1364 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 1365 2006, . 1367 [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet 1368 Control Message Protocol (ICMPv6) for the Internet 1369 Protocol Version 6 (IPv6) Specification", RFC 4443, DOI 1370 10.17487/RFC4443, March 2006, 1371 . 1373 [RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme, 1374 "IPv6 Flow Label Specification", RFC 6437, DOI 10.17487/ 1375 RFC6437, November 2011, 1376 . 1378 12.2. Informative References 1380 [IANA-6P] "Internet Protocol Version 6 (IPv6) Parameters", 1381 . 1384 [IANA-EH] "IPv6 Extension Header Types", 1385 . 1388 [IANA-MI] "Structure of Management Information (SMI) Numbers (MIB 1389 Module Registrations)", < http://www.iana.org/assignments/ 1390 smi-numbers/smi-numbers.xhtml>. 1392 [IANA-NI] "ONC RPC Network Identifiers (netids)", 1393 . 1396 [IANA-NL] "Network Layer Protocol Identifiers (NLPIDs) of Interest", 1397 . 1399 [IANA-NS] "Technical requirements for authoritative name servers", 1400 . 1402 [IANA-PN] "Assigned Internet Protocol Numbers", 1403 . 1406 [IANA-PR] "Protocol Registries", . 1408 [IANA-RH] "IANA Routing Types Parameter Registry", 1409 . 1412 [RFC1661] Simpson, W., Ed., "The Point-to-Point Protocol (PPP)", STD 1413 51, RFC 1661, DOI 10.17487/RFC1661, July 1994, 1414 . 1416 [RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery 1417 for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August 1418 1996, . 1420 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1421 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 1422 December 1998, . 1424 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1425 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 1426 December 2005, . 1428 [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI 1429 10.17487/RFC4302, December 2005, 1430 . 1432 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 1433 4303, DOI 10.17487/RFC4303, December 2005, 1434 . 1436 [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation 1437 of Type 0 Routing Headers in IPv6", RFC 5095, DOI 1438 10.17487/RFC5095, December 2007, 1439 . 1441 [RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments", 1442 RFC 5722, DOI 10.17487/RFC5722, December 2009, 1443 . 1445 [RFC5871] Arkko, J. and S. Bradner, "IANA Allocation Guidelines for 1446 the IPv6 Routing Header", RFC 5871, DOI 10.17487/RFC5871, 1447 May 2010, . 1449 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1450 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1451 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1452 . 1454 [RFC6946] Gont, F., "Processing of IPv6 "Atomic" Fragments", RFC 1455 6946, DOI 10.17487/RFC6946, May 2013, 1456 . 1458 [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing 1459 of IPv6 Extension Headers", RFC 7045, DOI 10.17487/ 1460 RFC7045, December 2013, 1461 . 1463 [RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of 1464 Oversized IPv6 Header Chains", RFC 7112, DOI 10.17487/ 1465 RFC7112, January 2014, 1466 . 1468 [RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6 1469 Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016, 1470 . 1472 [RFC7721] Cooper, A., Gont, F., and D. Thaler, "Security and Privacy 1473 Considerations for IPv6 Address Generation Mechanisms", 1474 RFC 7721, DOI 10.17487/RFC7721, March 2016, 1475 . 1477 [RFC7739] Gont, F., "Security Implications of Predictable Fragment 1478 Identification Values", RFC 7739, DOI 10.17487/RFC7739, 1479 February 2016, . 1481 Appendix A. Formatting Guidelines for Options 1483 This appendix gives some advice on how to lay out the fields when 1484 designing new options to be used in the Hop-by-Hop Options header or 1485 the Destination Options header, as described in section 4.2. These 1486 guidelines are based on the following assumptions: 1488 o One desirable feature is that any multi-octet fields within the 1489 Option Data area of an option be aligned on their natural 1490 boundaries, i.e., fields of width n octets should be placed at 1491 an integer multiple of n octets from the start of the Hop-by- 1492 Hop or Destination Options header, for n = 1, 2, 4, or 8. 