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RFC9359

  1. RFC 9359
Internet Engineering Task Force (IETF)                            X. Min
Request for Comments: 9359                                     ZTE Corp.
Category: Standards Track                                      G. Mirsky
ISSN: 2070-1721                                                 Ericsson
                                                                   L. Bo
                                                           China Telecom
                                                              April 2023


     Echo Request/Reply for Enabled In Situ OAM (IOAM) Capabilities

Abstract

   This document describes a generic format for use in echo request/
   reply mechanisms, which can be used within an IOAM-Domain, allowing
   the IOAM encapsulating node to discover the enabled IOAM capabilities
   of each IOAM transit and IOAM decapsulating node.  The generic format
   is intended to be used with a variety of data planes such as IPv6,
   MPLS, Service Function Chain (SFC), and Bit Index Explicit
   Replication (BIER).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9359.

Copyright Notice

   Copyright (c) 2023 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.  Conventions
     2.1.  Requirements Language
     2.2.  Abbreviations
   3.  IOAM Capabilities Formats
     3.1.  IOAM Capabilities Query Container
     3.2.  IOAM Capabilities Response Container
       3.2.1.  IOAM Pre-allocated Tracing Capabilities Object
       3.2.2.  IOAM Incremental Tracing Capabilities Object
       3.2.3.  IOAM Proof of Transit Capabilities Object
       3.2.4.  IOAM Edge-to-Edge Capabilities Object
       3.2.5.  IOAM DEX Capabilities Object
       3.2.6.  IOAM End-of-Domain Object
   4.  Operational Guide
   5.  IANA Considerations
     5.1.  IOAM SoP Capability Registry
     5.2.  IOAM TSF Capability Registry
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   In situ Operations, Administration, and Maintenance (IOAM) ([RFC9197]
   [RFC9326]) defines data fields that record OAM information within the
   packet while the packet traverses a particular network domain, called
   an "IOAM-Domain".  IOAM can complement or replace other OAM
   mechanisms, such as ICMP or other types of probe packets.

   As specified in [RFC9197], within the IOAM-Domain, the IOAM data may
   be updated by network nodes that the packet traverses.  The device
   that adds an IOAM header to the packet is called an "IOAM
   encapsulating node".  In contrast, the device that removes an IOAM
   header is referred to as an "IOAM decapsulating node".  Nodes within
   the domain that are aware of IOAM data and that read, write, and/or
   process IOAM data are called "IOAM transit nodes".  IOAM
   encapsulating or decapsulating nodes can also serve as IOAM transit
   nodes at the same time.  IOAM encapsulating or decapsulating nodes
   are also referred to as IOAM-Domain "edge devices", which can be
   hosts or network devices.  [RFC9197] defines four IOAM option types,
   and [RFC9326] introduces a new IOAM option type called the "Direct
   Export (DEX) Option-Type", which is different from the other four
   IOAM option types defined in [RFC9197] regarding how to collect the
   operational and telemetry information defined in [RFC9197].

   As specified in [RFC9197], IOAM is focused on "limited domains" as
   defined in [RFC8799].  In a limited domain, a control entity that has
   control over every IOAM device may be deployed.  If that's the case,
   the control entity can provision both the explicit transport path and
   the IOAM header applied to the data packet at every IOAM
   encapsulating node.

   In a case when a control entity that has control over every IOAM
   device is not deployed in the IOAM-Domain, the IOAM encapsulating
   node needs to discover the enabled IOAM capabilities at the IOAM
   transit and decapsulating nodes: for example, what types of IOAM
   tracing data can be added or exported by the transit nodes along the
   transport path of the data packet IOAM is applied to.  The IOAM
   encapsulating node can then add the correct IOAM header to the data
   packet according to the discovered IOAM capabilities.  Specifically,
   the IOAM encapsulating node first identifies the types and lengths of
   IOAM options included in the IOAM data fields according to the
   discovered IOAM capabilities.  Then the IOAM encapsulating node can
   add the IOAM header to the data packet based on the identified types
   and lengths of IOAM options included in the IOAM data fields.  The
   IOAM encapsulating node may use NETCONF/YANG or IGP to discover these
   IOAM capabilities.  However, NETCONF/YANG or IGP has some
   limitations:

   *  When NETCONF/YANG is used in this scenario, each IOAM
      encapsulating node (including the host when it takes the role of
      an IOAM encapsulating node) needs to implement a NETCONF Client,
      and each IOAM transit and IOAM decapsulating node (including the
      host when it takes the role of an IOAM decapsulating node) needs
      to implement a NETCONF Server, so complexity can be an issue.
      Furthermore, each IOAM encapsulating node needs to establish a
      NETCONF Connection with each IOAM transit and IOAM decapsulating
      node, so scalability can be an issue.

