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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT A. Conta, Transwitch 3 IPNG Working Group S. Deering, Cisco Systems 5 Internet Control Message Protocol (ICMPv6) 6 for the Internet Protocol Version 6 (IPv6) 7 Specification 9 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet- Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This internet draft will expire on January 19, 2002. 34 Abstract 36 This document specifies a set of Internet Control Message Protocol 37 (ICMP) messages for use with version 6 of the Internet Protocol 38 (IPv6). 40 Table of Contents 42 1. Introduction........................................3 44 2. ICMPv6 (ICMP for IPv6)..............................3 46 2.1 Message General Format.......................3 48 2.2 Message Source Address Determination.........4 50 2.3 Message Checksum Calculation.................5 52 2.4 Message Processing Rules.....................5 54 3. ICMPv6 Error Messages...............................8 56 3.1 Destination Unreachable Message..............8 58 3.2 Packet Too Big Message......................10 60 3.3 Time Exceeded Message.......................11 62 3.4 Parameter Problem Message...................12 64 4. ICMPv6 Informational Messages......................14 66 4.1 Echo Request Message........................14 68 4.2 Echo Reply Message..........................15 70 5. Security Considerations............................17 72 6. References.........................................19 74 7. Acknowledgments....................................19 76 8. Authors' Addresses.................................20 78 Appendix A - Changes since RFC 2463...................20 80 1. Introduction 82 The Internet Protocol, version 6 (IPv6) is a new version of IP. IPv6 83 uses the Internet Control Message Protocol (ICMP) as defined for IPv4 84 [RFC-792], with a number of changes. The resulting protocol is 85 called ICMPv6, and has an IPv6 Next Header value of 58. 87 This document describes the format of a set of control messages used 88 in ICMPv6. It does not describe the procedures for using these 89 messages to achieve functions like Path MTU discovery; such 90 procedures are described in other documents (e.g., [PMTU]). Other 91 documents may also introduce additional ICMPv6 message types, such as 92 Neighbor Discovery messages [IPv6-DISC], subject to the general rules 93 for ICMPv6 messages given in section 2 of this document. 95 Terminology defined in the IPv6 specification [IPv6] and the IPv6 96 Routing and Addressing specification [IPv6-ADDR] applies to this 97 document as well. 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 MUST be fully implemented by every IPv6 node. 110 2.1 Message General Format 112 ICMPv6 messages are grouped into two classes: error messages and 113 informational messages. Error messages are identified as such by 114 having a zero in the high-order bit of their message Type field 115 values. Thus, error messages have message Types from 0 to 127; 116 informational messages have message Types from 128 to 255. 118 This document defines the message formats for the following ICMPv6 119 messages: 121 ICMPv6 error messages: 123 1 Destination Unreachable (see section 3.1) 124 2 Packet Too Big (see section 3.2) 125 3 Time Exceeded (see section 3.3) 126 4 Parameter Problem (see section 3.4) 128 ICMPv6 informational messages: 130 128 Echo Request (see section 4.1) 131 129 Echo Reply (see section 4.2) 133 Every ICMPv6 message is preceded by an IPv6 header and zero or more 134 IPv6 extension headers. The ICMPv6 header is identified by a Next 135 Header value of 58 in the immediately preceding header. (NOTE: this 136 is different than the value used to identify ICMP for IPv4.) 138 The ICMPv6 messages have the following general format: 140 0 1 2 3 141 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 1 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 143 | Type | Code | Checksum | 144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 145 | | 146 + Message Body + 147 | | 149 The type field indicates the type of the message. Its value 150 determines the format of the remaining data. 152 The code field depends on the message type. It is used to create an 153 additional level of message granularity. 155 The checksum field is used to detect data corruption in the ICMPv6 156 message and parts of the IPv6 header. 158 2.2 Message Source Address Determination 160 A node that sends an ICMPv6 message has to determine both the Source 161 and Destination IPv6 Addresses in the IPv6 header before calculating 162 the checksum. If the node has more than one unicast address, it must 163 choose the Source Address of the message as follows: 165 (a) If the message is a response to a message sent to one of the 166 node's unicast addresses, the Source Address of the reply must 167 be that same address. 169 (b) If the message is a response to a message sent to a multicast or 170 anycast group in which the node is a member, the Source Address 171 of the reply must be a unicast address belonging to the 172 interface on which the multicast or anycast packet was received. 