Cisco Systems, Inc.

Canada rgandhi@cisco.com

Cisco Systems, Inc.

cfilsfil@cisco.com

Huawei

mach.chen@huawei.com

Colt

Bart.Janssens@colt.net

Nokia

footer.foote@nokia.com

tsv ippm Segment Routing (SR) leverages the source routing paradigm. SR is applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) forwarding planes. This document specifies Simple Two-Way Active Measurement Protocol (STAMP) extensions (as described in RFC 8762) for SR networks, for both the SR-MPLS and SRv6 forwarding planes, by augmenting the optional extensions defined in RFC 8972.

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 .

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 () 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

• .  Introduction
• .  Conventions Used in This Document
  • .  Requirements Language
  • .  Abbreviations
  • .  Reference Topology
• .  Destination Node Address TLV
• .  Return Path TLV
  • .  Return Path Sub-TLVs
    • .  Return Path Control Code Sub-TLV
    • .  Return Address Sub-TLVs
    • .  Return Path Segment List Sub-TLVs
• .  Interoperability with TWAMP Light
• .  Security Considerations
• .  IANA Considerations
• .  References
  • .  Normative References
  • .  Informative References
• .  Destination Node Address TLV Use-Case Example
• Acknowledgments
• Contributors
• Authors' Addresses

Introduction Segment Routing (SR) leverages the source routing paradigm for Software-Defined Networks (SDNs). SR is applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) forwarding planes . SR Policies as defined in are used to steer traffic through specific, user-defined paths using a stack of Segments. A comprehensive SR Performance Measurement (PM) toolset is one of the essential requirements to measure network performance to provide Service Level Agreements (SLAs). The Simple Two-Way Active Measurement Protocol (STAMP) provides capabilities for the measurement of various performance metrics in IP networks without the use of a control channel to pre-signal session parameters. defines optional extensions, in the form of TLVs, for STAMP. Note that the YANG data model defined in can be used to provision the STAMP Session-Sender and STAMP Session-Reflector. STAMP test packets are transmitted along an IP path between a Session-Sender and a Session-Reflector to measure performance delay and packet loss along that IP path. In SR networks, it may be desired that the same path (same set of links and nodes) between the Session-Sender and Session-Reflector be used for the STAMP test packets in both directions. This is achieved by using the STAMP extensions for SR-MPLS and SRv6 networks as specified in this document by augmenting the optional extensions defined in .

Conventions Used in This Document

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 when, and only when, they appear in all capitals, as shown here.

Abbreviations

MPLS:

Multiprotocol Label Switching

SID:

Segment Identifier

SR:

Segment Routing

SR-MPLS:

Segment Routing over MPLS

SRv6:

Segment Routing over IPv6

SSID:

STAMP Session Identifier

STAMP:

Simple Two-Way Active Measurement Protocol

Reference Topology In the reference topology shown below, the STAMP Session-Sender S1 initiates a STAMP test packet and the STAMP Session-Reflector R1 transmits a reply STAMP test packet. The reply test packet may be transmitted to the Session-Sender S1 on the same path (same set of links and nodes) or a different path in the reverse direction from the path taken towards the Session-Reflector R1. T1 is a transmit timestamp, and T4 is a receive timestamp added by node S1. T2 is a receive timestamp, and T3 is a transmit timestamp added by node R1. The nodes S1 and R1 may be connected via a link or an SR path . The link may be a physical interface, virtual link, Link Aggregation Group (LAG) , or LAG member. The SR path may be an SR Policy on node S1 (called "head-end") with a destination to node R1 (called "tail-end").

Reference Topology T1 T2 / \ +-------+ Test Packet +-------+ | | - - - - - - - - - ->| | | S1 |=====================| R1 | | |<- - - - - - - - - - | | +-------+ Reply Test Packet +-------+ \ / T4 T3 STAMP Session-Sender STAMP Session-Reflector

Destination Node Address TLV The Session-Sender may need to transmit test packets to the Session-Reflector with a Destination Address that is not a routable address (i.e., not suitable for use as the Source Address of the reply test packet) of the Session-Reflector. This can be facilitated, for example, by encapsulating the STAMP packet by a tunneling protocol; see for an example. defines STAMP Session-Sender and Session-Reflector test packets that can include one or more optional TLVs. In this document, the TLV Type (value 9 for IPv4 and IPv6) is defined for the Destination Node Address TLV for the STAMP test packet . The formats of the Destination Node Address TLVs are shown in :

Destination Node Address TLV Formats 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| Type=9 | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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| Type=9 | Length=16 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The TLV fields are defined as follows:

STAMP TLV Flags:

The STAMP TLV Flags follow the procedures described in and this document.