   *  When IGP is used in this scenario, the IGP and IOAM-Domains don't
      always have the same coverage.  For example, when the IOAM
      encapsulating node or the IOAM decapsulating node is a host, the
      availability can be an issue.  Furthermore, it might be too
      challenging to reflect enabled IOAM capabilities at the IOAM
      transit and IOAM decapsulating node if these are controlled by a
      local policy depending on the identity of the IOAM encapsulating
      node.

   This document specifies formats and objects that can be used in the
   extension of echo request/reply mechanisms used in IPv6 (including
   Segment Routing over IPv6 (SRv6) data plane), MPLS (including Segment
   Routing over MPLS (SR-MPLS) data plane), Service Function Chain
   (SFC), and Bit Index Explicit Replication (BIER) environments, which
   can be used within the IOAM-Domain, allowing the IOAM encapsulating
   node to discover the enabled IOAM capabilities of each IOAM transit
   and IOAM decapsulating node.

   The following documents contain references to the echo request/reply
   mechanisms used in IPv6 (including SRv6), MPLS (including SR-MPLS),
   SFC, and BIER environments:

   *  "Internet Control Message Protocol (ICMPv6) for the Internet
      Protocol Version 6 (IPv6) Specification" [RFC4443]

   *  "IPv6 Node Information Queries" [RFC4620]

   *  "Extended ICMP to Support Multi-Part Messages" [RFC4884]

   *  "PROBE: A Utility for Probing Interfaces" [RFC8335]

   *  "Detecting Multiprotocol Label Switched (MPLS) Data-Plane
      Failures" [RFC8029]

   *  "Active OAM for Service Function Chaining (SFC)" [OAM-for-SFC]

   *  "BIER Ping and Trace" [BIER-PING]

   It is expected that the specification of the instantiation of each of
   these extensions will be done in the form of an RFC jointly designed
   by the working group that develops or maintains the echo request/
   reply protocol and the IETF IP Performance Measurement (IPPM) Working
   Group.

   In this document, note that the echo request/reply mechanism used in
   IPv6 does not mean ICMPv6 Echo Request/Reply [RFC4443] but does mean
   IPv6 Node Information Query/Reply [RFC4620].

   Fate sharing is a common requirement for all kinds of active OAM
   packets, including echo requests.  In this document, that means an
   echo request is required to traverse the path of an IOAM data packet.
   This requirement can be achieved by, e.g., applying the same explicit
   path or ECMP processing to both echo request and IOAM data packets.
   Specifically, the same ECMP processing can be applied to both echo
   request and IOAM data packets, by populating the same value or values
   in any ECMP affecting fields of the packets.

2.  Conventions

2.1.  Requirements 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.

2.2.  Abbreviations

   BIER:  Bit Index Explicit Replication

   BGP:  Border Gateway Protocol

   DEX:  Direct Export

   ECMP:  Equal-Cost Multipath

   E2E:  Edge to Edge

   ICMP:  Internet Control Message Protocol

   IGP:  Interior Gateway Protocol

   IOAM:  In situ Operations, Administration, and Maintenance

   LSP:  Label Switched Path

   MPLS:  Multiprotocol Label Switching

   MTU:  Maximum Transmission Unit

   NETCONF:  Network Configuration Protocol

   NTP:  Network Time Protocol

   OAM:  Operations, Administration, and Maintenance

   PCEP:  Path Computation Element Communication Protocol

   POSIX:  Portable Operating System Interface

   POT:  Proof of Transit

   PTP:  Precision Time Protocol

   SoP:  Size of POT

   SR-MPLS:  Segment Routing over MPLS

   SRv6:  Segment Routing over IPv6

   SFC:  Service Function Chain

   TTL:  Time to Live (this is also the Hop Limit field in the IPv6
      header)