1494 o Another desirable feature is that the Hop-by-Hop or Destination 1495 Options header take up as little space as possible, subject to 1496 the requirement that the header be an integer multiple of 8 1497 octets long. 1499 o It may be assumed that, when either of the option-bearing 1500 headers are present, they carry a very small number of options, 1501 usually only one. 1503 These assumptions suggest the following approach to laying out the 1504 fields of an option: order the fields from smallest to largest, with 1505 no interior padding, then derive the alignment requirement for the 1506 entire option based on the alignment requirement of the largest field 1507 (up to a maximum alignment of 8 octets). This approach is 1508 illustrated in the following examples: 1510 Example 1 1512 If an option X required two data fields, one of length 8 octets and 1513 one of length 4 octets, it would be laid out as follows: 1515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1516 | Option Type=X |Opt Data Len=12| 1517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1518 | 4-octet field | 1519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1520 | | 1521 + 8-octet field + 1522 | | 1523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1525 Its alignment requirement is 8n+2, to ensure that the 8-octet field 1526 starts at a multiple-of-8 offset from the start of the enclosing 1527 header. A complete Hop-by-Hop or Destination Options header 1528 containing this one option would look as follows: 1530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1531 | Next Header | Hdr Ext Len=1 | Option Type=X |Opt Data Len=12| 1532 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1533 | 4-octet field | 1534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1535 | | 1536 + 8-octet field + 1537 | | 1538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1540 Example 2 1542 If an option Y required three data fields, one of length 4 octets, 1543 one of length 2 octets, and one of length 1 octet, it would be laid 1544 out as follows: 1546 +-+-+-+-+-+-+-+-+ 1547 | Option Type=Y | 1548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1549 |Opt Data Len=7 | 1-octet field | 2-octet field | 1550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1551 | 4-octet field | 1552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1554 Its alignment requirement is 4n+3, to ensure that the 4-octet field 1555 starts at a multiple-of-4 offset from the start of the enclosing 1556 header. A complete Hop-by-Hop or Destination Options header 1557 containing this one option would look as follows: 1559 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1560 | Next Header | Hdr Ext Len=1 | Pad1 Option=0 | Option Type=Y | 1561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1562 |Opt Data Len=7 | 1-octet field | 2-octet field | 1563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1564 | 4-octet field | 1565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1566 | PadN Option=1 |Opt Data Len=2 | 0 | 0 | 1567 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1569 Example 3 1571 A Hop-by-Hop or Destination Options header containing both options X 1572 and Y from Examples 1 and 2 would have one of the two following 1573 formats, depending on which option appeared first: 1575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1576 | Next Header | Hdr Ext Len=3 | Option Type=X |Opt Data Len=12| 1577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1578 | 4-octet field | 1579 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1580 | | 1581 + 8-octet field + 1582 | | 1583 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1584 | PadN Option=1 |Opt Data Len=1 | 0 | Option Type=Y | 1585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1586 |Opt Data Len=7 | 1-octet field | 2-octet field | 1587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1588 | 4-octet field | 1589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1590 | PadN Option=1 |Opt Data Len=2 | 0 | 0 | 1591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1594 | Next Header | Hdr Ext Len=3 | Pad1 Option=0 | Option Type=Y | 1595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1596 |Opt Data Len=7 | 1-octet field | 2-octet field | 1597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1598 | 4-octet field | 1599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1600 | PadN Option=1 |Opt Data Len=4 | 0 | 0 | 1601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1602 | 0 | 0 | Option Type=X |Opt Data Len=12| 1603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1604 | 4-octet field | 1605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1606 | | 1607 + 8-octet field + 1608 | | 1609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1611 Appendix B. Changes Since RFC2460 1613 This memo has the following changes from RFC2460. 