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Versions: (draft-herbert-6man-icmp-limits) 00 01 02 03 04 05

INTERNET-DRAFT                                                T. Herbert
Intended Status: Standard                                          Intel
Expires: March 2020

                                                      September 10, 2019


     ICMPv6 errors for discarding packets due to processing limits
                     draft-ietf-6man-icmp-limits-05


Abstract

   Network nodes may discard packets if they are unable to process
   protocol headers of packets due to processing constraints or limits.
   When such packets are dropped, the sender receives no indication so
   it cannot take action to address the cause of discarded packets. This
   specification defines several new ICMPv6 errors that can be sent by a
   node that discards packets because it is unable to process the
   protocol headers. A node that receives such an ICMPv6 error may be
   able to modify what it sends in future packets to avoid subsequent
   packet discards.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html


Copyright and License Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the



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   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1 Extension header limits  . . . . . . . . . . . . . . . . . .  4
     1.2 Aggregate header limits  . . . . . . . . . . . . . . . . . .  5
   2  ICMPv6 errors for extension header limits . . . . . . . . . . .  5
     2.1 Format . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2 Unrecognized Next Header type encountered (code 1) . . . . .  6
     2.3 Extension header too big (code TBA)  . . . . . . . . . . . .  6
     2.4 Extension header chain too long (code TBA) . . . . . . . . .  7
     2.5 Too many options in extension header (code TBA)  . . . . . .  7
     2.6 Option too big (code TBA)  . . . . . . . . . . . . . . . . .  7
   3  ICMPv6 error for aggregate header limits  . . . . . . . . . . .  8
     3.1 Format . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.2 Usage  . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4  Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.1 Priority of reporting  . . . . . . . . . . . . . . . . . . . 10
     4.2 Host response  . . . . . . . . . . . . . . . . . . . . . . . 10
   5  Applicability and use cases . . . . . . . . . . . . . . . . . . 11
     5.1 Nonconformant packet discard . . . . . . . . . . . . . . . . 11
     5.2 Reliability of ICMP  . . . . . . . . . . . . . . . . . . . . 12
     5.3 Processing limits  . . . . . . . . . . . . . . . . . . . . . 12
       5.3.1 Long headers and header chains . . . . . . . . . . . . . 12
       5.3.2 At end hosts . . . . . . . . . . . . . . . . . . . . . . 12
       5.3.3 At intermediate nodes  . . . . . . . . . . . . . . . . . 13
   6  Security Considerations . . . . . . . . . . . . . . . . . . . . 13
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 13
     7.1 Parameter Problem codes  . . . . . . . . . . . . . . . . . . 13
     7.2 Destination Unreachable codes  . . . . . . . . . . . . . . . 13
     7.3 ICMP Extension Object Classes and Class Sub-types  . . . . . 14
   8  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 14
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 14
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 15
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15



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1  Introduction

   This document specifies several new ICMPv6 errors that can be sent
   when a node discards a packet due to it being unable to process the
   necessary protocol headers because of processing constraints or
   limits. New ICMPv6 code points are defined as an update to [RFC4443].
   Five of the errors are specific to processing of extension headers;
   another error is used when the aggregate protocol headers in a packet
   exceed the processing limits of a node.

1.1 Extension header limits

   In IPv6, optional internet-layer information is carried in one or
   more IPv6 Extension Headers [RFC8200]. Extension Headers are placed
   between the IPv6 header and the Upper-Layer Header in a packet. The
   term "Header Chain" refers collectively to the IPv6 header, Extension
   Headers, and Upper-Layer Headers occurring in a packet. Individual
   extension headers may have a maximum length of 2048 octets and must
   fit into a single packet. Destination Options and Hop-by-Hop Options
   contain a list of options in Type-length-value (TLV) format. Each
   option includes a length of the data field in octets: the minimum
   size of an option (non-pad type) is two octets and the maximum size
   is 257 octets. The number of options in an extension header is only
   limited by the length of the extension header and the Path MTU from
   the source to the destination. Options may be skipped over by a
   receiver if they are unknown and the Option Type indicates to skip
   (first two high order bits are 00).

   Per [RFC8200], except for Hop by Hop options, extension headers are
   not examined or processed by intermediate nodes. Many intermediate
   nodes, however, do examine extension header for various purposes. For
   instance, a node may examine all extension headers to locate the
   transport header of a packet in order to implement transport layer
   filtering or to track connections to implement a stateful firewall.