   TSF:  TimeStamp Format

3.  IOAM Capabilities Formats

3.1.  IOAM Capabilities Query Container

   For echo requests, the IOAM Capabilities Query uses a container that
   has the following 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .            IOAM Capabilities Query Container Header           .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .                   List of IOAM Namespace-IDs                  .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 1: IOAM Capabilities Query Container of an Echo Request

   When this container is present in the echo request sent by an IOAM
   encapsulating node, the IOAM encapsulating node requests that the
   receiving node reply with its enabled IOAM capabilities.  If there is
   no IOAM capability to be reported by the receiving node, then this
   container MUST be ignored by the receiving node.  This means the
   receiving node MUST send an echo reply without IOAM capabilities or
   no echo reply, in the light of whether the echo request includes
   containers other than the IOAM Capabilities Query Container.  A list
   of IOAM Namespace-IDs (one or more Namespace-IDs) MUST be included in
   this container in the echo request; if present, the Default-
   Namespace-ID 0x0000 MUST be placed at the beginning of the list of
   IOAM Namespace-IDs.  The IOAM encapsulating node requests only the
   enabled IOAM capabilities that match one of the Namespace-IDs.
   Inclusion of the Default-Namespace-ID 0x0000 elicits replies only for
   capabilities that are configured with the Default-Namespace-ID
   0x0000.  The Namespace-ID has the same definition as what's specified
   in Section 4.3 of [RFC9197].

   The IOAM Capabilities Query Container has a container header that is
   used to identify the type and, optionally, the length of the
   container payload.  The container payload (List of IOAM Namespace-
   IDs) is zero-padded to align with a 4-octet boundary.  Since the
   Default-Namespace-ID 0x0000 is mandated to appear first in the list,
   any other occurrences of 0x0000 MUST be disregarded.

   The length, structure, and definition of the IOAM Capabilities Query
   Container Header depend on the specific deployment environment.

3.2.  IOAM Capabilities Response Container

   For echo replies, the IOAM Capabilities Response uses a container
   that has the following 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .          IOAM Capabilities Response Container Header          .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .               List of IOAM Capabilities Objects               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 2: IOAM Capabilities Response Container for an Echo Reply

   When this container is present in the echo reply sent by an IOAM
   transit node or IOAM decapsulating node, the IOAM function is enabled
   at this node, and this container contains the enabled IOAM
   capabilities of the sender.  A list of IOAM capabilities objects (one
   or more objects) that contains the enabled IOAM capabilities MUST be
   included in this container of the echo reply unless the sender
   encounters an error (e.g., no matched Namespace-ID).

   The IOAM Capabilities Response Container has a container header that
   is used to identify the type and, optionally, the length of the
   container payload.  The container header MUST be defined such that it
   falls on a 4-octet boundary.

   The length, structure, and definition of the IOAM Capabilities
   Response Container Header depends on the specific deployment
   environment.

   Based on the IOAM data fields defined in [RFC9197] and [RFC9326], six
   types of objects are defined in this document.  The same type of
   object MAY be present in the IOAM Capabilities Response Container
   more than once, only if listed with a different Namespace-ID.

   Similar to the container, each object has an object header that is
   used to identify the type and length of the object payload.  The
   object payload MUST be defined such that it falls on a 4-octet
   boundary.

   The length, structure, and definition of the object header depends on
   the specific deployment environment.

3.2.1.  IOAM Pre-allocated Tracing Capabilities Object

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .     IOAM Pre-allocated Tracing Capabilities Object Header     .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               IOAM-Trace-Type                 |  Reserved   |W|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Namespace-ID          |          Ingress_MTU          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Ingress_if_id (short or wide format)         ......          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 3: IOAM Pre-allocated Tracing Capabilities Object

   When the IOAM Pre-allocated Tracing Capabilities Object is present in
   the IOAM Capabilities Response Container, the sending node is an IOAM
   transit node, and the IOAM pre-allocated tracing function is enabled
   at this IOAM transit node.

