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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 May 21, 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.........5 50 2.3 Message Checksum Calculation.................6 52 2.4 Message Processing Rules.....................6 54 3. ICMPv6 Error Messages...............................9 56 3.1 Destination Unreachable Message..............9 58 3.2 Packet Too Big Message......................11 60 3.3 Time Exceeded Message.......................12 62 3.4 Parameter Problem Message...................14 64 4. ICMPv6 Informational Messages......................16 66 4.1 Echo Request Message........................16 68 4.2 Echo Reply Message..........................17 70 5. Security Considerations............................19 72 6. References.........................................21 74 7. Acknowledgments....................................21 76 8. Authors' Addresses.................................22 78 Appendix A - Changes since RFC 2463...................22 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 The subclass of ICMPv6 messages used for reporting errors, i.e., 159 those with a Type value between 0 and 127, inclusive, all have the 160 following, more specific format: 162 0 1 2 3 163 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 1 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | Type | Code | Checksum | 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | type-specific data (32 bits) | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | As much of invoking packet | 170 + as will fit without the ICMPv6 packet + 171 | exceeding the minimum IPv6 MTU [IPv6] | 173 2.2 Message Source Address Determination 175 A node that sends an ICMPv6 message has to determine both the Source 176 and Destination IPv6 Addresses in the IPv6 header before calculating 177 the checksum. If the node has more than one unicast address, it must 178 choose the Source Address of the message as follows: 180 (a) If the message is a response to a message sent to one of the 181 node's unicast addresses, the Source Address of the reply must 182 be that same address. 184 (b) If the message is a response to a message sent to a multicast or 185 anycast group in which the node is a member, the Source Address 186 of the reply must be a unicast address belonging to the 187 interface on which the multicast or anycast packet was received. 189 (c) If the message is a response to a message sent to an address 190 that does not belong to the node, the Source Address should be 191 that unicast address belonging to the node that will be most 192 helpful in diagnosing the error. For example, if the message is 193 a response to a packet forwarding action that cannot complete 194 successfully, the Source Address should be a unicast address 195 belonging to the interface on which the packet forwarding 196 failed. 198 (d) Otherwise, the node's routing table must be examined to 199 determine which interface will be used to transmit the message 200 to its destination, and a unicast address belonging to that 201 interface must be used as the Source Address of the message. 203 2.3 Message Checksum Calculation 205 The checksum is the 16-bit one's complement of the one's complement 206 sum of the entire ICMPv6 message starting with the ICMPv6 message 207 type field, prepended with a "pseudo-header" of IPv6 header fields, 208 as specified in [IPv6, section 8.1]. The Next Header value used in 209 the pseudo-header is 58. (NOTE: the inclusion of a pseudo-header in 210 the ICMPv6 checksum is a change from IPv4; see [IPv6] for the 211 rationale for this change.) 213 For computing the checksum, the checksum field is first set to zero. 215 2.4 Message Processing Rules 217 Implementations MUST observe the following rules when processing 218 ICMPv6 messages (from [RFC-1122]): 220 (a) If an ICMPv6 error message of unknown type is received, it MUST 221 be passed to the upper layer. 223 (b) If an ICMPv6 informational message of unknown type is received, 224 it MUST be silently discarded. 226 (c) Every ICMPv6 error message (type < 128) includes as much of the 227 IPv6 offending (invoking) packet (the packet that caused the 228 error) as will fit without making the error message packet 229 exceed the minimum IPv6 MTU [IPv6]. 231 (d) In those cases where the internet-layer protocol is required to 232 pass an ICMPv6 error message to the upper-layer process, the 233 upper-layer protocol type is extracted from the original packet 234 (contained in the body of the ICMPv6 error message) and used to 235 select the appropriate upper-layer process to handle the error. 237 If the original packet had an unusually large amount of 238 extension headers, it is possible that the upper-layer protocol 239 type may not be present in the ICMPv6 message, due to truncation 240 of the original packet to meet the minimum IPv6 MTU [IPv6] 241 limit. In that case, the error message is silently dropped 242 after any IPv6-layer processing. 