Type:

Type (value 9) for the IPv4 Destination Node Address TLV or IPv6 Destination Node Address TLV.

Length:

A 2-octet field equal to the length of the Address field in octets. The length is 4 octets for an IPv4 address and 16 octets for an IPv6 address.

The Destination Node Address TLV indicates an address of the intended Session-Reflector node of the test packet. If the received Destination Node Address is one of the addresses of the Session-Reflector, it SHOULD be used as the Source Address in the IP header of the reply test packet. If the Destination Node Address TLV is sent, the SSID MUST also be sent. A Session-Reflector that recognizes this TLV MUST set the U flag in the reply test packet to 1 if the Session-Reflector determined that it is not the intended destination as identified in the Destination Node Address TLV. In this case, the Session-Reflector does not use the received Destination Node Address as the Source Address in the IP header of the reply test packet. Otherwise, the Session-Reflector MUST set the U flag in the Destination Node Address TLV in the reply test packet to 0.

Return Path TLV For end-to-end SR paths, the Session-Reflector may need to transmit the reply test packet on a specific Return Path. The Session-Sender can request this in the test packet to the Session-Reflector using a Return Path TLV. With this TLV carried in the Session-Sender test packet, signaling and maintaining dynamic SR network state for the STAMP sessions on the Session-Reflector are avoided. There are two modes defined for the behaviors on the Session-Reflector in : Stateless and Stateful. A Stateful Session-Reflector requires configuration that must match all Session-Sender parameters, including the Source Address, Destination Address, Source UDP Port, Destination UDP Port, and possibly SSID (assuming the SSID is configurable and not auto-generated). In this case, a local policy can be used to direct the test packet by creating additional states for the STAMP sessions on the Session-Reflector. In the case of promiscuous operation, the Stateless Session-Reflector will require an indication of how to return the test packet on a specific path, for example, for measurement in an ECMP environment. For links, the Session-Reflector may need to transmit the reply test packet on the same incoming link in the reverse direction. The Session-Sender can request this in the test packet to the Session-Reflector using a Return Path TLV. defines STAMP test packets that can include one or more optional TLVs. In this document, the TLV Type (value 10) is defined for the Return Path TLV that carries the Return Path for the Session-Sender test packet. The format of the Return Path TLV is shown in :

Return Path TLV 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |STAMP TLV Flags| Type=10 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Return Path Sub-TLVs | . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The TLV fields are defined as follows:

STAMP TLV Flags:

The STAMP TLV Flags follow the procedures described in and this document.

Type:

Type (value 10) for the Return Path TLV.

Length:

A 2-octet field equal to the length of the Return Path Sub-TLVs field in octets.

Return Path Sub-TLVs:

As defined in .

A Session-Sender MUST NOT insert more than one Return Path TLV in the STAMP test packet. A Session-Reflector that supports this TLV MUST only process the first Return Path TLV in the test packet and ignore other Return Path TLVs if present. A Session-Reflector that supports this TLV MUST reply using the Return Path received in the Session-Sender test packet, if no error was encountered while processing the TLV. A Session-Reflector that recognizes this TLV MUST set the U flag in the reply test packet to 1 if the Session-Reflector determined that it cannot use the Return Path in the test packet to transmit the reply test packet. Otherwise, the Session-Reflector MUST set the U flag in the reply test packet to 0.

Return Path Sub-TLVs The Return Path TLV contains one or more Sub-TLVs to carry the information for the requested Return Path. A Return Path Sub-TLV can carry a Return Path Control Code, Return Path IP Address, or Return Path Segment List. The STAMP Sub-TLV Flags are set using the procedures described in . A Return Path TLV MUST NOT contain more than one Control Code Sub-TLV, Return Address Sub-TLV, or Return Path Segment List Sub-TLV in a Session-Sender test packet. A Return Path TLV MUST NOT contain both a Control Code Sub-TLV and a Return Address or Return Path Segment List Sub-TLV in a Session-Sender test packet. A Return Path TLV MAY contain both a Return Address and a Return Path Segment List Sub-TLV in a Session-Sender test packet.

Return Path Control Code Sub-TLV The format of the Control Code Sub-TLV in the Return Path TLV is shown in .

