Update of the Simple Two-way Active Measurement Protocol Class-of-Service Extension - ECN
draft-ietf-ippm-stamp-cos-ecn-00
| Document | Type | Active Internet-Draft (ippm WG) | |
|---|---|---|---|
| Authors | Greg White , Greg Mirsky , Xiao Min | ||
| Last updated | 2026-01-05 | ||
| Replaces | draft-whimir-ippm-stamp-cos-ecn | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
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draft-ietf-ippm-stamp-cos-ecn-00
IP Performance Measurement G. White
Internet-Draft CableLabs
Updates: 8972 (if approved) G. Mirsky
Intended status: Standards Track Ericsson
Expires: 3 July 2026 X. Min
ZTE Corp.
30 December 2025
Update of the Simple Two-way Active Measurement Protocol Class-of-
Service Extension - ECN
draft-ietf-ippm-stamp-cos-ecn-00
Abstract
The Simple Two-Way Active Measurement Protocol (STAMP) enables one-
way and round-trip measurement of network metrics between IP hosts,
and has a facility for defining optional extensions. This document
updates the definition of the Class of Service TLV (originally
defined in RFC 8972) to enable the measurement of manipulation of the
value of the Explicit Congestion Notification (ECN) field of the IP
header by middleboxes between two STAMP hosts, and to enable
discovery and measurement of paths that provide differential
treatment of packets depending on the value of their ECN field.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 3 July 2026.
Copyright Notice
Copyright (c) 2025 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Class of Service TLV . . . . . . . . . . . . . . . . . . . . 3
3.1. TLV Definition . . . . . . . . . . . . . . . . . . . . . 3
3.2. Session-Reflector Behavior . . . . . . . . . . . . . . . 4
3.3. Interoperability with RFC 8972 . . . . . . . . . . . . . 5
3.4. Congestion Response . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . 8
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
[RFC8972] defined several extensions to the Simple Two-way Active
Measurement Protocol (STAMP). Among those is a Class of Service
(CoS) TLV that enables measurements that utilize the Differentiated
Services Code Point (DSCP) marking in both directions. Also, the CoS
TLV supports outbound measurements that utilize the Explicit
Congestion Notification (ECN) field, but it lacked support for such
measurements on the return path. Experience deploying STAMP and its
extensions demonstrated that it is helpful to an operator to monitor
ECN's consistency in both directions. This specification updates the
definition of the CoS TLV in a backward compatible manner to support
monitoring of ECN in the return path of the STAMP test session.
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Another STAMP extension header [I-D.ietf-ippm-stamp-ext-hdr] defines
a mechanism that can be used by a Session-Sender to request that the
Session-Reflector copy the entire IP header from the received test
packet into the reflected test packet. That capability could be used
in place of the CoS TLV to observe the DSCP and ECN values in the
forward direction in situations where there is no need to control the
return path DSCP or ECN value.
2. Conventions Used in This Document
2.1. Acronyms
CoS: Class of Service
DSCP: Differentiated Services Code Point
ECN: Explicit Congestion Notification
STAMP: Simple Two-way Active Measurement Protocol
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.
3. Class of Service TLV
3.1. TLV Definition
The STAMP Session-Sender MAY include a CoS TLV in the STAMP test
packet. The format of the CoS TLV is presented 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|STAMP TLV Flags| CoS Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSCP1 | DSCP2 |EC2|RPD|EC1|RPE| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Class of Service TLV
Where the fields are defined as follows.
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* STAMP TLV Flags: eight-bit field; format presented in Section 4 of
[RFC8972].
* CoS (Class of Service) Type: one-octet field; the value MUST be
set to 4.
* Length: two-octet field; set equal to the value 4 (octets).
* DSCP1: DSCP value intended by the Session-Sender to be used as the
DSCP value of the reflected test packet.
* DSCP2: received value in the DSCP field at the ingress of the
Session-Reflector.
* EC2: received value in the ECN field at the ingress of the
Session-Reflector.
* RPD (reverse path DSCP): two-bit field indicating whether the
Session-Reflector used DSCP1 or DSCP2 as the DSCP value of the
reflected test packet; a Session-Sender MUST set the value of the
RPD field to 0b00 on transmission.
* EC1: ECN value intended by the Session-Sender to be used as the
ECN value of the reflected test packet.
* RPE (reverse path ECN): two-bit field indicating whether the
Session-Reflector used EC1 as the ECN value of the reflected test
packet; a Session-Sender MUST set the value of the RPE field to
0b00 on transmission.
* Reserved: twelve-bit field; MUST be zeroed on transmission and
ignored on receipt.
3.2. Session-Reflector Behavior
A STAMP Session-Reflector that receives a test packet with the CoS
TLV MUST include the CoS TLV in the reflected test packet. The
Session-Reflector MUST copy the value of the DSCP and ECN fields of
the IP header of the received STAMP test packet into the DSCP2 and
EC2 fields, respectively, in the CoS TLV in the reflected test
packet.