1615 o Clarification that extension headers are not examined, processed, 1616 inserted, or deleted by any node along a packet's delivery path. 1618 o Added paragraph to Section 4 to clarify how Extension Headers are 1619 numbered and which are upper-layer headers. 1621 o Revision Section 4.5 on IPv6 Fragmentation based on updates from 1622 RFC5722, RFC6946 RFC7112, and RFC8021. This include: 1624 - Revised the text to handle the case of fragments that are whole 1625 datagrams (i.e., both the Fragment Offset field and the M flag 1626 are zero). If received they should be processed as a 1627 reassembled packet. Any other fragments that match should be 1628 processed independently. The revised Fragment creation process 1629 was modified to not create whole datagram fragments (Fragment 1630 Offset field and the M flag are zero). 1632 - Changed the text to require that IPv6 nodes must not create 1633 overlapping fragments. Also, when reassembling an IPv6 1634 datagram, if one or more its constituent fragments is 1635 determined to be an overlapping fragment, the entire datagram 1636 (and any constituent fragments) must be silently discarded. 1637 Includes a clarification that no ICMP error message should be 1638 sent if overlapping fragments are received. 1640 - Revised the text to require that all headers through the first 1641 Upper-Layer Header are in the first fragment. This changed the 1642 text describing how packets are fragmented and reassembled, and 1643 added a new error case. 1645 - Added text to Fragment Header process on handling exact 1646 duplicate fragments. 1648 - Updated the Fragmentation header text to correct the inclusion 1649 of AH and note no next header case. 1651 - Change terminology in Fragment header section from 1652 "Unfragmentable Headers" to "Per-Fragment Headers". 1654 - Removed the paragraph in Section 5 that required including a 1655 fragment header to outgoing packets if a ICMP Packet Too Big 1656 message reporting a Next-Hop MTU less than 1280. 1658 - Changed the text to clarify MTU restriction and 8-byte 1659 restrictions, and noting the restriction on headers in first 1660 fragment. 1662 o Changed requirement for HBH header to a may, and added a note to 1663 indicate what is expected regarding HBH headers. 1665 o Clarified the text in Section 3 about decrementing the hop limit. 1667 o Removed IP Next Generation from the Abstract. 1669 o Add reference to the end of Section 4 to IPv6 Extension Header 1670 IANA registry. 1672 o Added text in Section 1 that the Data Transmission Order is the 1673 same as IPv4 as defined in RFC791. 1675 o Add instruction to the IANA Considerations section to change 1676 references to RFC2460 to this document 1678 o Add a paragraph to the acknowledgement section acknowledging the 1679 authors of the updating documents 1681 o Update references to current versions and assign references to 1682 normative and informative. 1684 o Incorporated the update from RFC6564 to add a new Section 4.8 that 1685 describes recommendations for defining new Extension headers and 1686 options 1688 o Incorporate the update in made by RFC6935 "UDP Checksums for 1689 Tunneled Packets" in Section 8. Added an exception to the default 1690 behaviour for the handling of handling UDP packets with zero 1691 checksums for tunnels. 1693 o Incorporate the updates from RFC5095 and RFC5871 to remove the 1694 description of the RH0 Routing Header, that the allocations 1695 guidelines for routing headers are specified in RFC5871, and 1696 removed RH0 Routing Header from the list of required extension 1697 headers. 1699 o Changes to resolve the open Errata on RFC2460. These are: 1701 Errata ID: 2541: This errata notes that RFC2460 didn't update 1702 RFC2205 when the length of the Flow Label was changed from 24 1703 to 20 bits from RFC1883. This issue was resolved in RFC6437 1704 where the Flow Label is defined. This draft now references 1705 RFC6437. No change is required. 1707 Errata ID: 4279: This errata noted that the specification 1708 doesn't handle the case of a forwarding node receiving a packet 1709 with a zero Hop Limit. This is fixed in Section 3 of this 1710 draft. 