



6MAN                                                          T. Mizrahi
Internet-Draft                                                    Huawei
Intended status: Standards Track                                   X. He
Expires: 20 February 2026                                  China Telecom
                                                                 T. Zhou
                                                                  Huawei
                                                               R. Bonica
                                                                     HPE
                                                                  X. Min
                                                               ZTE Corp.
                                                          19 August 2025


         Internet Control Message Protocol (ICMPv6) Reflection
                  draft-ietf-6man-icmpv6-reflection-10

Abstract

   This document describes the ICMPv6 Reflection utility.  The ICMPv6
   Reflection utility is a diagnostic tool, similar to Ping and the
   ICMPv6 Probe utility.  It is similar to Ping and Probe in that it
   relies on a stateless message exchange between a probing node and a
   probed node.  The probing node sends a request to the probed node and
   the probed node responds to the request.

   The ICMPv6 Reflection utility differs from Ping and Probe because, in
   the ICMPv6 Reflection utility, the probing node requests a snapshot
   of the message that it sent, as it was when arrived at the probed
   node.  The probed node returns the requested snapshot.

   The ICMPv6 Reflection utility is useful because it can allow the user
   to see how the network modified the request as it traveled from the
   probing node to the probed node.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."



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   This Internet-Draft will expire on 20 February 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirement Language  . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Theory of Operation . . . . . . . . . . . . . . . . . . . . .   4
   5.  New ICMP Extension Object . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The ICMPv6 Reflection utility is an IPv6 [RFC8200] diagnostic tool.
   It is similar to Ping [RFC2151] and the ICMPv6 Probe
   [I-D.ietf-intarea-rfc8335bis] utility in the following respects:

   *  A probing node sends an ICMPv6 [RFC4443] message to a probed node.
      This ICMP message requests that it be reflected back to the
      probing node.

   *  The probed node receives the above-mentioned message, encodes it
      into another ICMPv6 message, and sends that ICMPv6 message back to
      the probing node.






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   For the purposes of this document, the ICMPv6 message that the
   probing node sends is called the "request message" and the ICMPv6
   message that the probed node sends is called the "reply message".

   The reply message includes a copy of the request message, starting
   from its IPv6 header, as was when it arrived at the probed node.

   The ICMPv6 Reflection utility uses the ICMPv6 Extended Echo Request
   and Extended Echo Reply message types [I-D.ietf-intarea-rfc8335bis].
   Each of these message types includes an ICMP Extension Structure
   [RFC4884].  The ICMP Extension Structure includes one or more
   extension objects.  This document defines the 'Reflect All' object,
   which is used for reflecting the request message, as it arrived at
   the probed node.

   An alternative approach involves the probing node sending a UDP
   packet with an unused destination port to the probed node.  This
   causes the probed node to send an ICMPv6 Destination Unreachable
   message, which includes "as much of invoking packet as possible
   without the ICMPv6 packet exceeding the minimum IPv6 MTU" [RFC4443].
   However, middle boxes modify the invoking packet in ICMPv6
   Destination Unreachable messages (e.g. [RFC3022]).  By contrast,
   middle boxes are not intended to modify the Reflect All object.

2.  Requirement Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Use Cases

   The following protocols define mutable IPv6 extension headers that
   can be used to trace a path and its performance:

   *  IPv6 Options for In Situ Operations, Administration, and
      Maintenance (IOAM) [RFC9486]

   *  Inband Flow Analyzer [I-D.kumar-ippm-ifa]

   *  Path Tracing in SRv6 networks [I-D.filsfils-ippm-path-tracing]

   These extensions are used to collect information along a packet's
   delivery path.  Currently, the collected information is sent to a
   controller for processing.  However, in some cases this information
   is relevant to the sender.



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   The ICMPv6 Reflection utility provides a mechanism by which this
   information can be returned to the probing node.

   The ICMPv6 Reflection utility can also be used to determine how the
   probe message's IPv6 header has changed along its delivery path.  For
   example, it can be used to determine how middleboxes have changed the
   Source Address, Destination Address, and Flow Label.

4.  Theory of Operation

   The probing node sends an ICMPv6 Extended Echo Request message
   [I-D.ietf-intarea-rfc8335bis] to the probed node.  The ICMPv6
   Extended Echo Request message contains an ICMP Extension Structure
   [RFC4884] and the ICMP Extension Structure contains an Extension
   Header.  The ICMP Extension Header MUST include the Length field, as
   defined in [I-D.ietf-intarea-icmp-exten-hdr-len].  The ICMP Extension
   structure includes a 'Reflect All' object, which is defined in this
   document.

