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'IPv6-DISC') (Obsoleted by RFC 4861) ** Obsolete normative reference: RFC 2463 (Obsoleted by RFC 4443) -- Obsolete informational reference (is this intentional?): RFC 2373 (ref. 'IPv6-ADDR') (Obsoleted by RFC 3513) -- Obsolete informational reference (is this intentional?): RFC 1981 (ref. 'PMTU') (Obsoleted by RFC 8201) -- Obsolete informational reference (is this intentional?): RFC 1825 (ref. 'IPv6-SA') (Obsoleted by RFC 2401) == Outdated reference: A later version (-06) exists of draft-ietf-ipsec-rfc2401bis-05 == Outdated reference: A later version (-05) exists of draft-gont-tcpm-icmp-attacks-03 Summary: 8 errors (**), 0 flaws (~~), 7 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Draft A. Conta, Transwitch 3 IPv6 Working Group S. Deering, Cisco Systems 4 11 July 2005 M. Gupta, Nokia (ed.) 6 Internet Control Message Protocol (ICMPv6) 7 for the Internet Protocol Version 6 (IPv6) 8 Specification 10 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 Jan 11 2006. 37 Copyright Notice 39 Copyright (C) The Internet Society (2005). 41 Abstract 43 This document describes the format of a set of control messages used 44 in ICMPv6 (Internet Control Message Protocol). ICMPv6 is the 45 Internet Control Message Protocol for Internet Protocol version 6 46 (IPv6). 48 Table of Contents 50 1. Introduction.....................................................3 51 2. ICMPv6 (ICMP for IPv6)...........................................3 52 2.1 Message General Format....................................3 53 2.2 Message Source Address Determination......................5 54 2.3 Message Checksum Calculation..............................6 55 2.4 Message Processing Rules..................................6 56 3. ICMPv6 Error Messages............................................9 57 3.1 Destination Unreachable Message...........................9 58 3.2 Packet Too Big Message...................................12 59 3.3 Time Exceeded Message....................................13 60 3.4 Parameter Problem Message................................14 61 4. ICMPv6 Informational Messages...................................16 62 4.1 Echo Request Message.....................................16 63 4.2 Echo Reply Message.......................................17 64 5. Security Considerations.........................................19 65 5.1 Authentication and Confidentiality of ICMP messages......19 66 5.2 ICMP Attacks.............................................19 67 6. IANA Considerations.............................................21 68 6.1 Procedure for new ICMPV6 Type and Code value assignments.22 69 6.2 Assignments for this document............................22 70 7. References......................................................23 71 7.1 Normative................................................22 72 7.2 Informative..............................................22 73 8. Acknowledgments.................................................23 74 9. Authors' Addresses..............................................23 75 Appendix A - Changes since RFC 2463................................24 77 1. Introduction 79 The Internet Protocol, version 6 (IPv6) uses the Internet Control 80 Message Protocol (ICMP) as defined for IPv4 [RFC-792], with a number 81 of changes. The resulting protocol is called ICMPv6, and has an IPv6 82 Next Header value of 58. 84 This document describes the format of a set of control messages used 85 in ICMPv6. It does not describe the procedures for using these 86 messages to chieve functions like Path MTU discovery; such procedures 87 are described in other documents (e.g., [PMTU]). Other documents may 88 also introduce additional ICMPv6 message types, such as Neighbor 89 Discovery messages [IPv6-DISC], subject to the general rules for 90 ICMPv6 messages given in section 2 of this document. 92 Terminology defined in the IPv6 specification [IPv6] and the IPv6 93 Routing and Addressing specification [IPv6-ADDR] applies to this 94 document as well. 96 This document obsoletes RFC 2463 [RFC2463] and updates RFC 2780 97 [RFC-2780]. 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 101 document are to be interpreted as described in [RFC-2119]. 103 2. ICMPv6 (ICMP for IPv6) 105 ICMPv6 is used by IPv6 nodes to report errors encountered in 106 processing packets, and to perform other internet-layer functions, 107 such as diagnostics (ICMPv6 "ping"). ICMPv6 is an integral part of 108 IPv6 and the base protocol (all the messages and behavior required by 109 this specification) MUST be fully implemented by every IPv6 node. 111 2.1 Message General Format 113 Every ICMPv6 message is preceded by an IPv6 header and zero or more 114 IPv6 extension headers. The ICMPv6 header is identified by a Next 115 Header value of 58 in the immediately preceding header. (NOTE: this 116 is different than the value used to identify ICMP for IPv4.) 