SPRING Working Group R. Gandhi, Ed. Internet-Draft C. Filsfils Intended status: Standards Track Cisco Systems, Inc. Expires: 2 August 2023 N. Vaghamshi Reliance M. Nagarajah Telstra R. Foote Nokia M. Chen Huawei A. Dhamija Rakuten 29 January 2023 Enhanced Performance Measurement Using Simple TWAMP in Segment Routing Networks draft-gandhi-spring-enhanced-srpm-03 Abstract Segment Routing (SR) leverages the source routing paradigm. SR is applicable to both Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes. This document defines procedure for Enhanced Performance Measurement of end-to-end SR paths including SR Policies for both SR-MPLS and SRv6 data planes using Simple Two-Way Active Measurement Protocol (STAMP) defined in RFC 8762. The procedure allows to improve the scale for number of sessions and the interval for failure detection. 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- Drafts is at https://datatracker.ietf.org/drafts/current/. 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 2 August 2023. Gandhi, et al. Expires 2 August 2023 [Page 1] Internet-Draft Enhanced Performance Measurement in SR January 2023 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3 2.3. Reference Topology . . . . . . . . . . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Enhanced Loopback Mode Enabled with Network Programming Function . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Enhanced Performance Measurement Procedure . . . . . . . . . 6 4.1. Enhanced Performance Measurement Procedure for SR-MPLS Policies . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1.1. Node Capability for MNA Sub-Stack with Opcode TSF . . 8 4.2. Enhanced Performance Measurement Procedure for SRv6 Policies . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2.1. Timestamp Endpoint Function Assignment . . . . . . . 9 4.2.2. Node Capability for Timestamp Endpoint Function . . . 9 5. Example Notifications . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 12 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Gandhi, et al. Expires 2 August 2023 [Page 2] Internet-Draft Enhanced Performance Measurement in SR January 2023 1. Introduction Segment Routing (SR) leverages the source routing paradigm and greatly simplifies network operations for Software Defined Networks (SDNs). SR is applicable to both Multiprotocol Label Switching (SR- MPLS) and IPv6 (SRv6) data planes [RFC8402]. SR Policies as defined in [RFC9256] are used to steer traffic through a specific, user- defined paths using a stack of Segments. A comprehensive SR Performance Measurement (PM) for delay and packet loss as well as Connectivity Verification (CV) 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 [RFC8762] without the use of a control channel to pre-signal session parameters. As described in [I-D.ietf-spring-stamp-srpm], STAMP can be used for performance measurement of one-way, two-way or round-trip delay and packet loss of end-to-end SR paths. STAMP requires RFC8762 protocol support on the Session-Reflector to process the received test packets, and hence the received test packets need to be punted from the forwarding fast path and return test packets need to be generated. This limits the scale for number test sessions and the ability to provide faster detection interval. The loopback measurement mode defined in [I-D.ietf-spring-stamp-srpm] does not require STAMP test packet processing on Session-Reflector, however, it does not provide accurate one-way delay. This document defines procedure for Enhanced Performance Measurement of end-to-end SR paths including SR Policies for both SR-MPLS and SRv6 data planes, using Simple Two-Way Active Measurement Protocol (STAMP) defined in [RFC8762]. The procedure allows to improve the scale for number of sessions and the interval for failure detection. 2. Conventions Used in This Document 2.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2.2. Abbreviations BSID: Binding Segment ID. Gandhi, et al. Expires 2 August 2023 [Page 3] Internet-Draft Enhanced Performance Measurement in SR January 2023 ECMP: Equal Cost Multi-Path. EB: Endpoint Behaviour. HMAC: Hashed Message Authentication Code. MBZ: Must be Zero. MNA: MPLS Network Action. MPLS: Multiprotocol Label Switching. PM: Performance Measurement. PTP: Precision Time Protocol. SID: Segment ID. SL: Segment List. SR: Segment Routing. SRH: Segment Routing Header. SR-MPLS: Segment Routing with MPLS data plane. SRv6: Segment Routing with IPv6 data plane. STAMP: Simple Two-way Active Measurement Protocol. TC: Traffic Class. TS: Timestamp. TSF: Timestamp and Forward. TTL: Time To Live. 2.3. Reference Topology In