   The IOAM-Trace-Type field has the same definition as what's specified
   in Section 4.4 of [RFC9197].

   The Reserved field MUST be zeroed on transmission and ignored on
   receipt.

   The W flag indicates whether Ingress_if_id is in short or wide
   format.  The W-bit is set if the Ingress_if_id is in wide format.
   The W-bit is clear if the Ingress_if_id is in short format.

   The Namespace-ID field has the same definition as what's specified in
   Section 4.3 of [RFC9197].  It MUST be one of the Namespace-IDs listed
   in the IOAM Capabilities Query Object of the echo request.

   The Ingress_MTU field has 16 bits and specifies the MTU (in octets)
   of the ingress interface from which the sending node received the
   echo request.

   The Ingress_if_id field has 16 bits (in short format) or 32 bits (in
   wide format) and specifies the identifier of the ingress interface
   from which the sending node received the echo request.  If the W-bit
   is cleared, the Ingress_if_id field has 16 bits; then the 16 bits
   following the Ingress_if_id field are reserved for future use, MUST
   be set to zero, and MUST be ignored when non-zero.

3.2.2.  IOAM Incremental Tracing Capabilities Object

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .      IOAM Incremental Tracing Capabilities Object Header      .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               IOAM-Trace-Type                 |  Reserved   |W|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Namespace-ID          |          Ingress_MTU          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Ingress_if_id (short or wide format)         ......          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 4: IOAM Incremental Tracing Capabilities Object

   When the IOAM Incremental Tracing Capabilities Object is present in
   the IOAM Capabilities Response Container, the sending node is an IOAM
   transit node, and the IOAM incremental tracing function is enabled at
   this IOAM transit node.

   The IOAM-Trace-Type field has the same definition as what's specified
   in Section 4.4 of [RFC9197].

   The Reserved field MUST be zeroed on transmission and ignored on
   receipt.

   The W flag indicates whether Ingress_if_id is in short or wide
   format.  The W-bit is set if the Ingress_if_id is in wide format.
   The W-bit is clear if the Ingress_if_id is in short format.

   The Namespace-ID field has the same definition as what's specified in
   Section 4.3 of [RFC9197].  It MUST be one of the Namespace-IDs listed
   in the IOAM Capabilities Query Object of the echo request.

   The Ingress_MTU field has 16 bits and specifies the MTU (in octets)
   of the ingress interface from which the sending node received the
   echo request.

   The Ingress_if_id field has 16 bits (in short format) or 32 bits (in
   wide format) and specifies the identifier of the ingress interface
   from which the sending node received the echo request.  If the W-bit
   is cleared, the Ingress_if_id field has 16 bits; then the 16 bits
   following the Ingress_if_id field are reserved for future use, MUST
   be set to zero, and MUST be ignored when non-zero.

3.2.3.  IOAM Proof of Transit Capabilities Object

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .       IOAM Proof of Transit Capabilities Object Header        .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Namespace-ID          | IOAM-POT-Type |SoP| Reserved  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 5: IOAM Proof of Transit Capabilities Object

   When the IOAM Proof of Transit Capabilities Object is present in the
   IOAM Capabilities Response Container, the sending node is an IOAM
   transit node and the IOAM Proof of Transit function is enabled at
   this IOAM transit node.

   The Namespace-ID field has the same definition as what's specified in
   Section 4.3 of [RFC9197].  It MUST be one of the Namespace-IDs listed
   in the IOAM Capabilities Query Object of the echo request.

   The IOAM-POT-Type field has the same definition as what's specified
   in Section 4.5 of [RFC9197].

   The SoP (Size of POT) field has two bits that indicate the size of
   "PktID" and "Cumulative" data, which are specified in Section 4.5 of
   [RFC9197].  This document defines SoP as follows:

   0b00:  64-bit "PktID" and 64-bit "Cumulative" data

   0b01~0b11:  reserved for future standardization

   The Reserved field MUST be zeroed on transmission and ignored on
   receipt.

