RFC 2463: Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification

This RFC is now obsolete

Network Working Group A. Conta
Request for Comments: 2463 Lucent
Obsoletes: 1885 S. Deering
Category: Standards Track Cisco Systems
 December 1998


 Internet Control Message Protocol (ICMPv6)
 for the Internet Protocol Version 6 (IPv6)
 Specification

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements. Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1998). All Rights Reserved.

Abstract

 This document specifies a set of Internet Control Message Protocol
 (ICMP) messages for use with version 6 of the Internet Protocol
 (IPv6).

Table of Contents

 1. Introduction........................................2
 2. ICMPv6 (ICMP for IPv6)..............................2
 2.1 Message General Format.......................2
 2.2 Message Source Address Determination.........3
 2.3 Message Checksum Calculation.................4
 2.4 Message Processing Rules.....................4
 3. ICMPv6 Error Messages...............................6
 3.1 Destination Unreachable Message..............6
 3.2 Packet Too Big Message...................... 8
 3.3 Time Exceeded Message....................... 9
 3.4 Parameter Problem Message...................10
 4. ICMPv6 Informational Messages......................11
 4.1 Echo Request Message........................11
 4.2 Echo Reply Message..........................12
 5. Security Considerations............................13
 6. References.........................................14
 7. Acknowledgments....................................15



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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 8. Authors' Addresses.................................16
 Appendix A - Changes since RFC 1885...................17
 Full Copyright Statement..............................18

1. Introduction

 The Internet Protocol, version 6 (IPv6) is a new version of IP. IPv6
 uses the Internet Control Message Protocol (ICMP) as defined for IPv4
 [RFC-792], with a number of changes. The resulting protocol is
 called ICMPv6, and has an IPv6 Next Header value of 58.

 This document describes the format of a set of control messages used
 in ICMPv6. It does not describe the procedures for using these
 messages to achieve functions like Path MTU discovery; such
 procedures are described in other documents (e.g., [PMTU]). Other
 documents may also introduce additional ICMPv6 message types, such as
 Neighbor Discovery messages [IPv6-DISC], subject to the general rules
 for ICMPv6 messages given in section 2 of this document.

 Terminology defined in the IPv6 specification [IPv6] and the IPv6
 Routing and Addressing specification [IPv6-ADDR] applies to this
 document as well.

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC-2119].

2. ICMPv6 (ICMP for IPv6)

 ICMPv6 is used by IPv6 nodes to report errors encountered in
 processing packets, and to perform other internet-layer functions,
 such as diagnostics (ICMPv6 "ping"). ICMPv6 is an integral part of
 IPv6 and MUST be fully implemented by every IPv6 node.

2.1 Message General Format

 ICMPv6 messages are grouped into two classes: error messages and
 informational messages. Error messages are identified as such by
 having a zero in the high-order bit of their message Type field
 values. Thus, error messages have message Types from 0 to 127;
 informational messages have message Types from 128 to 255.

 This document defines the message formats for the following ICMPv6
 messages:







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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 ICMPv6 error messages:

 1 Destination Unreachable (see section 3.1)
 2 Packet Too Big (see section 3.2)
 3 Time Exceeded (see section 3.3)
 4 Parameter Problem (see section 3.4)

 ICMPv6 informational messages:

 128 Echo Request (see section 4.1)
 129 Echo Reply (see section 4.2)


 Every ICMPv6 message is preceded by an IPv6 header and zero or more
 IPv6 extension headers. The ICMPv6 header is identified by a Next
 Header value of 58 in the immediately preceding header. (NOTE: this
 is different than the value used to identify ICMP for IPv4.)

 The ICMPv6 messages have the following general format:

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | |
 + Message Body +
 | |

 The type field indicates the type of the message. Its value
 determines the format of the remaining data.

 The code field depends on the message type. It is used to create an
 additional level of message granularity.

 The checksum field is used to detect data corruption in the ICMPv6
 message and parts of the IPv6 header.

2.2 Message Source Address Determination

 A node that sends an ICMPv6 message has to determine both the Source
 and Destination IPv6 Addresses in the IPv6 header before calculating
 the checksum. If the node has more than one unicast address, it must
 choose the Source Address of the message as follows:

 (a) If the message is a response to a message sent to one of the
 node's unicast addresses, the Source Address of the reply must
 be that same address.