the reference topology shown in Figure 1, the STAMP [RFC8762] Session-Sender S1 initiates a Session-Sender test packet and the Session-Reflector R1 returns the test packet. The return test packet may be transmitted back 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. Gandhi, et al. Expires 2 August 2023 [Page 4] Internet-Draft Enhanced Performance Measurement in SR January 2023 The Session-Sender S1 and Session-Reflector R1 are connected via an SR path [RFC8402]. The SR path can be an SR Policy [RFC9256] on node S1 (called head-end) with destination to node R1 (called tail-end). T1 T2 / \ +-------+ STAMP Test Packet +-------+ | | - - - - - - - - - - - | | | S1 |======================|| R1 | | |<- - - - - - - - - - - | | +-------+ Return Test Packet +-------+ \ T4 Session-Sender Session-Reflector (Timestamp, Pop and Forward) Figure 1: Loopback Mode Enabled with Network Programming Function 3. Overview 3.1. Enhanced Loopback Mode Enabled with Network Programming Function As described in [I-D.ietf-spring-stamp-srpm], in loopback mode, the STAMP Session-Sender S1 initiates Session-Sender test packets and the Session-Reflector R1 forwards them back to the Session-Sender S1. The received STAMP test packets are not punted out of the fast path in forwarding at the Session-Reflector. At the Session-Reflector, the loopback function simply makes the necessary changes to the encapsulation including IP and UDP headers to return the STAMP test packet to the Session-Sender S1. No STAMP test session is created on the Session-Reflector R1. As described in [I-D.ietf-spring-stamp-srpm], only round-trip delay can be measured in the loopback mode. In SR networks, there is also a need to measure the one-way delay metric to provide low latency services. This document defines a new STAMP measurement mode, called enhanced loopback mode, that is loopback mode enabled with network programming function. In this mode, both transmit (T1) and receive (T2) timestamps in data plane are collected by the Session-Sender test packets as shown in Figure 1. The network programming function optimizes the "operations of punt test packet and generate return test packet" on the Session-Reflector as timestamping is implemented in forwarding fast path in hardware. This helps to achieve higher number of STAMP test session scale and faster detection interval. Gandhi, et al. Expires 2 August 2023 [Page 5] Internet-Draft Enhanced Performance Measurement in SR January 2023 The Session-Sender adds transmit timestamp (T1) in the payload of the Session-Sender test packet. The Session-Reflector adds the receive timestamp (T2) in the payload of the received test packet in forwarding fast path in hardware without punting the test packet (e.g. to slow path or control-plane). The network programming function carried by the test packet enables the Session-Reflector to add the receive timestamp (T2) at the specified offset in the payload of the test packet. 4. Enhanced Performance Measurement Procedure For enhanced performance monitoring of an end-to-end SR path including SR Policy, STAMP Session-Sender test packets are transmitted in loopback mode enabled with network programming function to timestamp and forward the packet. For SR Policy, the Session-Sender test packets are transmitted using the Segment List (SL) of the Candidate-Path [RFC9256]. When a Candidate-Path has more than one Segment Lists, multiple Session- Sender test packets MUST be transmitted, one using each Segment List as described in [I-D.ietf-spring-stamp-srpm]. 4.1. Enhanced Performance Measurement Procedure for SR-MPLS Policies An SR-MPLS Policy may contain a number of Segment Lists (SLs). A Session-Sender test packet MUST be transmitted using each Segment List of the SR-MPLS Policy. The content of an example Session-Sender test packet for an end-to-end SR-MPLS Policy is shown in Figure 3. The loopback measurement mode for SR-MPLS Policies defined in Section 4.2.3.3 of [I-D.ietf-spring-stamp-srpm] is used and enhanced as described below. In this document, MPLS Network Action (MNA) Sub-Stack defined in [I-D.jags-mpls-mna-hdr] is used for SR-MPLS data plane to enable network programming function for "timestamp and forward" the received test packet, for unauthenticated mode and authenticated mode. The MNA Sub-Stack carries the MNA Label as defined in [I-D.jags-mpls-mna-hdr] and it is a base special purpose label [RFC9017]. In this document, new MNA Opcode TSF (value TBA2) is defined for the network action. The Ancillary Data field of the opcode carries 10-bits of timestamp offset in bytes and 3-bits of timestamp format (FMT) (value 1 for 64-bit PTPv2 