117 The ICMPv6 messages have the following general format: 119 0 1 2 3 120 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 1 121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 | Type | Code | Checksum | 123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 124 | | 125 + Message Body + 126 | | 128 The type field indicates the type of the message. Its value 129 determines the format of the remaining data. 131 The code field depends on the message type. It is used to create an 132 additional level of message granularity. 134 The checksum field is used to detect data corruption in the ICMPv6 135 message and parts of the IPv6 header. 137 ICMPv6 messages are grouped into two classes: error messages and 138 informational messages. Error messages are identified as such by 139 having a zero in the high-order bit of their message Type field 140 values. Thus, error messages have message Types from 0 to 127; 141 informational messages have message Types from 128 to 255. 143 This document defines the message formats for the following ICMPv6 144 messages: 146 ICMPv6 error messages: 148 1 Destination Unreachable (see section 3.1) 149 2 Packet Too Big (see section 3.2) 150 3 Time Exceeded (see section 3.3) 151 4 Parameter Problem (see section 3.4) 153 100 Private experimentation 154 101 Private experimentation 156 127 Reserved for expansion of ICMPv6 error messages 158 ICMPv6 informational messages: 160 128 Echo Request (see section 4.1) 161 129 Echo Reply (see section 4.2) 163 200 Private experimentation 164 201 Private experimentation 166 255 Reserved for expansion of ICMPv6 informational messages 168 Type values 100, 101, 200, and 201 are reserved for private 169 experimentation. These are not intended for general use. It is 170 expected that multiple concurrent experiments will be done with the 171 same type values. Any wide scale and/or uncontrolled usage should 172 obtain real allocations as defined in section 6. 174 Type value 255 is reserved for future expansion of the type value 175 range if there should be a shortage in the future. The details of 176 this are left for future work. One possible way of doing this that 177 would not cause any problems with current implementations is if the 178 type equals 255, use the code field for the new assignment. Existing 179 implementations would ignore the new assignments as specified in 180 section 2.4, section (b). The new messages using these expanded type 181 values, could assign fields in the message body for it's code values. 183 Sections 3 and 4 describe the message formats for the ICMPv6 error 184 message types 1 through 4 and informational message types 128 and 185 129. 187 Inclusion of, at least, the start of the invoking packet is intended 188 to allow the originator of a packet that has resulted in an ICMPv6 189 error message to identify the upper-layer protocol and process that 190 sent the packet. 192 2.2 Message Source Address Determination 194 A node that originates an ICMPv6 message has to determine both the 195 Source and Destination IPv6 Addresses in the IPv6 header before 196 calculating the checksum. If the node has more than one unicast 197 address, it MUST choose the Source Address of the message as follows: 199 (a) If the message is a response to a message sent to one of the 200 node's unicast addresses, the Source Address of the reply MUST 201 be that same address. 203 (b) If the message is a response to a message sent to any other 204 address, such as 205 - a multicast group address, 206 - an anycast address implemented by the node, or 207 - a unicast address which does not belong to the node 208 the Source Address of the ICMPv6 packet MUST be a unicast 209 address belonging to the node. The address SHOULD be chosen 210 according to the rules which would be used to select the source 211 address for any other packet originated by the node, given the 212 destination address of the packet, but MAY be selected in an 213 alternative way if this would lead to a more informative choice 214 of address which is reachable from the destination of the ICMPv6 215 packet. 217 2.3 Message Checksum Calculation 219 The checksum is the 16-bit one's complement of the one's complement 220 sum of the entire ICMPv6 message starting with the ICMPv6 message 221 type field, prepended with a "pseudo-header" of IPv6 header fields, 222 as specified in [IPv6, section 8.1]. The Next Header value used in 223 the pseudo-header is 58. (NOTE: the inclusion of a pseudo-header in 224 the ICMPv6 checksum is a change from IPv4; see [IPv6] for the 225 rationale for this change.) 227 For computing the checksum, the checksum field is first set to zero. 229 2.4 Message Processing Rules 231 Implementations MUST observe the following rules when processing 232 ICMPv6 messages (from [RFC-1122]): 234 (a) If an ICMPv6 error message of unknown type is received at its 235 destination, it MUST be passed to the upper-layer process that 236 originated the packet that caused the error, where this can be 237 identified (see Section 2.4(d)). 