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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 (b) If the message is a response to a message sent to a multicast or
 anycast group in which the node is a member, the Source Address
 of the reply must be a unicast address belonging to the
 interface on which the multicast or anycast packet was received.

 (c) If the message is a response to a message sent to an address
 that does not belong to the node, the Source Address should be
 that unicast address belonging to the node that will be most
 helpful in diagnosing the error. For example, if the message is
 a response to a packet forwarding action that cannot complete
 successfully, the Source Address should be a unicast address
 belonging to the interface on which the packet forwarding
 failed.

 (d) Otherwise, the node's routing table must be examined to
 determine which interface will be used to transmit the message
 to its destination, and a unicast address belonging to that
 interface must be used as the Source Address of the message.

2.3 Message Checksum Calculation

 The checksum is the 16-bit one's complement of the one's complement
 sum of the entire ICMPv6 message starting with the ICMPv6 message
 type field, prepended with a "pseudo-header" of IPv6 header fields,
 as specified in [IPv6, section 8.1]. The Next Header value used in
 the pseudo-header is 58. (NOTE: the inclusion of a pseudo-header in
 the ICMPv6 checksum is a change from IPv4; see [IPv6] for the
 rationale for this change.)

 For computing the checksum, the checksum field is set to zero.

2.4 Message Processing Rules

 Implementations MUST observe the following rules when processing
 ICMPv6 messages (from [RFC-1122]):

 (a) If an ICMPv6 error message of unknown type is received, it MUST
 be passed to the upper layer.

 (b) If an ICMPv6 informational message of unknown type is received,
 it MUST be silently discarded.

 (c) Every ICMPv6 error message (type < 128) includes as much of the
 IPv6 offending (invoking) packet (the packet that caused the
 error) as will fit without making the error message packet
 exceed the minimum IPv6 MTU [IPv6].





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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 (d) In those cases where the internet-layer protocol is required to
 pass an ICMPv6 error message to the upper-layer process, the
 upper-layer protocol type is extracted from the original packet
 (contained in the body of the ICMPv6 error message) and used to
 select the appropriate upper-layer process to handle the error.

 If the original packet had an unusually large amount of
 extension headers, it is possible that the upper-layer protocol
 type may not be present in the ICMPv6 message, due to truncation
 of the original packet to meet the minimum IPv6 MTU [IPv6]
 limit. In that case, the error message is silently dropped
 after any IPv6-layer processing.

 (e) An ICMPv6 error message MUST NOT be sent as a result of
 receiving:

 (e.1) an ICMPv6 error message, or

 (e.2) a packet destined to an IPv6 multicast address (there are
 two exceptions to this rule: (1) the Packet Too Big
 Message - Section 3.2 - to allow Path MTU discovery to
 work for IPv6 multicast, and (2) the Parameter Problem
 Message, Code 2 - Section 3.4 - reporting an unrecognized
 IPv6 option that has the Option Type highest-order two
 bits set to 10), or

 (e.3) a packet sent as a link-layer multicast, (the exception
 from e.2 applies to this case too), or

 (e.4) a packet sent as a link-layer broadcast, (the exception
 from e.2 applies to this case too), or

 (e.5) a packet whose source address does not uniquely identify
 a single node -- e.g., the IPv6 Unspecified Address, an
 IPv6 multicast address, or an address known by the ICMP
 message sender to be an IPv6 anycast address.

 (f) Finally, in order to limit the bandwidth and forwarding costs
 incurred sending ICMPv6 error messages, an IPv6 node MUST limit
 the rate of ICMPv6 error messages it sends. This situation may
 occur when a source sending a stream of erroneous packets fails
 to heed the resulting ICMPv6 error messages. There are a
 variety of ways of implementing the rate-limiting function, for
 example:

 (f.1) Timer-based - for example, limiting the rate of
 transmission of error messages to a given source, or to
 any source, to at most once every T milliseconds.



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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 (f.2) Bandwidth-based - for example, limiting the rate at which
 error messages are sent from a particular interface to
 some fraction F of the attached link's bandwidth.

 The limit parameters (e.g., T or F in the above examples) MUST
 be configurable for the node, with a conservative default value
 (e.g., T = 1 second, NOT 0 seconds, or F = 2 percent, NOT 100
 percent).

 The following sections describe the message formats for the above
 ICMPv6 messages.