or value 0 for NTP). In the Session-Sender test packets for SR-MPLS Policies, the MNA Sub- Stack with Opcode TSF (value TBA2) is added in the MPLS header as shown in Figure 3, to collect "Receive Timestamp" field in the payload of the test packet. The Ingress-to-Egress (I2E), Hop-By-Hop Gandhi, et al. Expires 2 August 2023 [Page 6] Internet-Draft Enhanced Performance Measurement in SR January 2023 (HBH), Select scope (IHS) is set to "I2E" when return path is IP/UDP and set to "Select" when the return path is SR-MPLS. The Network Action Sub-Stack Length (NASL) is set to 0 when there is no Label Stack Entry (LSE) after this Opcode in the MNA Sub-Stack. The P flag is set to 0 as no Post-Stack ancillary data is required for this network action. the U flag is set to skip the network action and forward the packet (and not drop the packet). The Label Stack for the reverse direction SR-MPLS path can be added after the MNA Sub- Stack (not shown in the Figure) to receive the return test packet on a specific path. When a Session-Reflector receives a packet with this MNA Sub-Stack with Opcode TSF (value TBA2), after timestamping the packet at the specified offset, the Session-Reflector pops the MNA Sub-Stack (after completing any other network actions) and forwards the packet using the next label or IP header in the packet (just like the data packets for the normal traffic). 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label(1) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label(n) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label (value TBA1) | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |7b Opcode=TSF| 10b TS Offset | FMT |P|IHS|S| RES |U|NASL=0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IP Header | . Source IP Address = Session-Sender IPv4 or IPv6 Address . . Destination IP Address = Session-Sender IPv4 or IPv6 Address . . Protocol = UDP . . . +---------------------------------------------------------------+ | UDP Header | . Source Port = As chosen by Session-Sender . . Destination Port = As chosen by Session-Sender . . . +---------------------------------------------------------------+ | Payload = Test Packet as specified in Section 3 of RFC 8972 | . in Figure 1 and Figure 3 . . . +---------------------------------------------------------------+ Gandhi, et al. Expires 2 August 2023 [Page 7] Internet-Draft Enhanced Performance Measurement in SR January 2023 Figure 2: Example STAMP Test Packet with Timestamp Label for SR-MPLS 4.1.1. Node Capability for MNA Sub-Stack with Opcode TSF The STAMP Session-Sender needs to know if the Session-Reflector can process the MNA Sub-Stack with Opcode TSF to avoid dropping the test packets. The signaling extension for this capability exchange or local configuration are outside the scope of this document. 4.2. Enhanced Performance Measurement Procedure for SRv6 Policies An SRv6 Policy may contain a number of Segment Lists. Each Segment List may contain a number of SRv6 SIDs as defined in [RFC8986], [I-D.filsfils-spring-net-pgm-extension-srv6-usid] and [I-D.ietf-spring-srv6-srh-compression]. A Session-Sender test packet MUST be transmitted using each Segment List of the SRv6 Policy. An SRv6 Policy may contain an SRv6 Segment Routing Header (SRH) carrying a Segment List as described in [RFC8754]. The content of an example Session-Sender test packet for an end-to-end SRv6 Policy using an SRH is shown in Figure 4. The loopback measurement mode for SRv6 Policies defined in Section 4.2.3.4 of [I-D.ietf-spring-stamp-srpm] is used and enhanced as described below. The [RFC8986] defines SRv6 Endpoint Behaviours (EB) for SRv6 nodes. In this document, two new Timestamp Endpoint Behaviours are defined for Segment Routing Header (SRH) [RFC8754] to enable "Timestamp and Forward (TSF)" function for the received test packets, one for unauthenticated mode and one for authenticated mode. In the Session-Sender test packets for SRv6 Policies, Timestamp Endpoint Function (End.TSF) is carried with the target Segment Identifier (SID) in SRH [RFC8754] as shown in Figure 4, to collect "Receive Timestamp" field in the payload of the test packet. The Segment List for the reverse direction path can be added after the target SID to receive the return test packet on a specific path. When a Session-Reflector receives a packet with Timestamp Endpoint (End.TSF) for the target SID which is local, after timestamping the packet at the specified offset, the Session-Reflector forwards the packet using the next SID in the SRH or inner IPv6 header in the packet (just like the data packets for the normal traffic). Gandhi, et al. Expires 2 