239 (b) If an ICMPv6 informational message of unknown type is received, 240 it MUST be silently discarded. 242 (c) Every ICMPv6 error message (type < 128) MUST include as much of 243 the IPv6 offending (invoking) packet (the packet that caused the 244 error) as possible without making the error message packet 245 exceed the minimum IPv6 MTU [IPv6]. 247 (d) In those cases where the internet-layer protocol is required to 248 pass an ICMPv6 error message to the upper-layer process, the 249 upper-layer protocol type is extracted from the original packet 250 (contained in the body of the ICMPv6 error message) and used to 251 select the appropriate upper-layer process to handle the error. 253 In the cases where it is not possible to retrieve the upper- 254 layer protocol type from the ICMPv6 message, the ICMPv6 message 255 is silently dropped after any IPv6-layer processing. One 256 example of such a case is an ICMPv6 message with unusually large 257 amount of extension headers that does not have the upper-layer 258 protocol type due to truncation of the original packet to meet 259 the minimum IPv6 MTU [IPv6] limit. Another example of such a 260 case is an ICMPv6 message with ESP extension header where it is 261 not possible to decrypt the original packet due to either 262 truncation or the unavailability of the state necessary to 263 decrypt the packet. 265 (e) An ICMPv6 error message MUST NOT be originated as a result of 266 receiving: 268 (e.1) an ICMPv6 error message, or 270 (e.2) an ICMPv6 redirect message [IPv6-DISC], or 272 (e.3) a packet destined to an IPv6 multicast address (there are 273 two exceptions to this rule: (1) the Packet Too Big 274 Message - Section 3.2 - to allow Path MTU discovery to 275 work for IPv6 multicast, and (2) the Parameter Problem 276 Message, Code 2 - Section 3.4 - reporting an unrecognized 277 IPv6 option (see section 4.2 of [IPv6]) that has the 278 Option Type highest-order two bits set to 10), or 280 (e.4) a packet sent as a link-layer multicast, (the exceptions 281 from e.3 apply to this case too), or 283 (e.5) a packet sent as a link-layer broadcast, (the exceptions 284 from e.3 apply to this case too), or 286 (e.6) a packet whose source address does not uniquely identify 287 a single node -- e.g., the IPv6 Unspecified Address, an 288 IPv6 multicast address, or an address known by the ICMP 289 message originator to be an IPv6 anycast address. 291 (f) Finally, in order to limit the bandwidth and forwarding costs 292 incurred by originating ICMPv6 error messages, an IPv6 node MUST 293 limit the rate of ICMPv6 error messages it originates. This 294 situation may occur when a source sending a stream of erroneous 295 packets fails to heed the resulting ICMPv6 error messages. 297 Rate-limiting of forwarded ICMP messages is out of scope of this 298 specification. 300 A recommended method for implementing the rate-limiting function 301 is a token bucket, limiting the average rate of transmission to 302 N, where N can either be packets/second or a fraction of the 303 attached link's bandwidth, but allowing up to B error messages 304 to be transmitted in a burst, as long as the long-term average 305 is not exceeded. 307 Rate-limiting mechanisms which cannot cope with bursty traffic 308 (e.g., traceroute) are not recommended; for example a simple 309 timer-based implementation, allowing an error message every T 310 milliseconds (even with low values for T), is not reasonable. 312 The rate-limiting parameters SHOULD be configurable. In the 313 case of a token-bucket implementation, the best defaults depend 314 on where the implementation is expected to be deployed (e.g., a 315 high-end router vs. an embedded host). For example, in a 316 small/mid -sized device, the possible defaults could be B=10, 317 N=10/s. 319 NOTE: THE RESTRICTIONS UNDER (e) AND (f) ABOVE TAKE PRECEDENCE OVER 320 ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR ORIGINATING ICMP ERROR 321 MESSAGES. 323 The following sections describe the message formats for the above 324 ICMPv6 messages. 326 3. ICMPv6 Error Messages 328 3.1 Destination Unreachable Message 330 0 1 2 3 331 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 1 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 | Type | Code | Checksum | 334 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 | Unused | 336 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 337 | As much of invoking packet | 338 + as possible without the ICMPv6 packet + 339 | exceeding the minimum IPv6 MTU [IPv6] | 341 IPv6 Fields: 343 Destination Address 345 Copied from the Source Address field of the invoking 346 packet. 