Internet Engineering Task Force (IETF) X. Min

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
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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, Éric 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: [email protected]

Greg Mirsky
Ericsson
United States of America
Email: [email protected]

Lei Bo
China Telecom
Beijing
China
Phone: +86 10 50902903
Email: [email protected]