Format of the Control Code Sub-TLV in the Return Path TLV 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| Type=1 | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Control Code Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The TLV fields are defined as follows:

Type:

Type (value 1) for the Return Path Control Code. The Session-Sender can request the Session-Reflector to transmit the reply test packet based on the flags defined in the Control Code Flags field.

STAMP TLV Flags:

The STAMP TLV Flags follow the procedures described in and this document.

Length:

A 2-octet field equal to the length of the Control Code flags, which is 4 octets.

Control Code Flags (32 bits):

Reply Request Flag at bit 31 (least significant bit) is defined as follows.

0x0:

No Reply Requested

0x1:

Reply Requested on the Same Link

All other bits are reserved and must be transmitted as 0 and ignored by the receiver. When Control Code flag for Reply Request is set to 0x0 in the Session-Sender test packet, the Session-Reflector does not transmit a reply test packet to the Session-Sender and terminates the STAMP test packet. Only the one-way measurement is applicable in this case. Optionally, the Session-Reflector may locally stream performance metrics via telemetry using the information from the received test packet. All other Return Path Sub-TLVs MUST be ignored in this case. When Control Code flag for Reply Request is set to 0x1 in the Session-Sender test packet, the Session-Reflector transmits the reply test packet over the same incoming link where the test packet is received in the reverse direction towards the Session-Sender. The link may be a physical interface, virtual link, LAG , or LAG member. All other Return Path Sub-TLVs MUST be ignored in this case. When using LAG member links, the STAMP extension for the Micro-Session ID TLV defined in can be used to identify the link.

Return Address Sub-TLVs The STAMP reply test packet may be transmitted to the Session-Sender to the specified Return Address in the Return Address Sub-TLV instead of transmitting to the Source Address in the Session-Sender test packet. The formats of the IPv4 and IPv6 Return Address Sub-TLVs in the Return Path TLV are shown in .

Formats of the Return Address Sub-TLVs in the Return Path TLV 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| Type=2 | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Return IPv4 Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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| Type=2 | Length=16 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Return IPv6 Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The TLV fields are defined as follows:

Type:

Type (value 2) for the Return IPv4 Address or Return IPv6 Address.

The Return Address requests that the Session-Reflector reply test packet be sent to the specified address rather than to the Source Address in the Session-Sender test packet.

STAMP TLV Flags:

The STAMP TLV Flags follow the procedures described in and this document.

Length:

A 2-octet field equal to the length of the Return Address field in octets. The length is 4 octets for an IPv4 address and 16 octets for an IPv6 address.

Return Path Segment List Sub-TLVs The format of the Segment List Sub-TLVs in the Return Path TLV is shown in Figures and . The Segments carried in Segment List Sub-TLVs are described in . The segment entries MUST be in network order. The Session-Sender MUST only insert one Return Path Segment List Sub-TLV in the test packet, and the Segment List MUST contain at least one Segment. The Session-Reflector MUST only process the first Return Path Segment List Sub-TLV in the test packet and ignore other Return Path Segment List Sub-TLVs if present. The TLV fields are defined as follows:

The Return Path Segment List Sub-TLV can be one of the following Types:

Type (value 3):

SR-MPLS Label Stack of the Return Path

Type (value 4):

SRv6 Segment List of the Return Path

STAMP TLV Flags:

The STAMP TLV Flags follow the procedures described in and this document.

Length:

A 2-octet field equal to the length of the Segment List field in octets. The length MUST NOT be 0.

Return Path SR-MPLS Label Stack Sub-TLV

Format of the SR-MPLS Label Stack Sub-TLV in the Return Path TLV 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| Type=3 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Segment(1) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Segment(n) (bottom of stack) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The SR-MPLS Label Stack contains a list of 32-bit Label Stack Entries (LSEs) that includes a 20-bit label value, an 8-bit Time-To-Live (TTL) value, a 3-bit Traffic Class (TC) value, and a 1-bit End-of-Stack (S) field. The length of the Sub-TLV modulo 4 MUST be 0. As an example, an SR-MPLS Label Stack Sub-TLV could carry only the Binding SID Label of the Return SR-MPLS Policy. The Binding SID Label of the Return SR-MPLS Policy is local to the Session-Reflector. The mechanism to signal the Binding SID Label to the Session-Sender is outside the scope of this document. As another example, an SR-MPLS Label Stack Sub-TLV could include the Path Segment Identifier Label of the Return SR-MPLS Policy in the Segment List of the SR-MPLS Policy.

