



IP Performance Measurement                                      G. White
Internet-Draft                                                 CableLabs
Updates: 8972 (if approved)                                    G. Mirsky
Intended status: Standards Track                                Ericsson
Expires: 26 December 2025                                         X. Min
                                                               ZTE Corp.
                                                            24 June 2025


   Update of the Simple Two-way Active Measurement Protocol Class-of-
                        Service Extension - ECN
                   draft-whimir-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

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 26 December 2025.

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
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   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 . . . . . . . . . . . . . .   2
     2.1.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  Class of Service TLV  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Interoperability with RFC 8972  . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

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.

2.  Conventions Used in This Document

2.1.  Acronyms

   CoS:  Class of Service

   DSCP:  Differentiated Services Code Point




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   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

   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.

   *  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.






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   *  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.

   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.

   The Session-Reflector MUST use the local policy to verify whether the
   use of the value of the DSCP1 field is permitted in the domain.  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.

   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.  The
   Session-Reflector MUST set the RPE field in the CoS TLV in the
   reflected test packet to the value 0b01.  As a result, the Session-
   Sender can detect whether the recommended value for ECN field in the
   reflected packet was used by inspecting the value of the RPE field in
   the received reflected test packet.









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3.1.  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
   the value 0b00 in the reflected STAMP packet, rather than sending the
   value 0b01.  Consequently, the Session-Sender will determine 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 0b01.  The Session-Sender will
   treat the RPE field as part of the Reserved field and will ignore its
   value.

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].








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   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>.

   [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>.




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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>.

Acknowledgements

   TBD

Contributors

   Karthik Sundaresan, William Hawkins III

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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