Extensions to IOAM Trace Option for Carrying Fixed-Size Data
draft-xiao-ippm-ioam-trace-extensions-03
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Xiao Min , Yisong Liu , Changwang Lin | ||
| Last updated | 2026-04-12 | ||
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| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
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draft-xiao-ippm-ioam-trace-extensions-03
IPPM Working Group X. Min
Internet-Draft ZTE Corp.
Intended status: Standards Track Y. Liu
Expires: 14 October 2026 China Mobile
C. Lin
New H3C Technologies
12 April 2026
Extensions to IOAM Trace Option for Carrying Fixed-Size Data
draft-xiao-ippm-ioam-trace-extensions-03
Abstract
In situ Operations, Administration, and Maintenance (IOAM) Trace-
Option data defined in RFC 9197 is a variable-length data, the length
of this kind of data varies with the number of transited IOAM-capable
nodes and the selection of data fields processed by each IOAM-capable
node. This document extends the IOAM Trace Option to carry a fixed-
size data, the length of this kind of data is fixed once the
selection of data fields processed by each IOAM-capable node is
determined, and doesn't vary with the number of transited IOAM-
capable nodes.
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
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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."
This Internet-Draft will expire on 14 October 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Problem with the current IOAM Trace Option . . . . . . . . . 4
4. Extension to the IOAM Trace Option's Flags . . . . . . . . . 5
5. Fixed-size aggregate data in the IOAM Trace Option . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7.1. IOAM Trace-Flags Registry . . . . . . . . . . . . . . . . 9
7.2. IOAM Fixed-Data Trace-Type Registry . . . . . . . . . . . 9
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC9197] defines In situ Operations, Administration, and Maintenance
(IOAM), which collects operational and telemetry information in the
packet while the packet traverses a path between two points in the
network. As specified in Section 4.1 of [RFC9197], IOAM tracing is
defined as two separate options: Pre-allocated Trace Option and
Incremental Trace Option. The two IOAM Trace Options share the same
format of IOAM Trace-Option header and data. The IOAM Trace-Option
data is composed of a set of node data lists; among them each node
data list is populated by a node along the forwarding path of IOAM
packet.
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The IOAM Trace-Option data defined in [RFC9197] is a variable-length
data, the length of this kind of data varies with the number of
transited IOAM-capable nodes and the selection of data fields
processed by each IOAM-capable node. This document extends the IOAM
Trace Option to carry a fixed-size data, the length of this kind of
data is fixed once the selection of data fields processed by each
IOAM-capable node is determined, and doesn't vary with the number of
transited IOAM-capable nodes.
Note that the difference between the fixed-size IOAM tracing data
defined in this document and the pre-allocated IOAM tracing data
defined in [RFC9197], is that the fixed-size IOAM tracing data is
processed in a compare-and-replace manner by each node along the
forwarding path, which makes the IOAM data size always fixed no
matter how many nodes get traversed.
2. Conventions Used in This Document
2.1. Abbreviations
ABW: Available Bandwidth
BU: Buffer Utilization
CSIG: Congestion Signaling
HPCC++: Enhanced High Precision Congestion Control
IOAM: In situ Operations, Administration, and Maintenance
LU: Link Utilization
PD: Per-hop delay
TTL: Time to Live
2.2. 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.
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3. Problem with the current IOAM Trace Option
As specified in Section 4.4 of [RFC9197], the IOAM Trace Option
(including IOAM Pre-allocated Trace Option and IOAM Incremental Trace
Option) has a format as shown in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID |NodeLen | Flags | RemainingLen|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM Trace-Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
| | |
| node data list [0] | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ D
| | a
| node data list [1] | t
| | a
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~ S
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ p
| | a
| node data list [n-1] | c
| | e
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | |
| node data list [n] | |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<-+
Figure 1: IOAM Trace Option defined in RFC 9197
The IOAM Trace Option defined in [RFC9197] is used to stack up
multiple metadata from multiple IOAM transit nodes. Specifically,
along the forwarding path, each IOAM-capable node adds its own
operational and telemetry information into the IOAM Trace Option
carried by a data packet in a stacking manner.
As described in [I-D.miao-ccwg-hpcc-info], the IOAM Trace Option Data
can be used as a congestion control signal for Enhanced High
Precision Congestion Control (HPCC++) congestion control mechanism,
and at the same time, Congestion Signaling (CSIG) Data can also be
used as a congestion control signal for HPCC++. As specified in
[I-D.ravi-ippm-csig], a CSIG tag carries a fixed-size aggregate
metric computed over the hop devices. Specifically, along the
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forwarding path, each CSIG-capable node optionally inputs its own
congestion information into the CSIG tag carried by a data packet in
a compare-and-replace manner.
In different application scenarios, either the IOAM Trace Option
defined in [RFC9197] or the CSIG tag defined in [I-D.ravi-ippm-csig]
is applicable, or even both of them can be used concurrently. In
other words, they're complementary to each other. Then the question
goes to that whether it's possible to integrate them together. That
is also the problem this document intends to address.