348 ICMPv6 Fields: 350 Type 1 352 Code 0 - no route to destination 353 1 - communication with destination 354 administratively prohibited 355 2 - beyond scope of source address 356 3 - address unreachable 357 4 - port unreachable 358 5 - source address failed ingress/egress policy 359 6 - reject route to destination 361 Unused This field is unused for all code values. 362 It must be initialized to zero by the originator 363 and ignored by the receiver. 364 Description 366 A Destination Unreachable message SHOULD be generated by a router, or 367 by the IPv6 layer in the originating node, in response to a packet 368 that cannot be delivered to its destination address for reasons other 369 than congestion. (An ICMPv6 message MUST NOT be generated if a 370 packet is dropped due to congestion.) 372 If the reason for the failure to deliver is lack of a matching entry 373 in the forwarding node's routing table, the Code field is set to 0 374 (NOTE: this error can occur only in nodes that do not hold a "default 375 route" in their routing tables). 377 If the reason for the failure to deliver is administrative 378 prohibition, e.g., a "firewall filter", the Code field is set to 1. 380 If the reason for the failure to deliver is that the destination is 381 beyond the scope of the source address, the Code field is set to 2. 382 This condition can occur only when the scope of the source address is 383 smaller than the scope of the destination address (e.g., when a 384 packet has a link-local source address and a global-scope destination 385 address) and the packet cannot be delivered to the destination 386 without leaving the scope of the source address. 388 If the reason for the failure to deliver can not be mapped to any of 389 other codes, the Code field is set to 3. The example of such cases 390 are inability to resolve the IPv6 destination address into a 391 corresponding link address, or a link-specific problem of some sort. 393 One specific case in which a Destination Unreachable message with a 394 code 3 is sent is in response to a packet received by a router from a 395 point-to-point link, destined to an address within a subnet assigned 396 to that same link (other than one of the receiving router's own 397 addresses). In such a case, the packet MUST NOT be forwarded back 398 onto the arrival link. 400 A destination node SHOULD originate a Destination Unreachable message 401 with Code 4 in response to a packet for which the transport protocol 402 (e.g., UDP) has no listener, if that transport protocol has no 403 alternative means to inform the sender. 405 If the reason for the failure to deliver is that packet with this 406 source address is not allowed due to ingress or egress filtering 407 policies, the Code field is set to 5. 409 If the reason for the failure to deliver is that the route to the 410 destination is a reject route, the Code field is set to 6. This may 411 occur if the router has been configured to reject all the traffic for 412 a specific prefix. 414 Codes 5 and 6 are more informative subsets of code 1. 416 For security reasons, it is recommended that implementations SHOULD 417 allow sending of ICMP destination unreachable messages to be 418 disabled, preferably on a per-interface basis. 420 Upper layer notification 422 A node receiving the ICMPv6 Destination Unreachable message MUST 423 notify the upper-layer process if the relevant process can be 424 identified (see section 2.4(d)). 426 3.2 Packet Too Big Message 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 | Type | Code | Checksum | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 433 | MTU | 434 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 435 | As much of invoking packet | 436 + as possible without the ICMPv6 packet + 437 | exceeding the minimum IPv6 MTU [IPv6] | 439 IPv6 Fields: 441 Destination Address 443 Copied from the Source Address field of the invoking 444 packet. 446 ICMPv6 Fields: 448 Type 2 450 Code Set to 0 (zero) by the originator and ignored by the 451 receiver 453 MTU The Maximum Transmission Unit of the next-hop link. 455 Description 457 A Packet Too Big MUST be sent by a router in response to a packet 458 that it cannot forward because the packet is larger than the MTU of 459 the outgoing link. The information in this message is used as part 460 of the Path MTU Discovery process [PMTU]. 462 Originating a Packet Too Big Message makes an exception to one of the 463 rules of when to originate an ICMPv6 error message, in that unlike 464 other messages, it is sent in response to a packet received with an 465 IPv6 multicast destination address, or a link-layer multicast or 466 link-layer broadcast address. 468 Upper layer notification 470 An incoming Packet Too Big message MUST be passed to the upper-layer 471 process if the relevant process can be identified (see section 472 2.4(d)). 