   Destination hosts are expected to process all extension headers and
   options in Hop-by-Hop and Destination Options.

   Due to the variable lengths, high maximum lengths, or potential for
   Denial of Service attack of extension headers, many devices impose
   operational limits on extension headers in packets they process.
   [RFC7045] discusses the requirements of intermediate nodes that
   discard packets because of unrecognized extension headers. [RFC8504]
   discusses limits that may be applied to the number of options in Hop-
   by-Hop Options or Destination Options extension headers. Both
   intermediate nodes and end hosts may apply limits to extension header
   processing. When a limit is exceeded, the typical behavior is to
   silently discard the packet.



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   This specification defines four Parameter Problem codes and extends
   the applicably of an existing code that may be sent by a node that
   discards a packet due to processing limits of extension headers being
   exceeded. A source host that receives an ICMPv6 error may modify its
   use of extension headers in subsequent packets sent to the
   destination in order to avoid further occurrences of packets being
   discarded.

1.2 Aggregate header limits

   Some hardware devices implement a parsing buffer of a fixed size to
   process packets. The parsing buffer is expected to contain all the
   headers (often up to a transport layer header for filtering) that a
   device needs to examine. If the aggregate length of headers in a
   packet exceeds the size of the parsing buffer, a device will either
   discard the packet or defer processing to a software slow path. In
   any case, no indication of a problem is sent back to the sender.

   This document defines one code for ICMPv6 Destination Unreachable
   that is sent by a node that is unable to process the headers of a
   packet due to the aggregate size of the packet headers exceeding a
   processing limit. A source host that receives an ICMPv6 error can
   modify the headers used in subsequent packets to try to avoid further
   occurrences of packets being discarded or relegated to a slow path.

2  ICMPv6 errors for extension header limits

   Four new codes are defined for the Parameter Problem type and
   applicability of one existing code is extended for ICMPv6 errors for
   extension header limits.

2.1 Format

   The format of the ICMPv6 Parameter Problem message [RFC4443] for an
   extension header limit exceeded error is:

    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 possible without the ICMPv6 packet           +
   |               exceeding the minimum IPv6 MTU [IPv6]           |





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   IPv6 Fields:

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

   ICMPv6 Fields:

      Type
         4 (Parameter Problem type)

      Code (pertinent to this specification)
         1 - Unrecognized Next Header type encountered
         TBA - Extension header too big
         TBA - Extension header chain too long
         TBA - Too many options in extension header
         TBA - Option too big

      Pointer
         Identifies the octet offset within the invoking packet where
         the problem occurred.

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

2.2 Unrecognized Next Header type encountered (code 1)

   [RFC8200] specifies that a destination host should send an
   "unrecognized next header type" when a Next Header value is
   unrecognized in a packet. This document extends this to allow
   intermediate nodes to send this same error for a packet that is
   discarded because the node does not recognize a Next Header type.

   This code SHOULD be sent by an intermediate node that discards a
   packet because it encounters a Next Header type that is unknown in
   its examination. The ICMPv6 Pointer field is set to the offset of the
   unrecognized next header value within the original packet.

   Note that when the original sender receives the ICMPv6 error it can
   differentiate between the message being sent by a destination host,
   per [RFC4443], and an error sent by an intermediate host based on
   matching the source address of the ICMPv6 packet and the destination
   address of the packet in the ICMPv6 data.

2.3 Extension header too big (code TBA)

   An ICMPv6 Parameter Problem with code for "extension header too big"
   SHOULD be sent when a node discards a packet because the size of an



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   extension header exceeds its processing limit. The ICMPv6 Pointer
   field is set to the offset of the first octet in the extension header
   that exceeds the limit.

2.4 Extension header chain too long (code TBA)

   An ICMPv6 Parameter Problem with code for "extension header chain too
   long" SHOULD be sent when a node discards a packet with an extension
   header chain that exceeds its processing limits.

   There are two different limits that might be applied: a limit on the
   total size in octets of the header chain, and a limit on the number
   of extension headers in the chain. This error code is used in both
   cases. In the case that the size limit is exceeded, the ICMPv6
   Pointer is set to first octet beyond the limit. In the case that the
   number of extension headers is exceeded, the ICMPv6 Pointer is set to
   the offset of first octet of the first extension header that is
   beyond the limit.