244 (e) An ICMPv6 error message MUST NOT be sent as a result of 245 receiving: 247 (e.1) an ICMPv6 error message, or 249 (e.2) an ICMPv6 redirect message [IPv6-DISC], or 251 (e.3) a packet destined to an IPv6 multicast address (there are 252 two exceptions to this rule: (1) the Packet Too Big 253 Message - Section 3.2 - to allow Path MTU discovery to 254 work for IPv6 multicast, and (2) the Parameter Problem 255 Message, Code 2 - Section 3.4 - reporting an unrecognized 256 IPv6 option that has the Option Type highest-order two 257 bits set to 10), or 259 (e.4) a packet sent as a link-layer multicast, (the exception 260 from e.3 applies to this case too), or 262 (e.5) a packet sent as a link-layer broadcast, (the exception 263 from e.3 applies to this case too), or 265 (e.6) a packet whose source address does not uniquely identify 266 a single node -- e.g., the IPv6 Unspecified Address, an 267 IPv6 multicast address, or an address known by the ICMP 268 message sender to be an IPv6 anycast address. 270 (f) Finally, in order to limit the bandwidth and forwarding costs 271 incurred sending ICMPv6 error messages, an IPv6 node MUST limit 272 the rate of ICMPv6 error messages it sends. This situation may 273 occur when a source sending a stream of erroneous packets fails 274 to heed the resulting ICMPv6 error messages. There are a variety 275 of ways of implementing the rate-limiting function, for example: 277 (f.1) Timer-based - for example, limiting the rate of 278 transmission of error messages to a given source, or to 279 any source, to at most once every T milliseconds. 281 (f.2) Bandwidth-based - for example, limiting the rate at which 282 error messages are sent from a particular interface to 283 some fraction F of the attached link's bandwidth. 285 (f.3) Token-bucket based - for example, allowing up to B back- 286 to-back error messages to be transmitted in a burst, but 287 limiting the average rate of transmission to N messages 288 per second. 290 The limit parameters (e.g., T or F in the above examples) MUST 291 be configurable for the node, with a conservative default value 292 (e.g., T = 0.5 second, NOT 0 seconds, or F = 2 percent, NOT 100 293 percent). 295 NOTE: THE RESTRICTIONS UNDER (e) AND (f) ABOVE TAKE PRECEDENCE OVER 296 ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR SENDING ICMP ERROR 297 MESSAGES. 299 The following sections describe the message formats for the above 300 ICMPv6 messages. 302 3. ICMPv6 Error Messages 304 3.1 Destination Unreachable Message 306 0 1 2 3 307 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 1 308 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 309 | Type | Code | Checksum | 310 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 311 | Unused | 312 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 | As much of invoking packet | 314 + as will fit without the ICMPv6 packet + 315 | exceeding the minimum IPv6 MTU [IPv6] | 317 IPv6 Fields: 319 Destination Address 321 Copied from the Source Address field of the invoking 322 packet. 324 ICMPv6 Fields: 326 Type 1 328 Code 0 - no route to destination 329 1 - communication with destination 330 administratively prohibited 331 2 - beyond scope of source address 332 3 - address unreachable 333 4 - port unreachable 335 Unused This field is unused for all code values. 336 It must be initialized to zero by the sender 337 and ignored by the receiver. 338 Description 340 A Destination Unreachable message SHOULD be generated by a router, or 341 by the IPv6 layer in the originating node, in response to a packet 342 that cannot be delivered to its destination address for reasons other 343 than congestion. (An ICMPv6 message MUST NOT be generated if a 344 packet is dropped due to congestion.) 346 If the reason for the failure to deliver is lack of a matching entry 347 in the forwarding node's routing table, the Code field is set to 0 348 (NOTE: this error can occur only in nodes that do not hold a "default 349 route" in their routing tables). 351 If the reason for the failure to deliver is administrative 352 prohibition, e.g., a "firewall filter", the Code field is set to 1. 354 If the reason for the failure to deliver is that the destination is 355 beyond the scope of the source address, the Code field is set to 2. 356 This condition can occur only when the scope of the source address is 357 smaller than the scope of the destination address (e.g., when a 358 packet has a site-local source address and a global-scope destination 359 address) and the packet cannot be delivered to the destination 360 without leaving the scope of the source address (e.g., without 361 leaving the source's site, in the case of a site-local source 362 address). 364 If there is any other reason for the failure to deliver, e.g., 365 inability to resolve the IPv6 destination address into a 366 corresponding link address, or a link-specific problem of some sort, 367 then the Code field is set to 3. 