3. ICMPv6 Error Messages

3.1 Destination Unreachable Message

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Unused |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | As much of invoking packet |
 + as will fit without the ICMPv6 packet +
 | exceeding the minimum IPv6 MTU [IPv6] |

 IPv6 Fields:

 Destination Address

 Copied from the Source Address field of the invoking
 packet.

 ICMPv6 Fields:

 Type 1

 Code 0 - no route to destination
 1 - communication with destination
 administratively prohibited
 2 - (not assigned)
 3 - address unreachable
 4 - port unreachable

 Unused This field is unused for all code values.
 It must be initialized to zero by the sender
 and ignored by the receiver.



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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 Description

 A Destination Unreachable message SHOULD be generated by a router, or
 by the IPv6 layer in the originating node, in response to a packet
 that cannot be delivered to its destination address for reasons other
 than congestion. (An ICMPv6 message MUST NOT be generated if a
 packet is dropped due to congestion.)

 If the reason for the failure to deliver is lack of a matching entry
 in the forwarding node's routing table, the Code field is set to 0
 (NOTE: this error can occur only in nodes that do not hold a "default
 route" in their routing tables).

 If the reason for the failure to deliver is administrative
 prohibition, e.g., a "firewall filter", the Code field is set to 1.

 If there is any other reason for the failure to deliver, e.g.,
 inability to resolve the IPv6 destination address into a
 corresponding link address, or a link-specific problem of some sort,
 then the Code field is set to 3.

 A destination node SHOULD send a Destination Unreachable message with
 Code 4 in response to a packet for which the transport protocol
 (e.g., UDP) has no listener, if that transport protocol has no
 alternative means to inform the sender.

 Upper layer notification

 A node receiving the ICMPv6 Destination Unreachable message MUST
 notify the upper-layer process.





















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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


3.2 Packet Too Big Message

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | MTU |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | As much of invoking packet |
 + as will fit without the ICMPv6 packet +
 | exceeding the minimum IPv6 MTU [IPv6] |

 IPv6 Fields:

 Destination Address

 Copied from the Source Address field of the invoking
 packet.

 ICMPv6 Fields:

 Type 2

 Code Set to 0 (zero) by the sender and ignored by the
 receiver

 MTU The Maximum Transmission Unit of the next-hop link.

 Description

 A Packet Too Big MUST be sent by a router in response to a packet
 that it cannot forward because the packet is larger than the MTU of
 the outgoing link. The information in this message is used as part
 of the Path MTU Discovery process [PMTU].

 Sending a Packet Too Big Message makes an exception to one of the
 rules of when to send an ICMPv6 error message, in that unlike other
 messages, it is sent in response to a packet received with an IPv6
 multicast destination address, or a link-layer multicast or link-
 layer broadcast address.

 Upper layer notification

 An incoming Packet Too Big message MUST be passed to the upper-layer
 process.





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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


3.3 Time Exceeded Message

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Unused |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | As much of invoking packet |
 + as will fit without the ICMPv6 packet +
 | exceeding the minimum IPv6 MTU [IPv6] |

 IPv6 Fields:

 Destination Address
 Copied from the Source Address field of the invoking
 packet.

 ICMPv6 Fields:

 Type 3

 Code 0 - hop limit exceeded in transit

 1 - fragment reassembly time exceeded

 Unused This field is unused for all code values.
 It must be initialized to zero by the sender
 and ignored by the receiver.

 Description

 If a router receives a packet with a Hop Limit of zero, or a router
 decrements a packet's Hop Limit to zero, it MUST discard the packet
 and send an ICMPv6 Time Exceeded message with Code 0 to the source of
 the packet. This indicates either a routing loop or too small an
 initial Hop Limit value.

 The rules for selecting the Source Address of this message are
 defined in section 2.2.

 Upper layer notification

 An incoming Time Exceeded message MUST be passed to the upper-layer
 process.





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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


3.4 Parameter Problem Message

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Pointer |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | As much of invoking packet |
 + as will fit without the ICMPv6 packet +
 | exceeding the minimum IPv6 MTU [IPv6] |

 IPv6 Fields:

 Destination Address

 Copied from the Source Address field of the invoking
 packet.

 ICMPv6 Fields:

 Type 4

 Code 0 - erroneous header field encountered

 1 - unrecognized Next Header type encountered

 2 - unrecognized IPv6 option encountered

 Pointer Identifies the octet offset within the
 invoking packet where the error was detected.