August 2023 [Page 8] Internet-Draft Enhanced Performance Measurement in SR January 2023 +---------------------------------------------------------------+ | IP Header | . Source IP Address = Session-Sender IPv6 Address . . Destination IP Address=Session-Reflector IPv6 Address | . . Segment List[Segments Left] . . Next-Header = 43, Routing Type = SRH (4) . . . +---------------------------------------------------------------+ | SRH as specified in RFC 8754 | . . . SRv6 Endpoint End.TSF (value TBA3 or TBA4) . . . +---------------------------------------------------------------+ | IP Header | . Source IP Address = Session-Sender IPv6 Address . . Destination IP Address = Session-Sender IPv6 Address . . Next-Header = UDP (17) . . . +---------------------------------------------------------------+ | UDP Header | . Source Port = As chosen by Session-Sender . . Destination Port = As chosen by Session-Sender . . . +---------------------------------------------------------------+ | Payload = Test Packet as specified in Section 3 of RFC 8972 | . in Figure 1 and Figure 3 . . . +---------------------------------------------------------------+ Figure 3: Example STAMP Test Packet with Endpoint Function for SRv6 4.2.1. Timestamp Endpoint Function Assignment Timestamp Endpoint Functions (values TBA3 and TBA4) assigned by IANA from the "SRv6 Endpoint Behaviors Registry". For endpoint behaviour (value TBA3), the timestamp offset is fixed at byte-offset 16 from the start of the payload for the STAMP test packets in unauthenticated mode, and endpoint behaviour (value TBA4) at byte- offset 32 from the start of the payload for the STAMP test packets in authenticated mode, both using the timestamp format 64-bit PTPv2. 4.2.2. Node Capability for Timestamp Endpoint Function The STAMP Session-Sender needs to know if the Session-Reflector can process the Timestamp Endpoint Function to avoid dropping test packets. The signaling extension for this capability exchange is outside the scope of this document. Gandhi, et al. Expires 2 August 2023 [Page 9] Internet-Draft Enhanced Performance Measurement in SR January 2023 5. Example Notifications The timestamps T1 and T2 are used to measure the one-way delay. The delay metrics for an end-to-end SR path are notified, for example, when consecutive M number of test packets have measured delay values exceed the user-configured threshold TH, where M (Delay Exceeded Packet Count) and TH (Absolute and Percentage Delay Exceeded Thresholds) are also locally provisioned values. The round-trip packet loss for an end-to-end SR path is calculated using the Sequence Number in the Session-Sender test packets. The packet loss metric is notified when X number of Session-Sender test packets were lost out of last Y number of test packets transmitted by the Session-Sender, where Threshold XofY is locally provisioned value. STAMP session state as UP (i.e. Connectivity Verification success) for an end-to-end SR path is initially notified as soon as one or more return test packets are received at the Session-Sender. STAMP session state as DOWN (i.e. Connectivity Verification failure due to packet loss) for an end-to-end SR path is notified when consecutive N number of return test packets are not received at the Session-Sender after the session state is UP, where N (Packet Loss Count) is a locally provisioned value. In the loopback mode where the Session-Reflector does not generate reply test packets, a Connectivity Verification failure on the reverse direction path can cause the return test packets to not reach the Session-Sender. This is also true in the case where the return test packets are generated by the stateless Session-Reflector, e.g., in two-way mode. The stateful Session-Reflector can solve this issue by maintaining the forwarding direction state and notifying a Connectivity Verification success and failure to the Session-Sender based on the Packet Loss Count, N. 6. Security Considerations The STAMP protocol is intended for deployment in limited domains [RFC8799]. As such, it assumes that a node involved in the STAMP protocol operation has previously verified the integrity of the path and the identity of the far-end Session-Reflector. The security considerations specified in [RFC8762] and [RFC8972] also apply to the procedures defined in this document. Specifically, the message integrity protection using HMAC, as defined in Section 4.4 of [RFC8762] also apply to the procedure described in this document. Gandhi, et al. Expires 2 August 2023 [Page 10] Internet-Draft Enhanced Performance Measurement in SR January 2023 7. IANA Considerations IANA request for MNA Base