174 (c) If the message is a response to a message sent to an address 175 that does not belong to the node, the Source Address should be 176 that unicast address belonging to the node that will be most 177 helpful in diagnosing the error. For example, if the message is 178 a response to a packet forwarding action that cannot complete 179 successfully, the Source Address should be a unicast address 180 belonging to the interface on which the packet forwarding 181 failed. 183 (d) Otherwise, the node's routing table must be examined to 184 determine which interface will be used to transmit the message 185 to its destination, and a unicast address belonging to that 186 interface must be used as the Source Address of the message. 188 2.3 Message Checksum Calculation 190 The checksum is the 16-bit one's complement of the one's complement 191 sum of the entire ICMPv6 message starting with the ICMPv6 message 192 type field, prepended with a "pseudo-header" of IPv6 header fields, 193 as specified in [IPv6, section 8.1]. The Next Header value used in 194 the pseudo-header is 58. (NOTE: the inclusion of a pseudo-header in 195 the ICMPv6 checksum is a change from IPv4; see [IPv6] for the 196 rationale for this change.) 198 For computing the checksum, the checksum field is first set to zero. 200 2.4 Message Processing Rules 202 Implementations MUST observe the following rules when processing 203 ICMPv6 messages (from [RFC-1122]): 205 (a) If an ICMPv6 error message of unknown type is received, it MUST 206 be passed to the upper layer. 208 (b) If an ICMPv6 informational message of unknown type is received, 209 it MUST be silently discarded. 211 (c) Every ICMPv6 error message (type < 128) includes as much of the 212 IPv6 offending (invoking) packet (the packet that caused the 213 error) as will fit without making the error message packet 214 exceed the minimum IPv6 MTU [IPv6]. 216 (d) In those cases where the internet-layer protocol is required to 217 pass an ICMPv6 error message to the upper-layer process, the 218 upper-layer protocol type is extracted from the original packet 219 (contained in the body of the ICMPv6 error message) and used to 220 select the appropriate upper-layer process to handle the error. 222 If the original packet had an unusually large amount of 223 extension headers, it is possible that the upper-layer protocol 224 type may not be present in the ICMPv6 message, due to truncation 225 of the original packet to meet the minimum IPv6 MTU [IPv6] 226 limit. In that case, the error message is silently dropped 227 after any IPv6-layer processing. 229 (e) An ICMPv6 error message MUST NOT be sent as a result of 230 receiving: 232 (e.1) an ICMPv6 error message, or 234 (e.2) an ICMPv6 redirect message [IPv6-DISC], or 236 (e.3) a packet destined to an IPv6 multicast address (there are 237 two exceptions to this rule: (1) the Packet Too Big 238 Message - Section 3.2 - to allow Path MTU discovery to 239 work for IPv6 multicast, and (2) the Parameter Problem 240 Message, Code 2 - Section 3.4 - reporting an unrecognized 241 IPv6 option that has the Option Type highest-order two 242 bits set to 10), or 244 (e.4) a packet sent as a link-layer multicast, (the exception 245 from e.2 applies to this case too), or 247 (e.5) a packet sent as a link-layer broadcast, (the exception 248 from e.2 applies to this case too), or 250 (e.6) a packet whose source address does not uniquely identify 251 a single node -- e.g., the IPv6 Unspecified Address, an 252 IPv6 multicast address, or an address known by the ICMP 253 message sender to be an IPv6 anycast address. 255 (f) Finally, in order to limit the bandwidth and forwarding costs 256 incurred sending ICMPv6 error messages, an IPv6 node MUST limit 257 the rate of ICMPv6 error messages it sends. This situation may 258 occur when a source sending a stream of erroneous packets fails 259 to heed the resulting ICMPv6 error messages. There are a variety 260 of ways of implementing the rate-limiting function, for example: 262 (f.1) Timer-based - for example, limiting the rate of 263 transmission of error messages to a given source, or to 264 any source, to at most once every T milliseconds. 266 (f.2) Bandwidth-based - for example, limiting the rate at which 267 error messages are sent from a particular interface to 268 some fraction F of the attached link's bandwidth. 270 The limit parameters (e.g., T or F in the above examples) MUST 271 be configurable for the node, with a conservative default value 272 (e.g., T = 1 second, NOT 0 seconds, or F = 2 percent, NOT 100 273 percent). 275 NOTE: THE RESTRICTIONS UNDER (e) AND (f) ABOVE TAKE PRECEDENCE OVER 276 ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR SENDING ICMP ERROR 277 MESSAGES. 279 The following sections describe the message formats for the above 280 ICMPv6 messages. 