 The pointer will point beyond the end of the ICMPv6
 packet if the field in error is beyond what can fit
 in the maximum size of an ICMPv6 error message.

 Description

 If an IPv6 node processing a packet finds a problem with a field in
 the IPv6 header or extension headers such that it cannot complete
 processing the packet, it MUST discard the packet and SHOULD send an
 ICMPv6 Parameter Problem message to the packet's source, indicating
 the type and location of the problem.

 The pointer identifies the octet of the original packet's header
 where the error was detected. For example, an ICMPv6 message with
 Type field = 4, Code field = 1, and Pointer field = 40 would indicate



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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 that the IPv6 extension header following the IPv6 header of the
 original packet holds an unrecognized Next Header field value.

 Upper layer notification

 A node receiving this ICMPv6 message MUST notify the upper-layer
 process.

4. ICMPv6 Informational Messages

4.1 Echo Request Message

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Identifier | Sequence Number |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Data ...
 +-+-+-+-+-

 IPv6 Fields:

 Destination Address

 Any legal IPv6 address.

 ICMPv6 Fields:

 Type 128

 Code 0

 Identifier An identifier to aid in matching Echo Replies
 to this Echo Request. May be zero.

 Sequence Number

 A sequence number to aid in matching Echo Replies
 to this Echo Request. May be zero.

 Data Zero or more octets of arbitrary data.








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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 Description

 Every node MUST implement an ICMPv6 Echo responder function that
 receives Echo Requests and sends corresponding Echo Replies. A node
 SHOULD also implement an application-layer interface for sending Echo
 Requests and receiving Echo Replies, for diagnostic purposes.

 Upper layer notification

 Echo Request messages MAY be passed to processes receiving ICMP
 messages.

4.2 Echo Reply Message

 0 1 2 3
 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
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Type | Code | Checksum |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Identifier | Sequence Number |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | Data ...
 +-+-+-+-+-

 IPv6 Fields:

 Destination Address

 Copied from the Source Address field of the invoking
 Echo Request packet.

 ICMPv6 Fields:

 Type 129

 Code 0

 Identifier The identifier from the invoking Echo Request message.

 Sequence The sequence number from the invoking Echo Request
 Number message.

 Data The data from the invoking Echo Request message.








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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 Description

 Every node MUST implement an ICMPv6 Echo responder function that
 receives Echo Requests and sends corresponding Echo Replies. A node
 SHOULD also implement an application-layer interface for sending Echo
 Requests and receiving Echo Replies, for diagnostic purposes.

 The source address of an Echo Reply sent in response to a unicast
 Echo Request message MUST be the same as the destination address of
 that Echo Request message.

 An Echo Reply SHOULD be sent in response to an Echo Request message
 sent to an IPv6 multicast address. The source address of the reply
 MUST be a unicast address belonging to the interface on which the
 multicast Echo Request message was received.

 The data received in the ICMPv6 Echo Request message MUST be returned
 entirely and unmodified in the ICMPv6 Echo Reply message.

 Upper layer notification

 Echo Reply messages MUST be passed to the process that originated an
 Echo Request message. It may be passed to processes that did not
 originate the Echo Request message.

5. Security Considerations

5.1 Authentication and Encryption of ICMP messages

 ICMP protocol packet exchanges can be authenticated using the IP
 Authentication Header [IPv6-AUTH]. A node SHOULD include an
 Authentication Header when sending ICMP messages if a security
 association for use with the IP Authentication Header exists for the
 destination address. The security associations may have been created
 through manual configuration or through the operation of some key
 management protocol.

 Received Authentication Headers in ICMP packets MUST be verified for
 correctness and packets with incorrect authentication MUST be ignored
 and discarded.

 It SHOULD be possible for the system administrator to configure a
 node to ignore any ICMP messages that are not authenticated using
 either the Authentication Header or Encapsulating Security Payload.
 Such a switch SHOULD default to allowing unauthenticated messages.






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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 Confidentiality issues are addressed by the IP Security Architecture
 and the IP Encapsulating Security Payload documents [IPv6-SA, IPv6-
 ESP].

5.2 ICMP Attacks

 ICMP messages may be subject to various attacks. A complete
 discussion can be found in the IP Security Architecture [IPv6-SA]. A
 brief discussion of such attacks and their prevention is as follows:

 1. ICMP messages may be subject to actions intended to cause the
 receiver believe the message came from a different source than the
 message originator. The protection against this attack can be
 achieved by applying the IPv6 Authentication mechanism [IPv6-Auth]
 to the ICMP message.