A Session-Reflector might have a local policy configuration that
limits the DSCP values that it can use for reflected test packets.
This local policy could be (for example) a system default policy, a
global policy for the Session-Reflector, or a policy that is
configured for specific destination addresses or networks. The
Session-Reflector MUST verify whether the use of the value of the
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DSCP1 field is permitted in the reflected test packet. If it is, the
Session-Reflector MUST set the DSCP field's value in the IP header of
the reflected test packet equal to the value of the DSCP1 field of
the received test packet. Otherwise, the Session-Reflector MUST use
the DSCP value of the received STAMP packet and set the value of the
RPD field to 0b01. Upon receiving the reflected packet, if the value
of the RPD field is 0b00, the Session-Sender will save the DSCP value
for analysis of the CoS in the reverse direction. If the value of
the RPD field in the received reflected packet is 0b01, only CoS in
the forward direction can be analyzed.
A Session-Reflector might have a local policy configuration that
limits the ECN values that it can use for reflected test packets.
This local policy could be (for example) a system default policy, a
global policy for the Session-Reflector, or a policy that is
configured for specific destination addresses or networks.
Additionally, a Session-Reflector could have platform limitations
that prevent it from setting the ECN value in reflected test packets.
The Session-Reflector MUST set the ECN value in the IP header of the
reflected STAMP test packet to the value of the EC1 field, if it is
permitted and capable to do so. If the Session-Reflector is able to
set the ECN value in the IP header of the reflected STAMP test packet
to the EC1 value, it MUST then set the RPE field in the CoS TLV in
the reflected test packet to the value 0b11. If the Session-
Reflector is unable to set the ECN value in the IP header of the
reflected STAMP test packet to the EC1 value, it MUST instead set the
RPE field in the CoS TLV in the reflected test packet to the value
0b10. As a result, the Session-Sender can detect whether the EC1
value was used by inspecting the value of the RPE field in the
received reflected test packet.
3.3. Interoperability with RFC 8972
The extended CoS TLV defined in this draft is backward compatible
with the specification in Section 4.4 of [RFC8972]. The handling of
the DSCP1, DSCP2, EC2 and RPD fields defined here is identical to the
handling defined for the equivalent fields in Section 4.4 of
[RFC8972].
Consider a case when an implementation that supports this
specification performs as Session-Sender, and the intended Session-
Reflector's support of the CoS TLV is according to Section 4.4 of
[RFC8972]. If the operator requires monitoring ECN in the reverse
direction, the value of the EC1 field will be set to a non-zero
value. Because the Session-Reflector would treat the EC1 field as
part of the Reserved field, it would ignore its value as per
Section 4.4 of [RFC8972]. Further, the Session-Reflector would treat
the RPE field as part of the Reserved field and thus it would send
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the value 0b00 in the reflected STAMP packet, rather than sending the
value 0b10 or 0b11. Consequently, the Session-Sender will determine
that the Session-Reflector does not implement the current version of
the CoS TLV, and that the ECN value in the IP header of the reflected
test packet was not set as requested.
Also, this specification supports the case when the Session-Reflector
supports the extended CoS TLV as defined in this specification and
the Session-Sender supports the CoS TLV according to Section 4.4 of
[RFC8972]. In that scenario, the Session-Sender will set its
[RFC8972] Reserved field to zeros. The Session-Reflector will
interpret the first two bits of that field as the EC1 field, as shown
in Figure 1 and thus will set the value of the ECN field in the IP
header of the reflected packet to 0b00. Further the Session-
Reflector will set the RPE field to 0b11. The Session-Sender will
treat the RPE field as part of the Reserved field and will ignore its
value.
3.4. Congestion Response
[RFC3168] and [RFC9330] mandate that applications that send packets
marked with the ECT0 or ECT1 codepoints implement a response to
congestion notifications from the network. While the STAMP protocol
doesn't include the concept of a connection between a Session-Sender
and a Session-Reflector, there are situations in which the Session-
Sender may send multiple STAMP packets to the same Session-Reflector
within the round-trip time between them, and there are situations in
which the Session-Sender may elicit multiple STAMP packets from a
Session-Reflector in response to a single sent STAMP packet. As
such, the Session-Sender is generally responsible for dictating both
its sending rate, and the sending rate of the packets sent in
response by an individual Session-Reflector, and so is not exempt
from this mandate.
When using this CoS TLV with either an ECT0 or an ECT1 value in the
ECN field of the IP header of the STAMP packet, the Session-Sender
gains the ability (via observing a CE reflected value in the EC2
field) to detect that congestion was present on the path from the
Session-Sender to the Session-Reflector. Similarly, when using this
CoS TLV with either an ECT0 or an ECT1 value in the EC1 field, the
Session-Sender gains the ability (via observing a CE in the ECN field
of the IP header of the reflected packet) to detect that congestion
was present on the path from the Session-Reflector to the Session-
Sender.