2.5 Too many options in extension header (code TBA)

   An ICMPv6 Parameter Problem with code for "too many options in
   extension header" SHOULD be sent when a node discards a packet with
   an extension header that has a number of options that exceed the
   processing limits of the node. This code is applicable for
   Destination options and Hop-by-Hop options. The ICMPv6 Pointer field
   is set to the first octet of the first option that exceeds the limit.

2.6 Option too big (code TBA)

   An ICMPv6 Parameter Problem with code for "option too big" is sent in
   two different cases: when the length of an individual Hop-by-Hop or
   Destination option exceeds a limit, or when the length or number of
   consecutive Hop-by-Hop or Destination padding options exceeds a
   limit. In the case that the length of an option exceeds a processing
   limit, the ICMPv6 Pointer field is set to the offset of the first
   octet of the option that exceeds the limit. In the cases that the
   length or number of padding options exceeds a limit, the ICMPv6
   Pointer field is set to the offset of first octet of the padding
   option that exceeds the limit.

   Possible limits related to padding include:

      * The number of consecutive PAD1 options in destination options or
        hop-by-hop options is limited to seven octets [RFC8504].

      * The length of a PADN options in destination options or hop-by-
        hop options is limited seven octets [RFC8504].



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      * The aggregate length of a set of consecutive PAD1 or PADN
        options in destination options or hop-by-hop options is limited
        to seven octets.

3  ICMPv6 error for aggregate header limits

   One code is defined for Destination Unreachable type for aggregate
   header limits.

3.1 Format

   The error for aggregate header limits employs a multi-part ICMPv6
   message format as defined in [RFC4884]. An ICMP extension structure
   contains one ICMP extension object which contains a Pointer field.

   The format of the ICMPv6 message for an aggregate header limit
   exceeded is:

    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             | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I
   |    Length     |                  Unused                       | C
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ M
   |                       Original Datagram                       | P
   ~     Internet Header + leading octets of original datagram     ~ |
   |                                                               | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/
   |Version|       Reserved        |           Checksum            |\
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ E
   |             Length            |   Class-Num   |   C-Type      | X
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ T
   |                            Pointer                            | |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/

   IPv6 Fields:

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

   ICMPv6 Fields:

      Type
         1 - Destination Unreachable type

      Code (pertinent to this specification)
         TBA - Headers too long



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      Length
         Length of the padded Original Datagram field Measured in 64-bit
         words. The ICMP extension structure immediately follows the
         padded original datagram.

      Original Datagram
         As much of invoking packet as possible without exceeding the
         minimum ICMPv6 packet minus twelve bytes (for the ICMP
         extension structure and the ICMP extension object) and any
         necessary padding. The Original Datagram field MUST be zero
         padded to the nearest 64-bit boundary [RFC4884]. If the
         original datagram did not contain 128 octets, the Original
         Datagram field MUST be zero padded to 128 octets.

   ICMP Extension Fields:

      Version
         2 - per [RFC4884]

      Reserved
         0

      Checksum
         The one's complement checksum of the ICMP extension [RFC4884]

      Length
         8 - length of the object header and Pointer field

      Class-Num
         TBA - Extended Information class

      C-Type
         TBA - Pointer sub-type

      Pointer
         Identifies the octet offset within the invoking packet where a
         limit was exceeded.

         The pointer will point beyond the end of the original datagram
         if the field exceeding the limit is beyond what can fit in the
         maximum size of an ICMPv6 error message with the ICMP
         extension.

3.2 Usage

         An ICMPv6 Destination Unreachable error with code for "headers
         too long" SHOULD be sent when a node discards a packet because
         the aggregate length of headers in the packet exceeds the



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         processing limits of the node. The Pointer in the extended
         ICMPv6 structure is set to the offset of the first octet that
         exceeds the limit.

4  Operation

         Nodes that send or receive ICMPv6 errors due to header
         processing limits MUST comply with ICMPv6 processing as
         specified in [RFC4443].

4.1 Priority of reporting

         More than one ICMPv6 error may be applicable to report for a
         packet. For instance, the number of extension headers in a
         packet might exceed a limit and the aggregate length of
         protocol headers might also exceed a limit. Only one ICMPv6
         error SHOULD be sent for a packet, so a priority is defined to
         determine which error to report.