282 3. ICMPv6 Error Messages 284 3.1 Destination Unreachable Message 286 0 1 2 3 287 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 1 288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 289 | Type | Code | Checksum | 290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 291 | Unused | 292 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 | As much of invoking packet | 294 + as will fit without the ICMPv6 packet + 295 | exceeding the minimum IPv6 MTU [IPv6] | 297 IPv6 Fields: 299 Destination Address 301 Copied from the Source Address field of the invoking 302 packet. 304 ICMPv6 Fields: 306 Type 1 308 Code 0 - no route to destination 309 1 - communication with destination 310 administratively prohibited 311 2 - beyond scope of source address 312 3 - address unreachable 313 4 - port unreachable 315 Unused This field is unused for all code values. 316 It must be initialized to zero by the sender 317 and ignored by the receiver. 318 Description 320 A Destination Unreachable message SHOULD be generated by a router, or 321 by the IPv6 layer in the originating node, in response to a packet 322 that cannot be delivered to its destination address for reasons other 323 than congestion. (An ICMPv6 message MUST NOT be generated if a 324 packet is dropped due to congestion.) 326 If the reason for the failure to deliver is lack of a matching entry 327 in the forwarding node's routing table, the Code field is set to 0 328 (NOTE: this error can occur only in nodes that do not hold a "default 329 route" in their routing tables). 331 If the reason for the failure to deliver is administrative 332 prohibition, e.g., a "firewall filter", the Code field is set to 1. 334 If the reason for the failure to deliver is that the destination is 335 beyond the scope of the source address, the Code field is set to 2. 336 This condition can occur only when the scope of the source address is 337 smaller than the scope of the destination address (e.g., when a 338 packet has a site-local source address and a global-scope destination 339 address) and the packet cannot be delivered to the destination 340 without leaving the scope of the source address (e.g., without 341 leaving the source's site, in the case of a site-local source 342 address). 344 If there is any other reason for the failure to deliver, e.g., 345 inability to resolve the IPv6 destination address into a 346 corresponding link address, or a link-specific problem of some sort, 347 then the Code field is set to 3. 349 A destination node SHOULD send a Destination Unreachable message with 350 Code 4 in response to a packet for which the transport protocol 351 (e.g., UDP) has no listener, if that transport protocol has no 352 alternative means to inform the sender. 354 Upper layer notification 356 A node receiving the ICMPv6 Destination Unreachable message MUST 357 notify the upper-layer process. 359 3.2 Packet Too Big Message 361 0 1 2 3 362 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 1 363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 364 | Type | Code | Checksum | 365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 | MTU | 367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 368 | As much of invoking packet | 369 + as will fit without the ICMPv6 packet + 370 | exceeding the minimum IPv6 MTU [IPv6] | 372 IPv6 Fields: 374 Destination Address 376 Copied from the Source Address field of the invoking 377 packet. 379 ICMPv6 Fields: 381 Type 2 383 Code Set to 0 (zero) by the sender and ignored by the 384 receiver 386 MTU The Maximum Transmission Unit of the next-hop link. 388 Description 390 A Packet Too Big MUST be sent by a router in response to a packet 391 that it cannot forward because the packet is larger than the MTU of 392 the outgoing link. The information in this message is used as part 393 of the Path MTU Discovery process [PMTU]. 395 Sending a Packet Too Big Message makes an exception to one of the 396 rules of when to send an ICMPv6 error message, in that unlike other 397 messages, it is sent in response to a packet received with an IPv6 398 multicast destination address, or a link-layer multicast or link- 399 layer broadcast address. 401 Upper layer notification 403 An incoming Packet Too Big message MUST be passed to the upper-layer 404 process. 406 3.3 Time Exceeded Message 408 0 1 2 3 409 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 1 410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 411 | Type | Code | Checksum | 412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 413 | Unused | 414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 415 | As much of invoking packet | 416 + as will fit without the ICMPv6 packet + 417 | exceeding the minimum IPv6 MTU [IPv6] | 419 IPv6 Fields: 421 Destination Address 422 Copied from the Source Address field of the invoking 423 packet. 425 ICMPv6 Fields: 427 Type 3 429 Code 0 - hop limit exceeded in transit 431 1 - fragment reassembly time exceeded 433 Unused This field is unused for all code values. 434 It must be initialized to zero by the sender 435 and ignored by the receiver. 437 Description 439 If a router receives a packet with a Hop Limit of zero, or a router 440 decrements a packet's Hop Limit to zero, it MUST discard the packet 441 and send an ICMPv6 Time Exceeded message with Code 0 to the source of 442 the packet. This indicates either a routing loop or too small an 443 initial Hop Limit value. 