3.2.4.  IOAM Edge-to-Edge Capabilities Object

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .          IOAM Edge-to-Edge Capabilities Object Header         .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Namespace-ID          |         IOAM-E2E-Type         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |TSF|         Reserved          |           Reserved            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 6: IOAM Edge-to-Edge Capabilities Object

   When the IOAM Edge-to-Edge Capabilities Object is present in the IOAM
   Capabilities Response Container, the sending node is an IOAM
   decapsulating node and IOAM edge-to-edge function is enabled at this
   IOAM decapsulating node.

   The Namespace-ID field has the same definition as what's specified in
   Section 4.3 of [RFC9197].  It MUST be one of the Namespace-IDs listed
   in the IOAM Capabilities Query Object of the echo request.

   The IOAM-E2E-Type field has the same definition as what's specified
   in Section 4.6 of [RFC9197].

   The TSF field specifies the timestamp format used by the sending
   node.  Aligned with three possible timestamp formats specified in
   Section 5 of [RFC9197], this document defines TSF as follows:

   0b00:  PTP truncated timestamp format

   0b01:  NTP 64-bit timestamp format

   0b10:  POSIX-based timestamp format

   0b11:  Reserved for future standardization

   The Reserved field MUST be zeroed on transmission and ignored on
   receipt.

3.2.5.  IOAM DEX Capabilities Object

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .              IOAM DEX Capabilities Object Header              .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               IOAM-Trace-Type                 |    Reserved   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Namespace-ID          |           Reserved            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 7: IOAM DEX Capabilities Object

   When the IOAM DEX Capabilities Object is present in the IOAM
   Capabilities Response Container, the sending node is an IOAM transit
   node and the IOAM direct exporting function is enabled at this IOAM
   transit node.

   The IOAM-Trace-Type field has the same definition as what's specified
   in Section 3.2 of [RFC9326].

   The Namespace-ID field has the same definition as what's specified in
   Section 4.3 of [RFC9197].  It MUST be one of the Namespace-IDs listed
   in the IOAM Capabilities Query Object of the echo request.

   The Reserved field MUST be zeroed on transmission and ignored on
   receipt.

3.2.6.  IOAM End-of-Domain Object

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     .                                                               .
     .               IOAM End-of-Domain Object Header                .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Namespace-ID          |            Reserved           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 8: IOAM End-of-Domain Object

   When the IOAM End-of-Domain Object is present in the IOAM
   Capabilities Response Container, the sending node is an IOAM
   decapsulating node.  Unless the IOAM Edge-to-Edge Capabilities Object
   is present, which also indicates that the sending node is an IOAM
   decapsulating node, the IOAM End-of-Domain Object MUST be present in
   the IOAM Capabilities Response Container sent by an IOAM
   decapsulating node.  When the IOAM edge-to-edge function is enabled
   at the IOAM decapsulating node, including only the IOAM Edge-to-Edge
   Capabilities Object, not the IOAM End-of-Domain Object, is
   RECOMMENDED.

   The Namespace-ID field has the same definition as what's specified in
   Section 4.3 of [RFC9197].  It MUST be one of the Namespace-IDs listed
   in the IOAM Capabilities Query Container.

   Reserved field MUST be zeroed on transmission and ignored on receipt.

4.  Operational Guide

   Once the IOAM encapsulating node is triggered to discover the enabled
   IOAM capabilities of each IOAM transit and IOAM decapsulating node,
   the IOAM encapsulating node will send echo requests that include the
   IOAM Capabilities Query Container as follows:

   *  First, with TTL equal to 1 to reach the closest node (which may or
      may not be an IOAM transit node).

   *  Then, with TTL equal to 2 to reach the second-nearest node (which
      also may or may not be an IOAM transit node).

   *  Then, further increasing by 1 the TTL every time the IOAM
      encapsulating node sends a new echo request, until the IOAM
      encapsulating node receives an echo reply sent by the IOAM
      decapsulating node (which contains the IOAM Capabilities Response
      Container including the IOAM Edge-to-Edge Capabilities Object or
      the IOAM End-of-Domain Object).

   As a result, the echo requests sent by the IOAM encapsulating node
   will reach all nodes one by one along the transport path of IOAM data
   packet.

   Alternatively, if the IOAM encapsulating node knows precisely all the
   IOAM transit and IOAM decapsulating nodes beforehand, once the IOAM
   encapsulating node is triggered to discover the enabled IOAM
   capabilities, it can send an echo request to each IOAM transit and
   IOAM decapsulating node directly, without TTL expiration.