1712 Errata ID: 2843: This errata is marked rejected. No change was 1713 made. 1715 o Simplify the text in Section 6 about Flow Labels and remove 1716 Appendix A, and instead point to the current specifications of the 1717 IPv6 Flow Label field as defined in [RFC6437] and the Traffic 1718 Class as defined in [RFC2474] and [RFC3168]. 1720 o Revised and expanded the Security Consideration section. 1722 B.1. Change History Since RFC2460 1724 NOTE TO RFC EDITOR: Please remove this subsection prior to RFC 1725 Publication 1727 This section describes change history made in each Internet Draft 1728 that went into producing this version. The numbers identify the 1729 Internet-Draft version in which the change was made. 1731 Working Group Internet Drafts 1733 10) Revised and expanded Security Consideration Section based on 1734 IESG Discuss comments. 1736 10) Editorial changes. 1738 09) Based on results of IETF last call, changed text in Section 4 1739 to add clarification that extension headers are not examined, 1740 processed, inserted, or deleted by any node along a packet's 1741 delivery path. 1743 09) Changed reference from draft-ietf-6man-rfc4291bis to RFC4291 1744 because the bis draft won't be advanced as the same time. 1746 09) Revised "Changes since RFC2460" Section to have a summary of 1747 changes since RFC2460 and a separate subsection with a change 1748 history of each Internet Draft. This subsection will be 1749 removed when the RFC is published. 1751 09) Editorial changes. 1753 08) Revised header insertion text in Section 4 based on the 1754 results of w.g. survey that concluded to describe the 1755 problems with header insertion. 1757 08) Editorial changes. 1759 07) Expanded Security Considerations section to include both 1760 IPsec and encryption at higher levels in the protocol stack 1761 as ways to mitigate IP level security issues. 1763 07) Added paragraph to Section 4 to clarify how Extension Headers 1764 are numbered and which are upper-layer headers. 1766 07) Moved the text regarding network duplicated fragments to the 1767 received fragment error section. 1769 07) Added clarification that no ICMP error message should be sent 1770 if overlapping fragments are received. 1772 07) Revised the text in Section 4.8 regarding new hop-by-hop 1773 options and new Extension headers to be closer to the -05 1774 version. 1776 07) Added additional registries to the IANA Considerations 1777 section that IANA needs to update. 1779 07) Editorial changes. 1781 06) Added the Routing Header to the list required extension 1782 headers that a full implementation includes. 1784 06) Moved the text in Section 4.5 regarding the handling of 1785 received overlapping fragments to the list of error 1786 conditions 1788 06) Rewrote the text in Section 4.8 "Defining New Extension 1789 Headers and Options" to be clearer and remove redundant text. 1791 06) Editorial changes. 1793 05) Changed requirement for HBH header from a should to a may, 1794 and added a note to indicate what is expected. 1796 05) Corrected reference to point to draft-ietf-6man-rfc4291bis 1797 instead of draft-hinden-6man-rfc4291bis. 1799 05) Change to text regarding not inserting extension headers to 1800 cite using encapsulation as an example. 1802 04) Changed text discussing Fragment ID selection to refer to 1803 RFC7739 for example algorithms. 1805 04) Editorial changes. 1807 03) Clarified the text about decrementing the hop limit. 1809 03) Removed IP Next Generation from the Abstract. 1811 03) Add reference to the end of Section 4 to IPv6 Extension 1812 Header IANA registry. 1814 03) Editorial changes. 1816 02) Added text to Section 4.8 "Defining New Extension Headers and 1817 Options" clarifying why no new hop by hop extension headers 1818 should be defined. 1820 02) Added text to Fragment Header process on handling exact 1821 duplicate fragments. 1823 02) Editorial changes. 1825 01) Added text that Extension headers must never be inserted by 1826 any node other than the source of the packet. 1828 01) Change "must" to "should" in Section 4.3 on the Hop-by-Hop 1829 header. 1831 01) Added text that the Data Transmission Order is the same as 1832 IPv4 as defined in RFC791. 1834 01) Updated the Fragmentation header text to correct the 1835 inclusion of AH and note no next header case. 1837 01) Change terminology in Fragment header section from 1838 "Unfragmentable Headers" to "Per-Fragment Headers". 