369 One specific case in which a Destination Unreachable message with a 370 code 3 is sent is in response to a packet received by a router from a 371 point-to-point link, destined to an address within a subnet assigned 372 to that same link (other than one of the receiving router's own 373 addresses). In such a case, the packet MUST NOT be forwarded back 374 onto the arrival link. 376 A destination node SHOULD send a Destination Unreachable message with 377 Code 4 in response to a packet for which the transport protocol 378 (e.g., UDP) has no listener, if that transport protocol has no 379 alternative means to inform the sender. 381 Upper layer notification 383 A node receiving the ICMPv6 Destination Unreachable message MUST 384 notify the upper-layer process. 386 3.2 Packet Too Big Message 388 0 1 2 3 389 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 1 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | Type | Code | Checksum | 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 | MTU | 394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 395 | As much of invoking packet | 396 + as will fit without the ICMPv6 packet + 397 | exceeding the minimum IPv6 MTU [IPv6] | 399 IPv6 Fields: 401 Destination Address 403 Copied from the Source Address field of the invoking 404 packet. 406 ICMPv6 Fields: 408 Type 2 410 Code Set to 0 (zero) by the sender and ignored by the 411 receiver 413 MTU The Maximum Transmission Unit of the next-hop link. 415 Description 417 A Packet Too Big MUST be sent by a router in response to a packet 418 that it cannot forward because the packet is larger than the MTU of 419 the outgoing link. The information in this message is used as part 420 of the Path MTU Discovery process [PMTU]. 422 Sending a Packet Too Big Message makes an exception to one of the 423 rules of when to send an ICMPv6 error message, in that unlike other 424 messages, it is sent in response to a packet received with an IPv6 425 multicast destination address, or a link-layer multicast or link- 426 layer broadcast address. 428 Upper layer notification 430 An incoming Packet Too Big message MUST be passed to the upper-layer 431 process. 433 3.3 Time Exceeded Message 435 0 1 2 3 436 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 1 437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 438 | Type | Code | Checksum | 439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 440 | Unused | 441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 442 | As much of invoking packet | 443 + as will fit without the ICMPv6 packet + 444 | exceeding the minimum IPv6 MTU [IPv6] | 446 IPv6 Fields: 448 Destination Address 449 Copied from the Source Address field of the invoking 450 packet. 452 ICMPv6 Fields: 454 Type 3 456 Code 0 - hop limit exceeded in transit 458 1 - fragment reassembly time exceeded 460 Unused This field is unused for all code values. 461 It must be initialized to zero by the sender 462 and ignored by the receiver. 464 Description 466 If a router receives a packet with a Hop Limit of zero, or a router 467 decrements a packet's Hop Limit to zero, it MUST discard the packet 468 and send an ICMPv6 Time Exceeded message with Code 0 to the source of 469 the packet. This indicates either a routing loop or too small an 470 initial Hop Limit value. 472 An ICMPv6 Time Exceeded message with Code 1 is used to report 473 fragment reassembly timeout, as specified in [IPv6, Section 4.5]. 475 The rules for selecting the Source Address of this message are 476 defined in section 2.2. 478 Upper layer notification 480 An incoming Time Exceeded message MUST be passed to the upper-layer 481 process. 483 3.4 Parameter Problem Message 485 0 1 2 3 486 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 1 487 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 488 | Type | Code | Checksum | 489 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 490 | Pointer | 491 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 492 | As much of invoking packet | 493 + as will fit without the ICMPv6 packet + 494 | exceeding the minimum IPv6 MTU [IPv6] | 496 IPv6 Fields: 498 Destination Address 500 Copied from the Source Address field of the invoking 501 packet. 503 ICMPv6 Fields: 505 Type 4 507 Code 0 - erroneous header field encountered 509 1 - unrecognized Next Header type encountered 511 2 - unrecognized IPv6 option encountered 513 Pointer Identifies the octet offset within the 514 invoking packet where the error was detected. 516 The pointer will point beyond the end of the ICMPv6 517 packet if the field in error is beyond what can fit 518 in the maximum size of an ICMPv6 error message. 520 Description 522 If an IPv6 node processing a packet finds a problem with a field in 523 the IPv6 header or extension headers such that it cannot complete 524 processing the packet, it MUST discard the packet and SHOULD send an 525 ICMPv6 Parameter Problem message to the packet's source, indicating 526 the type and location of the problem. 