474 3.3 Time Exceeded Message 476 0 1 2 3 477 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 1 478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 479 | Type | Code | Checksum | 480 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 481 | Unused | 482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 483 | As much of invoking packet | 484 + as possible without the ICMPv6 packet + 485 | exceeding the minimum IPv6 MTU [IPv6] | 487 IPv6 Fields: 489 Destination Address 490 Copied from the Source Address field of the invoking 491 packet. 493 ICMPv6 Fields: 495 Type 3 497 Code 0 - hop limit exceeded in transit 499 1 - fragment reassembly time exceeded 501 Unused This field is unused for all code values. 502 It must be initialized to zero by the originator 503 and ignored by the receiver. 505 Description 507 If a router receives a packet with a Hop Limit of zero, or a router 508 decrements a packet's Hop Limit to zero, it MUST discard the packet 509 and originate an ICMPv6 Time Exceeded message with Code 0 to the 510 source of the packet. This indicates either a routing loop or too 511 small an initial Hop Limit value. 513 An ICMPv6 Time Exceeded message with Code 1 is used to report 514 fragment reassembly timeout, as specified in [IPv6, Section 4.5]. 516 Upper layer notification 518 An incoming Time Exceeded message MUST be passed to the upper-layer 519 process if the relevant process can be identified (see section 520 2.4(d)). 522 3.4 Parameter Problem Message 524 0 1 2 3 525 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 1 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 527 | Type | Code | Checksum | 528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 529 | Pointer | 530 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 531 | As much of invoking packet | 532 + as possible without the ICMPv6 packet + 533 | exceeding the minimum IPv6 MTU [IPv6] | 535 IPv6 Fields: 537 Destination Address 539 Copied from the Source Address field of the invoking 540 packet. 542 ICMPv6 Fields: 544 Type 4 546 Code 0 - erroneous header field encountered 548 1 - unrecognized Next Header type encountered 550 2 - unrecognized IPv6 option encountered 552 Pointer Identifies the octet offset within the 553 invoking packet where the error was detected. 555 The pointer will point beyond the end of the ICMPv6 556 packet if the field in error is beyond what can fit 557 in the maximum size of an ICMPv6 error message. 559 Description 561 If an IPv6 node processing a packet finds a problem with a field in 562 the IPv6 header or extension headers such that it cannot complete 563 processing the packet, it MUST discard the packet and SHOULD 564 originate an ICMPv6 Parameter Problem message to the packet's source, 565 indicating the type and location of the problem. 567 Codes 1 and 2 are more informative subsets of Code 0. 569 The pointer identifies the octet of the original packet's header 570 where the error was detected. For example, an ICMPv6 message with 571 Type field = 4, Code field = 1, and Pointer field = 40 would indicate 572 that the IPv6 extension header following the IPv6 header of the 573 original packet holds an unrecognized Next Header field value. 575 Upper layer notification 577 A node receiving this ICMPv6 message MUST notify the upper-layer 578 process if the relevant process can be identified (see section 579 2.4(d)). 581 4. ICMPv6 Informational Messages 583 4.1 Echo Request Message 585 0 1 2 3 586 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 | Type | Code | Checksum | 589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 | Identifier | Sequence Number | 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | Data ... 593 +-+-+-+-+- 595 IPv6 Fields: 597 Destination Address 599 Any legal IPv6 address. 601 ICMPv6 Fields: 603 Type 128 605 Code 0 607 Identifier An identifier to aid in matching Echo Replies 608 to this Echo Request. May be zero. 610 Sequence Number 612 A sequence number to aid in matching Echo Replies 613 to this Echo Request. May be zero. 615 Data Zero or more octets of arbitrary data. 617 Description 619 Every node MUST implement an ICMPv6 Echo responder function that 620 receives Echo Requests and originates corresponding Echo Replies. A 621 node SHOULD also implement an application-layer interface for 622 originating Echo Requests and receiving Echo Replies, for diagnostic 623 purposes. 625 Upper layer notification 627 Echo Request messages MAY be passed to processes receiving ICMP 628 messages. 630 4.2 Echo Reply Message 632 0 1 2 3 633 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 1 634 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 | Type | Code | Checksum | 636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 637 | Identifier | Sequence Number | 638 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 639 | Data ... 640 +-+-+-+-+- 642 IPv6 Fields: 644 Destination Address 646 Copied from the Source Address field of the invoking 647 Echo Request packet. 