   The IOAM encapsulating node may be triggered by the device
   administrator, the network management system, the network controller,
   or data traffic.  The specific triggering mechanisms are outside the
   scope of this document.

   Each IOAM transit and IOAM decapsulating node that receives an echo
   request containing the IOAM Capabilities Query Container will send an
   echo reply to the IOAM encapsulating node.  For the echo reply, there
   is an IOAM Capabilities Response Container containing one or more
   Objects.  The IOAM Capabilities Query Container of the echo request
   would be ignored by the receiving node unaware of IOAM.

   Note that the mechanism defined in this document applies to all kinds
   of IOAM option types, whether the four types of IOAM options defined
   in [RFC9197] or the DEX type of IOAM option defined in [RFC9326].
   Specifically, when applied to the IOAM DEX option, the mechanism
   allows the IOAM encapsulating node to discover which nodes along the
   transport path support IOAM direct exporting and which trace data
   types are supported to be directly exported at these nodes.

5.  IANA Considerations

   IANA has created a registry named "In Situ OAM (IOAM) Capabilities".

   This registry includes the following subregistries:

   *  IOAM SoP Capability

   *  IOAM TSF Capability

   The subsequent subsections detail the registries herein contained.

   Considering the Containers/Objects defined in this document that
   would be carried in different types of Echo Request/Reply messages,
   such as ICMPv6 or LSP Ping, it is intended that the registries for
   Container/Object Type would be requested in subsequent documents.

5.1.  IOAM SoP Capability Registry

   This registry defines four codepoints for the IOAM SoP Capability
   field for identifying the size of "PktID" and "Cumulative" data as
   explained in Section 4.5 of [RFC9197].

   A new entry in this registry requires the following fields:

   *  SoP (Size of POT): a 2-bit binary field as defined in
      Section 3.2.3.

   *  Description: a terse description of the meaning of this SoP value.

   The registry initially contains the following value:

          +======+=============================================+
          | SoP  | Description                                 |
          +======+=============================================+
          | 0b00 | 64-bit "PktID" and 64-bit "Cumulative" data |
          +------+---------------------------------------------+

                       Table 1: SoP and Description

   0b01 - 0b11 are available for assignment via the IETF Review process
   as per [RFC8126].

5.2.  IOAM TSF Capability Registry

   This registry defines four codepoints for the IOAM TSF Capability
   field for identifying the timestamp format as explained in Section 5
   of [RFC9197].

   A new entry in this registry requires the following fields:

   *  TSF (TimeStamp Format): a 2-bit binary field as defined in
      Section 3.2.4.

   *  Description: a terse description of the meaning of this TSF value.

   The registry initially contains the following values:

                 +======+================================+
                 | TSF  | Description                    |
                 +======+================================+
                 | 0b00 | PTP Truncated Timestamp Format |
                 +------+--------------------------------+
                 | 0b01 | NTP 64-bit Timestamp Format    |
                 +------+--------------------------------+
                 | 0b10 | POSIX-based Timestamp Format   |
                 +------+--------------------------------+

                        Table 2: TSF and Description

   0b11 is available for assignment via the IETF Review process as per
   [RFC8126].

6.  Security Considerations

   Overall, the security needs for IOAM capabilities query mechanisms
   used in different environments are similar.

   To avoid potential Denial-of-Service (DoS) attacks, it is RECOMMENDED
   that implementations apply rate-limiting to incoming echo requests
   and replies.

   To protect against unauthorized sources using echo request messages
   to obtain IOAM Capabilities information, implementations MUST provide
   a means of checking the source addresses of echo request messages
   against an access list before accepting the message.

   A deployment MUST ensure that border-filtering drops inbound echo
   requests with an IOAM Capabilities Container Header from outside of
   the domain and that drops outbound echo requests or replies with IOAM
   Capabilities Headers leaving the domain.

   A deployment MUST support the configuration option to enable or
   disable the IOAM Capabilities Discovery feature defined in this
   document.  By default, the IOAM Capabilities Discovery feature MUST
   be disabled.