Return Path SRv6 Segment List Sub-TLV

Format of the SRv6 Segment List Sub-TLV in the Return Path TLV 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| Type=4 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment(1) (128-bit IPv6 Address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Segment(n) (128-bit IPv6 Address) (bottom of stack) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The SRv6 Segment List contains a list of 128-bit IPv6 addresses representing the SRv6 SIDs. The length of the Sub-TLV modulo 16 MUST be 0. As an example, a Return Path SRv6 Segment List Sub-TLV could carry only the SRv6 Binding SID of the Return SRv6 Policy. The SRv6 Binding SID of the Return SRv6 Policy is local to the Session-Reflector. The mechanism to signal the SRv6 Binding SID to the Session-Sender is outside the scope of this document. As another example, a Return Path SRv6 Segment List Sub-TLV could include the SRv6 Path Segment Identifier of the Return SRv6 Policy in the Segment List of the SRv6 Policy.

Interoperability with TWAMP Light This document does not introduce any additional considerations for interoperability with the Two-Way Active Measurement Protocol (TWAMP) Light than those described in . As described in , there are two possible combinations for such an interoperability use case:

• STAMP Session-Sender with TWAMP Light Session-Reflector
• TWAMP Light Session-Sender with STAMP Session-Reflector

If any of the STAMP extensions defined in this document are used by STAMP Session-Sender, the TWAMP Light Session-Reflector will view them as the Packet Padding field.

Security Considerations The security considerations specified in and also apply to the extensions defined in this document. Specifically, the authenticated mode and the message integrity protection using Hashed Message Authentication Code (HMAC), as defined in , also apply to the procedures described in this document. STAMP uses the well-known UDP port number that could become a target of denial of service (DoS) or could be used to aid on-path attacks. Thus, the security considerations and measures to mitigate the risk of the attack documented in equally apply to the STAMP extensions in this document. If desired, attacks can be mitigated by performing basic validation checks of the timestamp fields (such as T2 is later than T1 in the reference topology in ) in received reply test packets at the Session-Sender. The minimal state associated with these protocols also limit the extent of measurement disruption that can be caused by a corrupt or invalid test packet to a single test cycle. The usage of STAMP extensions defined in this document is intended for deployment in a single network administrative domain. As such, the Session-Sender address, Session-Reflector address, and Return Path are provisioned by the operator for the STAMP session. It is assumed that the operator has verified the integrity of the Return Path and identity of the far-end Session-Reflector. The STAMP extensions defined in this document may be used for potential address spoofing. For example, a Session-Sender may specify a Return Path IP Address that is different from the Session-Sender address. The Session-Reflector MAY drop the Session-Sender test packet when it cannot determine whether the Return Path IP Address is local on the Session-Sender. To help the Session-Reflector to make that determination, the Return Path IP Address may also be provisioned by the operator, for example, in an access control list.

IANA Considerations IANA has allocated a value for the Destination Address TLV Type and a value for the Return Path TLV Type from the IETF Review TLV range in the "STAMP TLV Types" registry as follows. STAMP TLV Types

Value	Description	Reference
9	Destination Node IPv4 or IPv6 Address	RFC 9503
10	Return Path	RFC 9503

IANA has created the "Return Path Sub-TLV Types" registry. All code points in the range 1 through 175 in this registry shall be allocated according to the "IETF Review" procedure as specified in . Code points in the range 176 through 239 shall be allocated according to the "First Come First Served" procedure as specified in . Remaining code points shall be allocated according to : Return Path Sub-TLV Types Registry

Range	Registration Procedures
1-175	IETF Review
176-239	First Come First Served
240-251	Experimental Use
252-254	Private Use

IANA has allocated values for the following Sub-TLV Types in the "Return Path Sub-TLV Types" registry. Return Path Sub-TLV Types

Value	Description	Reference
0	Reserved	RFC 9503
1	Return Path Control Code	RFC 9503
2	Return IPv4 or IPv6 Address	RFC 9503
3	SR-MPLS Label Stack of the Return Path	RFC 9503
4	SRv6 Segment List of the Return Path	RFC 9503
255	Reserved	RFC 9503

IANA has created the "Return Path Control Code Flags" registry for Return Path Control Code Sub-TLVs. All code points in the bit position 31 (counting from bit 31 as the least significant bit) through 12 in this registry shall be allocated according to the "IETF Review" procedure as specified in . Code points in the bit position 11 through 8 shall be allocated according to the "First Come First Served" procedure as specified in . Remaining code points shall be allocated according to : Return Path Control Code Flags Registry

Range	Registration Procedures
31-12	IETF Review
11-8	First Come First Served
7-4	Experimental Use
3-0	Private Use