If a Session-Sender sends multiple STAMP packets with the CoS TLV to
a Session-Reflector within an RTT with either the ECT0 or ECT1 value
in the ECN field of the IP header, it MUST observe the reflected EC2
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field and reduce its sending rate upon observation of a CE value. If
a Session-Sender sends multiple STAMP packets with the CoS TLV to a
Session-Reflector within an RTT with either the ECT0 or ECT1 value in
the EC1 field, it MUST observe the ECN value in the IP header of the
reflected packets and reduce its sending rate upon observation of a
CE value. If a Session-Sender sends a STAMP packet containing both
the CoS TLV and the Reflected Test Packet Control TLV
([I-D.ietf-ippm-asymmetrical-pkts]) to a Session-Reflector, and
specifies either the ECT0 or ECT1 value in the EC1 field, it MUST
observe the ECN value in the IP header of the reflected packets and
adjust the Reflected Test Packet Control parameters in any future
STAMP packet sent to the same Session-Reflector based on the
observation of CE values.
4. IANA Considerations
This document includes no request to IANA.
5. Security Considerations
This document extends the functionality of the CoS TLV ([RFC8972])
and inherits all the security considerations applicable to the base
STAMP specification [RFC8762] and [RFC8972].
As this specification defines a mechanism to set ECN values, this
document inherits all the security considerations discussed in
[RFC3168] and [RFC9330]. Monitoring and optional control of ECN for
a reflected STAMP test packet using the extended CoS TLV may be used
across the Internet such that the Session-Sender and the Session-
Reflector are located in different domains.
6. References
6.1. 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>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
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[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<https://www.rfc-editor.org/info/rfc3168>.
[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>.
[RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
Two-Way Active Measurement Protocol", RFC 8762,
DOI 10.17487/RFC8762, March 2020,
<https://www.rfc-editor.org/info/rfc8762>.
[RFC8972] Mirsky, G., Min, X., Nydell, H., Foote, R., Masputra, A.,
and E. Ruffini, "Simple Two-Way Active Measurement
Protocol Optional Extensions", RFC 8972,
DOI 10.17487/RFC8972, January 2021,
<https://www.rfc-editor.org/info/rfc8972>.
[RFC9330] Briscoe, B., Ed., De Schepper, K., Bagnulo, M., and G.
White, "Low Latency, Low Loss, and Scalable Throughput
(L4S) Internet Service: Architecture", RFC 9330,
DOI 10.17487/RFC9330, January 2023,
<https://www.rfc-editor.org/info/rfc9330>.
[I-D.ietf-ippm-asymmetrical-pkts]
Mirsky, G., Ruffini, E., Nydell, H., Foote, R. F., and W.
Hawkins, "Performance Measurement with Asymmetrical
Traffic Using STAMP", Work in Progress, Internet-Draft,
draft-ietf-ippm-asymmetrical-pkts-08, 28 June 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-ippm-
asymmetrical-pkts-08>.
6.2. Informative References
[RFC8311] Black, D., "Relaxing Restrictions on Explicit Congestion
Notification (ECN) Experimentation", RFC 8311,
DOI 10.17487/RFC8311, January 2018,
<https://www.rfc-editor.org/info/rfc8311>.
[RFC9331] De Schepper, K. and B. Briscoe, Ed., "The Explicit
Congestion Notification (ECN) Protocol for Low Latency,
Low Loss, and Scalable Throughput (L4S)", RFC 9331,
DOI 10.17487/RFC9331, January 2023,
<https://www.rfc-editor.org/info/rfc9331>.
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[I-D.ietf-ippm-stamp-ext-hdr]
Gandhi, R., Zhou, T., Li, Z., and W. Hawkins, "Simple Two-
Way Active Measurement Protocol (STAMP) Extensions for
Reflecting STAMP Packet IP Headers", Work in Progress,
Internet-Draft, draft-ietf-ippm-stamp-ext-hdr-07, 6
November 2025, <https://datatracker.ietf.org/doc/html/
draft-ietf-ippm-stamp-ext-hdr-07>.
Acknowledgements
TBD
Contributors
Karthik Sundaresan, William Hawkins III, Gorry Fairhurst, Rüdiger
Geib
Authors' Addresses
Greg White
CableLabs
858 Coal Creek Circle
Louisville, Colorado 80027
United States of America
Email: g.white@cablelabs.com
URI: http://www.cablelabs.com
Greg Mirsky
Ericsson
Email: gregimirsky@gmail.com
Xiao Min
ZTE Corp.
Nanjing
China
Email: xiao.min2@zte.com.cn
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