         The RECOMMENDED reporting priority of ICMPv6 errors for
         processing limits is from highest to lowest priority:

      1) Real error (existing codes)

      2) "Unrecognized Next Header type" encountered by an intermediate
         node

      3) "Extension header too big"

      4) "Option too big" for length or number of consecutive padding
         options exceeding a limit

      5) "Option too big" for the length of an option exceeding a limit

      6) "Too many options in an extension header"

      7) "Extension header chain too long" for number of extension
         headers exceeding a limit

      8) "Extension header chain too long" for size of an extension
         header chain exceeding a limit

      9) "Headers too long"

4.2 Host response

   When a source host receives an ICMPv6 error for a processing limit
   being exceeded, it SHOULD verify the ICMPv6 error is valid and take



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   appropriate action as suggested below.

   The general validations for ICMP as described in [RFC4443] are
   applicable. The packet in the ICMP data SHOULD be validated to match
   the upper layer process or connection that generated the original
   packet. Other validation checks that are specific to the upper layers
   may be performed and are out of the scope of this specification.

   The ICMPv6 error SHOULD be logged with sufficient detail for
   debugging packet loss. The details of the error, including the
   addresses and the offending extension header or data, should be
   retained. This, for instance, would be useful for debugging when a
   node is mis-configured and unexpectedly discarding packets, or when a
   new extension header is being deployed.

   A host MAY modify its usage of protocol headers in subsequent packets
   to avoid repeated occurrences of the same error.

   For ICMPv6 errors caused by extension header limits being exceeded:

      * An error SHOULD be reported to an application if the application
        enabled extension headers for its traffic. In response, the
        application may terminate communications if extension headers
        are required, stop using extension headers in packets to the
        destination indicated by the ICMPv6 error, or attempt to modify
        its use of extension headers or headers to avoid further packet
        discards.

      * A host system SHOULD take appropriate action if it is creating
        packets with extension headers on behalf of the application. If
        the offending extension header is not required for
        communication, the host may either stop sending it or otherwise
        modify its use in subsequent packets sent to the destination
        indicated in the ICMPv6 error.

5  Applicability and use cases

5.1 Nonconformant packet discard

   The ICMP errors defined in this specification may be applicable to
   scenarios for which a node is dropping packets outside the auspices
   of any standard specification. For instance, an intermediate node
   might send a "Headers too long" code in the case that it drops a
   packet because it is unable to parse deep enough to extract transport
   layer information needed for packet filtering. Such behavior might be
   considered nonconformant (with respect to [RFC8200] for instance).

   This specification does not advocate behaviors that might be



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   considered nonconformant. However, packet discard does occur in real
   deployments and the intent of this specification is provide
   visibility as to why packets are being discarded. In the spirit that
   providing some reason is better than silent drop, this specification
   RECOMMENDS the sending of ICMP errors even in cases where a node
   might be discarding packets per a nonconformant behavior.

5.2 Reliability of ICMP

   ICMP is fundamentally an unreliable protocol and in real deployment
   it may consistently fail over some paths. As with any other use of
   ICMP, it is assumed that the errors defined in this document are only
   best effort to be delivered. No protocol should be implemented that
   relies on reliable delivery of ICMP messages. If necessary,
   alternative or additional mechanisms may used to augment the
   processes used to to deduce the reason that packets are being
   discarded. Such alternative mechanisms are out of scope of this
   specification.

5.3 Processing limits

   This section discusses the trends and motivations of processing
   limits that warrant ICMP errors.

5.3.1 Long headers and header chains

   The trend towards longer and more complex headers and header chains
   needing to be processed by end nodes, as well as intermediate nodes,
   is driven by:

      * Increasing prevalence of deep packet inspection in middleboxes.
        In particular, many intermediate nodes now parse network layer
        encapsulation protocols or transport layer protocols.

      * Deployment of routing headers. For instance, [SRH] defines an
        extension header format that includes a list of IPv6 addresses
        which may consume a considerable number of bytes.

      * Development of In-situ OAM headers that allow a rich set of
        measurements to be gathered in the data path at the cost of
        additional header overhead which may be significant [IOAM].

      * Other emerging use cases of Hop-by-Hop and Destination options.

5.3.2 At end hosts

   End hosts may implement limits on processing extension headers as
   described in [RFC8504]. Host implementations are usually software



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   stacks that typically don't have inherent processing limitations.
   Limits imposed by a software stack are more likely to be for denial
   of service mitigation or performance.

5.3.3 At intermediate nodes

   Hardware devices that process packet headers may have limits as to
   how many headers or bytes of headers they can process. For instance,
   a middlebox hardware implementation might have a parsing buffer that
   contains some number of bytes of packet headers to process. Parsing
   buffers typically have a fixed size such as sixty-four, 128, or 256
   bytes. In addition, hardware implementations (and some software
   implementations) often don't have loop constructs. Processing of a
   TLV list might be implemented as an unrolled loop so that the number
   of TLVs that can be processed is limited.