   The 'Reflect All' object contains an object payload field whose
   length SHOULD be sufficient to carry the IPv6 and ICMP header of the
   reflected request message.  The total length of both the request and
   reply packets SHOULD NOT exceed the IPv6 minimum MTU (1280 bytes), to
   avoid triggering fragmentation.

   The probed node receives the ICMPv6 Extended Echo Request and formats
   an ICMPv6 Extended Echo Reply message.  The total length of the
   ICMPv6 Extended Echo Reply message MUST be equal to the total length
   of the corresponding request message.  The main body of the ICMPv6
   Extended Echo Reply message reflects the status of an interface on
   the probed node.

   The ICMPv6 Extended Echo Reply message also contains an ICMP
   Extension Structure.  The ICMP Extension Header MUST include the
   Length field, as defined in [I-D.ietf-intarea-icmp-exten-hdr-len].
   The value of the Length field in the reply message MUST be equal to
   the value of the Length in the ICMP Extension Header of the request
   message.  The ICMP Extension Structure also MUST contain the 'Reflect
   All' object that the ICMPv6 Extended Echo Request message contained.
   The length of the 'Reflect All' object in the reply message MUST be
   equal to the length of the 'Reflect All' object in the request
   message.  If the following requirements are satisfied, the probed
   node populates the payload field of the 'Reflect All' object:

   *  The probed node supports the 'Reflect All' object.

   *  Responding to the request message does not violate the probed
      node's security policy.



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   Otherwise, the probed node sets the object payload field to all
   zeros.

   An example of a request and a reply is provided in Figure 1.  In this
   example the request message includes the 'Reflect All' object.  The
   reply also includes the 'Reflect All' object, containing the IPv6
   header, ICMPv6 header and ICMP Extension Header of the request
   message.  The request and reply messages have the same length.  The
   length of the IPv6 header of the request message is at least 40
   octets, depending on whether there are extension headers, followed by
   an 8-octet ICMPv6 header, a 4-octet ICMP Extension Header, and a
   4-octet Object Header.  For example, if the length of the IPv6 header
   is H octets, and the length of the object payload is H+12 octets, the
   reply includes the reflected request message starting from the IPv6
   header and up to and including the ICMP Extension Header, as shown in
   Figure 1.

   Middle boxes must not modify the Reflect All extension object.  This
   ensures that the reflected information reaches the probing node
   exactly as sent by the probed node.

         +----------------------------+   +----------------------------+
         |        IPv6 Header         |   |        IPv6 Header         |
         |    and extension headers   |   |    and extension headers   |
         +----------------------------+   +----------------------------+
         |       ICMPv6 Header        |   |       ICMPv6 Header        |
         |   Extended Echo Request    |   |    Extended Echo Reply     |
         +----------------------------+   +----------------------------+
         |   ICMP Extension Header    |   |   ICMP Extension Header    |
         +----------------------------+   +----------------------------+
         |'Reflect All' Object Header |   |'Reflect All' Object Header |
         +----------------------------+   +----------------------------+
         |       Object payload       |   |   Request's IPv6 Header    |
         |  (placeholder for reply)   |   |   and extension headers    |
         |                            |   |  ------------------------  |
         |                            |   |  Request's ICMPv6 Header   |
         |                            |   |   Extended Echo Request    |
         |                            |   |  ------------------------  |
         |                            |   | Request's ICMP Ext. Header |
         +----------------------------+   +----------------------------+

         ^                            ^   ^                            ^
         |                            |   |                            |
         +-- Extended Echo Request ---+   +--- Extended Echo Reply ----+


               Figure 1: ICMPv6 Reflection Message Formats




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   If a node that does not support the 'Reflect All' object receives an
   ICMP Extended Echo Request containing this object, the expected
   behavior according to [I-D.ietf-intarea-rfc8335bis] and [RFC8335] is
   to respond with an ICMP Echo Reply message that includes the
   "Malformed Query" code in the Code field.

5.  New ICMP Extension Object

   This document defines the 'Reflect All' object.

   An implementation that supports ICMPv6 Reflection MUST support the
   'Reflect All' object.