IANA has allocated a value in the "Return Path Control Code Flags" registry as follows. Return Path Control Code Flags

Value	Description	Reference
31	Reply Request	RFC 9503

References Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document describes the Simple Two-way Active Measurement Protocol (STAMP), which enables the measurement of both one-way and round-trip performance metrics, like delay, delay variation, and packet loss. This document describes optional extensions to Simple Two-way Active Measurement Protocol (STAMP) that enable measurement of performance metrics. The document also defines a STAMP Test Session Identifier and thus updates RFC 8762. Informative References IEEE Ericsson ZTE Corp. Ericsson This document specifies the data model for implementations of Session-Sender and Session-Reflector for Simple Two-way Active Measurement Protocol (STAMP) mode using YANG. Work in Progress Ciena Corporation Cisco Systems, Inc. Nvidia Huawei Technologies Huawei Technologies Work in Progress Many protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA). To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry. This is the third edition of this document; it obsoletes RFC 5226. Segment Routing (SR) leverages the source routing paradigm. A node steers a packet through an ordered list of instructions, called "segments". A segment can represent any instruction, topological or service based. A segment can have a semantic local to an SR node or global within an SR domain. SR provides a mechanism that allows a flow to be restricted to a specific topological path, while maintaining per-flow state only at the ingress node(s) to the SR domain. SR can be directly applied to the MPLS architecture with no change to the forwarding plane. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. Upon completion of a segment, the related label is popped from the stack. SR can be applied to the IPv6 architecture, with a new type of routing header. A segment is encoded as an IPv6 address. An ordered list of segments is encoded as an ordered list of IPv6 addresses in the routing header. The active segment is indicated by the Destination Address (DA) of the packet. The next active segment is indicated by a pointer in the new routing header. This memo explains the motivation and describes the reassignment of well-known ports for the One-Way Active Measurement Protocol (OWAMP) and the Two-Way Active Measurement Protocol (TWAMP) for control and measurement. It also clarifies the meaning and composition of these Standards Track protocol names for the industry. This memo updates RFCs 4656 and 5357, in terms of the UDP well-known port assignments, and it clarifies the complete OWAMP and TWAMP protocol composition for the industry. Segment Routing (SR) allows a node to steer a packet flow along any path. Intermediate per-path states are eliminated thanks to source routing. SR Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. Packet flows are steered into an SR Policy on a node where it is instantiated called a headend node. The packets steered into an SR Policy carry an ordered list of segments associated with that SR Policy. This document updates RFC 8402 as it details the concepts of SR Policy and steering into an SR Policy. China Mobile Huawei ZTE Corp. Ericsson Cisco Work in Progress

Destination Node Address TLV Use-Case Example STAMP test packets can be encapsulated with 1) an SR-MPLS Label Stack and IPv4 header containing an IPv4 Destination Address from the 127/8 range or 2) an outer IPv6 header and a Segment Routing Header (SRH) with an inner IPv6 header containing an IPv6 Destination Address from the ::1/128 range. In an ECMP environment, the hashing function in forwarding may decide the outgoing path using the Source Address, Destination Address, UDP ports, IPv6 flow-label, etc. from the packet. Hence, for IPv4, for example, different values of an IPv4 Destination Address from the 127/8 range may be used in the IPv4 header of the STAMP test packets to measure different ECMP paths. For IPv6, for example, different values of flow-label may be used in the IPv6 header of the STAMP test packets to measure different ECMP paths. In those cases, the STAMP test packets may reach a node that is not the Session-Reflector for this STAMP session in an error condition, and this unintended node may transmit a reply test packet that can result in the reporting of invalid measurement metrics. The intended Session-Reflector address can be carried in the Destination Node Address TLV to help detect this error.

Acknowledgments The authors would like to thank Thierry Couture for the discussions on the use cases for Performance Measurement in Segment Routing. The authors would also like to thank , , , , , , , , , and for providing comments and suggestions. Thank you to for the Gen-ART review, for the AD review, and for the Security review. The authors would also like to thank , , , , , , , , and for the IESG review.

Contributors The following person has contributed substantially to this document: Bell Canada

daniel.voyer@bell.ca

Authors' Addresses Cisco Systems, Inc.

Canada rgandhi@cisco.com

Cisco Systems, Inc.

cfilsfil@cisco.com

Huawei

mach.chen@huawei.com

Colt

Bart.Janssens@colt.net

Nokia

footer.foote@nokia.com