4. Extension to the IOAM Trace Option's Flags
In order to integrate the variable-size superimposed data and fixed-
size aggregate data into IOAM Trace Option, this document defines the
reserved Bit 3 of the Flags field of the IOAM Trace Option as shown
in Figure 2.
0 1 2 3
+-+-+-+-+
|O|L|A|F|
+-+-+-+-+
Figure 2: IOAM Trace Option's Flags format
Bit 0 "Overflow" (O-bit): When set, the Overflow flag indicates that
there are not enough octets left to record the node data, as defined
in Section 4.4.1 of [RFC9197].
Bit 1 "Loopback" (L-bit): When set, the Loopback flag triggers the
sending of a copy of a packet back towards the source, as defined in
Section 3 of [RFC9322].
Bit 2 "Active" (A-bit): When set, the Active flag indicates that a
packet is an active measurement packet rather than a data packet, as
defined in Section 3 of [RFC9322].
Bit 3 "Fixed-size" (F-bit): When set, the Fixed-size flag indicates
that a fixed-size aggregate data rather than a variable-size
superimposed data is carried, as defined in Section 5 of this
document. As defined in Section 4.4 of [RFC9197], there are two
types of IOAM Trace Options, Pre-allocated Trace-Option and
Incremental Trace-Option, the F-bit defined in this document can only
be used for Pre-allocated Trace-Option. In other words, if the F-bit
is set while the IOAM Trace Option-Type indicates it's an Incremental
Trace-Option, then the F-bit MUST be ignored by the receiver.
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5. Fixed-size aggregate data in the IOAM Trace Option
When the IOAM Trace Option is used to carry fixed-size aggregate
data, the format of the IOAM Trace Option is shown in Figure 3.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID |NodeLen | Flags | RemainingLen|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM Fixed-Data Trace-Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ One or More Fixed-size Aggregate Data ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IOAM Trace Option carrying fixed-size aggregate data
Namespace-ID: The same as defined in [RFC9197].
NodeLen: The same as defined in [RFC9197]. MUST be set to 0.
Flags: The same as defined in [RFC9197] and [RFC9322]. This
document allocates a single flag as follows:
Bit 3 "Fixed-size" (F-bit) (least significant bit). As defined
in Section 4 of this document. When set, a fixed-size data
space as shown in Figure 3 is carried in the IOAM Trace Option.
RemainingLen: The same as defined in [RFC9197]. MUST be set to 0.
IOAM Fixed-Data Trace-Type: The similar as the IOAM Trace-Type
defined in Section 4.4.1 of [RFC9197]. The only difference with
the IOAM Trace-Type is that each bit of IOAM Fixed-Data Trace-Type
indicates the presence of a fixed-size 8-octet data space called
Fixed-size Aggregate Data, whose length is independent of the
number of transited IOAM-capable nodes.
One or More Fixed-size Aggregate Data: Each Fixed-size Aggregate
Data is a 8-octet data space. When only one bit within the bitmap
of IOAM-Fixed-Data Trace-Type is set, the length of this field is
eight octets. When more than one bit within the bitmap of IOAM
Fixed-Data Trace-Type is set, the length of this field is equal to
the number of set bits multiplied by eight octets.
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This document defines the format of Fixed-size Aggregate Data, as
shown in Figure 4.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Value | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator Metadata |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Fixed-size Aggregate Data Format
The fields are defined as follows:
* Signal Value: A 20-bit field. Its meaning depends on the
position of set bit in IOAM Fixed-Data Trace-Type.
* Locator Metadata: A 4-octet field. This field indicates the
relevant metadata about the bottleneck device and port,
specifically, it contains 12-bit Port ID, 12-bit Device ID, and
8-bit TTL (also called Hop Limit for IPv6).
* Reserved: A 12-bit field that MUST be zeroed on transmission
and ignored on receipt.
The 24-bit identifier of IOAM Fixed-Data Trace-Type and
corresponding Signal Values are defined as follows:
Bit 0 Most significant bit. When set, indicates the Signal Value
in the data space is Minimum Available Bandwidth - min(ABW).
This field indicates the minimum absolute available bandwidth
(in Mbps) across all the nodes' egress interfaces from where
the packet is forwarded out. Each node along the forwarding
path would compare its available bandwidth of the egress
interface with the received field value. If a node finds that
its available bandwidth of the egress interface is smaller,
then the node would populate this field with a value of its
available bandwidth; If a node finds that its available
bandwidth of the egress interface is not smaller, then the node
would not change this field.
Bit 1 When set, indicates the Signal Value in the data space is
Maximum Link Utilization - max(LU). This field value devided
by 0xFFFFF equals the link utilization rate of the egress
interface from where the packet is forwarded out. Each node
along the forwarding path would compare its link utilization
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rate of the egress interface, i.e. utilized bandwidth devided
by the whole capacity, with the calculated link utilization
rate by the received field value. If a node finds that its
link utilization rate of the egress interface is bigger, then
the node would populate this field with a value of 0xFFFFF
multiplied by its link utilization rate; If a node finds that
its link utilization rate of the egress interface is not
bigger, then the node would not change this field.
