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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



Conta & Deering             Standards Track                     [Page 1]

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:







Conta & Deering             Standards Track                     [Page 2]

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.



Conta & Deering             Standards Track                     [Page 3]

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].





Conta & Deering             Standards Track                     [Page 4]

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.



Conta & Deering             Standards Track                     [Page 5]

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.



Conta & Deering             Standards Track                     [Page 6]

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.





















Conta & Deering             Standards Track                     [Page 7]

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.





Conta & Deering             Standards Track                     [Page 8]

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.





Conta & Deering             Standards Track                     [Page 9]

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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   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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   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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   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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   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

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

   [IPv6-ADDR]  Hinden, R. and S. Deering, "IP Version 6 Addressing
                Architecture", RFC 2373, July 1998.

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





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

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

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

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

   [IPv6-SA]    Kent, S. and R. Atkinson, "Security Architecture for the
                Internet Protocol", RFC 2401, November 1998.

   [IPv6-Auth]  Kent, S. and R. Atkinson, "IP Authentication Header",
                RFC 2402, November 1998.

   [IPv6-ESP]   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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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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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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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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