Special Purpose Label in [I-D.jags-mpls-mna-hdr]. +-------------+--------------------------------+---------------------+ | Value | Description | Reference | +-------------+--------------------------------+---------------------+ | TBA1 | MNA Label | [jags-mpls-mna-hdr] | +-------------+--------------------------------+---------------------+ IANA maintains the "MNA Opcode" registry when created from IANA request in [I-D.jags-mpls-mna-hdr]. IANA is requested to allocate a value for Network Action (NA) Opcode for Timestamp and Forward from this registry: +-------------+--------------------------------+---------------------+ | Value | Description | Reference | +-------------+--------------------------------+---------------------+ | TBA2 | Timestamp and Forward NA Opcode| This document | +-------------+--------------------------------+---------------------+ IANA is requested to allocate, within the "SRv6 Endpoint Behaviors Registry" sub-registry belonging to the top-level "Segment Routing Parameters" registry [RFC8986], the following allocation: +-------------+---------------------------------+---------------+ | Value | Endpoint Behavior | Reference | +-------------+---------------------------------+---------------+ | TBA3 | End.TSF (Timestamp and Forward) | This document | | | for offset 16 for STAMP | | | | in Unauthenticated Mode | | +-------------+---------------------------------+---------------+ | TBA4 | End.TSF (Timestamp and Forward) | This document | | | for offset 32 for STAMP | | | | in Authenticated Mode | | +-------------+---------------------------------+---------------+ 8. References 8.1. 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, . Gandhi, et al. Expires 2 August 2023 [Page 11] Internet-Draft Enhanced Performance Measurement in SR January 2023 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple Two-Way Active Measurement Protocol", RFC 8762, DOI 10.17487/RFC8762, March 2020, . [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, . [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", RFC 8986, DOI 10.17487/RFC8986, February 2021, . [I-D.ietf-spring-stamp-srpm] Gandhi, R., Filsfils, C., Voyer, D., Chen, M., Janssens, B., and R. Foote, "Performance Measurement Using Simple TWAMP (STAMP) for Segment Routing Networks", Work in Progress, Internet-Draft, draft-ietf-spring-stamp-srpm-05, 25 August 2022, . [I-D.jags-mpls-mna-hdr] Rajamanickam, J., Ed., Gandhi, R., Ed., Zigler, R., Ed., Song, H., Ed., and K. Kompella, Ed., "MPLS Network Action Header Encodings", Work in Progress, Internet-Draft, draft-jags-mpls-mna-hdr-05, January 2023, . 8.2. Informative References [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, July 2018, . [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, . Gandhi, et al. Expires 2 August 2023 [Page 12] Internet-Draft Enhanced Performance Measurement in SR January 2023 [RFC8799] Carpenter, B. and B. Liu, "Limited Domains and Internet Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020, . [RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special- Purpose Label Terminology", RFC 9017, DOI 10.17487/RFC9017, April 2021, . [I-D.ietf-spring-srv6-srh-compression] Cheng, W., Filsfils, C., Li, Z., Decraene, B., Cai, D., Voyer, D., Clad, F., Zadok, S., Guichard, J. N., Aihua, L., Raszuk, R., and C. Li, "Compressed SRv6 Segment List Encoding in SRH", Work in Progress, Internet-Draft, draft- ietf-spring-srv6-srh-compression-03, 11 January 2023, . [I-D.filsfils-spring-net-pgm-extension-srv6-usid] Filsfils, C., Garvia, P. C., Cai, D., Voyer, D., Meilik, I., Patel, K., Henderickx, W., Jonnalagadda, P., Melman, D., Liu, Y., and J. Guichard, "Network Programming extension: SRv6 uSID instruction", Work in Progress, Internet-Draft, draft-filsfils-spring-net-pgm-extension- srv6-usid-14, 12 December 2022, . [RFC9256] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", RFC 9256, DOI 10.17487/RFC9256, July 2022, . Acknowledgments The authors would like to thank Greg Mirsky, Kireeti Kompella, and Adrian Farrel for providing useful comments. Authors' Addresses Rakesh Gandhi (editor) Cisco Systems, Inc. Canada Email: rgandhi@cisco.com Clarence Filsfils Cisco Systems, Inc. Gandhi, et al. Expires 2 August 2023 [Page 13] Internet-Draft Enhanced Performance Measurement in SR January 2023 Email: cfilsfil@cisco.com Navin Vaghamshi Reliance Email: Navin.Vaghamshi@ril.com Moses Nagarajah Telstra Email: Moses.Nagarajah@team.telstra.com Richard Foote Nokia Email: footer.foote@nokia.com Mach(Guoyi) Chen Huawei Email: mach.chen@huawei.com Amit Dhamija Rakuten Email: amit.dhamija@rakuten.com Gandhi, et al. Expires 2 August 2023 [Page 14]