649 ICMPv6 Fields: 651 Type 129 653 Code 0 655 Identifier The identifier from the invoking Echo Request message. 657 Sequence The sequence number from the invoking Echo Request 658 Number message. 660 Data The data from the invoking Echo Request message. 662 Description 664 Every node MUST implement an ICMPv6 Echo responder function that 665 receives Echo Requests and originates corresponding Echo Replies. A 666 node SHOULD also implement an application-layer interface for 667 originating Echo Requests and receiving Echo Replies, for diagnostic 668 purposes. 670 The source address of an Echo Reply sent in response to a unicast 671 Echo Request message MUST be the same as the destination address of 672 that Echo Request message. 674 An Echo Reply SHOULD be sent in response to an Echo Request message 675 sent to an IPv6 multicast or anycast address. In this case, the 676 source address of the reply MUST be a unicast address belonging to 677 the interface on which the Echo Request message was received. 679 The data received in the ICMPv6 Echo Request message MUST be returned 680 entirely and unmodified in the ICMPv6 Echo Reply message. 682 Upper layer notification 684 Echo Reply messages MUST be passed to the process that originated an 685 Echo Request message. An Echo Reply message MAY be passed to 686 processes that did not originate the Echo Request message. 688 Note that there is no limitations on the amount of data that can be 689 put in Echo Request and Echo Reply Messages. 691 5. Security Considerations 693 5.1 Authentication and Confidentiality of ICMP messages 695 ICMP protocol packet exchanges can be authenticated using the IP 696 Authentication Header [IPv6-AUTH] or IP Encapsulating Security 697 Payload Header [IPv6-ESP]. Confidentiality for the ICMP protocol 698 packet exchanges can be achieved using IP Encapsulating Security 699 Payload Header [IPv6-ESP]. 701 [SEC-ARCH] describes the IPsec handling of ICMP traffic in detail. 703 5.2 ICMP Attacks 705 ICMP messages may be subject to various attacks. A complete 706 discussion can be found in the IP Security Architecture [IPv6-SA]. A 707 brief discussion of such attacks and their prevention is as follows: 709 1. ICMP messages may be subject to actions intended to cause the 710 receiver to believe the message came from a different source than 711 the message originator. The protection against this attack can be 712 achieved by applying the IPv6 Authentication mechanism [IPv6-AUTH] 713 to the ICMP message. 715 2. ICMP messages may be subject to actions intended to cause the 716 message or the reply to it go to a destination different than the 717 message originator's intention. The protection against this 718 attack can be achieved by using the Authentication Header 719 [IPv6-AUTH] or the Encapsulating Security Payload Header 720 [IPv6-ESP]. Authentication Header provides the protection against 721 change for the source and the destination address of the IP 722 packet. Encapsulating Security Payload Header does not provide 723 this protection but the ICMP checksum calculation includes the 724 source and the destination addresses and the Encapsulating 725 Security Payload Header protects the checksum. Therefore, the 726 combination of ICMP checksum and the Encapsulating Security 727 Payload Header provides the protection against this attack. The 728 protection provided by the Encapsulating Security Payload Header 729 will not be as strong as the protection provided by the 730 Authentication Header. 732 3. ICMP messages may be subject to changes in the message fields, or 733 payload. The authentication [IPv6-AUTH] or encryption [IPv6-ESP] 734 of the ICMP message is a protection against such actions. 736 4. ICMP messages may be used as attempts to perform denial of service 737 attacks by sending back to back erroneous IP packets. An 738 implementation that correctly followed section 2.4, paragraph (f) 739 of this specifications, would be protected by the ICMP error rate 740 limiting mechanism. 742 5. The exception number 2 of rule e.3 in section 2.4 gives the 743 opportunity to a malicious node to cause a denial of service 744 attack to a multicast source. A malicious node can send a 745 multicast packet with an unknown destination option marked as 746 mandatory with the IPv6 source address of a valid multicast 747 source. A large number of destination nodes will send ICMP 748 Parameter Problem Message to the multicast source causing a denial 749 of service attack. The way multicast traffic is forwarded by the 750 multicast routers does require the malicious node to be part of 751 the correct multicast path i.e. near to the multicast source. 752 This attack can only be avoided by securing the multicast traffic. 753 The multicast source should be careful while sending multicast 754 traffic with the destination options marked as mandatory because 755 they can cause a denial of service attack to themselves if the 756 destination option is unknown to a large number of destinations. 