528 The pointer identifies the octet of the original packet's header 529 where the error was detected. For example, an ICMPv6 message with 530 Type field = 4, Code field = 1, and Pointer field = 40 would indicate 531 that the IPv6 extension header following the IPv6 header of the 532 original packet holds an unrecognized Next Header field value. 534 Upper layer notification 536 A node receiving this ICMPv6 message MUST notify the upper-layer 537 process. 539 4. ICMPv6 Informational Messages 541 4.1 Echo Request Message 543 0 1 2 3 544 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 1 545 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 546 | Type | Code | Checksum | 547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 548 | Identifier | Sequence Number | 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 | Data ... 551 +-+-+-+-+- 553 IPv6 Fields: 555 Destination Address 557 Any legal IPv6 address. 559 ICMPv6 Fields: 561 Type 128 563 Code 0 565 Identifier An identifier to aid in matching Echo Replies 566 to this Echo Request. May be zero. 568 Sequence Number 570 A sequence number to aid in matching Echo Replies 571 to this Echo Request. May be zero. 573 Data Zero or more octets of arbitrary data. 575 Description 577 Every node MUST implement an ICMPv6 Echo responder function that 578 receives Echo Requests and sends corresponding Echo Replies. A node 579 SHOULD also implement an application-layer interface for sending Echo 580 Requests and receiving Echo Replies, for diagnostic purposes. 582 Upper layer notification 584 Echo Request messages MAY be passed to processes receiving ICMP 585 messages. 587 4.2 Echo Reply Message 589 0 1 2 3 590 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 1 591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | Type | Code | Checksum | 593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 | Identifier | Sequence Number | 595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | Data ... 597 +-+-+-+-+- 599 IPv6 Fields: 601 Destination Address 603 Copied from the Source Address field of the invoking 604 Echo Request packet. 606 ICMPv6 Fields: 608 Type 129 610 Code 0 612 Identifier The identifier from the invoking Echo Request message. 614 Sequence The sequence number from the invoking Echo Request 615 Number message. 617 Data The data from the invoking Echo Request message. 619 Description 621 Every node MUST implement an ICMPv6 Echo responder function that 622 receives Echo Requests and sends corresponding Echo Replies. A node 623 SHOULD also implement an application-layer interface for sending Echo 624 Requests and receiving Echo Replies, for diagnostic purposes. 626 The source address of an Echo Reply sent in response to a unicast 627 Echo Request message MUST be the same as the destination address of 628 that Echo Request message. 630 An Echo Reply SHOULD be sent in response to an Echo Request message 631 sent to an IPv6 multicast or anycast address. In this case, the 632 source address of the reply MUST be a unicast address belonging to 633 the interface on which the Echo Request message was received. 635 The data received in the ICMPv6 Echo Request message MUST be returned 636 entirely and unmodified in the ICMPv6 Echo Reply message. 638 Upper layer notification 640 Echo Reply messages MUST be passed to the process that originated an 641 Echo Request message. An Echo Reply message MAY be passed to 642 processes that did not originate the Echo Request message. 644 5. Security Considerations 646 5.1 Authentication and Encryption of ICMP messages 648 ICMP protocol packet exchanges can be authenticated using the IP 649 Authentication Header [IPv6-AUTH]. A node SHOULD include an 650 Authentication Header when sending ICMP messages if a security 651 association for use with the IP Authentication Header exists for the 652 destination address. The security associations may have been created 653 through manual configuration or through the operation of some key 654 management protocol. 656 Received Authentication Headers in ICMP packets MUST be verified for 657 correctness and packets with incorrect authentication MUST be ignored 658 and discarded. 660 It SHOULD be possible for the system administrator to configure a 661 node to ignore any ICMP messages that are not authenticated using 662 either the Authentication Header or Encapsulating Security Payload. 663 Such a switch SHOULD default to allowing unauthenticated messages. 665 Confidentiality issues are addressed by the IP Security Architecture 666 and the IP Encapsulating Security Payload documents [IPv6-SA, 667 IPv6-ESP]. 