   The integrity protection on IOAM Capabilities information carried in
   echo reply messages can be achieved by the underlying transport.  For
   example, if the environment is an IPv6 network, the IP Authentication
   Header [RFC4302] or IP Encapsulating Security Payload Header
   [RFC4303] can be used.

   The collected IOAM Capabilities information by queries may be
   considered confidential.  An implementation can use secure underlying
   transport of echo requests or replies to provide privacy protection.
   For example, if the environment is an IPv6 network, confidentiality
   can be achieved by using the IP Encapsulating Security Payload Header
   [RFC4303].

   An implementation can also directly secure the data carried in echo
   requests and replies if needed, the specific mechanism on how to
   secure the data is beyond the scope of this document.

   An implementation can also check whether the fields in received echo
   requests and replies strictly conform to the specifications, e.g.,
   whether the list of IOAM Namespace-IDs includes duplicate entries and
   whether the received Namespace-ID is an operator-assigned or IANA-
   assigned one, once a check fails, an exception event indicating the
   checked field should be reported to the management.

   Except for what's described above, the security issues discussed in
   [RFC9197] provide good guidance on implementation of this
   specification.

7.  References

7.1.  Normative References

   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

   [RFC9197]  Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
              Ed., "Data Fields for In Situ Operations, Administration,
              and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
              May 2022, <https://www.rfc-editor.org/info/rfc9197>.

   [RFC9326]  Song, H., Gafni, B., Brockners, F., Bhandari, S., and T.
              Mizrahi, "In Situ Operations, Administration, and
              Maintenance (IOAM) Direct Exporting", RFC 9326,
              DOI 10.17487/RFC9326, November 2022,
              <https://www.rfc-editor.org/info/rfc9326>.

7.2.  Informative References

   [BIER-PING]
              Nainar, N. K., Pignataro, C., Akiya, N., Zheng, L., Chen,
              M., and G. Mirsky, "BIER Ping and Trace", Work in
              Progress, Internet-Draft, draft-ietf-bier-ping-08, 6 March
              2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
              bier-ping-08>.

   [OAM-for-SFC]
              Mirsky, G., Meng, W., Ao, T., Khasnabish, B., Leung, K.,
              and G. Mishra, "Active OAM for Service Function Chaining
              (SFC)", Work in Progress, Internet-Draft, draft-ietf-sfc-
              multi-layer-oam-23, 23 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-sfc-
              multi-layer-oam-23>.

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,
              <https://www.rfc-editor.org/info/rfc4302>.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [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>.

   [RFC4620]  Crawford, M. and B. Haberman, Ed., "IPv6 Node Information
              Queries", RFC 4620, DOI 10.17487/RFC4620, August 2006,
              <https://www.rfc-editor.org/info/rfc4620>.

   [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>.

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
              Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029,
              DOI 10.17487/RFC8029, March 2017,
              <https://www.rfc-editor.org/info/rfc8029>.

   [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>.

   [RFC8799]  Carpenter, B. and B. Liu, "Limited Domains and Internet
              Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
              <https://www.rfc-editor.org/info/rfc8799>.

Acknowledgements

   The authors would like to acknowledge Tianran Zhou, Dhruv Dhody,
   Frank Brockners, Cheng Li, Gyan Mishra, Marcus Ihlar, Martin Duke,
   Chris Lonvick, √Čric Vyncke, Alvaro Retana, Paul Wouters, Roman
   Danyliw, Lars Eggert, Warren Kumari, John Scudder, Robert Wilton,
   Erik Kline, Zaheduzzaman Sarker, Murray Kucherawy, and Donald
   Eastlake 3rd for their careful review and helpful comments.

   The authors appreciate the f2f discussion with Frank Brockners on
   this document.

   The authors would like to acknowledge Tommy Pauly and Ian Swett for
   their good suggestion and guidance.

Authors' Addresses

   Xiao Min
   ZTE Corp.
   Nanjing
   China
   Phone: +86 25 88013062
   Email: xiao.min2@zte.com.cn


   Greg Mirsky
   Ericsson
   United States of America
   Email: gregimirsky@gmail.com


   Lei Bo
   China Telecom
   Beijing
   China
   Phone: +86 10 50902903
   Email: leibo@chinatelecom.cn
  1. RFC 9359