758 6. As the ICMP messages are passed to the upper-layer processes, it 759 is possible to perform attacks on the upper layer protocols (e.g., 760 TCP) with ICMP [TCP-attack]. It is recommended for the upper 761 layers to perform some form of validation of ICMP messages (using 762 the information contained in the payload of the ICMP message) 763 before acting upon them. The actual validation checks are 764 specific to the upper layers and are out of the scope of this 765 spec. Protecting the upper layer with IPsec mitigates these 766 attacks. 768 ICMP error messages signal network error conditions that were 769 encountered while processing an internet datagram. Depending on 770 the particular scenario, the error conditions being reported might 771 or might not get solved in the near term. Therefore, reaction to 772 ICMP error messages may depend not only on the error type and 773 code, but also on other factors such as the time the error 774 messages are received, previous knowledge of the network error 775 conditions being reported, and knowledge of the network scenario 776 in which the receiving host is operating. 778 6. IANA Considerations 780 6.1 Procedure for new ICMPV6 Type and Code value assignments 782 The IPv6 ICMP header [ICMPV6] contains the following fields that 783 carry values assigned from IANA-managed name spaces: Type and Code. 784 Code field values are defined relative to a specific Type value. 786 Values for the IPv6 ICMP Type fields are allocated using the 787 following procedure: 789 1. The IANA should allocate and permanently register new ICMPv6 type 790 codes from IETF RFC publication. This is for all RFC types 791 including standards track, informational, and experimental status 792 that originate from the IETF and have been approved by the IESG 793 for publication. 795 2. IETF working groups with working group consensus and area director 796 approval can request reclaimable ICMPV6 type code assignments from 797 the IANA. The IANA will tag the values as "reclaimable in 798 future". 800 The "reclaimable in the future" tag will be removed when an RFC is 801 published documenting the protocol as defined in 1). This will 802 make the assignment permanent and update the reference on the IANA 803 web pages. 805 At the point where the ICMPv6 type values are 85% assigned, the 806 IETF will review the assignments tagged "reclaimable in the 807 future" and inform the IANA which ones should be reclaimed and 808 reassigned. 810 3. Requests for new ICMPv6 type value assignments from outside the 811 IETF are only made through the publication of an IETF document, 812 per 1) above. Note also that documents published as "RFC Editor 813 contributions" [RFC 3667] are not considered to be IETF documents. 815 The assignment of new Code values for the Type values defined in this 816 document require standards action or IESG approval. The policy for 817 assigning Code values for new IPv6 ICMP Types not defined in this 818 document should be defined in the document defining the new Type 819 values. 821 6.2 Assignments for this document 823 The following should update the assignments located at: 825 http://www.iana.org/assignments/icmpv6-parameters 827 The IANA is requested to reassign ICMPv6 type 1 "Destination 828 Unreachable" code 2, that was unassigned in [RFC-2463], to: 830 2 - beyond scope of source address 832 The IANA is requested to assign the following two new codes values 833 for ICMPv6 type 1 "Destination Unreachable": 835 5 - source address failed ingress/egress policy 836 6 - reject route to destination 838 The IANA is requested to assign the following new type values: 840 100 Private experimentation 841 101 Private experimentation 843 200 Private experimentation 844 201 Private experimentation 846 255 Reserved for expansion 848 7. References 850 7.1 Normative 852 [IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6, 853 Specification", RFC2460, December 1998. 855 [IPv6-DISC] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery 856 for IP Version 6 (IPv6)", RFC2461, December, 1998. 858 [RFC-792] Postel, J., "Internet Control Message Protocol", STD 5, 859 RFC792, September 1981. 861 [RFC-2463] Conta, A., S. Deering, "Internet Control Message 862 Protocol (ICMPv6) for the Internet Protocol Version 6 863 (IPv6) Specification", RFC2463, December, 1998. 865 [RFC-1122] Braden, R., "Requirements for Internet Hosts - 866 Communication Layers", STD 5, RFC1122, August 1989. 868 [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate 869 Requirement Levels", BCP14, RFC2119, March 1997. 871 7.2 Informative 873 [RFC-2780] Bradner, S., V. Paxson, "IANA Allocation Guidelines For 874 Values In the Internet Protocol and Related Headers", 875 RFC 2780, March 2000. 