445 The rules for selecting the Source Address of this message are 446 defined in section 2.2. 448 Upper layer notification 450 An incoming Time Exceeded message MUST be passed to the upper-layer 451 process. 453 3.4 Parameter Problem Message 455 0 1 2 3 456 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 1 457 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 458 | Type | Code | Checksum | 459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 460 | Pointer | 461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 462 | As much of invoking packet | 463 + as will fit without the ICMPv6 packet + 464 | exceeding the minimum IPv6 MTU [IPv6] | 466 IPv6 Fields: 468 Destination Address 470 Copied from the Source Address field of the invoking 471 packet. 473 ICMPv6 Fields: 475 Type 4 477 Code 0 - erroneous header field encountered 479 1 - unrecognized Next Header type encountered 481 2 - unrecognized IPv6 option encountered 483 Pointer Identifies the octet offset within the 484 invoking packet where the error was detected. 486 The pointer will point beyond the end of the ICMPv6 487 packet if the field in error is beyond what can fit 488 in the maximum size of an ICMPv6 error message. 490 Description 492 If an IPv6 node processing a packet finds a problem with a field in 493 the IPv6 header or extension headers such that it cannot complete 494 processing the packet, it MUST discard the packet and SHOULD send an 495 ICMPv6 Parameter Problem message to the packet's source, indicating 496 the type and location of the problem. 498 The pointer identifies the octet of the original packet's header 499 where the error was detected. For example, an ICMPv6 message with 500 Type field = 4, Code field = 1, and Pointer field = 40 would indicate 501 that the IPv6 extension header following the IPv6 header of the 502 original packet holds an unrecognized Next Header field value. 504 Upper layer notification 506 A node receiving this ICMPv6 message MUST notify the upper-layer 507 process. 509 4. ICMPv6 Informational Messages 511 4.1 Echo Request Message 513 0 1 2 3 514 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 1 515 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 516 | Type | Code | Checksum | 517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 518 | Identifier | Sequence Number | 519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 520 | Data ... 521 +-+-+-+-+- 523 IPv6 Fields: 525 Destination Address 527 Any legal IPv6 address. 529 ICMPv6 Fields: 531 Type 128 533 Code 0 535 Identifier An identifier to aid in matching Echo Replies 536 to this Echo Request. May be zero. 538 Sequence Number 540 A sequence number to aid in matching Echo Replies 541 to this Echo Request. May be zero. 543 Data Zero or more octets of arbitrary data. 545 Description 547 Every node MUST implement an ICMPv6 Echo responder function that 548 receives Echo Requests and sends corresponding Echo Replies. A node 549 SHOULD also implement an application-layer interface for sending Echo 550 Requests and receiving Echo Replies, for diagnostic purposes. 552 Upper layer notification 554 Echo Request messages MAY be passed to processes receiving ICMP 555 messages. 557 4.2 Echo Reply Message 559 0 1 2 3 560 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 1 561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 562 | Type | Code | Checksum | 563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 564 | Identifier | Sequence Number | 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 | Data ... 567 +-+-+-+-+- 569 IPv6 Fields: 571 Destination Address 573 Copied from the Source Address field of the invoking 574 Echo Request packet. 576 ICMPv6 Fields: 578 Type 129 580 Code 0 582 Identifier The identifier from the invoking Echo Request message. 584 Sequence The sequence number from the invoking Echo Request 585 Number message. 587 Data The data from the invoking Echo Request message. 589 Description 591 Every node MUST implement an ICMPv6 Echo responder function that 592 receives Echo Requests and sends corresponding Echo Replies. A node 593 SHOULD also implement an application-layer interface for sending Echo 594 Requests and receiving Echo Replies, for diagnostic purposes. 596 The source address of an Echo Reply sent in response to a unicast 597 Echo Request message MUST be the same as the destination address of 598 that Echo Request message. 600 An Echo Reply SHOULD be sent in response to an Echo Request message 601 sent to an IPv6 multicast or anycast address. In this case, the 602 source address of the reply MUST be a unicast address belonging to 603 the interface on which the Echo Request message was received. 605 The data received in the ICMPv6 Echo Request message MUST be returned 606 entirely and unmodified in the ICMPv6 Echo Reply message. 608 Upper layer notification 610 Echo Reply messages MUST be passed to the process that originated an 611 Echo Request message. An Echo Reply message MAY be passed to 612 processes that did not originate the Echo Request message. 