6  Security Considerations

   The security considerations for ICMPv6 described in [RFC4443] are
   applicable. The ICMP errors described in this document MAY be
   filtered by firewalls in accordance with [RFC4890].

   In some circumstances, the sending of ICMP errors might conceptually
   be exploited for denial of service attack or as a means to covertly
   deduce processing capabilities of nodes. As such, an implementation
   SHOULD allow configurable policy to withhold sending of the ICMP
   errors described in this specification in environments where security
   of ICMP errors is a concern.

7  IANA Considerations

7.1 Parameter Problem codes

   IANA is requested to assign the following codes for ICMPv6 type 4
   "Parameter Problem" [IANA-ICMPV6]:

         * Extension header too big

         * Extension header chain too long

         * Too many options in extension header

         * Option too big

7.2 Destination Unreachable codes

    IANA is requested to assign the following code for ICMPv6 type 1
   "Destination Unreachable" [IANA-ICMPV6]:



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         * Headers too long

7.3 ICMP Extension Object Classes and Class Sub-types

   IANA is requested to assign the following Class value in the "ICMP
   Extension Object Classes and Class Sub-types" registry [IANA-
   ICMPEXT]:

         * Extended information

   IANA is requested to assign the following Sub-type within the
   aforementioned "Extended information" ICMP extension object class:

         * Pointer

8  Acknowledgments

   The author would like to thank Ron Bonica, Bob Hinden, Nick Hilliard,
   Michael Richardson, Mark Smith, and Suresh Krishnan for their
   comments and suggestions that improved this document.

9  References

9.1  Normative References

   [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
             Control Message Protocol (ICMPv6) for the Internet Protocol
             Version 6 (IPv6) Specification", RFC 4443, DOI
             10.17487/RFC4443, March 2006, <http://www.rfc-
             editor.org/info/rfc4443>.

   [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
             (IPv6) Specification", STD 86, RFC 8200, DOI
             10.17487/RFC8200, July 2017, <https://www.rfc-
             editor.org/info/rfc8200>.

   [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing of
             IPv6 Extension Headers", RFC 7045, DOI 10.17487/RFC7045,
             December 2013, <http://www.rfc-editor.org/info/rfc7045>.












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   [RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
             "Extended ICMP to Support Multi-Part Messages", RFC 4884,
             DOI 10.17487/RFC4884, April 2007, <https://www.rfc-
             editor.org/info/rfc4884>.

   [IANA-ICMPV6] "Internet Control Message Protocol version 6 (ICMPv6)
             Parameters", <https://www.iana.org/assignments/icmpv6-
             parameters/icmpv6-parameters.xhtml#icmpv6-parameters-codes-
             2>

   [IANA-ICMPEXT] ICMP Extension Object Classes and Class Sub-types,
             <https://www.iana.org/assignments/icmp-parameters/icmp-
             parameters.xhtml#icmp-parameters-ext-classes>

9.2  Informative References

   [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node
             Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504,
             January 2019, <https://www.rfc-editor.org/info/rfc8504>.

   [RFC4890] Davies, E. and J. Mohacsi, "Recommendations for Filtering
             ICMPv6 Messages in Firewalls", RFC 4890, DOI
             10.17487/RFC4890, May 2007, <https://www.rfc-
             editor.org/info/rfc4890>.

   [SRH]     Filsfils, C., Ed.. Dukes, D., Ed., Previdi, S., Leddy, J.,
             Matsushima, S., Voyer, D., "IPv6 Segment Routing Header
             (SRH)", draft-ietf-6man-segment-routing-header-21 (work in
             progress), August 2019. February

   [IOAM]    Bhandari, S., Brockners, F., Pignataro, C., Gredler, H.,
             Leddy, J., Youell, S., Mizrahi, T., Kfir, A., Gafni, B.,
             Lpaukhov, P., Spiegel, M., Krishnan, S., Asati, R., "In-
             situ OAM IPv6 Options", draft-ioametal-ippm-6man-ioam-ipv6-
             options-02, March 2018



Author's Address

   Tom Herbert
   Intel
   Santa Clara, CA
   USA


   Email: tom@quantonium.net




T. Herbert               Expires March 11, 2020                [Page 15]


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