877 [IPv6-ADDR] Hinden, R., S. Deering, "IP Version 6 Addressing 878 Architecture", RFC2373, July 1998. 880 [PMTU] McCann, J., S. Deering, J. Mogul, "Path MTU Discovery 881 for IP version 6", RFC1981, August 1996. 883 [IPv6-SA] Kent, S., R. Atkinson, "Security Architecture for the 884 Internet Protocol", RFC1825, November 1998. 886 [IPv6-AUTH] Kent, S., "IP Authentication Header", draft-ietf-ipsec- 887 rfc2402bis-11.txt, work in progress. 889 [IPv6-ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", 890 draft-ietf-ipsec-esp-v3-10.txt, work in progress. 892 [SEC-ARCH] Kent, S., K. Seo, "Security Architecture for the 893 Internet Protocol", draft-ietf-ipsec-rfc2401bis-05.txt, 894 work in progress. 896 [TCP-attack] Gont, F., "ICMP attacks against TCP", draft-gont-tcpm- 897 icmp-attacks-03.txt, work in progress. 899 8. Acknowledgments 901 The document is derived from previous ICMP drafts of the SIPP and 902 IPng working group. 904 The IPng working group and particularly Robert Elz, Jim Bound, Bill 905 Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner, 906 Dimitri Haskin, Bob Hinden, Jun-ichiro Itojun Hagino, Tatuya Jinmei, 907 Brian Zill, Pekka Savola, Fred Templin and Elwyn davies (in 908 chronological order) provided extensive review information and 909 feedback. 911 Bob Hinden was the document editor for this document. 913 9. Authors' Addresses 915 Alex Conta 916 Transwitch Corporation 917 3 Enterprise Drive 918 Shelton, CT 06484 919 USA 920 Email: aconta@txc.com 922 Stephen Deering 923 Cisco Systems, Inc. 924 170 West Tasman Drive 925 San Jose, CA 95134-1706 926 USA 928 Mukesh Gupta (ed.) 929 Nokia 930 313 Fairchild Drive 931 Mountain View, CA 94043 932 US 933 Phone: +1 650-625-2264 934 Email: mukesh.k.gupta@nokia.com 936 Appendix A - Changes since RFC 2463 938 The following changes were made from RFC 2463: 940 - Edited the Abstract to make it a little more elaborate. 942 - Corrected typos in section 2.4, where references to sub-bullet e.2 943 were supposed to be references to e.3. 945 - Removed the Timer-based and the Bandwidth-based methods from the 946 example rate-limiting mechanism for ICMP error messages. Added 947 Token-bucket based method. 949 - Added specification that all ICMP error messages shall have 950 exactly 32 bits of type-specific data, so that receivers can 951 reliably find the embedded invoking packet even when they don't 952 recognize the ICMP message Type. 954 - In the description of Destination Unreachable messages, Code 3, 955 added rule prohibiting forwarding of packets back onto point-to- 956 point links from which they were received, if their destination 957 addresses belong to the link itself ("anti-ping-ponging" rule). 959 - Added description of Time Exceeded Code 1 (fragment reassembly 960 timeout). 962 - Added "beyond scope of source address", "source address failed 963 ingress/egress policy", and "reject route to destination" messages 964 to the family of "unreachable destination" type ICMP error 965 messages (section 3.1). 967 - Reserved some ICMP type values for experimentation. 969 - Added a NOTE in section 2.4, that specifies ICMP message 970 processing rules precedence. 972 - Added ICMP REDIRECT to the list in Section 2.4 e) of cases in 973 which ICMP error messages are not to be generated. 975 - Made minor editorial changes in Section 2.3 on checksum 976 calculation, and in Section 5.2. 978 - Clarified in section 4.2, regarding the Echo Reply Message, that 979 the source address of an Echo Reply to an anycast Echo Request 980 should be a unicast address, as in the case of multicast. 982 - Revised the Security Considerations section. Added the use of 983 Encapsulating Security Payload Header for authentication. Changed 984 the requirement of an option of "not allowing unauthenticated ICMP 985 messages" to MAY from SHOULD. 987 - Added a new attack in the list of possible ICMP attacks in section 988 5.2. 990 - Separated References into Normative and Informative. 992 - Added reference to RFC-2780 "IANA Allocation Guidelines For Values 993 In the Internet Protocol and Related Headers". Also added a note 994 that this document updates RFC-2780. 996 - Added a procedure for new ICMPv6 Type and Code value assignments 997 in the IANA Consideration section. 999 - Replaced word "send" with "originate" to make it clear that ICMP 1000 packets being forwarded are out of scope of this specification. 1002 - Changed the ESP and AH references to the updated ESP and AH 1003 drafts. 1005 - Added reference to the updated IPsec Security Architecture draft. 1007 - Added a SHOULD requirement for allowing the sending of ICMP 1008 destination unreachable messages to be disabled. 1010 - Simplified the source address selection of the ICMPv6 packet. 1012 - Reorganized the General Message Format (section 2.1). 1014 - Removed the general packet format from section 2.1. 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