614 5. Security Considerations 616 5.1 Authentication and Encryption of ICMP messages 618 ICMP protocol packet exchanges can be authenticated using the IP 619 Authentication Header [IPv6-AUTH]. A node SHOULD include an 620 Authentication Header when sending ICMP messages if a security 621 association for use with the IP Authentication Header exists for the 622 destination address. The security associations may have been created 623 through manual configuration or through the operation of some key 624 management protocol. 626 Received Authentication Headers in ICMP packets MUST be verified for 627 correctness and packets with incorrect authentication MUST be ignored 628 and discarded. 630 It SHOULD be possible for the system administrator to configure a 631 node to ignore any ICMP messages that are not authenticated using 632 either the Authentication Header or Encapsulating Security Payload. 633 Such a switch SHOULD default to allowing unauthenticated messages. 635 Confidentiality issues are addressed by the IP Security Architecture 636 and the IP Encapsulating Security Payload documents [IPv6-SA, 637 IPv6-ESP]. 639 5.2 ICMP Attacks 641 ICMP messages may be subject to various attacks. A complete 642 discussion can be found in the IP Security Architecture [IPv6-SA]. A 643 brief discussion of such attacks and their prevention is as follows: 645 1. ICMP messages may be subject to actions intended to cause the 646 receiver to believe the message came from a different source than 647 the message originator. The protection against this attack can be 648 achieved by applying the IPv6 Authentication mechanism [IPv6-AUTH] 649 to the ICMP message. 651 2. ICMP messages may be subject to actions intended to cause the 652 message or the reply to it go to a destination different than the 653 message originator's intention. The ICMP checksum calculation 654 provides a protection mechanism against changes by a malicious 655 interceptor in the destination and source address of the IP packet 656 carrying that message, provided the ICMP checksum field is 657 protected against change by authentication [IPv6-AUTH] or 658 encryption [IPv6-ESP] of the ICMP message. 660 3. ICMP messages may be subject to changes in the message fields, or 661 payload. The authentication [IPv6-AUTH] or encryption [IPv6-ESP] 662 of the ICMP message is a protection against such actions. 664 4. ICMP messages may be used as attempts to perform denial of service 665 attacks by sending back to back erroneous IP packets. An 666 implementation that correctly followed section 2.4, paragraph (f) 667 of this specifications, would be protected by the ICMP error rate 668 limiting mechanism. 670 6. References 672 [IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6, 673 Specification", RFC2460, December 1998. 675 [IPv6-ADDR] Hinden, R., S. Deering, "IP Version 6 Addressing 676 Architecture", RFC2373, July 1998. 678 [IPv6-DISC] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery 679 for IP Version 6 (IPv6)", RFC2461, December, 1998. 681 [RFC-792] Postel, J., "Internet Control Message Protocol", STD 5, 682 RFC792, September 1981. 684 [RFC-1122] Braden, R., "Requirements for Internet Hosts - 685 Communication Layers", STD 5, RFC1122, August 1989. 687 [PMTU] McCann, J., S. Deering, J. Mogul, "Path MTU Discovery 688 for IP version 6", RFC1981, August 1996. 690 [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate 691 Requirement Levels", BCP14, RFC2119, March 1997. 693 [IPv6-SA] Kent, S., R. Atkinson, "Security Architecture for the 694 Internet Protocol", RFC1825, November 1998. 696 [IPv6-AUTH] Kent, S., R. Atkinson, "IP Authentication Header", RFC 697 2402, November 1998. 699 [IPv6-ESP] Kent, S., R. Atkinson, "IP Encapsulating Security 700 Protocol (ESP)", RFC 2406, November 1998. 702 7. Acknowledgments 704 The document is derived from previous ICMP drafts of the SIPP and 705 IPng working group. 707 The IPng working group and particularly Robert Elz, Jim Bound, Bill 708 Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner, 709 Dimitri Haskin, and Bob Hinden (in chronological order) provided 710 extensive review information and feedback. 712 Bob Hinden was the document editor for this document. 714 8. Authors' Addresses 716 Alex Conta Stephen Deering 717 Transwitch Corporation Cisco Systems, Inc. 718 3 Enterprise Drive 170 West Tasman Drive 719 Shelton, CT 06484 San Jose, CA 95134-1706 720 US US 722 phone: +1 408 527-8213 723 email: aconta@txc.com email: deering@cisco.com 725 Appendix A - Changes from RFC 2463 727 The following changes were made from RFC 2463: 729 - Added "beyond scope of source address" message to the family of 730 "unreachable destination" type ICMP error messages (section 3.1). 732 - Added a NOTE in section 2.4, that specifies ICMP message 733 processing rules precedence. 735 - Added ICMP REDIRECT to the list in Section 2.4 e) of cases in 736 which ICMP error messages are not to be generated. 738 - Made minor editorial changes in Section 2.3 on checksum 739 calculation, and in Section 5.2. 741 - Clarified in section 4.2, regarding the Echo Reply Message, that 742 the source address of an Echo Reply to an anycast Echo Request 743 should be a unicast address, as is the case of multicast.