Bit 2 When set, indicates the Signal Value in the data space is
Maximum Buffer Utilization - max(BU). This field value devided
by 0xFFFFF equals the buffer utilization rate of the egress
interface from where the packet is forwarded out. Each node
along the forwarding path would compare its buffer utilization
rate of the egress interface, i.e. occupied buffer devided by
the whole buffer, with the calculated buffer utilization rate
by the received field value. If a node finds that its buffer
utilization rate of the egress interface is bigger, then the
node would populate this field with a value of 0xFFFFF
multiplied by its buffer utilization rate; If a node finds that
its buffer utilization rate of the egress interface is not
bigger, then the node would not change this field.
Bit 3-22 Undefined. These values are available for future
assignment in the IOAM Fixed-Data Trace-Type Registry. An IOAM
encapsulating node MUST set the value of each undefined bit to
0. If an IOAM transit node receives a packet with one or more
of these bits set to 1, it MUST ignore these bits and SHOULD
log and/or report an error.
Bit 23 Reserved; MUST be set to zero upon transmission and be
ignored upon receipt. This bit is reserved to allow for future
extensions of the IOAM Fixed-Data Trace-Type bit field.
6. Security Considerations
As discussed in [RFC9322], IOAM is assumed to be deployed in a
restricted administrative domain, thus limiting the scope of the
threats above and their effect. However, even given this limited
scope, security threats should still be considered and mitigated.
Security issues discussed in [RFC9197] apply to this document.
7. IANA Considerations
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7.1. IOAM Trace-Flags Registry
IANA is requested to allocate the following bit in the "IOAM Trace-
Flags" registry as follows:
Bit 3 "Fixed-size" (F-bit)
This document is specified as the "Reference" in the registry for
this bit.
Note that bit 0 is the most significant bit in the "IOAM Trace-Flags"
registry. This bit was allocated by [RFC9197] as the 'Overflow' bit.
7.2. IOAM Fixed-Data Trace-Type Registry
IANA is requested to create a new registry "IOAM Fixed-Data Trace-
Type" within the defined registry group "In Situ OAM (IOAM)". This
registry defines code points for each bit in the 24-bit IOAM Fixed-
Data Trace-Type field for the Pre-allocated Trace Option-Type When
the F-bit is set. Bits 0-2 are defined in Section 5 of this
document:
Bit 0 Minimum Available Bandwidth - min(ABW) and Locator Metadata
Bit 1 Maximum Link Utilization - max(LU) and Locator Metadata
Bit 2 Maximum Buffer Utilization - max(BU) and Locator Metadata
Bit 23 reserved
Bits 3-22 are available for assignment via the "IETF Review" process,
as per [RFC8126].
New registration requests MUST use the following template:
Bit: desired bit to be allocated in the 24-bit IOAM Fixed-Data
Trace-Type field for the Pre-allocated Trace Option-Type when the
F-bit is set
Description: brief description of the newly registered bit
Reference: reference to the document that defines the new bit
8. Acknowledgements
The authors would like to acknowledge Wei Duan and Jun Feng for their
very helpful comments.
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9. References
9.1. 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>.
[RFC9322] Mizrahi, T., Brockners, F., Bhandari, S., Gafni, B., and
M. Spiegel, "In Situ Operations, Administration, and
Maintenance (IOAM) Loopback and Active Flags", RFC 9322,
DOI 10.17487/RFC9322, November 2022,
<https://www.rfc-editor.org/info/rfc9322>.
9.2. Informative References
[I-D.miao-ccwg-hpcc-info]
Miao, R., Anubolu, S., Pan, R., Lee, J., Gafni, B.,
Tantsura, J., Alemania, A., and Y. Shpigelman, "Inband
Telemetry for HPCC++", Work in Progress, Internet-Draft,
draft-miao-ccwg-hpcc-info-04, 6 January 2025,
<https://datatracker.ietf.org/doc/html/draft-miao-ccwg-
hpcc-info-04>.
[I-D.ravi-ippm-csig]
Ravi, A., Dukkipati, N., Mehta, N., and J. Kumar,
"Congestion Signaling (CSIG)", Work in Progress, Internet-
Draft, draft-ravi-ippm-csig-01, 2 February 2024,
<https://datatracker.ietf.org/doc/html/draft-ravi-ippm-
csig-01>.
Authors' Addresses
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Xiao Min
ZTE Corp.
Nanjing
China
Phone: +86 18061680168
Email: xiao.min2@zte.com.cn
Yisong Liu
China Mobile
Beijing
China
Email: liuyisong@chinamobile.com
Changwang Lin
New H3C Technologies
Beijing
China
Email: linchangwang.04414@h3c.com
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