   In the ICMPv6 Reflection utility, the 'Reflect All' object MUST be
   included in the Extension Structure.  If there is more than one
   object, the 'Reflect All' object MUST be the first object.  An ICMPv6
   message MUST NOT include more than one 'Reflect All' object.

   The structure of the 'Reflect All' object follows the specification
   of ICMP Extension Objects as defined in [RFC4884] and MUST include
   the following fields:

   *  The Length of the 'Reflect All' object.

   *  An object class (as specified in Section 6).

   *  C-Type as described below.

   *  An object payload field.

   The Length field specifies the number of octets in the object.  The
   Length in the 'Reflect All' object of a reply message MUST be equal
   to the Length in the 'Reflect All' object of the respective request
   message.

   The C-Type value is used for indicating whether the probed node was
   able to process the object.  The following C-Type values are
   supported:

   *  (0) Request

   *  (1) Reply - No Error

   *  (2) Reply - Unsupported Object

   The C-Type field of a Reflection object in a request message MUST be
   set to the 'Request' value.  If the probed node is able to process
   the 'Reflect All' object, it MUST copy the request message into the



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   object payload and update the C-Type field to the 'Reply - No Error'
   value.  If the probed node is not able to process the object, it MUST
   update the C-Type value of the object in the Extended Echo Reply to
   'Reply - Unsupported Object'.

   The object payload field in the ICMPv6 Extended Echo Request message
   is a placeholder for the corresponding reply message.  Its length
   determines the number of bytes, starting from the beginning of the
   IPv6 header, that the probed node includes in the object payload of
   the reply.  The object payload field in a request message MAY contain
   all zeros.  Alternatively, this field MAY contain arbitrary data.  In
   reply messages the object payload field MUST contain the received
   request message starting from the beginning of the IPv6 header and
   according to the length of the object payload, provided that the
   probed node supports the 'Reflect All' object and that responding
   does not conflict with its security policy.

   If the 'Reflect All' object is sufficiently long, the reply message
   includes the initial octets of the 'Reflect All' object.  A notable
   use case for including arbitrary data in the object payload is the
   inclusion of a transmission timestamp, similar to how conventional
   Ping utilities incorporate timestamps into the ICMP payload.  If the
   initial octets of the 'Reflect All' object payload contain a
   timestamp and the object is long enough, the timestamp is reflected
   back to the probing node, enabling round-trip time calculations.

6.  IANA Considerations

   IANA is requested to allocate the following values in the "ICMP
   Extension Object Classes and Class Sub-types" registry.


+-----------+------------------+--------+---------------+-----------------+
| Class-Num |    Object Name   | C-Type |  C-Type Name  |     Reference   |
+-----------+------------------+--------+---------------+-----------------+
|   TBD1    | Reflect All      |  0-2   |  See below    | [This document] |
|           |                  |        |               |                 |
+-----------+------------------+--------+---------------+-----------------+

                      Figure 2: IANA Allocation

   For each of the object classes above the following C-Type values are
   defined:

   *  (0) Request

   *  (1) Reply - No Error




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   *  (2) Reply - Unsupported Object

7.  Security Considerations

   Since this document uses technologies from [RFC4443], [RFC4884], and
   [I-D.ietf-intarea-rfc8335bis], it inherits security considerations
   from those documents.

   The Reflection procedure that is defined in this document is
   symmetric in terms of the length of the request and reply messages.
   This symmetry mitigates the potential for amplification attacks,
   which would be possible if the reply message was longer than the
   request message.

   Depending on the network policy and the location of nodes in the
   network, ICMPv6 informational and/or error messages are sometimes
   filtered or not supported.  For example, some nodes do not reply to
   ICMPv6 Echo or do not send ICMPv6 Time Exceeded messages (used in
   Traceroute), due to policy considerations that may be related to DoS
   mitigation or to privacy.  Network operators SHOULD apply similar
   considerations to ICMPv6 Extended Echo messages when they are used
   for Reflection.  For example, an operator can choose to disable
   support for ICMPv6 Reflection in networks or in nodes that do not
   respond to ICMPv6 Echo and/or do not generate ICMPv6 Time Exceeded
   messages.

   As specified in [I-D.ietf-intarea-rfc8335bis], in order to protect
   local resources, implementations SHOULD rate-limit incoming ICMP
   Extended Echo Request messages.  Moreover, as per
   [I-D.ietf-intarea-rfc8335bis], by default, ICMP Extend Echo
   functionality is disabled.