 2. ICMP messages may be subject to actions intended to cause the
 message or the reply to it go to a destination different than the
 message originator's intention. The ICMP checksum calculation
 provides a protection mechanism against changes by a malicious
 interceptor in the destination and source address of the IP packet
 carrying that message, provided the ICMP checksum field is
 protected against change by authentication [IPv6-Auth] or
 encryption [IPv6-ESP] of the ICMP message.

 3. ICMP messages may be subject to changes in the message fields, or
 payload. The authentication [IPv6-Auth] or encryption [IPv6-ESP]
 of the ICMP message is a protection against such actions.

 4. ICMP messages may be used as attempts to perform denial of service
 attacks by sending back to back erroneous IP packets. An
 implementation that correctly followed section 2.4, paragraph (f)
 of this specifications, would be protected by the ICMP error rate
 limiting mechanism.

6. References

 [] Deering, S. and R. Hinden, "Internet Protocol, Version
 6, (IPv6) Specification", RFC 2460, December 1998.

 [] Hinden, R. and S. Deering, "IP Version 6 Addressing
 Architecture", RFC 2373, July 1998.

 [] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
 Discovery for IP Version 6 (IPv6)", RFC 2461, December
 1998.





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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


 [] Postel, J., "Internet Control Message Protocol", STD 5,
 RFC 792, September 1981.

 [] Braden, R., "Requirements for Internet Hosts -
 Communication Layers", STD 5, RFC 1122, August 1989.

 [] McCann, J., Deering, S. and J. Mogul, "Path MTU
 Discovery for IP version 6", RFC 1981, August 1996.

 [] Bradner, S., "Key words for use in RFCs to Indicate
 Requirement Levels", BCP 14, RFC 2119, March 1997.

 [] Kent, S. and R. Atkinson, "Security Architecture for the
 Internet Protocol", RFC 2401, November 1998.

 [] Kent, S. and R. Atkinson, "IP Authentication Header",
 RFC 2402, November 1998.

 [] Kent, S. and R. Atkinson, "IP Encapsulating Security
 Protocol (ESP)", RFC 2406, November 1998.

7. Acknowledgments

 The document is derived from previous ICMP drafts of the SIPP and
 IPng working group.

 The IPng working group and particularly Robert Elz, Jim Bound, Bill
 Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner,
 Dimitri Haskin, and Bob Hinden (in chronological order) provided
 extensive review information and feedback.





















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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


8. Authors' Addresses

 Alex Conta
 Lucent Technologies Inc.
 300 Baker Ave, Suite 100
 Concord, MA 01742
 USA

 Phone: +1 978 287-2842
 EMail: aconta@lucent.com


 Stephen Deering
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA 95134-1706
 USA

 Phone: +1 408 527-8213
 EMail: deering@cisco.com































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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


Appendix A - Changes from RFC 1885

 Version 2-02

 - Excluded mentioning informational replies from paragraph (f.2) of
 section 2.4.
 - In "Upper layer notification" sections changed "upper-layer
 protocol" and "User Interface" to "process".
 - Changed section 5.2, item 2 and 3 to also refer to AH
 authentication.
 - Removed item 5. from section 5.2 on denial of service attacks.
 - Updated phone numbers and Email addresses in the "Authors'
 Addresses" section.

 Version 2-01

 - Replaced all references to "576 octets" as the maximum for an ICMP
 message size with "minimum IPv6 MTU" as defined by the base IPv6
 specification.
 - Removed rate control from informational messages.
 - Added requirement that receivers ignore Code value in Packet Too
 Big message.
 - Removed "Not a Neighbor" (code 2) from destination unreachable
 message.
 - Fixed typos and update references.

 Version 2-00

 - Applied rate control to informational messages
 - Removed section 2.4 on Group Management ICMP messages
 - Removed references to IGMP in Abstract and Section 1.
 - Updated references to other IPv6 documents
 - Removed references to RFC-1112 in Abstract, and Section 1, and to
 RFC-1191 in section 1, and section 3.2
 - Added security section
 - Added Appendix A - changes















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RFC 2463 ICMPv6 (ICMP for IPv6) December 1998


Full Copyright Statement

 Copyright (C) The Internet Society (1998). All Rights Reserved.

 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works. However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.

 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.

 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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