1840 01) Removed paragraph in Section 5 that required including a 1841 fragment header to outgoing packets if a ICMP Packet Too Big 1842 message reporting a Next-Hop MTU less than 1280. This is 1843 based on the update in RFC8021. 1845 01) Changed to Fragmentation Header section to clarify MTU 1846 restriction and 8-byte restrictions, and noting the 1847 restriction on headers in first fragment. 1849 01) Editorial changes. 1851 00) Add instruction to the IANA to change references to RFC2460 1852 to this document 1854 00) Add a paragraph to the acknowledgement section acknowledging 1855 the authors of the updating documents 1857 00) Remove old paragraph in Section 4 that should have been 1858 removed when incorporating the update from RFC7045. 1860 00) Editorial changes. 1862 Individual Internet Drafts 1864 07) Update references to current versions and assign references 1865 to normative and informative. 1867 07) Editorial changes. 1869 06) The purpose of this draft is to incorporate the updates 1870 dealing with Extension headers as defined in RFC6564, 1871 RFC7045, and RFC7112. The changes include: 1873 RFC6564: Added new Section 4.8 that describe 1874 recommendations for defining new Extension headers and 1875 options 1877 RFC7045: The changes were to add a reference to RFC7045, 1878 change the requirement for processing the hop-by-hop 1879 option to a should, and added a note that due to 1880 performance restrictions some nodes won't process the Hop- 1881 by-Hop Option header. 1883 RFC7112: The changes were to revise the Fragmentation 1884 Section (Section 4.5) to require that all headers through 1885 the first Upper-Layer Header are in the first fragment. 1886 This changed the text describing how packets are 1887 fragmented and reassembled and added a new error case. 1889 06) Editorial changes. 1891 05) The purpose of this draft is to incorporate the updates 1892 dealing with fragmentation as defined in RFC5722 and RFC6946. 1893 Note: The issue relating to the handling of exact duplicate 1894 fragments identified on the mailing list is left open. 1896 05) Fix text in the end of Section 4 to correct the number of 1897 extension headers defined in this document. 1899 05) Editorial changes. 1901 04) The purpose of this draft is to update the document to 1902 incorporate the update made by RFC6935 "UDP Checksums for 1903 Tunneled Packets". 1905 04) Remove Routing (Type 0) header from the list of required 1906 extension headers. 1908 04) Editorial changes. 1910 03) The purpose of this draft is to update the document for the 1911 deprecation of the RH0 Routing Header as specified in RFC5095 1912 and the allocations guidelines for routing headers as 1913 specified in RFC5871. Both of these RFCs updated RFC2460. 1915 02) The purpose of this version of the draft is to update the 1916 document to resolve the open Errata on RFC2460. 1918 Errata ID: 2541: This errata notes that RFC2460 didn't 1919 update RFC2205 when the length of the Flow Label was 1920 changed from 24 to 20 bits from RFC1883. This issue was 1921 resolved in RFC6437 where the Flow Label is defined. This 1922 draft now references RFC6437. No change is required. 1924 Errata ID: 4279: This errata noted that the specification 1925 doesn't handle the case of a forwarding node receiving a 1926 packet with a zero Hop Limit. This is fixed in Section 3 1927 of this draft. Note: No change was made regarding host 1928 behaviour. 1930 Errata ID: 2843: This errata is marked rejected. No 1931 change is required. 1933 02) Editorial changes to the Flow Label and Traffic Class text. 1935 01) The purpose of this version of the draft is to update the 1936 document to point to the current specifications of the IPv6 1937 Flow Label field as defined in [RFC6437] and the Traffic 1938 Class as defined in [RFC2474] and [RFC3168]. 1940 00) The purpose of this version is to establish a baseline from 1941 RFC2460. The only intended changes are formatting (XML is 1942 slightly different from .nroff), differences between an RFC 1943 and Internet Draft, fixing a few ID Nits, and updates to the 1944 authors information. There should not be any content changes 1945 to the specification. 1947 Authors' Addresses 1949 Stephen E. Deering 1950 Retired 1951 Vancouver, British Columbia 1952 Canada 1954 Robert M. Hinden 1955 Check Point Software 1956 959 Skyway Road 1957 San Carlos, CA 94070 1958 USA 1960 Email: bob.hinden@gmail.com