8.  Acknowledgements

   The authors gratefully acknowledge Sebastian Moeller, Zafar Ali, Bob
   Hinden, Jen Linkova, Jeremy Duncan, Greg Mirsky, Nick Buraglio and
   Maciej Zenczykowski for their insightful comments.

9.  References

9.1.  Normative References

   [I-D.ietf-intarea-icmp-exten-hdr-len]
              Bonica, R., hexiaoming, X., Min, X., and T. Mizrahi, "ICMP
              Extension Structure Length Field", Work in Progress,
              Internet-Draft, draft-ietf-intarea-icmp-exten-hdr-len-07,
              14 August 2025, <https://datatracker.ietf.org/doc/html/
              draft-ietf-intarea-icmp-exten-hdr-len-07>.



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   [I-D.ietf-intarea-rfc8335bis]
              Fenner, B., Bonica, R., Thomas, R., Linkova, J., Lenart,
              C., and M. Boucadair, "PROBE: A Utility for Probing
              Interfaces", Work in Progress, Internet-Draft, draft-ietf-
              intarea-rfc8335bis-01, 21 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-intarea-
              rfc8335bis-01>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.

   [RFC8335]  Bonica, R., Thomas, R., Linkova, J., Lenart, C., and M.
              Boucadair, "PROBE: A Utility for Probing Interfaces",
              RFC 8335, DOI 10.17487/RFC8335, February 2018,
              <https://www.rfc-editor.org/info/rfc8335>.

9.2.  Informative References

   [I-D.filsfils-ippm-path-tracing]
              Filsfils, C., Abdelsalam, A., Camarillo, P., Yufit, M.,
              Su, Y., Matsushima, S., Valentine, M., and Dhamija, "Path
              Tracing in SRv6 networks", Work in Progress, Internet-
              Draft, draft-filsfils-ippm-path-tracing-04, 4 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-filsfils-
              ippm-path-tracing-04>.




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   [I-D.kumar-ippm-ifa]
              Kumar, J., Anubolu, S., Lemon, J., Manur, R., Holbrook,
              H., Ghanwani, A., Cai, D., Ou, H., Li, Y., and X. Wang,
              "Inband Flow Analyzer", Work in Progress, Internet-Draft,
              draft-kumar-ippm-ifa-08, 26 April 2024,
              <https://datatracker.ietf.org/doc/html/draft-kumar-ippm-
              ifa-08>.

   [RFC2151]  Kessler, G. and S. Shepard, "A Primer On Internet and TCP/
              IP Tools and Utilities", FYI 30, RFC 2151,
              DOI 10.17487/RFC2151, June 1997,
              <https://www.rfc-editor.org/info/rfc2151>.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              DOI 10.17487/RFC3022, January 2001,
              <https://www.rfc-editor.org/info/rfc3022>.

   [RFC9486]  Bhandari, S., Ed. and F. Brockners, Ed., "IPv6 Options for
              In Situ Operations, Administration, and Maintenance
              (IOAM)", RFC 9486, DOI 10.17487/RFC9486, September 2023,
              <https://www.rfc-editor.org/info/rfc9486>.

Contributors



























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      Shahar Belkar
      Huawei
      8-2 Matam
      Haifa 3190501
      Israel
      Email: shahar.belkar@huawei.com


      Chongfeng Xie
      China Telecom
      Email: xiechf@chinatelecom.cn


      Zhenqiang Li
      China Mobile
      Email: li_zhenqiang@hotmail.com


      Justin Iurman
      Universite de Liege
      10, Allee de la decouverte (B28)
      4000 Sart-Tilman
      Belgium
      Email: justin.iurman@uliege.be

Authors' Addresses

   Tal Mizrahi
   Huawei
   25 Matam
   Haifa 3190501
   Israel
   Email: tal.mizrahi.phd@gmail.com


   Xiaoming He
   China Telecom
   Email: hexm4@chinatelecom.cn


   Tianran Zhou
   Huawei
   156 Beiqing Rd.
   Beijing
   100095
   China
   Email: zhoutianran@huawei.com




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   Ron Bonica
   HPE
   United States of America
   Email: rbonica@juniper.net


   Xiao Min
   ZTE Corp.
   Email: xiao.min2@zte.com.cn










































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