669 5.2 ICMP Attacks 671 ICMP messages may be subject to various attacks. A complete 672 discussion can be found in the IP Security Architecture [IPv6-SA]. A 673 brief discussion of such attacks and their prevention is as follows: 675 1. ICMP messages may be subject to actions intended to cause the 676 receiver to believe the message came from a different source than 677 the message originator. The protection against this attack can be 678 achieved by applying the IPv6 Authentication mechanism [IPv6-AUTH] 679 to the ICMP message. 681 2. ICMP messages may be subject to actions intended to cause the 682 message or the reply to it go to a destination different than the 683 message originator's intention. The ICMP checksum calculation 684 provides a protection mechanism against changes by a malicious 685 interceptor in the destination and source address of the IP packet 686 carrying that message, provided the ICMP checksum field is 687 protected against change by authentication [IPv6-AUTH] or 688 encryption [IPv6-ESP] of the ICMP message. 690 3. ICMP messages may be subject to changes in the message fields, or 691 payload. The authentication [IPv6-AUTH] or encryption [IPv6-ESP] 692 of the ICMP message is a protection against such actions. 694 4. ICMP messages may be used as attempts to perform denial of service 695 attacks by sending back to back erroneous IP packets. An 696 implementation that correctly followed section 2.4, paragraph (f) 697 of this specifications, would be protected by the ICMP error rate 698 limiting mechanism. 700 6. References 702 [IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6, 703 Specification", RFC2460, December 1998. 705 [IPv6-ADDR] Hinden, R., S. Deering, "IP Version 6 Addressing 706 Architecture", RFC2373, July 1998. 708 [IPv6-DISC] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery 709 for IP Version 6 (IPv6)", RFC2461, December, 1998. 711 [RFC-792] Postel, J., "Internet Control Message Protocol", STD 5, 712 RFC792, September 1981. 714 [RFC-1122] Braden, R., "Requirements for Internet Hosts - 715 Communication Layers", STD 5, RFC1122, August 1989. 717 [PMTU] McCann, J., S. Deering, J. Mogul, "Path MTU Discovery 718 for IP version 6", RFC1981, August 1996. 720 [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate 721 Requirement Levels", BCP14, RFC2119, March 1997. 723 [IPv6-SA] Kent, S., R. Atkinson, "Security Architecture for the 724 Internet Protocol", RFC1825, November 1998. 726 [IPv6-AUTH] Kent, S., R. Atkinson, "IP Authentication Header", RFC 727 2402, November 1998. 729 [IPv6-ESP] Kent, S., R. Atkinson, "IP Encapsulating Security 730 Protocol (ESP)", RFC 2406, November 1998. 732 7. Acknowledgments 734 The document is derived from previous ICMP drafts of the SIPP and 735 IPng working group. 737 The IPng working group and particularly Robert Elz, Jim Bound, Bill 738 Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner, 739 Dimitri Haskin, Bob Hinden, Jun-ichiro Itojun Hagino, Tatuya Jinmei, 740 and Brian Zill (in chronological order) provided extensive review 741 information and feedback. 743 Bob Hinden was the document editor for this document. 745 8. Authors' Addresses 747 Alex Conta Stephen Deering 748 Transwitch Corporation Cisco Systems, Inc. 749 3 Enterprise Drive 170 West Tasman Drive 750 Shelton, CT 06484 San Jose, CA 95134-1706 751 US US 753 phone: +1 408 527-8213 754 email: aconta@txc.com email: deering@cisco.com 756 Appendix A - Changes from RFC 2463 758 The following changes were made from RFC 2463: 760 - Corrected typos in section 2.4, where references to sub-bullet e.2 761 were supposed to be references to e.3. 763 - Added token-bucket method as an example rate-limiting mechanism 764 for ICMP error messages, and changed default value for the fixed 765 timer approach, parameter T, from 1 second to 0.5 second. 767 - Added specification that all ICMP error messages shall have 768 exactly 32 bits of type-specific data, so that receivers can 769 reliably find the embedded invoking packet even when they don't 770 recognize the ICMP message Type. 772 - In the description of Destination Unreachable messages, Code 3, 773 added rule prohibiting forwarding of packets back onto point-to- 774 point links from which they were received, if their destination 775 addresses belong to the link itself ("anti-ping-ponging" rule). 777 - Added description of Time Exceeded Code 1 (fragment reassembly 778 timeout). 780 - Added "beyond scope of source address" message to the family of 781 "unreachable destination" type ICMP error messages (section 3.1). 783 - Added a NOTE in section 2.4, that specifies ICMP message 784 processing rules precedence. 786 - Added ICMP REDIRECT to the list in Section 2.4 e) of cases in 787 which ICMP error messages are not to be generated. 789 - Made minor editorial changes in Section 2.3 on checksum 790 calculation, and in Section 5.2. 792 - Clarified in section 4.2, regarding the Echo Reply Message, that 793 the source address of an Echo Reply to an anycast Echo Request 794 should be a unicast address, as in the case of multicast.